SiPM workshop: from fundamental research to industrial applications

2 Oct 2019, 14:00 → 4 Oct 2019, 19:20 Europe/Rome

Centro Polifunzionale Studenti (Università di Bari)

Elisabetta Bissaldi (BA), Francesco Giordano (BA), Leonardo Di Venere (BA)

 

The conference “SiPM workshop: from fundamental research to industrial applications” will be held in Bari, Italy from October 2, 2019 to October 4, 2019.

The conference is organized by Università degli Studi di Bari, Politecnico di Bari and Istituto Nazionale di Fisica Nucleare di Bari. 

 

The main goal of the workshop is to review the main fields in which Silicon Photomultipliers (SiPMs) are being employed, understand the present limitations and define R&D goals for their improvement.

Many experiments in medical, particle and astroparticle physics are adopting SiPMs for existing detectors or for future upgrades, with different requirements in terms of performances and operating conditions of these devices, for example cryogenic temperatures, space environments, high-intensity radiation, low to high light intensities, wavelengths from vacuum ultraviolet to infrared.

Applications involving medical imaging are also exploring SiPMs for the construction of detectors with high granularity with a relative low cost per channel.

Experts from different fields will meet to review SiPM requirements in their respective area of interest and discuss solutions, including most recent and emerging developments in SiPM design and production, front-end electronics, and new characterization methods for optimizing SiPM performances.

Participation from industry is welcomed and desired.

 

Scientific Programme

The workshop will cover the following topics:

• New development and characterization methods
• High-energy and nuclear experiments
• Astroparticle and space applications
• Medical applications
• Industrial development 

 

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sipm_workshop_bull2.pdf

Wednesday, 2 October

14:00 → 15:00 Registration

15:00 → 15:30 Welcome

15:00 Welcome

A warm welcome in Bari to the participants to the workshop

Speaker: Francesco Giordano (BA)

15:30 → 16:50 High-energy and nuclear physics: Part 1

Convener: Dr Guido Haefeli (EPFL)

15:30 Silicon Photomultipliers in the Scintillating Fibre Tracker at the LHCb experiment

In order to cope with 5-10 times higher instantaneous luminosities at the LHCb detector, a large Scintillating Fibre Tracker has been developed to replace the tracking detectors downstream of the dipole magnet. This detector is currently being installed and will be commissioned after the Long Shutdown 2 (LS2) of the LHC in 2021.
The detector is based on plastic scintillating fibres read out by multi-channel Silicon Photomultiplier arrays. The technology was chosen to build a large area (300m$^2$), high granularity (250$\mu$m and 500K channels) and fast tracking detector.
The major challenge is to reach a sufficiently high signal to noise ratio in a harsh radiation environment, to obtain high detection efficiency.
The photodetectors will be exposed to fast neutrons at an equivalent fluence of 6$\cdot$10$^{11}$n$_{eq}$/cm$^2$ and ionising radiation dose of 50Gy. To limit the severe increase of the dark count rate,  cold operation down to -40\degC is foreseen.
We report on the application of the Silicon Photomultipliers in this context regarding the optimisation of their characteristics, packaging, integration into the system and production quality assurance.  Our R$\&$D focus for the future upgrades of LHCb and other Scintillating Fibre Tracker applications is to improve photodetection efficiency using micro-lenses and to reduce noise with cryogenic operation.

Speaker: Maria Elena Stramaglia (AEC-LHEP Bern University)

LHCbSiPMWorkshop.pdf

16:10 SiPMs for the Photon Detection System of DUNE

The DUNE (Deep Underground) experiment will bring the technology of Liquid Argon TPC to an unprecedented size in order to study neutrino oscillations at very long baselines and establish CP violation in the leptonic sector. The observation of the VUV photons from the scintillation of Argon plays a prominent role in the DUNE physics programme and requires the development of a novel Photon Detection System (PDS) based on NUV SIPMs.
In this talk, we summarize the requirements for the DUNE SiPMs, the structure, the characteristics and the expected performance of the Photon Detection System. Special emphasis is given on the developments performed in collaboration with FBK for the DUNE first module, the cold tests of the NUV-HD sensors and the design of the cold amplifiers.
Innovative solutions based on monolithic devices for the next DUNE modules will also be discussed.

Speaker: Andrea Falcone (Istituto Nazionale di Fisica Nucleare)

BariWorkshop_Falcone.pdf

16:30 Silicon Photomultipliers for the decay tunnel instrumentation of the ENUBET neutrino beam

The ERC funded ENUBET project is developing detectors suitable for positron reconstruction in the decay tunnel of a narrow band beam to monitor at 1% level the neutrino flux from the three-body semileptonic decays of kaons. The baseline option for the tunnel instrumentation employs a fine-grained shashlik calorimeter with a 4.3 $X_{0}$ longitudinal segmentation to separate positrons and pions coming from other decay modes of kaons. The iron-plastic scintillator stack composing each basic unit (UCM) is crossed by 9 WLS fibers with a density of 1 fiber/cm$^2$. These fibers are directly coupled to small-area SiPMs hosted on a PCB on the back of each module, hence avoiding dead zones from fiber bundling. The instrumentation is complemented by rings of plastic scintillator doublets below the calorimeter, acting as a photon veto to suppress the $\pi^0$ background and providing timing informations. Each tile is readout by a WLS fiber optically linked to a SiPM.
Since march 2019, ENUBET is also a CERN Neutrino Platform experiment (NP06/ENUBET) and collaborates both with CERN accelerator physicists on the development of the beamline and with Research Centers in Italy and Croatia (Fondazione Bruno Kessler and the Photonics and Quantum Optics Lab. of the Institut Ruđer Bošković) for the photosensors. In this context, we are also developing the required triggerless front-end electronics for SiPM readout to cope with the needs of a monitored/time-tagged neutrino beam.
SiPMs instrumenting the calorimeter will be exposed to sizeble amounts of neutrons arising in hadronic showers. In order to reproduce such a working environment, SiPMs with different cell size (from 12 to 20 $\mu$m) produced by FBK employing the RGB-HD technology were irradiated at the INFN-LNL Irradiation Test facility with neutron fluences up to 2$\times$10$^{11}$ n/cm$^2$ (1 MeV-eq.). The exposed light sensors were characterized in situ in terms of I-V curves at different irradiation levels, and their response in the ENUBET UCMs was tested at CERN with electrons, muons and pions.
In this contribution we will report the results of the described tests on SiPMs, together with the advances in their integration with the ENUBET detectors and in the dedicated readout electronics.

References:

• F. Acerbi et al., Irradiation and performance of RGB-HD Silicon Photomultipliers for calorimetric applications, JINST 14 (2019) P02029.
• G. Ballerini et al, Testbeam performance of a shashlik calorimeter with fine-grained longitudinal segmentation, JINST 13 (2018) P01028.
• A. Berra et al., Shashlik Calorimeters With Embedded SiPMs for Longitudinal Segmentation, IEEE Trans. Nucl. Sci. 64 (2017) no.4, 1056-1061.
• A. Berra et al., Longitudinally segmented shashlik calorimeters with SiPM readout, Nucl. Instrum. Meth. A845 (2017) 511-514.

Speaker: Michele Pozzato (BO)

20191002_Pozzato_ENUBET.pdf

16:50 → 17:20 Coffee Break

17:20 → 19:00 High-energy and nuclear physics: Part 2

Convener: Riccardo Rando (PD)

17:20 Photon counting with solid state detectors: from high energy physics to LiDAR

The capability to detect faint light events at few photon level is of extreme importance for a number of application ranging from base research to medicine, to industry as well as daily life needs. Until few years ago, photon counting was synonym of Photomultiplier Tube and Solid State devices were considered not sensitive enough for this demanding use. Since the introduction of SPADs and SiPM, and their internal multiplication mechanism, this opinion greatly changed and now Solid State technology allows photon counting even in critical environmental conditions where the PMTs can not be used. A snapshot of the progresses and successes achieved in applying this technology to Physics and Industrial applications will be presented.

Speaker: Francesco Giovenale (Hamamatsu Photonics Italia)

17:40 JUNO-TAO Experiment with Large Area High Performance SiPMs

Taishan Antineutrino Observatory (TAO) is a ton scale liquid scintillator (LS) detector and proposed to precisely measure reactor neutrino energy spectrum with as high as possible energy resolution, which can provide a reference spectrum for Jiangmen Underground Neutrino Observatory (JUNO) and a benchmark to verify the nuclear database. Tao is a satellite experiment of JUNO and will be installed near the reactor core with a distance of ~30 m. The detector uses 2.6 ton gadolinium-doped LS (1 ton fiducial volume) contained in a spherical acrylic vessel. To maximize the photon collection efficiency in the detector, 10 m2 SiPM array is proposed to fully cover the acrylic vessel and collect scintillation photons as many as possible. The preferred photon detection efficiency of SiPM should be larger than 50%, in order to achieve the desired energy resolution (1.5%/sqrt(E) photon statistical resolution). Meanwhile, the SiPMs will also be operated at low temperature (-50 degree or lower) to reduce the dark noise. The detector R&D has been started for more than one year, and the JUNO-TAO experiment is expected to be online in 2021. In this talk, an overview of the JUNO-TAO will be reported, then put the emphasis on the requirements of SiPMs, and ongoing R&D work related to SiPM characterizations and electronics readout.

Speaker: Dr Guofu Cao (Institute of High Energy Physics)

JUNO-TAO Experiment with Large Area High Performance SiPMs.pdf

18:00 SiPM development for nEXO

Silicon photo-multipliers (SiPMs) have been chosen for detecting liquid Xenon scintillation light in the nEXO experiment being designed to search for neutrinoless double beta decay. SiPMs from FBK and Hamamatsu more or less fulfill nEXO's specifications achieving more than 15% photo-detection efficiency (PDE) at 175nm. However, the interplay between PDE, reflectivity (as high as 55% at 175nm), gain, correlated avalanches (after-pulsing cross-talk both internal and external) is being studied in details using a wide range of setups (mini-nEXO, Light only liquid Xenon, reflectivity measurement setup in vacuum and liquid Xenon,...). In addition the nEXO collaboration continues to drive the development of SiPMs with towards PDE>25% at 175nm and is exploring using 3D integrated digital SiPMs, that would minimize power dissipation in liquid Xenon over conventional electronics. In this talk, we will describe the SiPM development effort for achieving unprecedented sensitivity to neutrinoless double beta decay in nEXO.

Speaker: Dr Fabrice Retiere (Fabrice)

EXOBariSiPMWksp2019.pdf

18:20 SiPMs characteristics after very high Radiation at low Temperature for the SLHC CMS PHASE II upgrade

The design of the CMS phase II upgrade for the SHLC uses SiPMs for the Barrel Timing Layer (BTL) and the Behind HCAL detector (BH). In both sub-detectors the SiPMs will see a 1 MeV Equivalent dose of around 10E14 n/cm2. To lower the noise in the SiPMs the design is to run at a low temperature of -30C .
Different samples from two manufactures of SiPMs were radiated up to a very high total dose of 4*10E14 at the TRIGA reactor at the JSI in Slovenia.
We compare samples of 4 different wafers with different internal electric field from FBK-irst (Italy). We study the noise vs temperature down to -40C after different irradiations. We also report on PDE change and breakdown voltage shifts after the highest neutron doses.

Speaker: Adriaan Heering (University of Notre Dame (US))

Bari.pdf

18:40 Discussion

19:30 → 22:30 Welcome: Guided tour & "Panzerottata"

Thursday, 3 October

09:00 → 11:00 Astroparticle and space applications: Part 1

Convener: Hiro Tajima (Dept. of Physical Science, Hiroshima Univ. ISEE, Nagoya Univ.)

09:00 Properties of large area SiPM at room temperature

I will illustrate the main parameter extraction methods and calibration strategy of large area SiPM operating in a large noise environment.
I will also discuss a camera developed for gamma-ray astronomy and its operation and calibration.

Speaker: Teresa Montaruli (university of geneva)

SiPMBari_Montaruli.pdf

09:40 Characterization method to achieve simultaneously the absolute PDE of all pixels of an ASTRI camera tile in one measurement

Recently, the ASTRI project has placed a contract with Hamamatsu Photonics to acquire hundreds of SiPM tiles to build 10 cameras with 37 tiles each for the mini array of 9 Cherenkov telescopes of the ASTRI Project. Each tile is constituted by 8x8 pixels of 7x7 mm2 with micro-cell of 75 µm. To check the quality of the delivered tiles a complex and fine test plan has been studied. The possibility to analyse simultaneously as many pixels as possible becomes of crucial importance.
Dark Count Rate (DCR) versus overvoltage and versus temperature and Optical Cross Talk (OCT) versus overvoltage can be easily measured simultaneously for all pixels because are carried out in dark conditions. On the contrary, simultaneous PDE measurement of all pixels of a tile is not easily achievable and needs an appropriate optical set-up. Simultaneous measurements have the advantage of speed-up the entire procedure and enable quick PDE comparison of all pixels’ tile.
The paper describes the preliminary steps to guarantee an accurate absolute PDE measurement, the investigation on the capability of the electronics to obtain simultaneous PDE measurements, the possibility to use a calibrated SiPM as reference detector instead of a calibrated photodiode and finally, the method to achieve accurate absolute PDE of four central pixels of a tile.

Speaker: Dr Giovanni Bonanno (INAF . Catania)

G. Bonanno Bari SiPM Workshop.ppt

10:00 SiPM experience from more than seven years operation of FACT.

The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of SiPMs in Imaging Atmospheric Cherenkov Telescopes. Its camera consists of 1440 SiPMs, each coupled to a solid light-guide and an individual read out channel. In October 2011, the camera was installed in a refurbished telescope structure with a mirror area of 9.5m^2 at the Canary island La Palma, and successful data taking started within few hours. Since then, FACT is taking data whenever observation conditions and safety regulations permit, with the primary goals of gaining long-term experience with operation of SiPMs under harsh conditions as well as monitoring a set of variable extragalactic high energy gamma-ray sources.

For the science goal, stable performance of the photo detectors is crucial and therefore has been studied in great detail. Special care has been taken with regards to keep the gain of the SiPMs constant despite their temperature varying by more than 25 deg. This is reached through implementation of a feedback system that regularly adjusts the applied voltage to the sensor temperature as well as to the current drawn due to varying night-sky brightness.

Several independent long term measurements were conducted to analyze and verify the stability of the SiPMs. As example, dark count spectra, which also make for an excellent self calibration mechanism, were used to study and model the temperature dependencies. Trigger thresholds are adjusted to the night-sky background by measuring the current drawn by individual groups of pixels.

With these methods, the performance of the FACT camera is kept stable and homogeneous without the need for any external calibration device. While each of the 1440 SiPMs has collected a charge of more than 600C so far, there is no indication of any ageing or any other sensor-related problems. The exceptional reliability of the system allows to operate FACT as the only Cherenkov telescope so far in a fully robotic way.

In this talk, the results of the long term performance studies and experience gained from the seven years operation of SiPMs will be presented.

Speaker: Dominik Neise (ETH Zürich)

Dneise_FACT_SiPM_Bari_2019_final.pdf

10:20 Status of the development of NUV SiPMs for INFN optical modules for the SCT Medium Size Telescope proposed for the CTA Observatory

Near UltraViolet High Density (NUV-HD) SiPMs produced by Fondazione Bruno Kessler in collaboration with INFN have been tested and characterized in INFN laboratories. The third generation of these devices (HD3) has proven to be suitable to equip the focal plane of the prototype Schwarzschild-Couder Medium Size Telescope (pSCT) proposed for the Cherenkov Telescope Array Observatory. Photosensors have been assembled in 4 16-pixel optical units coupled with TARGET-7 ASIC front-end electronics for amplification and digitization of the signal. At present, 9 modules have been successfully integrated on the pSCT camera and are currently taking data, while studies are being conducted on an improved thin substrate technology. In this contribution we report on the performances of the HD3 technology as single sensor and as assembled optical units, showing their performance and homogeneity in terms of gain and dark count rate.

Speaker: Serena Loporchio (BA)

sipm_workshop_loporchio.pptx

10:40 Optical feasibility of an upgrade of the CTA LST camera to SiPM

The Large Size Telescope (LST) is the largest telescope of the Cherenkov Telescope Array project, with a diameter of 23m and a focal plane instrumentation of 4 square meters. In the current design, it comprises cameras equipped with arrays of 1855 photomultiplier tubes (PMTs). Each PMT has a light concentrator in front to reduce the stray light as well as to reduce the dead space between PMTs. These cameras are built to detect the nanosecond flashes of Cherenkov light from atmospheric air showers generated by gamma rays entering the atmosphere. Thanks to rapid development, silicon photomultipliers (SiPMs) are becoming valid and economical alternatives to PMTs in several fields, due to their lower operating voltage, larger photon efficiency, reduced ageing and insensitivity to magnetic fields. These properties make SiPMs suitable for gamma-ray astronomy and for imaging atmospheric Cherenkov telescopes. Here we discuss a minimal-effort scenario for an upgrade of an LST PMT-based camera to a SiPM-based camera, in which most of the hardware is maintained. Thanks to a ray-tracing software, we show that the minimal valid solution consists of replacing each PMT by several SiPMs. In particular, the existing light funnel in front of each pixel does not have to be exchanged considering the angular distribution of light at the SiPM surface and its angular response. We briefly discuss the effect on the sensitivity of the instrument of an upgrade to SiPMs.

Speaker: Cédric Perennes (PD)

Perennes_LST SiPM.pdf

11:00 → 11:30 Coffee Break

11:30 → 12:50 Astroparticle and space applications: Part 2

Convener: Eugenio Scapparone (BO)

11:30 OMEGA chips for SiPM redaout

The use of SiPMs has been very early associated to readout ASICs as they were used in often large numbers to cover a reasonable area. OMEGA laboratory started in the early days to design readout ASICs for calorimetry in high enery physics, with chips as SPIROC or EASIROC/CITIROC. The performance and compactness provided by these ASICs helped to make the SiPM arrays easy to use. The excellent timing properties of SiPMs were quickly recognized and there again fast ASICs allowed to exploit this feature and were used in time of flight PET medical applications. More recently LHC upgrades at CERN make use of large quantites of SiPMs and need new ASICs to read them out at high rate.
The talk will start from the fundamental aspects of signal handling in SiPM to get the best charge and time measurements and show some examples and performance achieved with various chips developed by OMEGA and WEEROC.

Speaker: Christophe de LA TAILLE (OMEGA CNRS/IN2P3 Ecole Polytechnique)

CdLT_Bari_3oct019.pdf

11:50 Evaluation of a multi-channel silicon photomultiplier with a light concentrator for Medium-Sized Telescopes of Cherenkov Telescope Array

The Cherenkov Telescope Array is the new gamma-ray observatory consisting of three types of telescopes to cover the energy range from 20 GeV to 300 TeV. In the current design of medium- sized and large-sized telescopes, photomultiplier tubes (PMTs) are used as photon detectors in camera modules. Initially they were chosen due to their low cost and quantum efficiency (QE) curve corresponding well to the Cherenkov spectrum. The main disadvantage of PMTs is the degradation of their performance over time. The larger is the total charge emitted from the last dynode of a PMT, the more its gain decreases, thus it is not advisable to operate PMTs under high night sky background (NSB) conditions. Due to the improvement of silicon photomultipliers’ (SiPMs) performance and a decrease of their price in recent years it is now viable to consider them as an alternative option. Unlike PMTs, SiPMs are highly NSB tolerant, so by using them instead of PMTs we might be able to extend the duty cycle of the telescopes thus increasing sensitivity and energy range.
A single pixel of a camera module consists of a photon detector and a special reflective cone (a light concentrator) that is made to increase the collection area of a detector. Said cones are not designed to be used with SiPMs and introduce a wide spread of the photons’ angle of incidence at SiPMs’ surface, which is expected to cause reflection, refraction and interference effects that are not well studied at the moment. Furthermore, SiPMs’ spectral sensitivity differs from that of PMTs, which gives even more reason to carefully examine the behaviour of new camera pixels and compare it to the current design.
We are going to present measurement data of SiPM- and a PMT-based MST camera pixels’ response at 8 different wavelengths as well as our simulated comparison of these camera pixels for wavelengths of interest and provide an estimate of the total Cherenkov light collection efficiencies at camera modules. These results will allow us to make preliminary conclusions regarding the viability of such an upgrade and discuss its advantages and disadvantages.

Speaker: Mr Anatolii Zenin (Nagoya University, ISEE)

sipmwrkshp_pres_zenin_v4.pdf

12:10 An ASIC Front-End for Fluorescence and Cherenkov light detection with SiPM for space applications.

Astroparticle and High Energy Astrophysics space missions measuring extensive air showers produced by cosmic rays and neutrinos in atmosphere require detection of very faint and intense UV-VIS light. Characteristics of the new generation of SiPM (Silicon PhotoMultiplier) are potentially right for this purpose. Their high intrinsic gain, low power consumption, low weight and robustness against accidental exposure to light are particularly important for spaceborn multipixels imaging cameras. Their high-performance detection makes them promising for photon counting, where extreme photodetector sensitivity is needed, as well as for charge integration, where the total amount of charge in the signal is required. The capability to operate SiPM contemporarily in photon counting and in charge integration is strictly dependent indeed by the design of the front-end electronics. In this context, the challenge is to find the right balance and a feasible solution for managing SiPM with a front-end electronics to be able to work, contemporarily and efficiently, in photon counting and charge integration.

Speaker: Dr Giovanni Contino (IASF Palemo/INAF)

FluChe_presentation_Bari_fin.pptx

12:30 Evaluation and integration of SiPMs in air-shower imaging telescopes for the detection of ultrahigh energy neutrinos

We present the development status of a Cherenkov telescope for the detection of earth-skimming ultrahigh energy (UHE) tau neutrinos. While the telescope is developed for a long-duration balloon mission and serves as a precursor for the space-borne PEOMMA mission, the SiPM camera and readout electronics also meet the requirements for a ground-based air-shower UHE neutrino telescope. The design of the camera is driven by the unique characteristics of air showers initiated by UHE neutrinos in the lower atmosphere. I discuss the requirements, which derive from the air-shower physics and put them into context with the results obtained from our evaluation of blue and red sensitive SiPMs and the evaluation of the signal chain we have developed for the camera.

Speaker: Nepomuk Otte (Georgia Institute of Technology)

BariWorkshop2019.pdf

12:50 → 13:26 Poster: Mini-talks

Convener: Dr Elisabetta Bissaldi (BA)

12:50 Development and test of a cluster for a SiPM version of the CTA-LST camera

The Large Size Telescopes (LSTs) are the largest telescopes of the Cherenkov Telescope Array (CTA). Their cameras are equipped with 1855 photomultiplier tube (PMT) pixels with GHz readout, to image the flashes of Cherenkov light emitted from atmospheric air-showers initiated by cosmic gamma rays.
Silicon photomultipliers (SiPMs) are becoming valid alternatives for PMTs, and in fact many of the smaller telescopes in the array will feature a SiPM camera. To evaluate the performance of an LST SiPM-based camera we are building one of the LST camera elements (a cluster of 7 pixels with the readout electronics), replacing the PMTs with SiPM pixels. Most of the hardware of the baseline design is maintained, to keep the evaluation process simple and to use the existing calibration facilities. We discuss the design and construction of the demonstrator unit, and give a first evaluation of its performance.

Speaker: Riccardo Rando (PD)

rando-highlight.pdf

12:54 A full and customizable simulation of a scintillation tile equipped with SiPMs for Plastic Scintillator Detectors in the next generation of satellite experiments

Satellite experiments employ plastic scintillators to discriminate charged from neutral particles in order to correctly identify gamma-rays and nuclei. The latest results in the field of cosmic rays and dark matter highlight the necessity of new experiments covering energies beyond the TeV with improved performance compared to present satellite experiments. The Plastic Scintillators Detector (PSD) needs to have a very high detection efficiency for the charged cosmic rays, which constitute the main background in the identification of gamma rays, and also a very good capability in identifying charged nuclei.
In order to reduce the back-splash effect due to secondary particles generated within the satellite, a highly segmented PSD is required and the optimization of its geometry is crucial to maximize the detection efficiency.
Next-generation space missions will likely employ Silicon Photomultipliers (SiPMs) instead of classical Photomultiplier Tubes to read-out the scintillator light emission, to exploit their smaller sizes and lower power consumption.
We implemented a full and customizable simulation framework based on GEANT4 to investigate the performance of a segmented PSD made of scintillator tiles coupled to SiPMs. The purpose of this simulation is to study the effects of the scintillator optical properties and the coupling with SiPMs in order to be able to choose the best geometry of the tile and the best design for the SiPM-based readout system.
We simulated a single tile equipped with SiPMs with the possibility to customize the tile and the SiPMs dimensions and position in respect to the tile facets. We will present the results of this simulation, together with the study of the scintillation photons collected by the SiPMs, especially in terms of the spatial density of the detected photons and of their collection time.

Speaker: Davide Serini (BA)

Serini_PresSiPM2019.pptx

12:58 A SiPM-based gamma-ray imaging camera for ambient radioactivity detection

The aim of this work is to design a camera for gamma-ray imaging based on the coded mask technique widely used in astrophysics. The Camera will be made by 16 scintillators coupled with 16 SiPMs to have an instrument lightweigth, compact for real-time analysis, with low energy consumption. We built a prototype as proof of concept using 16 CsI scintillators doped with Tl (3x3x10 cm3). Each scintillator is coupled with optical grease to a Photo-Multiplier Tube (PMT) supplied by a Cockcroft-Walton voltage multiplier (HV3020CN). The signals produced are acquired and analyzed by a CAEN digitizer (V1725). The scintillators are arranged as a 4x4 matrix and packaged in a metallic frame. We used a 7x7 mask composed by transparent and opaque tiles (PVC and tungsten 3x3x1 cm3) to encode a point source image and decode it through a reconstruction algorithm. We tested the system with different radioisotopes source placed at a distance of about 40 cm from the mask. We will present the results obtained in terms of the angular resolution on the position of the source and of the energy resolution measured with the scintillators. Then we will compare those results obtained with the PMTs replacing them with an AdvanSiD NearUV SiPM.

Speaker: Corrado Altomare (Istituto Nazionale di Fisica Nucleare)

Altomare-SiPM Workshop.pptx

13:02 Characterisation of SiPMs for the LHCb scintillating fibre tracker

For the future data taking at LHC, the LHCb detector and in particular the tracking system is replaced to cope with the increased luminosity foreseen and a trigger-less read-out scheme. A scintillating fibre tracker with 500K channels and a total surface of (300 m$^2$) was developed, produced and is currently in the installation phase. One of the key components that enables the scintillating fibre tracker technology for this application is the silicon photomultiplier. SiPM technologies from different vendors as Hamamatsu, KETEK, SensL and FBK were evaluated with a characterisation method based on pulse response. The multichannel array S13552 manufactured by Hamamatsu was selected for its high photon detection efficiency, low correlated noise and short recovery time. It was tested for a radiation environment with a fluence of 12$\cdot$10$^{11}$MeV n$_{eq}$/cm$^2$. We present the characterisation method, the results and comparison between different devices and some statistics of the results of the quality assurance process for the LHCb scintillating fibre tracker production.

Speaker: Carina Trippl (EPFL)

trippl_SiPM_Characterisation.pdf

13:06 Displacement Damage Effects on Dark Count Rate in Irradiated CMOS SPADs Sensors

The aim of this work is to investigate the degradation induced by radiation on Dark Count Rate in a monolithic SPADs detector manufactured in a 150-nm CMOS process. This study has been done in order to check the suitability of CMOS SPADs for future applications requiring single-photon detection capability in radiation environments, like space or experiments at particle colliders.
For this purpose, an irradiation campaign has been carried out with protons and electrons to induce radiation damage effects on several test chips containing SPADs arrays with different geometries and implantation layouts.
The dark count rate has been measured as a function of the dose on a large amount of SPADs, showing that radiation-induced damage can be a serious issue for CMOS SPADs. Radiation can impact the device performance by creating interface traps of bulk defects responsible for the deterioration of the dark and noise performances of the detector.
We used the DCR analysis (specifically: its distribution, low frequency fluctuations, activation energy, annealing temperature) as a probe to study the basic mechanisms of radiation damage in silicon and the related induced defects.
Furthermore, we investigated cooling and thermal annealing, as possible methods of mitigation.
The obtained results have been investigated in the framework of several space mission case-studies. Expected radiation levels have been estimated by means of SPENVIS and considerations about the suitability of CMOS SPADS in space have been addressed.

Speaker: Francesco Di Capua (University of Naples "Federico II" and INFN)

MiniSlideDiCapua.pptx

13:10 The Liquid Argon Detector and Measurement of SiPM Array

Particle detectors based on liquid argon(LAr) have recently become recognized as an extremely attractive technology for the direct detection of dark matter as well as the measurement of coherent elastic neutrino-nucleus scattering(CEvNS). The Chinese argon group at Institute of High Energy Physics has been studying the LAr detector technology and a dual phase LAr detector has been operating steadily. A program of using a dual phase LAr detector to measure the CEvNS at Taishang Nuclear power plant has been proposed and the R&D work is ongoing.
Considering the requirements of ultra-low radio-purity and high photon collection efficiency, SiPMs will be a better choice and will be used in the detector. In this poster, an introduction of the LAr detector, the project of CEvNS measurement with LAr as well as the measurement results of SiPM array at LAr temperature will be presented.

Speaker: Dr Cong Guo (Institute of High Energy Physics)

Cong_poster.pdf

13:14 Some high energy physics application of NDL-SiPM

The NDL-SiPM is a bulk resistor type SiPM. It is a SiPM with epitaxial quenching resistors (EQR). Now, it is planed to used in high engergy physics.This SiPM was tried to be used in CEPC hardonic callorimeter. Some properties of NDL-SiPM were tested such as PDE, corss talk, light ourput. The result show that this type SiPM can be one candidate of CEPC callorimeter.

Speaker: Boxiang Yu (Institute of high energy physics, China)

The HEP application of NDL EQR-SiPM.pdf

13:18 Si-PM Performance Comparison for Readout of CsI / BGO Scintillators

CsI and BGO scintillators are available with large crystal sizes and utilized for veto detectors in X-/gamma-ray satellite missions. Since Si-PMs are compact and operated with low voltage, they are planned to be used the scintillation readout in future missions. We study the readout performance of the scintillation lights with the recently available Si-PMs (MPPCs) from Hamamatsu. Photonics K.K., 13360-6050CS and S14160-6050HS. They are both suitable for scintillators but slightly different in gain, dark current and photon detection efficiency (PDE). For 1cm3 CsI and BGO scintillators, S14160 shows the better energy resolution and achieve the lower energy threshold than S13360.
We think it is because the higher gain and PDE of S14160 overcomes the disadvantage of slightly more dark current.

Speaker: Hiromitsu Takahashi (Dept. of Physical Science, Hiroshima Univ. ISEE, Nagoya Univ.)

Hiromitsu_Takahashi_poster1page.pdf

13:22 The ASIC Citiroc 1A characterization

According to the recent developments in fundamental and applied physics (i.e. calorimetry for high energy experiments and PET scanners in medical physics), Silicon Photomultipliers (SiPMs) are the state-of-the-art sensors for light detection, sensitive to the single photons together with unprecedented counting capability. In addition, SiPMs provide significant advantages in terms of:

• cost and compactness, crucial when large number of channels have to be operated
• magnetic field immunity, important for detectors used in accelerator physics and for future medical systems as MR-PET scanners.
• low operating voltage and power consumption, essential for the qualification within medical appliances
• flexibility in the design, due to the silicon technology and the variety of vendors.

Since the early days of the SiPMs development, the focus shifted towards systems made of a large number of sensors, necessarily requiring front-end electronics integrated into Application Specific Integrated Circuits (ASIC). In the talk, we will report the qualification of the Citiroc 1A ASIC, designed by WEEROC.

The ASIC in use integrates the front-end for 32 SiPMs with tunable bias for each individual channel 0-4.5 V. Each channel has two independent branches with different amplification allowing to characterize the multiphoton spectrum (important for the detector calibration) and to exploit a large dynamic range (up to ~2500 photoelectrons with a typical gain ~10$^6$) at the same time. The signals from both branches are processed through a peak detection and track & hold circuit and the output is externally digitised. In addition, one of the two branches for each channel can be used for trigging and timing. The signal feeds a fast shaper amplifier before going into the fast comparator which allows to obtain time stamp with time resolution up to 100 ps. The initial ASIC qualification was performed using a general-purpose board DT5702 (produced by CAEN S.p.A) which provides the common bias to all the SiPMs together with the access to the basic functionalities of the Citiroc 1A and a data acquisition. A comprehensive analysis was performed using the new DT5550W board, featuring the full control of the ASIC functionality.

The features of the ASIC were investigated interfacing it to arrays of crystals in a module developed for a table-top PET system by the University of Aveiro. Moreover, particle imaging was performed by the reconstruction of the impact point of a particle through the center of gravity of the light emitted by a monolithic scintillator sensed by an array of SiPMs.

Speaker: Dr Nikolay Ampilogov (University of Insubria)

NAmpilogov_1_slide_presentation_of_Poster.pdf

13:26 → 15:00 Lunch

15:00 → 16:20 Astroparticle and space applications: Part 3

Convener: Giovanni Ambrosi (PG)

15:00 The Scintillating Fiber Tracker of the HERD facility

The High Energy cosmic-Radiation Detection (HERD) facility will be one of the future astronomy missions on board the Chinese Space Station (CSS).
The main objective of HERD is the direct detection of cosmic rays towards the “knee” region (∼ 1 PeV), with an excellent energy resolution (< 1% for electrons and photons at 200 GeV and 20% for nuclei from 100 GeV to PeV) and an
unprecedented acceptance (> 1 m2sr). The CSS assembly should be completed by 2022, and the installation of HERD on the CSS is planned for 2025, for an operation of at least 10 years. HERD is composed of an almost cubic calorimeter, a tracking system, plastic scintillator detectors and a transition radiation detector.
The tracker will provide a full coverage of the 5 sensitive sides of the calorimeter, allowing for a sub-degree angular resolution and multiple redundant and independent measurements of the charge of the nuclei. Two options are considered, the first one is a tracker fully equipped with silicon strip detectors. In the second option, the four side trackers are made of scintillating fibres connected to SiPM arrays.
This talk will describe the scintillating fibre tracker option. We will present the tracker design, the DAQ electronics studies as well as the SiPM array models taken into consideration. The results of SiPM array characterisation tests, as well as of prototype fibre module tests in particle beams at CERN will be presented. We will also mention the space qualification tests necessary to validate the detector design.

Speaker: Philipp Azzarello (DPNC, University of Geneva)

1.azzarello_20191003.pdf

15:40 Particle identification capability of Plastic scintillator tiles equipped with SiPMs for the High Energy cosmic-RadiationDetection (HERD) facility

The High Energy Cosmic Radiation Detection (HERD) facility onboard the future China’s Space Station (CSS) will be able to detect charged cosmic rays and gamma rays from few GeV to PeV energies, giving a valuable contribution in several scientific topics, such as dark matter searches in astrophysical objects, the study of cosmic ray chemical composition and high energy gamma-ray observations. The entire instrument is supposed to be surrounded by a plastic scintillator detector (PSD), which will be used to discriminate charged from neutral particles in order to correctly identify gamma-rays and nuclei. One configuration proposed and studied for the HERD PSD detector consists in a segmented plastic scintillator with a squared-tile geometry, coupled to Silicon Photomultipliers (SiPMs). SiPMs provide similar or even better performances to the standard photomultiplier tubes (PMTs) with lower power consumption and cost benefits. In 2018, beam test campaigns were performed at CERN PS and SPS to test two prototypes of plastic scintillator tiles, equipped with a set of SiPMs. One was tested with a beam of electrons and pions and another prototype with an ion beam. The results will be presented, showing the capabilities of these prototypes to detect charged particles with very high efficiency and to measure the charge of heavier nuclei.

Speaker: Fabio Gargano (BA)

Gargano_V0.pdf

Gargano_V0.pptx

16:00 SiPM Arrays for Space-Based Detectors

Silicon photomultipliers (SiPMs) are an attractive option for space-based detectors for astrophysics because of their ruggedness, low size/weight/power requirements, and reproducibility. The U.S. Naval Research Laboratory has utilized its in-house experience in both astrophysics and detector development to design, characterize, instrument, and deploy SiPM arrays for space applications. The Strontium Iodide Radiation Instrument (SIRI) was launched on 3 December 2018 and has been successfully operating in orbit since that time. Recent successes with SIRI as well as ongoing/future projects (e.g., GLOWBUG, AMEGO, SIRI-2, GARI) will be discussed.

Speaker: Dr Anthony L. Hutcheson (U.S. Naval Research Laboratory)

Bari_Presentation_2019_WideScreen_FINAL.pdf

Bari_Presentation_2019_WideScreen_FINAL.pptx

16:20 → 17:00 Coffee Break

17:00 → 19:00 Astroparticle and space applications: Part 4

Convener: Jon Lapington (University of Leicester)

17:00 FERS: a distributed front-end readout system for multidetector arrays

The FERS-5200 is the new CAEN Front-End Readout System, which is a cost effective, scalable and distributed
front-end & data acquisition system for large detector arrays. It consists in a compact and easy-deployable
solution integrating front-ends based on ASICs, A/D conversion, data processing, synchronization and readout.
Using the appropriate ASIC the solution perfectly fits a wide range of detectors such as SiPMs, multianode
PMTs, Silicon Strip detectors, Wire Chambers, Gas Tubes, etc. The first member of the FERS family is the
unit A5202, a 64 channel readout card for SiPMs, based on the Citiroc (Weeroc) ASIC chips. Each concentrator
board A5215 manages up to 128 A5202 cards, that is 8192 readout channels.

Speaker: Carlo Tintori

CAEN_Tintori_FERS-5200_Rev_0.2_Bari_3_Oct_2019.pdf

17:20 BurstCube: A CubeSat for Gravitational Wave Counterparts

The first simultaneous detection of a short gamma-ray burst (sGRB) with a gravitational-wave (GW) signal provided direct proof that binary neutron star mergers are a progenitor of short gamma-ray bursts (sGRBs) and propelled astronomy into the multi-messenger era. In order to further study the connection between gravitational waves and sGRBs, and thus enable multi-messenger science, we must increase the number of sGRB-GW simultaneous detections. To accomplish this we require full sky coverage in the gamma-ray regime. BurstCube aims to expand sky coverage in order to detect and localize gamma-ray bursts (GRBs). BurstCube is comprised of 4 Cesium Iodide scintillators coupled to arrays of Silicon photo-multipliers on a 6U bus and is sensitive to gamma-rays between 50 keV and 1MeV, the ideal energy range for GRB prompt emission. BurstCube will complement current observatories, such as Swift and Fermi, in the detection of GRBs as well as provide astronomical context to gravitational wave events detected by LIGO, Virgo, and KAGRA. BurstCube is currently in its development phase with an expected launch date of ~2022.

Speaker: Jacob Smith (University of Maryland Baltimore)

BurstCube_SiPMBari_JRS_present.pdf

17:40 Space-based Extensive Air Shower Measurements using SiPM Detectors in POEMMA

The Probe of Extreme Multi-Messenger Astrophysics (POEMMA) mission plans to use two orbiting Schmidt telescopes to stereoscopically measure the air fluorescence signal from extensive air showers (EASs) from ultra-high energy cosmic rays (UHECRs), above 20 EeV, as well as the Cherenkov signal from upward-moving EASs induced from tau neutrino interactions in the Earth. Each POEMMA focal plane is designed for both fluorescence and Cherenkov detection, with the later optimized by the use of SiPMs to provide neutrino sensitivity above 20 PeV. In this talk, the properties of the Cherenkov EAS signal in the context of wide wavelength range offered by SiPMs will be discussed as well as the implementation for POEMMA. A comparison of the fluorescence response between SiPMs and the MAPMTs currently planned for POEMMA will also be discussed.

Speaker: John Krizmanic (CRESST/NASA/GSFC/UMBC)

6.POEMMA-BariSiPMworkshop-Krizmanic.pdf

18:00 Development and deployment of SiPM in space: from Lazio-Sirad to Mini-EUSO and SPB2

In this work we will describe the development of SiPM for space-borne
detectors for astroparticle physics research. The first known use of
SiPM in space was in 2005, installed in the Lazio-Sirad experiment in the
framework of Roberto Vittori's mission on board of the International
Space Station. The SiPM developed at Mephi by Dolgoshein have been used
as readout of a small calorimeter to measure radiation environment in space
and assess the effectiveness of shielding for astronauts. A more recent
usage of an array of SiPM (64 pixels array) is for an imaging detector
to study UV terrestrial emissions in the framework of the MINI-EUSO
mission, to be launched in Summer 2019.
In this contribution we will also discuss the synergy with the development of novel
readout and triggering techniques in the framework of FLUCHE, an
ASI-sponsored project to develop next-generation SiPM based detectors
for future applications such as the forthcoming SuperPressureBalloon 2
(SPB2) flight from New Zealand (to launched in spring 2022).

Speaker: Dr Marco Marco Casolino (INFN)

2019-10-03-barisipm.pptx

18:20 Radiation Hardness Tests of Si-PMs with a Proton Beam for Future Satellite Missions.

A scintillation detector for a gamma-ray satellite mission should have low power-consumption and be compact.
For observing the gamma-ray sky, low energy threshold and high energy resolution are required furthermore.
Silicon Photomultipliers (Si-PMs) are considered as a solid-state sensor alternative to photomultiplier tubes in a future satellite using scintillation materials as a radiation detection medium. Many of the Si-PMs fill these requirements. However, the performance-deterioration caused by the radiation damage is expected in the satellite orbit, since Si-PMs are directly exposed to the bombardment of galactic cosmic rays that mainly consist of the nuclear particles with the energy of several 100 MeV/ nucleon. In this experiment, we irradiated a dose of a few krad of 200 MeV protons to two of the latest Si-PMs developed by Hamamatsu Photonics K.K.: S14160-6050HS and S13360-6050CS. We compared the proton-irradiated and the non-irradiated Si-PMs in terms of the dark-current and the energy spectra by measuring the $^{241}$Am radiation sources with a CsI scintillator.
The results showed that the dark-current and the energy threshold got worse by proton irradiation even the proton dose is only 300 rad.
We report that the radiation hardness of these two Si-PMs in terms of the dark-current and energy spectrum.

Speaker: Nagomi Uchida (Dept. of Physical Science, Hiroshima Univ.,)

Uchida_2019_SiPM_WS_Bari_v191003.pdf

18:40 Discussion

20:00 → 23:00 Social Dinner

Friday, 4 October

09:00 → 10:40 Medical applications

Convener: Nepomuk Otte (Georgia Institute of Technology)

09:00 The SiPM revolution in time-domain diffuse optics

Time-domain diffuse optics is a powerful non-invasive, non-ionizing and label-free technique based on the use of picosecond pulsed laser light to probe highly scattering media like biological tissues down to a depth of few centimeters to obtain functional and compositional information. This technique is opening new perspectives in various fields spanning from oncology (e.g. characterization of breast or thyroid lesions, etc.) to neurology (e.g. diagnosis and monitoring of traumatic brain injuries, functional brain imaging, etc.), as well as in non-biomedical fields (e.g. characterization of fruits, wood, etc.). Time-domain diffuse optics is nowadays undergoing fascinating technology advancements, permitting for the first time the design of low-cost compact/wearable high performance systems. This revolution has been made possible also taking advantage from Silicon PhotoMultiplier (SiPM) progresses, originally driven by other applications, since time-domain diffuse optics is highly demanding in terms of performance, in particular requiring single-photon detectors with large collection area, high fill-factor, high single-photon timing resolution, low power dissipation and compact high-throughput front-end electronics. This presentation will review the recent advancements introduced by SiPMs in time-domain diffuse optics, mostly thanks to the support of different running EU H2020 projects (e.g. SOLUS -G.A.731877-, LUCA -G.A.688303-, BITMAP -G.A.675332-, ATTRACT -G.A.777222-, Laserlab-Europe -G.A.654148-), showing their present performances in this field, the inherent advantages that allowed the design of innovative diffuse optical imaging systems, as well as highlighting their present limitations in order to push forward the research towards the perfect SiPM for time-domain diffuse optics.

Speaker: Prof. Alberto Dalla Mora (Politecnico di Milano - Dipartimento di Fisica)

SiPMworkshop2019_DallaMora_subprot.pdf

09:40 Experimental study of the time resolution of SiPM coupled to scintillator

Since few years, SiPMs are replacing the standard PhotoMultiplier technology thanks to the many advantages (high efficiency, single photon sensitivity, high gain with low voltage, compact and robust, low power consumption ∼ 50 µW/mm$^2$) and lower costs, with the corresponding possibility to achieve also higher segmentations in calorimetry or other applications. Also in view of experiments at future colliders like HL-LHC or FCC or medical applications like TOF-PET, an important R&D on timing performances of SiPMs-scintillator detectors has started, with the goal of including them in the list of possible 4-D tracking-timing devices.
An R&D on SiPM coupled to scintillator time resolution has been performed. Here the results obtained using both a cosmic ray setup and a beam test setup are reported. Different geometries of SiPMs coupled to the scintillator and different size of scintillator have been also studied, together with the possibility to use optical fibers to move the sensor away from the hypothetical high-radiation area. A time resolution of ~60 ps, comprehensive of the full electronic chain, from the front-end to the readout electronics, has been reached with SiPMs coupled to a 2x2x3 cm$^3$ plastic scintillator.

Speaker: Francesca Carnesecchi (BO)

SiPM_Workshop_Carnesecchi.pdf

10:00 Large area SiPM and high-throughput electronics for next generation time-domain diffuse optics

The use of large area SiPMs represents an impressive breakthrough in time-domain diffuse optics (TD-DO) for non-invasive diagnostics and imaging. Large area detector can improve light harvesting allowing to detect the very low number of photons re-emitted from the sample at relatively late times that have probed deep in the tissue. Large area SiPMs could thus foster the measurement of deep organs such as liver, lung and heart that conventional detectors aren’t capable of.
We firstly present our system based on 3x3 mm2 SiPM coupled to a new high-throughput (up to 160 Mcps) timing electronics MultiHarp 150 (PicoQuant). To better exploit the large area, we work with a very high throughput thus overcoming the single-photon statistics limit. Using a suitable post processing correction, we show an improved depth sensitivity and a still good linearity and accuracy in the retrieval of optical properties. Such a result allows us to assess the suitability of large area detectors coupled to high throughput electronics as a tool overcome the actual limits of TD-DO systems.
We will then present the aim of the “SP-LADOS” project (within Attract H2020 project, grant agreement number 777222): the realization of a 1 cm2 SiPM detector, with low background noise (dark count rate lower than 2 Mcps in 1 cm2) and good timing resolution (full-width at half maximum < 500ps). This step represents a tough technological challenge but will pave the way to a completely new generation of instruments for non-invasive diagnosis and monitoring, potentially capable of revolutionizing the field.

Speaker: Laura Di Sieno (Politecnico di Milano, Dipartimento di Fisica)

2019_DiSieno_SiPMworkshop_sel.pdf

10:20 A SiPM based novel approach to cytosolic calcium detection by bioluminescence

Calcium is an universal second messenger which regulates a plethora of cellular processes including cell survival, gene transcription, neuro-transmission and mitochondrial functions.
Several methods have been developed for measuring calcium intracellular concentrations ([Ca$^{2+}$]) mainly based on fluorescent or bioluminescent probes. The light emission is due to the chemical reaction between probes and calcium ions in biological environment and it is proportional to the calcium concentration. Among bioluminescent probes, aequorin represents a common tool for measuring a wide range of [Ca$^{2+}$], from sub-micromolar to millimolar, offering as well the possibility to target the different sub-cellular compartments involved in the process under study. The aequorin response is directly proportional to the [Ca$^{2+}$] and the cells are preserved by photodamage because external excitation is obviously not needed. The major drawback of this technique is the low level of emitted light, consisting in a sequence of single photons.

Silicon Photo-Multipliers (SiPM) are a valuable device for this application not only for their well known single photon counting capability but also in perspective to analyse simultaneously calcium signals generated in different cellular subcompartments, like cytosol, mithocondria or lysosomes. This talk reports the results of a serie of tests aimed at qualifying a flexible, portable, low cost SiPM-based system for calcium sensing.

In this set-up the biological sample plate (with an area of ∼1 cm$^{2}$) is placed directly in contact with the sensitive area via an index matching grease. The detector in use is a Hamamatsu S13360-6050CS SiPM 6x6 mm$^{2}$ operated at 2.5V above the breakdown voltage, coupled to a custom, versatile and compact front-end electronics with a pole-zero cancellation filter. A full signal time development of 30 ns is reached in order to to be compliant with a single photon counting rate up to 2 MHz with a 5% probability of pile-up events. The system has been operated both in counting and gated current integration mode (separately and simultaneously) to cope with signal frequencies ranging from MHz level up to ∼100MHz.
In our experiments, the external stimulus that triggers intracellular [Ca$^{2+}$] release in the cells consists in the administration of adenosine-triphosphate (ATP) and the information of interest consists in both the intensity and the time development of the induced chemiluminescence signal, where anomalies are known to be correlated to the onset of age-age-rated and neurodegenerative diseases.

The SiPM system has been qualified in terms of sensitivity and linearity of the response varying the number of cells on the plate, over the range of biological interest. A good linearity with both photon counting and gated current methods is obtained, allowing to investigate different [Ca$^{2+}$] concentrations over a range of 5 order of magnitude. Moreover it was shown to be sensitive down to few cells on the field of view. Finally, a preliminary test was performed looking at the concentration of [Ca$^{2+}$] in mithocondria proving sensitivity also to induced signals in cellular subcompartments.
This prof-of-concept clearly showed the potential of the technique and identifies the specifications for the design of a dedicated system, targeting as well the integration of filters on a segmented SiPM area to measure simultaneously the concentration of fluorophores emitting at different wavelengths. This will open the possibility to engineer assays targeted to the simultaneous measurement of the activity in different subcellular compartments, providing a novel technique for studying genetic and age-related metabolic and neurodegenerative diseases at an early stage.

Speaker: Samuela Lomazzi (Università degli Studi dell'Insubria)

4.Lomazzi_Bari_4102019.pdf

10:40 → 11:20 Coffee Break

11:20 → 13:30 Industrial development and characterization methods: Part 1

Convener: Carla Aramo (NA)

11:20 Industrial Exploitation of SiPM Technology Developed for Basic Research

The Silicon PhotoMultiplier (SiPM) has been showing a growing interest in many field, from the fundamental research to the industry, where where very few photons must be detected and quantified with high precision. They are a good alternative to the Photo Multiplier Tubes (PMT) due to their compactness, low operational voltage and insensitivity to magnetic fields [1].
The FBK NUV-HD SiPM Technology [2], whose basic architecture is reported in Fig.1, has unique characteristics in terms of key parameters, as reported in Tab.1. These performances in the NUV spectrum, have attracted great interest from research institutes for large scientific experiments (like Darkside [4]). In order to satisfy the large volume required for such application, a technology transfer was done to LFoundry that has required the optimization and the re-engineering of several process steps. All the key parameters have been confirmed, demonstrating the intrinsic robustness of the chosen SiPM architecture and structure. Moreover, some behaviors have also been improved thanks to the integration into a fab already dedicated to a large volume production of optical sensors. Fig.2 shows the narrow distribution of the breakdown voltage, due to a more advanced process control. Also the leakage current has significantly decreased (Fig.3) due to the process steps already optimized for the reduction of the dark current into standard CMOS Image Sensors (CIS).
Such performances in a large volume manufacturing environment, have attracted electronic industries for large applications, especially in the medical field in the Near-UV range, but also in the automotive fields, requiring FBK and LFoundry to transfer also the NIR-HD technology optimized for the Near-IR range [4].
The process engineering capability at 8” will allow further optimization and development of SIPM with the introduction of dedicated module to further improve the performances, like, for example, the DiCT (Fig.4) and enlarge the working electromagnetic spectrum.

References
[1] Renker, D. Geiger-mode avalanche photodiodes, history, properties and problems. Nucl. Instrum. Meth. A 2006, 567, 48–56.
[2] A.Gola et al., Sensors 2019, 19, 308
[3] DarkSide Collaboration. “DarkSide-50 532-day Dark Matter Search with Low-Radioactivity Argon”. Physical Review D, 98 (2018): 102006. [ arXiv: 1802.07198 ]
[4] F.Acerbi et al., Nuclear Inst. And Methods in Physics Research, A, 912 (2018) 309-314

Speaker: Paolo Organtini (LFoundry, Avezzano, Italy)

LFoundrySiPM.pdf

11:40 In-Silico generation of random bit streams

Silicon PhotoMultipliers (SiPM) are rapidly approaching a significant maturity stage, making them a well recognised platform for the development of evolutionary and novel solutions in a wide range of applications for research and industry. However, they are still affected by stochastic terms, notably a high Dark Count Rate (DCR), limiting their use when single photo-electron pulses convey the required information, for instance in chemiluminescence or fluorescence analysis of biological samples. In such applications, randomness of the spontaneous generation of carriers triggering the avalanche and the rate of occurrences is significantly decreasing the sensitivity of the system against solutions based, for instance, on traditional photo-multiplier tubes.

However, unpredictability of the "dark" pulses has a potential value in domains connected to encryption and, in general terms, cybersecurity. "Random Power" is a project approved within the ATTRACT call for proposals (https://attract-eu.com), having as a main goal the generation of random bit streams by properly analysing the time sequence of the Dark Pulses.
The principle has been proven using laboratory equipment and its value assessed applying the National Institute of Standard and Technology (NIST) protocols, complemented by other test suites. The advantages against competing techniques have been thoroughly analysed and the development of a dedicated board, integrating the system in a low cost, low power, scalable design is on-going.

The principle, protected by a patent application entering its international phase by the time of writing (application no.102018000009064, deposited at the Office of the Minister of Economic Development, as required by the Italian law) will be described, together with the results obtained so far, the current development stage including an FPGA embedded Time-To-Digital Converter (TDC) and the future perspectives.

Speaker: Prof. Massimo Caccia (Università dell'Insubria)

MCa2019_Bari.pdf

12:00 Silicon Photomultiplier Technologies Developed at Fondazione Bruno Kessler

Since 2005, Fondazione Bruno Kessler (FBK, Trento) has continuously developed and improved its SiPM technology for a wide variety of applications, ranging from medical imaging to big science experiments and industrial applications. Current-generation Near Ultra Violet, High Density (NUV-HD) SiPM technology features a peak photon-detection efficiency (PDE) higher than 60% at 410 nm, low primary and correlated noise and is very well suited for medical imaging applications, such as time-of-flight positron emission tomography (TOF-PET). Indeed, using an advanced high-frequency readout, a research group at CERN demonstrated state-of-the-art coincidence resolving time of 58 ps FWHM, employing 4x4 mm2 NUV-HD SiPMs coupled to small LSO:Ce:Ca crystals. With a similar, optimized setup, a single-photon time resolution (SPTR) of 90 ps FWHM was also demonstrated, which is even more important when faint Cherenkov emission is used to improve timing performance in relatively slow scintillators such as BGO.
On the other hand, different applications require specific optimizations of SiPM parameters, especially in the field of big science experiments. To this end, several improvements of the NUVHD technology are ongoing, including reduction of optical crosstalk probability, optimization of SiPM performance for operation at cryogenic temperatures, for the readout of very large areas and for direct detection of vacuum ultra-violet (VUV) light, below 200 nm. Moreover, recent interest in using SiPMs in harsh radiation environment, such as in space missions or in accelerator experiments, poses additional challenges in detector optimization and partially redefines the typical design trade-offs.
At the lower-energy end of the sensitivity spectrum, we observe a growing interest from industry in using SiPMs for detection of near infrared light. Among different applications, the most important one is LIDAR, especially for advanced driver-assistance systems in the automotive field. NIR-sensitive SiPMs (NIR-HD) fabricated at FBK use a thicker epitaxial layer to enhance detection efficiency at longer wavelengths, achieving high PDE of 12 % 905nm, without micro lenses. Ongoing research is aimed at further improving this result by careful engineering of the SPAD structure.

Speaker: Alberto Giacomo Gola (Fondazione Bruno Kessler)

2019-10-01 - Alberto Gola - Custom FBK SiPM technologies - Bari workshop.pdf

12:20 Characterization of SiPM Avalanche Triggering Probabilities

Silicon Photo-Multipliers (SiPMs) have emerged as a compelling photo-sensor solution over the course of the last decade. In contrast to the widely used Photo-Multipliers Tubes (PMTs), SiPMs have high single Photon Detection Efficiency (PDE) with negligible gain fluctuations, are low-voltage powered, optimal for operation at cryogenic temperatures, and have low radioactivity levels. For these reasons, large-scale low-background cryogenic experiments, such as the next- generation Enriched Xenon Observatory experiment (nEXO), are migrating to a SiPM-based light detection system. The current generation of Vacuum UltraViolet (VUV) SiPMs achieve at best 25% PDE below 300 nm compared to more than 50% at 420 nm, being limited by reflections and charge carrier collection close to the surface. The aim of this talk is to show a quantitative understanding of the processes that affect the SiPM performances. In particular we will show how the SiPM PDE depends from the light quantum yield (number of electron-hole pairs produced per photon transmitted into the silicon) and how we can describe, for different wavelengths, the SiPM PDE as a function of the bias voltage using a minimum set of parameters extracting: (i) the relative contribution of electrons vs holes, (ii) the length of an effective photon collection region. We will then use this parametrization to describe the SiPM dark noise, after-pulsing and cross-talk. This characterization is part of the development of a new generation of VUV SiPMs with a very high efficiency in VUV (>50%) for operation in Liquid Argon and Liquid Xenon.

Speaker: Mr Giacomo Gallina (TRIUMF)

SiPM_presentation.pdf

12:40 Silicon Photomultiplier characterization on board a satellite in Low Earth Orbit

The LabOSat collaboration (acronym for "Laboratory On a Satellite") aims to increase the Technology Readiness Level (TRL) of electronic devices and components for space-borne applications. We have developed a single-board electronic platform which is able to operate in space conditions. This board harbors Devices Under Test and performs electric experiments on them. Since 2014, we have participated in six satellite missions (Satellogic small satellites) in Low Earth Orbits, in which we studied the performance of electronic devices such as resistive switching memories and dosimeters based on field-effect transistors.

In this work we present our efforts to increase the TRL of Silicon Photomultipliers (SiPMs). In early 2019 we have integrated four 6-mm SiPMs into a 40-kg satellite to study their performance in space. Each SiPM was encapsulated into individual light-tight aluminum housings, which included LEDs for excitation. The SiPMs and the LEDs are operated in DC current mode. Besides the SiPMs current and voltage measurements, the experiment also collects telemetry parameters like temperature, timestamp and orbital position.

Speaker: Federico Izraelevitch (UNSAM/CNEA/CONICET)

2019-10-04_Bari_SiPM_Izraelevitch.pdf

13:00 Discussion

13:30 → 15:00 Lunch

15:00 → 16:20 Industrial development and characterization methods: Part 2

Convener: Massimo Caccia (MI)

15:00 Cryogenic SiPM-based PhotoDetectors for DarkSide

The DarkSide collaboration is developing a new experiment capable of searching for dark matter with unprecedented sensitivity. The detector introduces many innovative technologies, among others the use of underground liquid argon, depleted in 39Ar to reduce the internal background, and the production of about 20 mq light sensitive low background surfaces, instrumented with SiPMs operating at 87 K. This talk will introduce the development in collaboration with FBK with the aim to produce SiPMs operating in cryogenic environment with low intrinsic noise, both primary and correlated (DCR < 80 mcps/mm2 and AP <15%) in high gain configuration (5-7 VoV). Then the talk will describe the technological transfer of the FBK technology to LFoundry, which was selected to mass produce the 200000 SiPMs required by the experiment.
Finally the design of a readout electronics capable to aggregate 25 cm2 of silicon detector with a SNR in excess of 24 and a time jitter of about 3 ns will be discussed.

Speaker: Alessandro Razeto (LNGS)

Cryogenic SiPM-based PhotoDetectors for DarkSide_Razeto.pdf

15:40 FBK VUV silicon photomultipliers optimized for cryogenic operation

Fondazione Bruno Kessler (FBK) has continuously developed and improved silicon photomultiplier technologies: in particular, one with peak efficiency in the blue region of the spectrum (near-ultra-violet, NUV), another one in the green (red-green-blue, RGB).
Over the last years there has been a growing interest in silicon photomultipliers applications at cryogenic temperatures (e.g.: for the detection of scintillation light from liquefied noble gases in rare-events experiments). One example is the DarkSide experiment, in which the 178nm scintillation light from LAr (87K), down-shifted to 430nm through TPB, is detected by silicon photomultipliers.
For this reason, a dedicated silicon photomultiplier technology has been designed and fabricated in FBK: the NUV-HD-Cryo. SiPMs made in such technology reach primary dark count rates of about 10 mHz/mm2 below 100K and an after-pulsing probability of about 15% when biased at 6V above breakdown.
In other experiments (e.g. in the nEXO experiment), direct detection of vacuum ultra-violet (VUV) light in cryogenic conditions is required. In this case, the sensitivity in VUV has to be combined with the advantages of the Cryo technology.
In this contribution, the latest results from the cryogenic characterization of FBK’s VUV-HD-Cryo technology will be presented. Among the produced devices, one promising split has been identified. In such split, the after-pulsing probability in liquid nitrogen amounts to 10% at 4V above breakdown, more than 6 times lower than a standard VUV-HD device at the same excess bias.

Speaker: Massimo Capasso (Fondazione Bruno Kessler)

16:00 Packaging strategies for large SiPM-based cryogenic photo-detectors

The DarkSide program aims to a WIMP direct detection using a dual phase argon time projection chamber. The next generation experiment, DS-20k, will be a detector in excess of 20 tonnes of fiducial mass. A pivotal aspect to the sensitivity of the experiment is its light detection technology. The DarkSide collaboration decided to adopt Silicon Photomultipliers for its Photo Detector Module (PDM). Each PDM includes a total active surface of 25 cm2 of SiPMs read-out by a front-end board capable of aggregating all the signal in a single analog output with a signal-to-noise ratio larger than 8. In this talk an overview of the silicon packaging strategies adopted by the DarkSide collaboration will be introduced with attention to the mass-production of about 10000 PDMs, corresponding to 200000 SiPMs and to the material selection in terms of cryogenic operation and high radiopurity.

Speaker: Izabela Anna Kochanek (LNGS)

packaging-for-DarkSide.pdf

16:20 → 17:00 Coffee Break

17:00 → 18:30 Industrial development and characterization methods: Part 3

17:00 Large Area Single Photon Sensors for Fast Applications

Silicon Photomultipliers (SiPMs) have been able to replace Photomultiplier Tubes (PMTs) and Avalanche Photodiodes (APDs) in many applications as they have significant advantages in some key aspects, especially the very high quantum efficiency compared to the established PMTs and the much higher gain (and lower excess noise factor) compared to APDs. However, SiPMs application in large area and fast detectors is an open question as the detector capacitance severely degrades performances (lower signal to noise ratio, worse timing resolution, wider pulse shape and therefore higher pile-up). We will present several developments which try to overcome this limitation. Those include Application Specific Circuits (ASICs) and a proposal for new generation of hybrid photosensors.

Speaker: Dr Sergio Gomez (IEEC-ICCUB)

4.Gomez_2019_10_04_SIPM_workshop_SG.pdf

17:20 Random Telegraph Signal fluctuations of the Dark Count Rate in CMOS SPADs

Single-Photon Avalanche Diodes (SPAD) are playing a significant role in the development of new generation photon-detectors for High-Energy and Astroparticle experiments. The excellent spatial and timing resolution achievable make it very attractive in astronomic imaging applications for the observation of fast transient phenomena.
For several employments large photosensor arrays are required. This could be satisfied by SPAD produced in CMOS technology which would benefit of low cost and of the possibility of additional pixel circuitry integration for signal processing.
In this work we studied the noise performances of two different SPAD layouts, designed and implemented in 150-nm CMOS process, after proton irradiation.
The two structures are characterized by different junction types: the first structure is constituted by P+/Nwell junction, while the second is formed by Pwell/Niso junction.
We focused our attention on Random Telegraph Signal (RTS) mechanism, consisting in the switching of the Dark Count Rate (DCR) between two or more discrete levels. The phenomenon is strictly related to the density and distribution of defects in the semiconductor lattice and oxides.
We investigated RTS effects before and after proton irradiation exposure to a 21 MeV proton beam. RTS occurrence has been measured in more than 500 SPAD pixels and the differences addressed in two layouts are motivated and discussed. The measurements show that RTS occurrence is correlated to doping profile of the device. For some RTS pixel of two layouts we performed measurements of the RTS characteristics: DCR level as function of excess bias voltage, RTS time constants as a function of the temperature. The measurements allow to formulate a hypothesis on type of defect clusters responsible for RTS. Understanding and modelling DCR fluctuations could be very useful to find and analyse defects in standard CMOS processes and to propose new solutions to limit their noise effects by design.

Speaker: Francesco Di Capua (Università Federico II di Napoli)

5.BARI-SIPM-DiCapua.pdf

17:40 Experimental and Extraction Procedure for the Electrical Characterisation of Silicon Photomultiplier Detectors

Silicon photomultipliers (SiPMs), owing to their low-level photon counting capabilities, have increased in popularity in the field of high energy astrophysics, particle physics and medical imaging. It is crucial to accurately characterise SiPMs so they can be optimised for a particular application such as the Compact High Energy Camera (CHEC-S) designed to image air Cherenkov showers. Extraction techniques applied to SiPMs can quantify opto-electrical parameters such as: gain; quenching resistance; junction, parasitic and grid capacitance; and slow and fast time constants. In this paper, we present electrical characterisations of two of the latest generation of SiPMs: Hamamatsu LVR3 S14520-6075 and Broadcom AFBR-S4N44C013. We apply and compare different extraction techniques to each sample, based on the Laplace Transform in the s-domain of the equivalent circuit model of an SiPM. These techniques typically utilise only the pulse tail, and therefore only parameterise the fast and slow fall times of the signal. We will discuss the improvement of existing methods that may be possible by including the discharge phase of the SiPM to parameterise the complete pulse including both the rise time and the fast and slow fall time constants.

Speaker: Mr Angaraj Duara (University of Leicester)

Angaraj_D.pptx

18:00 CAEN Award and concluding remarks

SiPMWorkshop_Concluding_Remarks.pdf