RPC2012 - XI Workshop on Resistive Plate Chambers and Related Detectors

5 Feb 2012, 08:00 → 10 Feb 2012, 17:15 Europe/Rome

<B>Aula B. Touschek, Bldg 36</B> (INFN-LNF <!-- ID_UTENTE=503 -->)

Stefano Bianco (LNF)

Sunday, 5 February

08:00 Arrivals

Monday, 6 February

09:30 Registration

13:30 Lunch @ Frascati lab Cafeteria (on the ENEA site)

Opening: (Chairperson S. Bianco)

Opening

1 Welcome Address

A Welcome address from the Frascati Lab Director.

Speaker: Umberto Dosselli (LNF)

2 Remembering Giuseppe Belli

Speaker: Giuseppe Iaselli (BA)

Slides 2_In_memory_of_Beppe.ppt

3 Remembering Anna Piccotti

Slides 1_annaP.pdf

4 Keynote

Keynote talk.

Speaker: Rinaldo Santonico (Univ. Tor Vergata and INFN Roma 2)

Slides 3_2012_2_6_RPC2012_Introductory_talk.pptx

Performance of RPC systems: (Chairpersons R.Santonico)

Performance of RPC systems

5 Calibration of the RPC working voltage in the CMS experiment

The working voltage of all the RPCs installed in the CMS experiment has been tuned with a dedicated HV scan with LHC collisions during the low luminosity operations. The procedures and the results of the HV calibration will be presented.

Speaker: Silvia Costantini (University of Ghent)

Slides RPC2012_SilviaCostantini.pdf

6 Performance and Operation of the ATLAS RPC Detector during the 2011 LHC run

Resistive Plate Chambers (RPC) provide the barrel region of the ATLAS detector with an independent muon trigger and a two-coordinate measurement. The chambers, arranged in three concentric double layers are operated in a strong magnetic toroidal field and cover a surface area of about 4000 m2. During 2011 the LHC has provided proton-proton collisions at 7 TeV in the center-of-mass frame with a steady increase in instantaneous luminosity over several orders of magnitude, summing up to 5fb-1. The operational experience for this running period is presented along with studies on the detector performance as a function of luminosity, environmental conditions and working point settings. The measurements presented allow defining a strategy for the data taking in next years and make predictions on the performance when higher luminosities will be reached.

Speaker: Alessandro Polini (BO)

Slides 2_-_polini-rpc2012.pdf

7 ATLAS RPC time-of-flight performance

We show ATLAS RPC timing performance measured with proton-proton collisions and cosmic rays in data recorded by the ATLAS detector in 2011 at LHC. In addition, we illustrate how RPC time-of-flight and spatial measurements can be used to determine particle velocity and direction at LHC.

Speaker: Gabriele Chiodini (INFN Lecce)

Slides 3_-_CHIODINI_-_RPC2012chiodini_3.pdf

17:40 coffee break

8 Performance of the ALICE muon trigger system in Pb–Pb collisions

ALICE (A Large Ion Collider Experiment) is the LHC experiment dedicated to the study of heavy-ion collisions at very high energy, where the formation of the Quark Gluon Plasma (QGP) is expected. Heavy flavor production is one of the key observables for the study of QGP. In ALICE, charmonium and bottomonium states are identified in the forward rapidity region via their muonic decays, by means of a dedicated muon spectrometer. A trigger system allows selecting events with high transverse momentum (pT) muons, while rejecting low pT background muons from pion and kaon decays. The trigger system is composed by four planes of 18 resistive plate chambers (RPC) each (for a total surface of 140 m^2 and 21000 electronics channels). The RPC are equipped with orthogonal copper strips of different pitches (1, 2 and 4 cm) for readout. The front-end electronics is based on a dual threshold discriminator which allows a time resolution better than 2 ns. The spatial information of the four RPC planes is used to estimate the muon charge and the pT via the relative angle with respect to a straight track from the interaction point. Single and dimuon trigger signals with two different pT cuts (pT >~ 0.5 Gev/c and pT >~ 1 GeV/c) are delivered. The performance of the detector in Pb-Pb collisions in 2010 and 2011 will be presented, with particular regard to the muon trigger selectivity above each of the two pT cuts. The multiplicity of detected muon tracks per event, versus centrality and transverse momentum, will be shown. The multiplicity of strips and clusters per event versus centrality are analyzed for the determination of the detector occupancy. The stability of the performance along the duration of the data taking periods (about one month in 2010 and 2011) will be presented. A comparison of the results with real simulations will be also shown.

Speaker: Massimiliano Marchisone (TO)

Slides presentazione_Frascati_06Feb2012.pdf

9 Performance of the MRPC-based Time-Of-Flight detector of ALICE at LHC

The large Time-Of-Flight (TOF) array is one of the main detectors devoted to charged hadron identification in the mid-rapidity region of the ALICE experiment at the LHC; it allows separation among pions, kaons and protons up to few GeV/c, covering the full azimuthal angle and -0.9 < η < 0.9. The TOF exploits the innovative MRPC technology capable of an intrinsic time resolution better than 50 ps with an overall efficiency close to 100% and a large operation plateau; the full array consists of 1593 MRPC chambers covering a cylindrical surface of about 150 m2. In this report, the performance achieved by the TOF detector is shown; the results have been obtained during the 2010 and 2011 data taking periods, both with pp and Pb-Pb collisions.

Speaker: Andrea Alici (BO)

Slides 5_-_ALICI__-_AA_RPC2012_v3.pdf

10 Performance and aging of OPERA bakelite RPCs.

OPERA is an experiment dedicated to the observation of numu into nutau oscillations through tau appearance on the CNGS beam. The experiment is composed by two identical super-modules, each with a target section (made of emulsion/lead bricks alternated to a scintillator Target Tracker) and a muon spectromter (instrumented with bakelite electrodes RPCs and drift tubes). The OPERA RPC system is composed of about 1000 RPCs for an instrumented area of 3000 m2. The RPCs are operated in streamer mode and flushed with the gas mixture Ar/R134a/isobutane/SF6=75.4/20/4/0.6 at five refills/day in open flow. The present performances of the RPC system after six years of operation are presented. The aging status of the detector is also described.

Speaker: Alessandro Paoloni (LNF)

Slides paoloni_opera.pdf

11 Results from the ARGO-YBJ experiment

The ARGO-YBJ experiment consists of a 5000 m2 single layer of Resistive Plate Chambers situated at Yangbajing, Tibet (P.R. of China), 4300 meters a.s.l. (atmospheric depth 600 g/cm2). The percentage of active area all over the carpet is 92% and a partially instrumented guard ring (1700 m2) around the central zone extends the instrumented area up to 11000 m2. The experiment is operated in scaler mode, shower mode and analog mode and is sensitive to cosmic rays in the 10^9-10^15 eV energy range. >From few hundreds GeV on, the arrival direction of cosmic rays is inferred by the study of the induced extensive air showers. A review of the most important results of the ARGO-YBJ experiment in gamma-ray astronomy and cosmic-ray physics will be given, focusing on the potential of RPCs in ground-based astroparticle physics.

Speaker: Roberto Iuppa (ROMA2)

Slides iuppa_20120206_4PDF.pdf

20:30 Welcome Cocktail - Villa Grazioli, Grottaferrata

Tuesday, 7 February

Performance of RPC systems: (Chairpersons D. González-Diaz , G. Iaselli)

Performance of RPC systems

Conveners: Davide Piccolo (LNF Frascati), Giuseppe Iaselli (University of Bari and INFN), Norbert Herrmann (University of Heidelberg), Sergio P. Ratti (University of Pavia and INFN), Sergio Patricelli (University of Napoli and INFN)

12 The Extreme Energy Events experiment: cosmics rays, multigap resistive plate chambers and high school students

The Extreme Energy Events experiment has been concieved by its leader, prof. A. Zichich, and joins the scientific interest of a real cosmic rays physics experiment with the enormous didactic potentiality deriving from letting it be carried on by high school students. It consists of an extended network of telescopes made by three Multigap Resistive Plate Chambers each, designed to monitor the muon cosmic rays flux and detect very-high energy extended atmospheric showers; each telescope is located in a high school on the Italian territory and, after the initial set up phase, is continuously operated and monitored just by students and teachers. A very good performance, in terms of efficiency, space and time resolution is essential to achieve its physics goals, and therefore the detectors used must assure a front-line performance, similar to the one presently achieved at the LHC experiments. In this talk, after briefly discussing the experiment layout, a review about the detector construction, installation and commissioning, will be done, and some measurements on the actual perfomance of the MRPCs installed in the various telescopes will be shown. After the initial phase, the experiment is starting to continously take data, and the first physics interesting results have been obtained, demonstrating the validity of the idea of running a real physics experiment in these peculiar conditions. A short review of the observations of extended showers by the stations of the EEE experiment, and of the 2011 February Forbush decrease, which both give very intriguing informations in this field, will complete the talk.

Speaker: Marcello Abbrescia (Università and INFN - Bari - Italy)

Slides Abbrescia@RPC2012.pptx

13 R&D and mass production of LMRPC module for the STAR-MTD system

Data taken over the last several years have demonstrated that RHIC has created dense and rapidly thermalizing matter. One of the physics goals for the next decade of RHIC is to study the fundamental properties of hot, dense medium such as temperature, density profile, and color screening length via electro-magnetic probes such as di-leptons. Muons have a clear advantage over electrons due to reduced Bremsstrahlung radiation in the detector material. A novel and compact Muon Telescope Detector (MTD) in STAR at mid-rapidity will be constructed. A lot of R&D work of Long-strip Multi-gap Resistive Plate Chamber (LMRPC) has been done to fulfill the requirement of the STAR-MTD system. Last year, a new 6 250-micrometer gap LMRPC prototype with wide strip was built and tested in cosmic-ray and in beam. The module had 12 strips. Each strip was 3.8cm wide and 90cm long with 0.6 intervals. In cosmic-ray test, the efficiency was higher than 95% and the time resolution was around 75ps in the gas mixture of 94% Freon, 5% iso-Butane and 1%SF6. The efficiency was also higher than 95% and the time resolution was around 97ps in the gas mixture of 95% Freon and 5% iso-Butane. In the beam test, the efficiency was close to 100% and a time resolution of 55ps was got for the gas mixture of 90% Freon, 5% iso-Butane and 5%SF6. A good uniformity of the performance along the strip and across the strip was also shown during the test. Another prototype with 5 gas-gaps was built in order to reduce the working high voltage of the STAR-MTD LMRPC module. This module was test in cosmic-ray. The efficiency was higher than 95% and the time resolution was around 95ps in the gas mixture of 95% Freon and 5% iso-Butane. A new cosmic-ray test system with long scintillators was design in order to speed up the process of quality control. The first batch of 8 LMRPC modules has already been produced and sent to UT Austin. Every channel was test in cosmic-ray during the QC process. All the modules are qualified. That means the efficiency of each module is higher than 90%, the noise rate of each channel is less than 1Hz/cm2 and each module has less than 3 channels with a time resolution worse than 120ps in the working gas mixture of 95% Freon and 5% iso-Butane and under the working electric field of 100.8kV/cm.

Speaker: Mr Huangshan Chen (Tsinghua University)

Slides 2_-_R&D_and_mass_production_of_LMRPC_module_for_the_STAR-M2TD_system.pdf

14 Aging test of high rate MRPC

The Compressed Baryonic Matter (CBM) experiment, proposed at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, has decided to use MRPC technology to build the TOF wall. Compared with other experiments (for instance Alice, STAR, et al), CBM-TOF requires a rate capability for MRPC as high as 20 kHz/cm2. Tsinghua University is a group member of CBM-TOF and is doing research on low-resistivity glass and high rate MRPC. The volume resistivity of our glass is on the order of 1010 Ωcm. Time resolution of high rate MRPC can reach 50ps and its rate capability can reach up to 300 kHz/cm2.

Speaker: Mr Xingming Fan (Tsinghua University)

Slides Aging_Test_of_MRPC_report.pdf Aging_Test_of_MRPC_report.pptx

15 Conceptual design of the CBM-TOF wall with real-size high-rate MRPC modules based on the newly developed chinese doped glass

The proposed Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, will use a TOF system based on MRPC technology for hadron identification. The challange is to keep efficiencies above 90 % and time resolutions well below 80 ps at particle fluxes up to 20 kHz/cm2, which is not accessible to conventional float-glass MRPCs. For this purpose, a kind of low-resistivity doped glass with bulk resistivity on the order of 1010 Ωcm was produced at Tsinghua University. Two real-size high rate prototypes based on this material were developed and tested in-beam. In the current conceptual design, the whole CBM-TOF wall is arranged in four “rate regions”. In the inner rate regions (region 1-3), the particle flux ranges from 3.5 kHz/cm2 to 25 kHz/cm2, thus high-rate MRPCs with low-resistive glass electrodes are presently the best choice. In the outmost rate region (region 4), the average particle flux is about 1 kHz/cm2, so MRPCs made out of float glass might be used. Here we propose a slightly different conceptual design for building the TOF wall by resorting to a single technology based on low-resistive doped glass and relying on small structural modifications of the two modules developed and tested during the last 2 years. It’s very inspiring that the appropriate MRPC prototypes have been already tested with high intensity beam and the performance can fulfill the CBM requirements. We will also present the results from the latest beam test of the two real-size modules at the continous electron beam of the Electron Linac with high Brilliance and low Emittance (ELBE) facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in April 2011. The counters show large efficiency plateaus by as much as 600volts, and intrinsic resolutions down to 50ps. Under conditions of localized irradiation, the rate capability of the strip counter reaches up to 200 kHz/cm2, while it is higher for the pad counter (~300 kHz/cm2).

Speaker: Mr Jingbo WANG (Tsinghua university)

Slides 4_-_Jingbo_Progress_on_the_real-size_high_rate_MRPC_modules_andConceptual_design_of_the_CBM-TOF_wall.ppt

16 A Multistrip-MRPC prototype for the CBM Time-of-Flight wall

The Compressed Baryonic Matter spectrometer (CBM) is expected to be operational in the year 2018 at the Facility for Anti-proton and Ion Research (FAIR) in Darmstadt, Germany. The key element providing hadron identification at incident energies between 2 and 45 AGeV is a time-of-flight wall placed at 10 m distance from the target covering the polar angular range from 2.5º - 25º and full azimuth. The necessary particle id capabilities require a 80 ps system time resolution at high efficiency and, simultaneously, a rate capability of up to 25 kHz/cm2. The existing conceptual design foresees a 120 m2 ToF-wall composed of Multi-gap Resistive Plate Chambers (MRPC) of which the outer-most part can be covered most likely with float glass RPCs in a multi-strip configuration. The CBM-TOF wall will therefore consist of the largest multi-strip RPC system to be used for timing world-wide. Based on in-beam tests at GSI/SIS18 at Darmstadt and COSY at Juelich we will present results on the performance reached with a fully differential multi-strip MRPC prototype with normal float glass developed at the Physikalisches Institut at University of Heidelberg.

Speaker: Mr Ingo Deppner (Pysikalisches Institut der Universität Heidelberg)

Slides 5_-_deppner_RPC_2012.ppt

10:40 break

17 Design and performance of large area, high resolution RPCs for LEPS2 at SPring-8

The hadron photo-production experiment at LEPS2/SPring-8 will start in 2013. The photon beam with energy up to 3 GeV is produced by backward Compton scattering of laser photons with 8-GeV electrons circulating in SPring-8 storage ring. The development of a 4pi detector is now underway. The momentum of a charged particle is analyzed with the solenoid magnet and drift chambers. The particle identification is performed with the mass reconstructed using the momentum and the velocity, which is measured from the flight length and the time of flight (TOF). For the TOF measurement, large area, high time resolution RPCs is now being developed. The gap size and readout strip size dependence of the time resolution and the efficiency of the RPC is reported. Pions and Kaons with momenta up to 2.5 GeV/c are produced in LEPS2 experiment. In order to separate 1.1-GeV/c K/pi with 3 sigma from the time difference while traveling 100 cm in the magnet, the time resolution better than 50 ps is required for the time of flight detector. In addition, the detection efficiency better than 99 % is required. The TOF detectors cover a cylindrical area of 550 * 100 cm^2. Although scintillation detectors are difficult to achieve 50 ps time resolution with large area and in magnetic field, RPC is well-suited for these requirements. In order to reduce the number of channels to be less than 1000, the area of each readout strip of the RPC should be larger than 120cm^2. We developed prototype RPCs with the area of 10 * 50 cm^2. We studied the time resolution and the efficiency by changing gap sizes and readout strip sizes. We tested three gap configurations, namely, 100 um * 14 gaps, 150 um * 12 gaps and 260 um * 10 gaps RPCs with strip sizes from 1.5 * 5.5 cm^2, which corresponds to 6000 channels, to 2.5 * 40 cm^2, which correspond to 1000 channels. We found that smallest strip of 150 um RPC has the best time resolution, 50 ps, and, the efficiency is better than 99%. However, the resolution and the efficiency become worse for larger strip because the pulse height is not enough and the time walk effect is large. The resolution of 260 um RPC does not depend on the strip size and both smallest and largest strip achieved 60 ps resolution with the efficiency better than 99 %. The efficiency of 100 um RPC is not enough even for the smallest strip and the resolution was worse than other gap size RPCs. The RPC with the 260 um gap works very well. As a future work, we will develop larger RPC with the area of 10 * 100 cm^2 and longer readout strip, which is used for the LEPS2 physics data taking.

Speaker: Natsuki Tomida (Kyoto University)

Slides TOF_RPCforLEPS2.pdf TOF_RPCforLEPS2.pptx

18 Phenolic Multigap RPCs for high-rate particle triggers in the CMS experiment

We report a systematic study of oiled phenolic multigap RPCs for high-rate particle triggers in high-energy physics experiments. In the current R&D, four- and six-gap detector structures were applied to the typical panel-type RPCs. Reduction of avalanche charges drawn in the trigger RPCs will be fairly conductive to lessen the possibility of radiation damage as well as to enhance the detector rate capability when they operate in the experimental condition with high-rate beam background. For the systematic study, prototype detectors built in four- and six-gap types were constructed and tested for cosmic muons and 0.662-MeV gamma rays irradiated by a 200 mCi 137Cs source with a maximum signal rate of 1.6 kHz cm-2. The mean fast charges of the cosmic muons at the mid of the operational plateau, measured by four- and six gap RPCs with proper threshold setups, were 1.3 and 0.8 pC, respectively, which were at least factor 2 smaller than the value drawn in the typical 2-mm-thick double gap RPCs. In addition, the gamma-ray induced currents drawn in unit area of the RPCs were measured to confirm the reduction of the mean avalanche charges. Finally, the rate capabilities of the prototype detectors were confirmed with the maximum rate. We conclude from the current study that the multigap detector structures are characteristically and practically feasible to construct large-size panel-type trigger RPCs for high-rate triggers in high-η region of the CMS experiment.

Speaker: Dr Kyong Sei Lee (Korea University)

Slides RPC2010kslee_f.pptx

19 Construction and Tests of new Resistive Plate Chambers for the Upgrade of the CMS Endcap System

The CMS muon endcap system presently comprises three disks of RPCs, with a fourth disk under preparation with detectors and associated services. This new station, RE4, will be installed in the LHC first Long Shutdown during 2013-2014. In this talk we describe the new RPCs developed for this upgrade, based on lessons learnt from the earlier work. We report on tests performed after the assembly of two first prototypes.

Speaker: Dr Lalit Pant (Bhabha Atomic Research Centre)

Slides 8_-_Construction-CMSRPC-RPC2012-L_Pant-BARC.pptx

20 Performance of timing-RPC prototypes with relativistic heavy ions

Since RPCs were proposed to build a time-of-flight wall for relativistic ions in the framework of the R3B experiment at FAIR-GSI [1], we have carried out an extensive programme to study the timing RPC performances under heavy ion irradiation [2, 3]. In the last two years, several detector tests at the heavy ion GSI facility (Darmstadt, Germany) and the electron beam ELSA facility at CEA/DAM (Bruyeres-le-Chatel, France) have allowed us to characterize the efficiency and the time resolution of our prototypes under different experimental conditions. Different RPC concepts (double gap, single gap) and sizes have been tested using own-developed front-end electronics together with GSI TacQuila acquisition cards. The most promising results with heavy ions have been obtained at low-rate irradiations (several Hz/cm2) , with full efficiency for a broad voltage plateau and time resolutions below 70 ps (sigma), reaching 40 ps for electron beams with a repetition rate of 1 Hz. [1] H. Alvarez-Pol et al. Nucl. Phys. B Proc. Supp. 158 (2006) 186-189 [2] Y. Ayyad et al. Nucl. Instrum. Meth. A (doi:10.1016/j.nima.2010.08.079) [3] E. Casarejos et al. Nucl. Instrum. Meth. A, submitted.

Speaker: Dr Carlos Paradela Dobarro (Universidad de Santiago de Compostela)

Slides paradela_RPC2012.ppt.ppt

21 Study of Angular Distribution of Cosmic Muons using INO-ICAL Prototype Detector at TIFR

The India-based Neutrino Observatory (INO) collaboration is planning to set up a magnetized 50kton Iron-CALorimeter (ICAL) with Resistive Plate Chambers (RPC) as active detectors to study neutrino oscillations and precisely measures its parameters. A prototype detector stack (without magnet) comprising of 12 layers of glass RPCs of 1m x 1m in area has been set-up in TIFR to track cosmic ray muons. Using the muon data, an attempt has been made to reproduce the cosmic muon intensity distribution on the earth’s surface. The general form of this distribution is I = I0 Cos^n(theta). Detector differential aperture, i.e., solid angular coverage of the detector is estimated and statistical minimization procedure is used to get the best fit value for ‘I0’ and ‘n’. Detector solid angle acceptance, efficiencies and minimization routine are presented here.

Speaker: Mr Sumanta Pal (TIFR)

Slides SPal_RPC2012.pdf

13:05 Lunch @ Restaurant Villa Mercede (shuttle from Conference Hall)

Performance of RPC systems: (Chairperson G.Iaselli)

Performance of RPC systems

22 Performance of FOPI MMRPC Barrel in Recent Heavy-Ion Experiments

The FOPI experiment has upgraded its Time-of-Flight detection system with a glass based RPC detector. This implementation is unique since readout electrodes are 1.64 mm narrow strips 90 cm long. Each counter is composed of 16 strips and referred to as the Multi-strip Multi-Gap Resistive Plate Counter (MMRPC). Counters are placed around the Central Drift Chamber of FOPI forming a cylindrical shell – the Barrel. Full MMRPC Barrel has 2400 strips that are readout from both ends. We will discuss its performance in recent HI experiments.

Speaker: Dr Mladen Kiš (GSI)

Slides M.Kis_RPC2012.pdf

23 ATLAS RPC detector as Luminosity monitor

ATLAS RPC Detector Control System has been mainly used to monitor and safely operate the RPC detector during 2010 and 2011 LHC run. The large number (~3500) of gap currents, individually monitored with nA accuracy, allowed us to study the detector behavior with a growing Luminosity and beam currents. A clear linear correlation between the average gap current and the luminosity has been observed over more than four decades. In this presentation will be shown how this method has a good potential for improving the accuracy and the stability of the standard luminosity measurements on a long time basis.

Speaker: Marcello Bindi (BO)

Slides Bindi_RPC2012_Lumi.pdf

Simulations and modeling: (Chairperson M. Abbrescia)

Simulations and modeling

24 Review of Simulation and Modeling

In spite of their apparent simplicity, RPCs feature a range of physical situations somewhat more complex than those found in most other gaseous detectors. These include the interplay between materials with different electrical characteristics, space-charge dominated avalanches evolving in very high electric fields and the propagation of fast signals on heterogeneous multiconductor transmission lines. In this communication the state-of-the-art of the simulation and modeling of many of these aspects will be reviewed and some aspects still requiring further work highlighted.

Speaker: Paulo Fonte (Coimbra)

Slides Review_of_Simulation_and_Modeling.ppt

25 Simulation studies on the Effect of SF6 in the RPC gas mixture

The India based Neutrino Observatory (INO) collaboration is planning to build a 50 kton magnetized iron calorimeter (ICAL) detector to study neutrino oscillations and measure their associated parameters[1]. ICAL will use 28,800 glass Resistive Plate Chambers (RPCs) of 2m X 2m in size and operated in the avalanche mode, as its active detector elements. As a part of the detector R&D to develop the RPCs required for this detector, we studied the effect of Sulfur hexaflouride (SF6) in the gas mixture on various RPC parameters. In this paper, we present a comparative study of signal development on the RPC pick-up electrodes using simulation and experimental data. In this study, the primary interactions of the incident particle in RPC gas volume is calculated using HEED[2], while the electron transport parameters are computed using MAGBOLTZ[3]. We used nearly exact Boundary Element Method (neBEM)[4] solver to calculate the weighting field and the electric fields accurately. And finally, the induced signal is obtained following the Ramo’s theorem[5]. Rererences: [1] INO Project Report, INO/2006/01, May 2006 [2] Igor Smirnov, HEED, program to compute energy loss of fast particles in gases, Version 2.10, CERN. [3] S. Biagi, MAGBOLTZ, program to compute gas transport parameters, Version 8.9.6, CERN. [4] N.Majumdar, S. Mukhopadhyay, Nucl. Instr. Meth. Phys. Research, A 566, p.489 (2006) [5] S. Ramo, Proc. IRE 27, p.584 (1939)

Speaker: Dr Bheesette Satyanarayana (Department of High Energy Physics, Tata Institute of Fundamental Research, Mumbai 400005, INDIA)

Slides salim-oral-id8.pptx

26 RPC simulations from a current stand-point

In the past, simulation of RPCs down to charge distributions, efficiency and resolution, has been done by working out the induction characteristics of the avalanches over one of the surrounding electrodes, resulting on a current generator that is sent to a (necessarily bandwidth-limited) charge-sensitive amplifier. This fact inherently hides a difficulty for including the role of the detector capacitance in the process and undermines the ability for a quantitative description of some of the detector characteristics, especially those concerning timing performances, cross-talk and transmission losses, where the signal shape is more important than its charge. Thus, under the 'standard' approach, the detector capacitance matrix (either total or distributed), the electronics frequency response, its gain and threshold are characterized by a single effective parameter, the equivalent charge at threshold Qth, that is left to the experimenter to determine. Despite its simplicity, this great conceptual simplification has allowed to obtain many useful simulation results in the field. Even the combined approach followed in D.Gonzalez-Diaz doi:10.1016/j.nima.2010.09.067 (where information from signal waveforms is used) does not escape fully from the aforementioned approach, although it allows to reasonably describing the most characteristic multi-strip observables like charge sharing and specially cross-talk. By further developing the conceptual work of W. Riegler in NIM A, 491(2002)258, D.Gonzalez-Diaz doi:10.1016/j.nima.2010.09.067 and D. Gonzalez-Diaz et al, NIM A 648(2011)52, we give (and discuss the validity) of a general formulation of the current generation problem in RPCs under the assumption that current induction and current transmission are independent processes, the first taking place ideally on a cross-section of the device. Thus, the multi-conductor transmission line (strip) excitation mechanism is driven by the solutions to a 2-dimensional weighting field problem, that are implemented as ideal current generators at the corresponding cross-section. This is, to date, the most obvious way to factor-out the intrinsically 3D electro-dynamic problem (P. Steinhaeuser, Yu. N. Pestov et al, NIM A 390(1997)86) in a computationally inexpensive way. We will discuss several limits of interest arising from this approach, like the transition from electrically-short (pad) to electrically-long (strip) systems. Our recent experimental results on cross-talk compensation (along the lines of D. Gonzalez-Diaz et al, NIM A 648(2011)52) will be briefly outlined, too.

Speaker: Dr Diego Gonzalez-Diaz (GSI and Tsinghua University)

Slides 15_-_RPCworkshop2012_diego.ppt

16:50 coffee break

27 Charge signal diffusion through resistive strip read-outs.

Charge signal propagation through a stand-alone resistive strip has been calculated as a function of different parameters, including linear resistivity, capacitance, and input signal properties. These calculations will be validated with new micromegas prototypes which have been specially designed to include different strip resistivities and capacitances. The method used to calculate the signal propagation, the specific electronic read-out used for this type of delayed signal and preliminar measurements with these prototypes will be shown.

Speaker: Dr Javier Galan (CEA Saclay)

Slides RPC2012_Galan.pdf RPC2012_Galan.pptx

28 The CMS RPC performance and simulation

The CMS RPC system operates successfully for more then two years. A brief history of the system performance will be presented, including the cosmic data, 2010 and 2011 collision data. The standard RPC simulation package will be described and some validation results will be shown.

Speaker: Mrs Roumyana Mileva Hadjiiska (University of Sofia)

Slides RPC_CMS_simulation.pdf RPC_CMS_simulation_v3.ppt

29 A multigap RPC based detector for gamma rays

Transforming the resistive plate chambers from charged-particle into gamma-quanta detectors opens the way towards their application as a basic element of a hybrid imaging system, which combines positron emission tomography (PET) with magnetic resonance imaging (MRI) in a single device. We present the first results towards the development of a hybrid imaging system based on multigap glass resistive plate chambers. A GEANT4 based simulations of the efficiency of the RPC photon detectors with different converter materials and geometry were performed, leading to an optimization of the detector design. The output from these simulations together with the prototypes test results will be presented and analyzed.

Speaker: Dr Borislav Pavlov (University of Sofia)

Slides BorislavPavlov_rpc2012_rpc_gamma_v4.pdf BorislavPavlov_rpc2012_rpc_gamma_v4.ppt

30 Simulations of an innovative ToF detector for high energy neutrons based on iron-less RPCs

In the upcoming years, radioactive beam facilities as RIBF (Tokyo, Japan)[ http://www.rarf.riken.jp/Eng/facilities/RIBF.html], FRIB (East Lansing, USA)[http://frib.msu.edu/] or FAIR (Darmstadt, Germany)[http://www.fair-center.de/index.php?id=1] will explore properties of unstable nuclei located within the limits of nuclear matter, the so-called "drip-lines". The detection of high energy neutrons is essential for the complete characterization of the reactions under studied. In most cases a high-resolution neutron ToF spectrometer is required to determine the momentum of high-energy neutrons resulting from the decay of the projectile with energies in the range of 200 MeV to 1000 MeV. A novel concept for the detection of these relativistic neutrons is based on Resistive Plate Chambers (RPCs). The detection principle of the RPC-based detector relies on the detection of charged the particles created in hadronic showers induced by the incoming neutrons. The presented design only considers glass plates for holding the active gas acting simultaneously as converters for neutron detection. For the optimization of a large area detector based on RPCs several simulations were performed using the Virtual Monte Carlo framework FAIRROOT [http://fairroot.gsi.de/]. The detector was design as a structure of single RPCs modules with 5 gas gaps grouped sequentially reaching a total efficiency of one neutron detection higher than 90%. In this work we present the results of the simulations carried out and the evaluation of the performance of the detector.

Speaker: Mr Machado JORGE (Centro de Física Nuclear da Universidade de Lisboa, 1649­‐003 Lisboa, Portugal))

Slides 19_-_RPC2012_Jorge_Machado.pdf RPC2012_Jorge_Machado.pdf

Poster session

Poster session

31 Response of the DHCAL to Hadrons and Positrons

The Digital Hadron Calorimeter (DHCAL) is a large scale prototype of an imaging calorimeter, using Resistive Plate Chambers (RPCs) as active medium. The calorimeter counts close to 500,000 readout channels. In this talk we will present the response of the DHCAL to hadrons and positrons in the energy range of 2 to 120 GeV. After detailing the event selection, the linearity of the response and the energy resolution will be discussed.

Speaker: Dr Burak Bilki (Argonne National Laboratory)

Poster RPC2012_Bilki.pdf

32 The on-line monitoring of the ALICE Muon Trigger at LHC

ALICE (A Large Ion Collider Experiment) is the experiment dedicated to the study of ultra-relativistic heavy ion collisions at LHC. The ALICE Muon Spectrometer is mostly designed to detect muons from quarkonia and heavy flavour decays in a large range of forward pseudo-rapidity. Its performance should fulfil an operation in the high multiplicity environment from central Pb-Pb collisions as well as in the high rate of pp collisions, both requiring a fast and efficient trigger system. The Muon Trigger is based on four planes of RPC (Resistive Plate Chamber) detectors each of them covering a total surface of about 36 m2. The RPCs are readout by means of 21,000 strips equipped with front-end (FE) electronics. The trigger decisions are delivered by a fast electronics, organized in three levels: Local (receiving the signals from the FE), Regional and Global. The Global decision is sent to the ALICE Central Trigger Processor. To monitor detector performance and assure good data quality, an on-line monitoring tool, AMORE (Automatic MOnitoRing Environment), has been developed by ALICE. AMORE is interfaced to the DAQ software framework (DATE) and follows the publish-subscribe paradigm where a large number of batch processes execute detector specific analysis on raw data samples and publish monitoring results on specialized servers. This poster aims at presenting the AMORE tool and the developments made for the Muon Trigger performance monitoring, including RPC detectors (strip scalers, strip patterns, strip multiplicities), algorithm decisions at all levels in the electronics, as well as overall trigger efficiency exploiting the redundancy of RPC planes.

Speaker: Mr yongwook baek (LPC, Univ. Blaise Pascal, CNRS-IN2P3, Clermont-Ferrand, France)

Poster rpc2012-Poster-a0.pdf

33 Electronics and data acquisition systems for the RPC based INO ICAL detector

The India based Neutrino Observatory (INO) collaboration is planning to build a 50 kton magnetized iron calorimeter (ICAL). ICAL will use about 28,800 single gap glass Resistive Plate Chambers (RPCs) of about 2m × 2m in size and operated in the avalanche mode, as its active detector elements. About 3.6 million electronic channels need to be instrumented in ICAL. ICAL’s Data Acquisition (DAQ) system records on receiving physics trigger signal, pattern of RPC pickup strips hit by the charged particles as well as precise time of crossing the detectors. The DAQ system performs a number of slow control and monitoring functions in the background. Architecture of the ICAL DAQ system is based on designating RPC as a standalone minimum unit. Therefore, the current scheme is to mount preamplifier and leading edge discriminators on two orthogonal edges of the RPC units and also mount rest of common processing electronics on the RPC unit. A processor, equipped with an optical data link is a part of this electronics. The processor takes care of all the DAQ needs, configuration of the front-end as well as data transfer needs between the RPC unit and backend servers. In this paper, we will describe the design features of the front-end systems and our current studies on their prototypes. We will also dwell on the controller or backend system options on which work is in progress.

Speaker: Dr Satyanarayana Bheesette (Tata Institute of Fundamental Research, Mumbai)

Poster bheesette-poster-id35.pdf

34 Study of RPCs for autonomous stations in cosmic ray research

The capability of covering very large areas at low cost, besides showing excellent performance in many aspects, motivated the application of RPCs to Nuclear and High-Energy Physics and also to Cosmic Ray research in experiments such as COVER-PLASTEX and ARGO/YBJ. Such detectors, however, require indoor conditions and support systems. For very high energy cosmic ray research, where shower sampling is mandatory, it would be convenient to develop detectors that could be deployed in small standalone stations, with very sparse opportunities for maintenance, and with good resilience to environmental conditions. With this aim we developed glass RPCs that are confined to a sealed plastic box housing all high voltage and gas distribution. The detector is impervious to humidity and requires only 1cc/min of gas, equivalent to 1kg/year of R134a. Arbitrary readout electrodes can be applied externally.

Speaker: Luis Lopes (Laboratório de Instrumentação e Física Experimental de Partículas (LIP))

Poster poster_RPC2012_L_Lopes.pdf

35 Analysis of the radiation background in the CMS RPCs

The radiation background levels in the CMS RPCs have been measured by using proton--proton collision data at $\sqrt{s} = 7$~\TeV collected by CMS in 2010 and 2011 and have been analyzed as a function of the LHC parameters. The dependence on the LHC instantaneous luminosity has been studied over several orders of magnitude. The background distribution in the RPC detector has been carefully analysed. Extrapolations to the LHC design conditions are also discussed.

Speaker: Mr Mircho rodozov (PhD student)

36 The RPC hits in the CMS muon reconstruction

Muon tracks in the events collected by the CMS detector are triggered and reconstructed using the Drift Tube (DT) in the barrel, Cathode Strip Chambers (CSC) in the endcap, and Resistive Plate Chambers (RPC) in both barrel and endcap regions. RPC hits are mainly used as dedicated trigger detector, however they give a contribution in the muon reconstruction as well. Efficiency contribution to the muon reconstruction with and without use of the RPC informations have been studied using the 2011 data and Monte Carlo samples. The results in terms of number of RPC hits and of number of stations crossed in the muon reconstruction and the track efficiency at the level of full muon system will be reported.

Speaker: Mr Minsuk Kim (postdoc)

37 Operational experience of the GGM at the CMS Experiment

Performance of the Gas Gain Monitoring system, installed in 2009 at CMS Experiment, are presented. The GGM is aiming to keep under control the gas quality of the CMS RPC closed loop gas system. To perform this task the GGM is made of single-gap RPCs arranged in a cosmic ray telescope, with charge readout for online monitoring of working point; this provides a fast and accurate determination of any shift of the working point conditions. The GGM is integrated in the main CMS detector control system while the DAQ runs standalone within the standard CMS XDAQ framework. The GGM showed very good sensitivity to gas changes, moreover in the second part of the year we adopted a different algorithm to correct the environmental variables so that performance were enhanced.

Speaker: Mr Stefano Colafranceschi (LNF)

38 RPC monitoring tools in the CMS experiment

The Resistive Plate Chambers are used in the CMS experiment as a dedicated muon detector system which covers the whole geometric acceptance up to a pseudorapidity of 1.6 with a total of 480 chambers in the barrel and 432 in the endcaps. In order to guarantee the quality of the data collected and to monitor on-line the detector performance, a set of tools have been developed in CMS and heavily used in the RPC system: the web based monitoring (WBM) tools and the data quality monitor (DQM) tools. The former ones is a set of java servlets which allows the user to check the performance of the hardware during data taking providing distributions and history plots of all the parameters. The latter is composed by a set of algorithms which can work both during data taking, and off line, running on stored data, to check the quality of reconstructed physical variables. Both these monitoring systems will be described here with a particular emphasys on their structure, functionalities and performance.

Speaker: Umberto Maria Riccardo Berzano (PV)

39 Analysis of the front structure of EAS with the HADES tRPC wall

In the last months of 2009, during the commissioning of the HADES tRPC TOF wall at the GSI (Darmstadt, Germany), more than 500 million cosmic ray data were taken with a precision in time measurement below 100ps for each tRPC cell. The six sectors, with an area greater than 1 square meter each, were placed horizontally in pairs, with their axes pointing in the direction east-west, and a distance of about 30cm. Each sector consisted on two layers of RPC cells partially overlapped to avoid dead zones and each cell was read-out from both ends so that in the optimal case, a cosmic particle went through up to 4 cells allowing a fit of high quality. The mean position resolution was approximately 1cm in north-south and about 3cm in the east-west directions. The mean granularity of each detector was about 20cm2. This arrangement allows us to reconstruct the arrival direction of cosmic rays with an accuracy of about 1 degree in the north-south and about 3 degrees east-west directions. Although data were taken over an surface of scarcely one square meter, the knowledge of the very accurate time of arrival of the particles, together with its position and direction, has allowed us an analysis of the temporal structure of the fronts of cosmic air showers and their correlations with the direction of incidence of the particles of the showers never made so far. The results can be of interest to understand the evolution of cosmic ray showers in the atmosphere and to find new signatures allowing a better estimation of the variables describing the primary cosmic rays incident upon the Earth.

Speaker: Mr Georgy Kornakov (Univ. Santiago de Compostela)

40 Resistive Plate Chambers in the ARGO-YBJ experiment: operational features, monitoring and control

The Resistive Plate Chambers used in the ARGO-YBJ experiment have been working uninterruptedly since the deployment of the detector was completed in October, 2007. The ARGO-YBJ Detector Control System provides constant monitoring of the environmental parameters and of the operational conditions of the RPCs. Here we summarize the monitoring records collected in the last four years by correlating the environmental trends (temperature and pressure) with the current absorbed by the RPCs in order to show the stability of the detector operation. In addition, a monitoring telescope of RPCs was installed at the experimental site in order to test the regulation of the applied voltage on the ARGO-YBJ RPCs accounting for the monitored changes in the environmental parameters, with the goal to keep the effective voltage constant. The test results, which are crucial in view of the implementation of this procedure in the experiment, are presented here.

Speaker: Dr Paolo Camarri (ROMA2)

41 A model for the chemistry of defects in bakelite plates exposed to high-radiation environment

Lineseed oil coated bakelite plates have been widely used over the past 15 years for small and large RPC systems. The formation of defects responsible for dark current increase and eventually discharge in high-radiation applications was observed in the past. Studies have been recently performed to identify and characterize the defects. Results of a new high-statistics survey of the defect formation and localization inside RPC gaps exposed to high-radiation environments will be presented.

Speaker: Ferdinando Felli (Laboratori Nazionali di Frascati dell'INFN and Sapienza Universita` di Roma)

42 Development of 1 mm low resistivity Bakelite plate for thin-gap RPC detector

As part of the R&D efforts for ATLAS Forward Muon detector upgrade, we are developing low resistivity Bakelite plate with about 1mm thickness for thin-gap RPC as the added level-1 trigger system arming to provide high rate capability and small cluster size to achieve fine granularity required for the upgrade in super-LHC running environment. The resistivity, uniformity of the Bakelite plate thickness and surface quality, as well as the long term stability with respected to temperature and humidity variance are studied at USTC laboratory. Measurements on new Bakelite plate properties, along with results of a TGRPC prototype cosmic ray test will be reported.

Speaker: Dr Liang HAN (Univ. of Science & Technology of China (USTC))

Poster Poster_RPC2012_USTC-ThinGapRPC.pdf

43 TDC Readout Board v3

Most of the physics experiments involving charged particle identification require precise time measurements. The rising requirements concerning the time resolution, the channel density, the accepted hit rate and finally the price per channel, force the development of new and versatile solutions which can be used in many applications. In order to meet these requirements, a Time to Digital Converter (TDC) module realized in FPGAs with integrated DAQ has been developed, produced and is currently under tests. High time resolution of less than 14 ps RMS and a high channel density (~256) allow to efficiently measure the time of flight of particles, being applicable for detectors like RPCs, scintillation counters with PMT readout or STTs. Together with the implemented network functionality, the module can serve as a standalone measurement device or a part of a larger system for of data acquisition. Optical links provide all the connectivity features needed in order to transfer data out to the event builders as well as for slow control purpose. Each link can be configured as a GbE link and connected directly to a standard Ethernet switch or as a generic serial link with a data rate up to 3.2 Gbps. One FPGA is responsible for collecting data from the 4 remaining FPGA-TDCs, sending it out and maintaining slow control channel over GbE network with a PC in control of the system. Basic network protocols have been implemented as FPGA logic, providing the “plug-and-play” functionality to the board, which after connecting to the network is able to receive IP address via DHCP, download configuration and be ready for measurements. The board is composed of 5x Lattice ECP3-150 FPGAs as compute power and 4x 208-pin connectors as well as 8x 3.2Gbps optical transceivers as IO interface. Its functionality can be additionally extended by connecting one AddOn-PCB or four Small AddOn-PCBs which can introduce different connection types or measurement devices. Its size is 20 cm times 23 cm and it is powered by a galvanically isolated 48V low noise power supply, predicted to consume around 30W electrical power at full speed operation.

Speaker: Mr Grzegorz Korcyl (Jagiellonian University)

Poster rpc2012.pdf

44 CAD: A Current-Mode Amplifier and Discriminator ASIC for MRPC-TOF Detectors

A fully current-mode front-end ASIC has been developed for MRPC detectors for TOF measurements. Unlike NINO or PADI developed by CERN and GSI respectively, it uses direct current discrimination to get the timing signal. It has fast time response at low power consumption and high time resolution can be achieved even for small signals. A detailed analysis and demonstration will be described in this paper. The first prototype was implemented in single-ended chain and was fabricated in 0.35um CMOS process. The preliminary test results shows that 20ps time jitter can be achieved for signals ~10uA above the threshold. The threshold is set to 263uA and it is limited by the oscillation caused by the feedback from ground and/or power supply. A newer version was designed and under test. Oscillation was highly suppressed. Detailed results will be reported in this presentation.

Speaker: Ms Xin ZHOU (TSINGHUA UNIVERSITY)

45 An improved gas distribution system for the ATLAS RPCs

A new gas distribution system has been designed to optimize the fine structure of the gas distribution of each single gas gap in view of the increasing LHC luminosity. Taking as input the present background rate distribution the new input impedances will take in to account the gap current in the gas change rate calculation. The new system will also be designed to maintain proportionality on a wide range of flow, minimizing the flow non linear dependence on input pressure

Speaker: Enrico Pastori (RM2)

Poster poster.pdf

46 Gas purifiers for closed-loop gas systems

Gas purifiers in closed-loop gas systems are widely used in large experiments at LHC. A study and characterization of chemical performances has been performed.

Speaker: Carla Lupi (Sapienza Universita` di Roma)

47 Tests of gas contaminants and interaction with materials in closed loop recirculation systems

Gas recirculation systems are widely used in RPC detectors to cope with large gas mixture volumes and costs. A new long-term systematic study of gas purifiers has been carried out at CERN in a low-radiation test area, with the use of RPC chambers with currents monitoring, and gas analysis sampling points. The study aimed to measure the lifetime of purifiers after regeneration, to confirm the release of contaminants, and to characterize the behaviour of dark currents as a function of contaminants.

Speaker: Stefano Colafranceschi (Laboratori Nazionali di Frascati dell'INFN, Sapienza Universita' di Roma and CERN)

48 A study of gas mixtures and HV feedback in a RPC single-gap monitoring system

Environmental variables such as temperature, atmospheric pressure and humidity affect dramatically the response of RPC detectors, as well as of all gas-based detectors. A redundant single-gap system composed of 15 RPC detectors is in operation in a cosmic ray telescope at Frascati, with ADC charge readout and detailed environmental sensor system. Results on new algorithms for online compensation of the effect of environmental variables changes will be presented, as well as on fine-grained gas mixture scan studies.

Speaker: Cristian Vendittozzi (Laboratori Nazionali di Frascati dell'INFN and Sapienza Universita` di Roma)

19:30 Meeting of the IAC - Room B1 Bldg 36

20:30 Meeting of the IAC - Al Fico, Grottaferrata - Taxi transportation from LNF-Bldg. 36

Wednesday, 8 February

Ageing and interactions with materials: (Chairpersons A. Sharma, A. Musso)

Ageing and interactions with materials

49 Ageing and conductivity of electrodes of high rate RPCs from an ion conductivity approach

It is well known that electrodes for high rate resistive plate chambers need to show some electrical properties which are more demanding than the low rate ones. As expected from the stationary DC mode, the rate capability is limited by the product d · ρ · q, where an avalanche average charge q is depleted by a material of thickness d with a resistivity ρ. Using this approximation, the only free parameter useful for a real optimization is the plate resistivity ρ. Moreover, it has to be stable during the detector lifetime. In order to keep the detector performance at a reasonable level, the electric field inside the gaps is not allowed to fall more than 15% under MIPs radiation; it means roughly φ·ρ ≃ 1−5, where φ is the particle flux given in kHz/cm2 and the resistivity ρ is given in TΩcm. For instance, coping with particle fluxes as high as 20kHz/cm2, as intended at the CBM experiment at FAIR, will require to use materials having resistivities in the range ρ = (0.05, 0.25)T Ωcm. It is difficult to find ’well-behaved’ materials in this range with no issues on the charge depletion in long times, or without savage electric discharges which can damage seriously both the front-end electronics and the material itself. Several ceramic composites have been built and compared with some materials already used in several timing RPCs. Ceramic RPC plates electric properties have been compared with the electrical response of a classic solid electrolyte in order to understand the ageing phenomena. Thus, simple estimations can be made for determining the maximum RPC working time before instabilities related to inside electrochemical processes arise.

Speaker: Mr Miguel Morales (Univ. Santiago de Compostela)

Slides 1_-_MiguelMorales_AgingAndConductivity_RPC2012.pdf

50 Cavern background measurement with the ATLAS RPC system

The measurement of cavern background has been carried out systematically since the beginning of LHC, as soon as the luminosity produced a detectable signal, from L=1028 cm-2s-1 of the early 2010 operation up to L=3.5x1033 cm-2s-1 at the end of 2011 proton-proton run, which is just 1/3 of the nominal LHC luminosity. The reason for this is to early foresee the running condition for the detector for the nominal LHC luminosity and beyond, in view of the super-LHC upgrade. Background Montecarlo calculations have been validated against data and the background map analysis pointed out hotspots due to localized cracks in the radiation shielding. The RPCs participated to this effort since the earliest stages providing an accurate correlation between luminosity and background, a 3D background map in the barrel region and a direct measurement of the cavern activation. Moreover due to the high sensitivity and very good signal to noise ratio of the proposed method, based on the gap current, the measurement was provided in real time through the DCS, revealing as a strong diagnostic element of the RPC system. In this presentation the method and the results will be shown in comparison with Montecarlo estimates and other measurements coming from different systems.

Speaker: Giulio Aielli (ROMA2)

Slides rpcbackground.pptx

51 Study on Surface Asperities in Bakelite-RPC

Experimental evidences indicate that the surface treatment of the electrodes with silicone in Bakelite-RPC improves the detector peformance in a significant way [S. Biswas et al., NIM A602 (2009) 749, NIM A604 (2009) 310]. Studies on the morphological features of the Bakelite grades used for building the detectors reveal the presence of surface asperities in these materials. Thus, a detailed investigation becomes necessary to understand the role of non-planarity of the Bakelite surface in affecting the detector performance. It is conceivable that depending on their shape and height, these asperities which are predominantly three dimensional, can distort the local electric field configuration which is otherwise uniform in the parallel plate-like configuration of RPC and thus even lead to local discharges inside the active volume. A numerical simulation has been carried out to probe effects of surface asperities on the field configuration of the detector and eventually its performance. The data obtained from the measurments of surface profiles of Bakelite sheets of different grades using profilometer and AFM have been used to model the asperities in a Bakelite-RPC. The field configuration in the active volume of the device has been computed using neBEM-GARFIELD package [http://garfield.web.cern.ch, http://nebem.web.cern.ch]. The calculation for a typical Bakelite-RPC with a rectangular ridge of height about 4 micron on one of the Bakelite sheets has shown a change of around 10% in the field values. A few preliminary results for very simple models were reported in RPC2010 [S. Biswas et al.]. However, it is obvious that much more detailed modeling of the device is required in order to investigate the actual effect of surface irregularities on the detector performance. In this work, several models with volumes of different shapes and sizes have been used to represent the measured asperities more realistically. In addition, modelling has been carried out to simulate the effect of surface treatment with a layer of silicone on the electrostatic configuration. Trends observed in the computation seem to agree well with the experimental observations.

Speaker: Prof. Nayana Majumdar (Saha Institute of Nuclear Physics)

Slides

• RPCRoughness_v1.pptx
• RPCRoughness_v1.pptx
• RPCRoughness_v2.pdf

52 Preliminary results on optimization of gas flow rate for RPCs

The India-based Neutrino Observatory (INO) collaboration is planning to build a 50kt magnetized iron calorimeter (ICAL) detector using glass Resistive Plate Chambers (RPCs) as active detector elements. A stack of 12 glass RPCs of 1mx1m in area was developed to study and characterize the performance of the RPCs. In this paper, we describe the study carried out for the optimization of gas flow using this prototype stack. The gas flow was stopped up to about 3 months and RPC parameters were studied during this period. Rate of increase in the RPC’s strip rate and their dark current was found to be correlated with the leak rate of its gas gap. With leak free RPCs, reducing the refreshing frequency by a factor of 30 was found possible, without compromising on the RPC performances.

Speaker: Mr Suresh Kalmani (Tata Institute of Fundamental Research)

Slides SDK_talk_RPC2012.pptx

53 Development of small, easy to build and low gas consumming timing RPCs

We have developed several prototypes of small size timing RPCs able to work with very small gas fluxes or even without any gas supply. Such detectors could be very useful for those purposes requiring a compact, easy to handle and easy to transport small detector offering at the same time sub-ns time resolution. We have built several 2-gap tRPC chambers of glass, 160mm long and 50mm wide, with 0.3mm wide gaps. At the middle of the chamber, either an aluminum plate placed between the external glasses or two parallel copper electrodes placed between two glass plates provided the high voltage. The RPCs were sealed all around except on two small holes where two capillary tubes of silicone provided them a low gas flux. At the outer sides of the external glass plates, the induced electric pulses were read-out independently at both ends of two parallel Cu-tape electrodes 20mm wide. In all the cases, the amplifying electronics is based on the Philips BGA2712 amplifier that provides a factor 10 of gain. Both chambers have been filled with a gas mixture of Freon-R134a/ SF6 with a ratio 0.9/0.1 Two tRPCs chambers may be placed parallel in an ordinary stainless steal box of 188 × 120 × 55mm3 offering a total occupancy of around 70% and allowing to built bigger many-box structures. In this poster we summarize the main performances provided by those proto- types. We have also tested the ageing effects on those performances without any gas supply during several weeks time.

Speaker: Miguel Morales (Univ. Santiago de Compostela)

Slides 5_-_MiguelMorales_LowGasConsumming_tRPCs_rpc2012.pdf

10:40 coffee break

Coffee Break

54 Long Term Validation of the Optimal Filters Configuration for the Resistive Plate Chambers Gas System at the Large Hadron Collider Experiments

Resistive Plate Chambers (RPCs) are widely employed as muon trigger systems at the Large Hadron Collider (LHC) experiments. Their large detector volume and the use of a relatively expensive gas mixture make a closed-loop gas circulation unavoidable. The return gas of RPCs operated in conditions similar to the experimental background foreseen at LHC contains large amount of impurities potentially dangerous for long-term operation. Several gas-cleaning agents, characterized during the past years, are currently in use. Results of new these tests have revealed an optimized configuration that is now under long-term validation at the Gamma Irradiation Facility (GIF) set-up. A very important feature of the new configuration is the increase of the cycle duration for each purifier that results in better system stability and, if needed, it would permit to increase the gas flow in the detectors during the high luminosity running periods at LHC. During the test of the new filters configuration, the detector performances are monitored in terms of current stability and Bakelite resistivity. A new model has been developed to correct directly the detector current for the effect of the environmental conditions: temperature, pressure, environmental and gas relative humidity. It is now under evaluation the possibility to apply the same correction to a larger set of data, such as a full LHC-RPC detector system. The Bakelite resistivity can be affected by the water content in the mixture, but also by the deposition of impurities on the internal electrodes surface. This parameter is regularly monitored in special runs where the normal RPC mixture is substituted with Argon only. Results about the stability of RPC gaps produced with new Bakelite (from Puricelli company) are also reported. The filtering optimization studies are complemented with a finite element simulation of the gas flow distribution in the RPCs, aiming at its eventual optimization in terms of gas flow distribution and rate. Simulation results on the standard configuration for the RPC gas distribution has shown regions in which the gas velocity is 100 times lower than in others. With a gas flow of 1 volume exchange every 4 hours (considered the lower limit for a safe operation without radiation) these regions represent one third of the detector surface. A new RPC prototype with a flexible distribution of gas inlets and outlets has been built in order to experimentally quantify the impact of those critical regions on the detector performance and also to verify if a new, more effective solution can be found. An efficient removal of the used gas mixture inside the RPC volume would permit to reduce the overall gas flow rate.

Speaker: Beatrice Mandelli (CERN)

Slides RPC2012_Mandelli.pdf

55 QUALITY ASSURANCE OF LARGE AREA RPC DETECTOR : TECHNIQUES FOR MEASUREMENT OF GAS LEAK RATE

ABSTRACT QUALITY ASSURANCE OF LARGE AREA RPC DETECTOR:TECHNIQUES FOR MEASUREMENT OF GAS LEAK RATE AVINASH V. JOSHI(a), N.K.MONDAL(b), B.SATYANARAYANA(b), S.D.KALMANI(b),P.VERMA(b) a Alpha Pneumatics ,Unit No. 24 , Digvijay Ind. Estate 1, Upvan , Thane 400602 (INDIA) b DHEP,Tata Institute of Fundamental Research, Homi Bhabha Road , Colaba , Mumbai 400005 (INDIA) Hazardous Gas leaks from operational RPC detector body cause pollution , increase operational cost and degrade detector performance. Working of close loop system ,commonly used for detector stacks , is severely affected by gas leakages . Factors such as Fabrication defects, radiation embrittlement of plastics, gas flow rate , differential pressure , drift and diffusion coefficients of gases are related to leak rate and effects . Ingress of contamination into through a leak can occur under strong concentration gradient . The problems are further compounded with formation of radicals - a threat to quality and life of detectors . There is a distinct change in localized gas concentration near a leak ,especially at low velocities. Leak detection techniques such as Pressure decay, Tracer techniques, acoustic technique and mass spectroscopy are studied for quantitative estimate of leak rate. Liquid free IN-SITU leak test for working RPC is described. Design and Construction of equipment required to conduct leak tests is detailed. International standards for gas leak rates equivalent to BS EN 13192:2002 are discussed . Acceptable range of Leak rate for working RPC- with and without close loop recirculation system, is estimated . Implementation of Leak test procedures into a Quality Assurance Plan for RPC Fabrication Process is considered. _____________________________

Speaker: Mr AVINASH JOSHI (ALPHA PNEUMATICS)

Slides RPC2012_AVJ_32.pptx

56 Surface resistivity measurements and related performance studies of the Bakelite RPC detectors

During the last few years at SINP/VECC, significant work on the prototype silicone coated bakelite based resistive plate chamber (RPC) for the Iron Calorimeter (ICAL) of the proposed India-based Neutrino Observatory (INO) has been carried out. Bakelite RPC detectors of various sizes from 10 cm X 10 cm to 1 m X 1 m, with capacitive read-out strips made of 16-conductor ribbon cables, have been fabricated, characterized and optimized for efficiency and time resolution. Thin layers of different grades of silicone compound are applied to the inner electrode surfaces to make them smooth and also to reduce the surface resistivity. Effectiveness of different silicone coating in modifying the surface resistivity was evaluated by an instrument developed for monitoring the I-V curve of a high resistive surface. The results indicate definite correlation of the detector efficiency for the atmospheric muons and the RPC noise rates with the surface resistivity and its variation with the applied bias voltage. It was also found that the surface resistivity varies for different grades of silicone material applied as coating, and the results are found to be consistent with the detector efficiency measurements done with these RPCs.

Speaker: Dr Saikat Biswas (GSI, Darmstadt)

57 Production of RPC gaps for CMS upgrade

The CMS collaboration intends to improve the muon trigger efficiency in the forward region. In order to achieve this goal, 144 new Resistive Plate Chambers (RPCs) at RE4/2, RE4/3 will be installed on the existing york YE3 to trigger high momentum muons from the proton-proton interaction. In this paper, we present the detailed procedures used in the production of the CMS RPC gas gaps adopted in the CMS upgrade. Quality assurance is enforced as ways to maintain the quality of RPC gas gaps as the previous CMS endcap RPC chambers. Both the production procedures and the quality assurance are mature and effective for the mass production of these RPC gas gaps. Key words: CMS, Resistive Plate Chamber (RPC), Muon trigger detector, Production procedures, Quality assurance

Speaker: Prof. Sung Keun Park (Korea University)

Slides 9_-_SungPark-CMS-rpc-2012-2.pdf

12:30 Lunch @ Foyer Aula Touschek

13:30 Social Tour and Refreshment @ Rome - Galleria Borghese, Museo di Zoologia

Thursday, 9 February

Triggering at high rates: (Chairpersons R. Cardarelli, P. Dupieux)

Triggering at high rates

58 A comparison of gaseous detectors for high rate tracking and triggering applications at high luminosity colliders

Gaseous detectors have come a long way from the invention of the multiwire proportional chamber, and have been exploited for charged particle tracking over the last few decades. This progress, from previous generation experiments to the present Large Hadron Collider experiments has had a dramatic impact on the conception and design of large area gaseous detectors for muon trigger and tracking. In this review a progress chart of technological advancements will be drawn with a focus on choices made amongst the different experiments and the possibilities for upgrades. In this paper I will review the state-of-the-art and compare gaseous detectors for their applications in high rate tracking and triggering at high luminosities.

Speaker: Dr Archana SHARMA (CERN)

Slides RPC-2012-ASharma-09022012.pdf

59 Performance of the ALICE RPC-based muon trigger system in the first two years of data taking at the LHC

The ALICE muon spectrometer is equipped with a trigger system made of four RPC planes, arranged in two stations. The aim of the system is to deliver single and di-muon triggers with suitable transverse momentum cut, optimised for the physics of quarkonia and open heavy flavour. In the first two years of LHC operation, the RPCs (72 in total) were operated in highly saturated avalanche mode for data-taking in both pp and Pb--Pb collisions. The integrated number of hits is about 10 Mhit/cm2 on average and 30 Mhit/cm2 for the most exposed detectors. The performances of the RPCs and of the system as a whole are discussed, with particular regard to their stability in time.

Speakers: Mr Francesco Bossù (Università deglli Studi e INFN Torino), Dr Martino Gagliardi (INFN Sezione di Torino)

Slides Gagliardi_RPC2012.ppt

60 The RPC based muon trigger of the CMS Experiment

PAttern Comparator Trigger (PACT) is a component of the Level-1 Muon Trigger of the CMS experiment. PACT uses signals from RPC detectors to reconstruct muon candidates for CMS. This trigger component was contributing to CMS trigger decision during LHC operation in 2010 and 2011. In this presentation the PACT system is described. Its performance is given.

Speaker: Mr Karol Bunkowski (Warsaw University)

Slides 120205_RPC2012_The_RPC_based_muon_trigger_of_the_CMS_v2.pptx

61 TRIGGER RATE DEPENDENCE AND GAS MIXTURE OF MRPC FOR THE LEPS2 EXPERIMENT AT SPRING-8, JAPAN

The LEPS2/SPring-8 experiment of photo-production of vector mesons and hyperons is scheduled to start in 2013. The photon beam with energy up to 3 GeV is produced by backward Compton scattering of laser photon with 8 GeV electrons inside SPring-8 storage ring. The development of a 4pi detectors and the construction of a solenoid magnet is currently underway. Pions and kanos with their momenta up to 2.5 GeV/c are produced from the high-energy photon with nucleon target. In order to separate 1.1 GeV/c of K/pi with time of flight (TOF) while traveling in a distance of 100cm in the magnet, we need a large-area, high-efficiency TOF detector with a time resolution of 50-100 ps. The multigap resistive plate chamber (MRPC) is chosen in LEPS2. We made a 150um*12 gaps MRPC with an active area of 10*50 cm^2.The pad size was 1.5*5.5 cm^2.We studied the trigger rate dependence and gas mixture for the optimized design of MRPC. The positron from the pair production of high-energy photon via convertor is used for the beam test. The trigger rate of positron beam was mainly determined by the intensity of injected laser. We found that high enough voltage is necessary to achieve a good time resolution and high efficiency at a large trigger rate. When the trigger rate is as high as 20 Hz/cm^2, it has a good time resolution (50ps) and high efficiency (~99%) at 12 kV. We also investigated the effect of gas mixture. We chose Butane as the quencher, because Butane is cheaper than Iso-butane and both of them play a similar role as the quencher. A gas mixture of R134a:SF6:Iso-butane is 90%:5%:5% is our optimized choice with 50-ps time resolution and 99% efficiency. In the future we will study further the effect of the impedance of pad and develop the amplifier for the readout of MRPC. In the final, a total area of 10*100 cm^2 MRPC will be produced for the LEPS2 experiment.

Speaker: Ms Chia-Yu Hsieh (Institute of Physics,Acdemia Sinica, Taipei, 115, Taiwan)

Slides RPC2012_V5.pptx

62 The RPC based proposal for the ATLAS forward muon trigger upgrade in view of super-LHC

The present ATLAS forward muon spectrometer (Small Wheel), which covers a range in rapidity 1.3 < η < 2.7, is not designed to withstand the super LHC luminosity up to 5 x 1034 cm-2s-1. The main issues are coming from the very high background rate, up to 14 kHz/cm2, extrapolated from the present data, and from the necessity to drastically improve the muon momentum trigger selectivity. To fulfill this extremely challenging requirements it has been shown that a fast tracking trigger system is needed, capable of suppressing fake tracks by a factor of 10 and to measure the particle position with a precision of 300μm, needed to define a 1 mrad accurate impact angle. A major constraint is given by the available level 1 trigger latency of 1 μs. An international collaboration participated by American Chinese and Italian institutes has been established to develop one of the candidate proposal, based on an enhanced RPC system. This is comparable with the former ATLAS for cost and robustness but with a much higher rate capability and timing performance. The high timing resolution of RPCs is here the key feature to suppress the background allowing a much simpler trigger scheme. A new generation front end electronics, a very fast readout circuit allowing a precise localization the particle impact point and a mean-timer based sharp coincidence system have been designed to exploit fully the detector performance matching the trigger requirements.

Speaker: Prof. Junjie Zhu (University of Michigan)

Slides Zhu.pdf.pdf Zhu.pdf.pdf

10:50 coffee break

63 The phase 1 extension of the CMS endcap Resistive Plate Chamber system

During the first two long shutdowns of the Large Hadron Collider which are presently scheduled for 2013/2014 and 2017/2018, several detector upgrades are foreseen by the CMS Collaboration to prepare for the ultimate luminosity of more than 10^34/cm^2/s at 14 TeV that should be achieved during the first 10 year period of the accelerator (LHC Phase 1). In particular, the present Resistive Plate Chamber (RPC) detector, which serves as a dedicated muon triggering system, will be enlarged with the addition of a fourth layer in the endcap region, on either side of the CMS detector. Such an extension is required to be able to preserve a low Pt threshold for the Level 1 Muon Trigger at the expected high instantaneous luminosity. During the first long shutdown, these new endcap stations will be equipped in the region |eta|<1.6 with 144 High Pressure Laminate (HPL) double-gap RPCs operating in avalance mode, with a similar design as the existing CMS endcap chambers. The present phase 1 upgrade plans for the CMS RPC system will be presented, including trigger simulation studies for the extended system, and details on the new HPL production, and the chamber assembly and quality control procedures.

Speaker: Dr Michael Tytgat (UGent)

Slides CMSRPCUpgrade.pdf CMSRPCUpgrade.pptx

64 Thin-gap RPC Test Results

A joint effort from China, Italy and US institutes and laboratories on thin-gap RPC development for high rate capability, excellent time precision and good spatial resolution will be reported with test beam results. The performance of several prototype RPCs which have 1 mm gas gaps and 1-3 mm readout strip sizes will be addressed. Tests at backgrounds as high as 7KHz/cm**2 will be discussed. High rate capability, high efficiency, and low noise are demonstrated in the test beam results. The small cluster sizes observed in the data indicate sub-mm spatial resolution is available. The mean-timer readout from both sides of the strips shows that high precision timing can be achieved using RPCs; it also provides a most robust and effective means to reject beam background in the super-LHC high luminosity environment.

Speaker: Prof. Liang HAN (University of Science and Technology of China (USTC))

Slides 120209-hanl_RPC2012@INFN_ATLAS-TGRPC.pdf

65 Test for upgrading the RPCs at very high counting rate

Very large systems of RPCs with 2 mm gas gap are presently working at LHC as muon trigger detectors. In order to conceive a new generation of RPCs, fully adequate to the needs of the high luminosity super-colliders of the next future, two aspects have to be reconsidered: the gap width which determines the amount of charge delivered in the gas per detected avalanche and the front end electronics which determines the minimum charge that can be discriminated from the noise. Both aspects have a crucial effect on the rate capability. We present here the results of a cosmic ray test carried out on small size RPCs of gap width 2.0, 1.0 and 0.5 mm respectively. The wave forms of both the prompt signal due to the fast drifting electrons and the signal generated in the HV circuit, which is dominated by the slow ion drift, are recorded for each detected cosmic muon. The analysis of these signals is crucial to understand the RPC working features.

Speaker: Lorenzo Paolozzi (INFN - Roma2)

Slides RPC_2012adc.pdf

66 Ceramic Resistive Plate Chambers for High Rate Environments

Multi-gap resistive plate chambers are proposed to build the Time of Flight wall of the Compressed Baryonic Matter experiment (CBM) with a time resolution better than 80 ps. The high fluxes expected at the innermost part of the detector, ~20 x 10^3 cm^{-2} s^{-1} have made necessary the development of new materials capable of withstanding such fluxes. At Helmholtz Zentrum Dresden-Rossendorf, several RPC prototypes of 10x10 cm^2 and 20x20 cm^2 have been built with ceramic plates with bulk resistivities in the range of 10^9-10^10 Ohm cm [1]. They have been tested at the superconducting electron accelerator facility ELBE with 30 MeV electrons. We will present characteristics of the ceramic electrodes and the latest results concerning the performance of these prototypes in electron beams up to fluxes of 10^6 cm^{-2} s^{-1}. [1] L. Naumann et al., NIMA 628(2011) 138-141

Speaker: Mr Alejandro Laso Garcia (Helmholtz Zentrum Dresden Rossendorf)

Slides Laso_CRPC2012.pdf

67 High counting rate, differential, strip read-out, multi gap RPC

A new architecture of differential strip structure symmetric multi gap RPC was developed. The results on efficiency, two dimensions position resolution, time resolution and performance in high counting rate environment using low resistivity glass electrodes will be reported.

Speaker: Prof. Mihai Petrovici (National Institute for Physics and Nuclear Engineering)

Slides presentation_RPC_Workshop_2012.pdf

68 CMS RPC project overview

Present and upgrade RPC system will be described. 2010 and 2011 results will be presented to give a full picture of how this so large system is performing.

Speaker: Pierluigi Paolucci (NA)

Slides 11_-_RPCprojectOverview8Feb2012.pptx

13:15 Lunch @ Restaurant Villa Mercede (shuttle from Conference)

Triggering at high rates: (Chairpersons R. Cardarelli, P. Dupieux)

Triggering at high rates

69 Proposed Trigger Scheme for the ICAL Detector of India-based Neutrino Observatory

The India-based Neutrino Observatory (INO) collaboration has proposed to build a 50kton magnetized Iron Calorimeter (ICAL) detector with the primary goal to study neutrino oscillations, employing around 28,800 Resistive Plate Chambers (RPCs) as active detector elements. The ICAL detector will comprise of three modules, each of dimension 16m x 16m x 14.5m, housed inside a cavern with a rock cover of 1.3km, in order to reduce the cosmic muon background. The expected overall event rate is around 10Hz. The trigger scheme for such a low event-rate experiment should achieve an optimization of the detection efficiency of desired events and the chance trigger rates. It should also ensure feasibility of hardware implementation considering the vast volume of the detector module. In this paper, a trigger scheme with a distributed and hierarchical architecture is proposed for one module of the ICAL detector, which would satisfy these criteria. Chance coincidence rates have been calculated for different combinations of the trigger parameters which help to fix the criteria for an admissible chance trigger rate. Results from a simulation framework, developed in order to evaluate trigger efficiency of the scheme for different events of interest for the ICAL detector, are also discussed.

Speaker: Ms Sudeshna Dasgupta (Tata Institute of Fundamental Research)

Slides RPC2012_SDG.pdf RPC2012_SDG.pptx

70 A fast electronics for RPC based precision tracking muon trigger at high luminosity LHC

Muon triggering at the super LHC luminosity imposes very strict requirements on the trigger concerning not only the rate capability but also to the tracking accuracy. This is particularly true for the very forward regions for which the LHC experiments are scheduling upgrade plans. An accurate 3D tracking allows defining a sharp threshold in the muon transverse momentum. Moreover high resolution timing is crucial to reject as much as possible fake triggers generated by correlated and uncorrelated background. We propose here a new trigger idea, exploiting the RPC sub-ns / sub-mm RPCs space-time resolution, based on a very fast multi channel front end circuit capable of selecting in few ns the maximum charge deposition among the input channels. The fake triggers are heavily suppressed by means of a mean-timer based local coincidence circuit gating the readout. We will present this electronics in terms of functionality and performance, supporting a detector design with a relatively low overall electronics complexity and cost with respect to other more conventional schemes.

Speaker: Roberto Cardarelli (ROMA2)

Slides frascati_2012.pptx frascati_2012inPDF.pdf

New ideas: (Chairpersons P. Fonte, V. Peskov)

New ideas

71 Resistive microstrip and microdot detectors: a novel approach in developing spark protected micropattern detectors

P. Fonte1, E. Nappi2, P. Martinengo3, R. Olivera3, V. Peskov3,4, P. Pietropaolo5, P. Picchi6 1LIP, Coimbra, Portugal 2INFN Bari, Bari, Italy 3CERN, Geneva, Switzerland 4. UNAM, Mecico city, Mexico 5.INFN Padova, Padova, Italy 6INFN Frascati, Frascati, Italy A new family of spark-protected micropattern gaseous detectors is introduced: a 2-D resistive microstrip and microdot counters, and hybrid configurations, which combine in one design a resistive GEM with a microstrip/ microdot detector. These novel detectors have several important advantages over the conventional micropattern detectors including GEM and MICROMEGAS. For example they feature higher values of the maximum gas gains, a simpler design containing at the same time less components, a simpler production technique and cost effectiveness. Our studies have revealed many interesting features of such detectors, for example in some gas mixtures the microdot detector can operate in self quenched streamer mode and at higher voltages in streamer mode similarly to RPCs. These resistive microstrip/microdot detectors can be used in many applications. As an example, we will describe successful tests of prototypes oriented to the RICH application (for the ALICE RICH upgrade) and for noble liquid dual phase TPCs.

Speaker: Prof. Vladimir Peskov (CERN)

Slides 1_-_Peskov_RPC2012.pptm

72 Development of spark-resistance MICROMEGAS with resistive anode strips

Development of spark-resistance MICROMEGAS with resistive anode strips

Speaker: Marcin Byszewski

Slides byszewski_micromegas.pdf.pdf

73 SiOx coated plastic fiber optic sensor for gas monitoring in RPC

A new sensor for the measurement of fluoride ions in dielectric gas mixtures has been developed. The sensor has been specifically designed to be installed at the RPC Closed Loop gas system in the CMS experiment at the Large Hadron Collider at CERN. The sensor employs a plastic optic fiber (POF) coated with a SiO2-like thin film. F- ions attack the glass-like layer and alter the fiber transmission capability that can be revealed by a photodiode. The coated POF is obtained by means of low pressure plasma processes that allow both the etching of the fiber cladding and the PECVD deposition of SiOx films at low temperature directly onto the fiber core, without damaging it. The sensor exploits a cumulative behavior so that long expositions to extremely low concentrations can be detected. The characteristics of fiber optics sensors, such as immunity to electrostatic discharge and the intrinsic small sensor dimension, make them particularly suitable for an in situ monitoring in the presence of ionizing radiations. Some tests at the Gamma Irradiation Facility (GIF) at CERN confirm the sensor feasibility; no changes in the transmission ratio were recorded on fibers left in place for about six months exposing them to a dose of about 2 Gy, corresponding to several months of typical CMS operation. Prototypes of POF sensors coated with SiOx films deposited in different conditions have been tested in laboratory by exposing them to fluoride vapors showing sensitivities of up to 0.02% / (ppm x hour).

Speaker: Dr Sabrina GRASSINI (Politecnico di Torino)

Slides RPC2012_Grassini.ppt

74 Use of fiber optic technology for Relative Humidity monitoring in RPC detectors

Large volume RPC detectors for charged particles are widely used in HEP experiments. For such detectors monitoring gas temperature and RH working condition is important because they both can affect the performance of the detector. We propose a gas RH monitoring system, specifically suited for large scale RPC detectors, based on fiber optic technology with use of Fiber Gragg Grating (FBG) sensors as RH probes. The proposed technology allows to connect sensors in series along one single optical fiber, thus greatly simplifying cable routing. Moreover, the proposed technology neither suffers nor causes e.m. disturbances. We have designed and successfully tested a prototype sensing device on a fully functional RPC module. We show experimental results including long term stability, precision and resolution.

Speaker: Dr michele caponero (enea; infn)

Slides 4_-_RPC2012_Caponero.ppt

17:15 Coffee break

75 Technical design of the RPC-based ToF wall (iTOF) for the R3B experiment at FAIR

Part of the experimental programs proposed for the R3B setup at the FAIR facility, requires a time-of-flight (ToF) measurement for the mass identification of ions in the large range of charges Z=1 to 92, at energies of several hundreds of MeV/u. For flight paths about 15 m, the ToF measurement require resolutions well below 100 ps, and a detection surface of the order of 2x1 squared meters. Also the tracking and the granularity to resolve multiplicities impose requirements to the setup. Our group proposed the use of timing-RPCs made of strips for this detector [1]. An active R-and-D program was dedicated to define the RPC design, materials, and front-end electronics, adequate to measure heavy ions with the detector efficiency, timing and rate capabilities according to the R3B purposes. The results obtained so far [2-4] allowed to pass from the conceptual design of the iToF detector [5], to a technical and construction phase. We have developed a RPC design based on self-supported modules, made of soda-lime glass sheets of 1 mm thickness, gas gaps of 0.3 mm, and 15 copper strips of 2 cm x 100 cm each. A group of modules can complete a detection plane of the required size for R3B. Several of such planes can achieve a time resolution low enough as to identify any ion of interest, overcoming the resolution limit of the RPC itself.

Speaker: Dr Enrique Casarejos (University of Vigo, Spain)

Slides 5_-_casarejos-RPC2012_itof_v4.pdf

76 Construction of a Digital Hadron Calorimeter with Resistive Plate Chambers

We report on the construction of a large scale prototype of a Digital Hadron Calorimeter (DHCAL), utilizing Resistive Plate Chambers (RPCs) with 1 x 1 cm^2 readout pads as the active medium. The design of the calorimeter was optimized for the application of Particle Flow Algorithms to the measurement of hadronic jet energies. The calorimeter prototype measures about two cubic meter and contains 52 active layers, interspersed with steel absorber plates. The total number of readout channels is close to 500,000. Each channel is read out with a 1-bit resolution, hence the designation of digital calorimeter. Construction of the prototype was completed in October 2010. Since then, the calorimeter has undergone extensive testing in the Fermilab test beam. In this talk, after a general introduction into imaging calorimetry, we will review the design and construction of the RPCs and of the electronic readout system.

Speaker: Dr Lei Xia (Argonne National Laboratory)

Slides DHCALconstruction.ppt

77 Calibration of the DHCAL

The Digital Hadron Calorimeter (DHCAL) is a large scale prototype of an imaging calorimeter, using Resistive Plate Chambers (RPCs) as active medium. The calorimeter counts close to 500,000 readout channels. In this talk we will present the measurement of the performance parameters of the RPCs, i.e. the noise rate, the MIP detection efficiency and the pad multiplicity. The measurements were performed using trigger-less, as well as triggered data taking in the muon beam of the Fermilab test beam facility. Results are presented on the geometrical alignment, the scan of the response across a single readout pad and the response over the entire surface of the active layers of the calorimeter. The noise rate measurements identify uncorrelated and correlated noise, as well as effects from the electronic readout system. When appropriate the measurements are compared to Monte Carlo simulations of the setup.

Speaker: Jose Repond (Argonne National Laboratory)

Slides DHCAL_Repond.pptx.pptx

78 Development of large GRPC for an ultra-granular Semi-Digital Hadronic Calorimeter

Large GRPC detectors equipped with semi-digital electronics readout and 1 cm2 lateral granularity were conceived to be used as a sensitive medium in the hadronic calorimeter of the future linear collider experiments. The GRPC detector was designed to provide high detection efficiency, excellent homogeneity and negligible dead zones. The readout electronics was developed to associate performance and compactness. A hadronic calorimeter of 1 m3 was built with 48 GRPCs. The GRPCs were tested in cosmic rays bench before to be assembeled into the HCAL prototype. The HCAL was then tested with pion beams at CERN. The preliminary results confirm the expectations. Future tests at the SPS will allow to validate definitely the choice of the GRPC as a good candidate for the sensitive medium of a semi-digital hadronic calorimeter.

Speaker: Mr imad laktineh (ipnl)

Slides RPC2012.pdf

79 Performance of the HADES-TOF RPC wall in a Au-Au beam

In this work we present results concerning in beam operation of the new Resistive Plate Chamber (RPC) Time of Flight (TOF) wall for the High-Acceptance DiElectron Spectrometer (HADES) spectrometer at GSI. The new RPC-TOF wall, fully integrated in the spectrometer, has been successfully operated under final operation conditions corresponding to collision of Au + AU @ 1.25 GeV. Results confirm an uniform time response below 85 ps sigma, crosstalk on the few % level and moderate timing tails along with an average longitudinal position resolution better than 10 mm sigma. The multihit capability of the system has also been investigated revealing a slight degradation of timing resolution when particles hit the detector at neighboring cells. Additionally, the PID (particle identification) capability of the spectrometer, after preliminary system calibration, shows a good separation capability of the different species.

Speaker: Mr Alberto Blanco Castro (LIP-Coimbra)

Slides Blanco.pdf Blanco.ppt

20:30 Social Dinner - Villa Tuscolana Frascati

Friday, 10 February

New ideas: (Chairperson Sung Park)

New ideas

80 Muon scattering tomography with resistive plate chambers

Resistive Plate Chambers are widely used in high energy physics experiments as reliable trigger systems due to their excellent time resolution and rate capability, while generally the track spatial information is obtained by means of different detectors. Studies show that it is possible to produce RPC with good spatial resolution (~ 0.5 mm) by appropriate choice of the pitch of the readout strips. High resolution RPC (HRPC) can be economically produced to cover large area and represent a valid alternative to more expensive detectors in applications when a spatial resolution of 0.5 mm is sufficient. Our group has successfully produced a Muon Scattering Tomography (MST) prototype based on 12 HRPCs which provide 3D information on muons scattering in a volume ~ 50 cm x 50 cm x 80 cm (suitable for scanning a suitcase). Both the incoming and the outgoing tracks of the muon are reconstructed. The required spatial granularity is achieved using ~300 readout strips per HRPC, with a pitch of 1.5 mm. All the strips from an HRPC are multiplexed into a single differential analog line by four Helix 3.0 chips daisy chained on a hybrid circuit. The detector has been collecting data since June 2011, with the HRPC showing an efficiency above 99% and purity above 98%. The spatial resolution on the tracks is ~0.8 mm. This is a preliminary measurement and includes the intrinsic detector resolution as well as the extrapolation errors due to multiple scattering in the detectors and separation of the planes. Additional results will be presented.

Speaker: Dr Paolo Baesso (University of Bristol)

Slides 1Final_Baesso_RPC2012_.pdf

81 A 2m x 0.5m prototype of a MRPC-based neutron detector with steel converter plates

M. Röder¹² D. Bemmerer², T. E. Cowan¹², Z. Elekes², M. Kempe², M. Sobiella², D. Stach², A. Wagner², J. Wüstenfeld², D. Yakorev², K. Zuber¹, for the R3B collaboration A 2 m long prototype detector for the detection of neutrons in an energy range from 200 MeV to 1 GeV has been successfully realized. The working principle is based on steel converter plates followed by an MRPC structure to detect charged particles produced by hadronic interactions. In order to study time resolution and efficiency, a 2m x 0.5m large module has been built which includes a 2 x 2 gap MRPC structure. An efficiency >90% and a time resolution of sigma < 100 ps have been measured for minimum ionizing electrons. This experiment has been done using the new one-electron-per-bunch mode of the superconducting electron linear accelerator ELBE, Dresden. Another test has been done using 175 MeV quasi-monochromatic neutrons at Uppsala. A test using tagged high-energy neutrons is scheduled at GSI. Extensive Monte Carlo simulations have been carried out, both for the electron-beam tests and for the final application as a neutron detector. The present approach offers a cost-effective way for the time-of-flight detection of high energy neutrons. supported by BMBF (06DR9058I) and GSI F&E (DR-ZUBE) ¹ = Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Germany ² = Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, Germany

Speaker: Mr Marko Roeder (Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Germany, Institut für Strahlenphysik, Helmholtz-Zentrum Dresden-Rossendorf, Germany)

Slides Frascati_presentation_014.pdf

82 TOFtracker: combination of time-of-flight and high-accuracy bidimensional tracking in a single gaseous detector

A 5-gaps timing RPC equipped with patterned electrodes coupled to both charge-sensitive and timing circuits yields a time accuracy of 80 ps along with a bidimensional position accuracy of 51 µm. These results were obtained over the full active area of 8x8 cm2 by calculating the straight-line fit residuals to the positions provided by a 3-layer telescope made out of identical detectors, detecting almost perpendicular cosmic-ray muons.

Speaker: Paulo Fonte (LIP-Laboratório de Instrumentação e Física Experimental de Partículas)

Slides TOFtracker.ppt

83 A Free-Streaming Readout for the CBM Time of Flight wall

The Compressed Baryonic Matter (CBM) experiment will be built at the new Facility for Antiproton and Ions Research (FAIR) in Darmstadt, Germany. This fixed target experiment will investigate Heavy Ion collision up to 35 AGeV for Au beams and 89 GeV for protons beams, with high interactions rates: up to 10MHz in Au+Au collision at 25 AGeV. To avoid the limitations of triggered systems at such rates, most CBM detectors will operate a free-streaming readout. Charged hadrons identification, especially a Kaons-Pions separation up to 3.5 GeV/c, is provided in CBM by a Time of Flight (ToF) wall placed 10m after the target. This requires a time resolution for the full ToF system in the order of 80ps combined with a high efficiency. To achieve these performances, the wall is made of MRPC detectors with resistive materials and channel layout both adapted to the particle rates found in the 2.5° to 25° polar angle range. This design induces hit rates up to 200 kHz/channel in some of the detectors and a total channel count between 70k and 120k. Because of those characteristics, the electronics needs a time resolution of 30 to 40ps, Time over Threshold capability and free-streaming readout. This free-streaming mode also requires a special care in the synchronization of the system and in the data analysis. A first prototype of the complete high resolution, free-streaming chain was built in Heidelberg, from differential detector to dedicated softwares, and later tested at COSY in Juelich. It will be described in this contribution and its first in-beam performances will be presented.

Speaker: Mr Pierre-Alain Loizeau (Physikalisches Institut der Universität Heidelberg)

Slides 4_rpc2012_loizeau_2012_02_10.pdf

10:20 Coffee break

Closing

Closing

slides RPC2012panel.ppt

84 Challenges of RPCs and Resistive Micropattern Detectors in the Coming Years

After a long and fruitful “wire detectors era” two major breakthroughs happened in the field of gaseous detectors: the development of RPCs and the invention of micropattern detectors. Nowadays RPCs are widely used in many experiments and the latest achievements are highlighted in the talks presented at this workshop. The main attraction of the micropattern detectors is that they are manufactured by a microelectronic technology that offers high granularity and thus unprecedented position resolution. However, as a consequence of their fine electrode structure these detectors are very fragile and for example, could easily be damaged by sparks. The recently suggested resistive electrode approach makes them robust and spark-protected and gives a new momentum in their developments and applications. These innovative detectors are actually hybrids between RPCs and the “classical” micropattern detectors with metallic electrodes (GEM, MICROMEGAS, microstrip, microdot, micropin and so on). The aim of this presentation is to shortly highlight the latest achievements in the fields of RPC detectors and resistive electrode micropattern detectors as well as focus on the challenges these detectors should be meeting in the coming years. Examples could be: new and difficult requirements from experiments and applications, optimization and improvements of the existing detector designs (gas, gas systems, electronics), improvement of their characteristics (timing /rate performance, aging, dark current, etc), investigation of new materials, development of large-area detections and much more. A discussion of all of these issues with the conference participants is expected after the presentation in order to formulate together what should be done in hardware and software technologies in order to meet these challenges.

Speaker: Prof. Vladimir Peskov (CERN)

Slides Comclusion_talk.pptx

11:25 Discussion Panel : "Challenges for RPC's" - Moderated by D.Gonzalez-Diaz and A.Sharma

Discussion with IAC panel and conference participants, moderated by Archana Sharma and Diego Gonzalez-Diaz.

12:25 Best talk/poster awards, RPC 2014 announcement and goodbyes

12:55 Lunch @ Hotel Flora (upon request on Thursday)

13:55 Departures

the BUS to Fiumicino will leave at 13.00 from Hotel FLORA