The recent detection of the merger of two high stellar mass black holes, thereby confirming the existence in nature of GW sources that have heretofore only been hypothesized, will surely influence the design of future GW detectors. Massive binary systems have luminosities allowing the advanced detectors to see them to cosmological distance and provide most of their SNR in the mid-to-low frequency band of GW interferometers. However, we must ensure, in our design efforts, that frequencies both above and below this range are also adequately covered. With aLIGO having completed its first observational run and now in full commissioning mode to prepare for the second run later this year, with aVirgo expected to join this next run once they have performed preliminary commissioning, and with KAGRA in an advanced construction phase, we are entering the regime of observational astronomy using GWs. This is a propitious time to consider the impact of GW150914 on ideas for near term detector enhancements as well as on the design of future detectors. This workshop will explore a variety of technologies and concepts relevant to these goals.
At GWADW 2015, in Alaska, a new format was introduced which had two days of parallel sessions. The new format was deemed successful, and we will repeat it this year with slight variations. There will be three parallel sessions instead of last year’s four, and these will be spread over three days, instead of two, thereby providing more time to interact.
Plenary 3 - Workshop goalsSala Maria Luisa (La Biodola, Isola d'Elba)
Sala Maria Luisa
La Biodola, Isola d'Elba
Dennis Coyne(LIGO Lab), Eric Gustafson(Caltech), Fabrice Matichard(MIT), Giampietro Cagnoli(LMA - UCBL), Iain Martin(University of Glasgow), Jan Harms(FI), Jo van den Brand(Nikhef - VU), Riccardo Bassiri(Stanford University)
A. Low frequency
Jan Harms(FI), Jo van den Brand(Nikhef - VU)
B. Introduction to thermal noise workshop and goals
GIANPIETRO CAGNOLI(LMA - UCBL)
Dennis Coyne(LIGO Lab), Fabrice Matichard(MIT)
coffee breakParking area (La Biodola, Isola d'Elba)
La Biodola, Isola d'Elba
Plenary 4 - CryogenicsSala Maria Luisa (La Biodola,Isola d'Elba)
Sala Maria Luisa
La Biodola,Isola d'Elba
Kazuhiro Yamamoto(Institute for Cosmic Ray Research, The university of Tokyo), Kentaro Somiya(Caltech), Seiji Kawamura(ICRR - The University of Tokyo)
Cyogenics session overview
Giles Hammond(University of Glasgow)
Overview of the 20 K configuration
KAZUHIRO YAMAMOTO(Institute for Cosmic Ray Research, The university of Tokyo)
Overview of the 120 K configuration
Christopher Wipf(Caltech LIGO)
Cryogenics Round Table
Christopher Wipf(Caltech LIGO), Giles Hammond(University of Glasgow), KAZUHIRO YAMAMOTO(Institute for Cosmic Ray Research, The university of Tokyo), Rana Adhikari(Caltech), Ronny Nawrodt(Friedrich-Schiller-University Jena)
Atomic structure investigations of amorphous coatings
Riccardo Bassiri(Stanford University)
Modeling coating thermal noise for gravitational wave detectors
Chris Billman(University of Florida)
New results on losses correlation with structure
Low frequency workshopSala Maria Luisa
Sala Maria Luisa
Hotel Hermitage, La Biodola, Isola d'Elba
Towards Low Frequency Gravitational Force Sensing
Bram Slagmolen(The Australian National University)
TOBA: a Low-frequency Gravitational-Wave AntennaMasaki
Masaki Ando(Univ. of Tokyo)
Sensitivity limits of atom interferometry gravity gradiometers and strainmeters
Fiodor Sorrentino(INFN - Genova)
Thermal noise & coatings workshopSala Elena
Hotel Hermitage, La Biodola, Isola d'Elba
lunchFuoco di bosco
Fuoco di bosco
Hotel Hermitage, La Biodola, Isola d'Elba
Plenary 5 - LISA PathfinderSala Maria Luisa
Sala Maria Luisa
Hotel Hermitage, La Biodola, Isola d'Elba
Stefano Vitale(MIT - LIGO)
LISA in the post detection and post LISA Pathfinder era
Karsten Danzmann(AEI Hannover)
Toward LISA in the USA
John Conklin(University of Florida)
LISA Pathfinder scientific operations
Hotel Hermitage, La Biodola, Isola d'Elba
A high-isolation, low-loss, in-vacuum, thermally-controlled Faraday isolator
A novel simple Faraday isolator system allowing for a good isolation factor and low throughput losses, under high vacuum and exposed to a source of medium-near infra-red continuous laser radiation is presented. An isolation factor as high as 40dB and losses lower than 3% can be reached in the presented set-up. The mechanical and optical configuration is detailed and the performances achieved are presented.
A study of contamination in gravitational wave detectors
The cryogenic sapphire mirrors in KAGRA are expected to suffer from many contaminations due to dust adhesion and gas molecules. The contamination due to dust particles is occurred during their installation process. The cryogenic contamination effect has not been studied correctly in the actual KAGRA cryostat system. To estimate these possible total contaminations in the cryostat, we firstly try to find how much dust is put on mirrors and how much optical loss will be generated from various size of dust. For this purpose, we prepared high reflective mirrors contaminated by the NIST traceable standard particles that have uniform size and the optical loss was checked by the storage time and transfer function of Fabry-Perot cavity composed of these contaminated mirrors. The distribution density of the NIST particle on mirrors was checked by microscope and image analysis method. As the next step, we are going to measure the dependence of optical loss on the number and size of particles.
MrKunihiko Hasegawa(Institute for Cosmic Ray Research, the University of Tokyo,)
A Tunable Resonant Detector for Low Frequency Gravitational Waves
All practical proposals to detect low frequency gravitational waves in the frequency range 0.001 Hz to 0.1 Hz involve multi-satellite spaceborne devices with laser interferometry over very large distances. Here I outline the concept study of a single resonant interferometer detector operating within a single drag-free satellite, capable of strain sensitivity better than 10^-20/√(Hz) for gravitational waves in the frequency range 0.001 Hz to 0.1 Hz. The resonance frequency and bandwidth are optically tunable, enabling continuous tracking of slowly evolving massive BH binary sources emitting in this frequency range. The interferometer operates in the Fabry-Perot mode with weakly coupled mass-mirrors with low resonance frequency and high Q, and a near-resonant auxiliary laser tunes the frequency using optical spring effect. The F-P cavity and moderate Q enables resonant strain sensitivity about 10^-20/√(Hz) and tunability enables resonant tracking for long integration.
Prof.CS Unnikrishnan(Tata Institute of Fundamental Research, Mumbai, India)
Ambient seismic noise and its potential use in seismic exploration and monitoring
We investigate to what extent subsurface information can be extracted from ambient seismic noise. Seismic noise is always present in seismic records and can be measured around the world, even in the quietest deserts. This makes noise an excellent candidate for seismic exploration or monitoring (and a nuisance for gravitational wave detection). The modal structure and strength of the noise field depend on several factors, such as noise-source distribution and mechanism, depth of observation, atmospheric conditions, geographical location of observation, local geology, regional tectonic activity, etc. We study the characteristics of seismic noise in the frequency range 0.05-10 Hz. We discuss the measurement and analysis of seismic noise and present results from experiments in The Netherlands, Libya, Egypt and Saudi Arabia. Next, we review methods to extract subsurface information from noise. Finally we show examples of successful surface-wave or body-wave retrieval from seismic noise.
Xander Campman(Shell Global Solutions International B.V.)
Amorphous silicon as low loss, high refractive index material for dielectric mirror coatings
The dielectric mirror coatings in aLIGO are made of alternating layers of silica and tantala. Such materials exhibit high mechanical loss at low temperature, therefore reducing the advantages of cooling as the primary solution to coating thermal noise. Amorphous silicon is a promising candidate as a replacement of tantala as high refractive index material in a Bragg stack. Having a refractive index higher than tantala, it allows for thinner layers, its low loss enables low thermal noise coatings. High optical absorption is the main limitation in exploiting aSi. We report on the characterisation of optical absorption and microscopic structure of amorphous silicon films.
MrZeno Tornasi(University of Glasgow)
Angular control of Advanced Virgo suspended benches
Most of the Advanced Virgo light sensing devices are located on 5 in
vacuum suspended benches. The benches are suspended from a triple
stage mSAS suspension, and the angular degrees of freedom are sensed
and controlled from the ground using LVDTs and coil-magnet
actuators. The angular control has stringent requirements 30 nrad rms
and 3e-15 rad/rtHz above 10 Hz. After introducing the system design,
we present the first in air results of controlling the fully
integrated system and striving to achieve these requirements.
Characterisation of the aLIGO monolithic suspensions
At Glasgow we are working to improve the characterization of the aLIGO detector monolithic suspensions.
We have utilized realtime monitoring software to extract frequency, phase and amplitude of the fused silica suspension fibre violin modes. This has allowed the measurement of the Q-factors of some of these modes.
In addition, we have used preliminary FEA modeling of the fibre profiles, measured during aLIGO detector suspension installation, to predict the observed departure of the frequencies of violin mode harmonics from whole multiples of the fundamental frequency.
Using these analysis techniques for the lower glass stage of the suspension, in the future we shall compare the measured violin mode Q values with detailed FEA modeling of the aLIGO detectors monolithic suspensions. This information will help to better understand the aLIGO detectors low frequency noise performance.
DrBorja Sorazu(University of Glasgow)
Coil-Coil Actuator for reduction of magnetic noise
For reduction of magnetic noise of coil-magnet actuators, we developed a new type of actuator; coil-coil actuator. It consists of only coils instead of magnet and current applied to the coils is modulated. We can choose any modulation frequency to reduce ambient magnetic noise coupling, while keeping the actuation force sufficiently strong. In this poster, we show our experimental results for evaluation and reduction of the magnetic noise of a coil-coil actuator.
MrNaoki Aritomi(University of Tokyo)
Comparison of ring-Sagnac and sloshing-Sagnac interferometer
Speedmeters are becoming interesting for third generation gravitational wave detectors. Here we compare a new kind of sloshing-Sagnac interferometer with the ring-Sagnac interferometer. The sloshing-Sagnac requires only linear cavities and has alternating resonant and anti-resonant cavities, which act as a type of Khalili-cavities. These have the potential advantage of allowing a reduction of the coating thermal noise. Here we evaluate the quantum noise limited sensitivity and the coating noise reduction compared to a conventional position-meter (such as Advanced LIGO).
DrSabina Huttner(University of Glasgow)
Cryogenic mechanical loss of IBS silica
Coating thermal noise is the limiting factor for detector strain sensitivity in the most sensitive frequency band. Future gravitational wave detectors are proposed to operate at cryogenic temperatures, where the mechanical loss of the low-index, amorphous silica coating layers is not well characterized and stands to be the dominant source of noise in the multi-layer mirror coating stack if amorphous silicon is found to be a viable replacement for the high-index layers (currently 25% Ti:Ta2O5). The low temperature mechanical loss of ion-beam sputtered silica is presented for a number of post-deposition heat treatments.
MrRaymond Robie(University of Glasgow)
Developing a squeezed light source at Virgo site
Recent works (AEI-GEO600 and LIGO collaboration) demonstrated that the squeezing technology is one of the major and more urgent upgrades of the 2nd generation of GW detectors. They demonstrated also that to completely benefit from the injection of a squeezed state into the ITF (IFO), frequency dependent squeezing is a must. The LIGO collaboration already started to realize his own freq. dependent squeezer, to be implemented into the ITFs.
In this framework, I’ll present the steps undertaken from various INFN groups to realize a first prototype of freq. independent squeezer with the specific aim to be implemented in Advanced Virgo.
Development of ultra-low optical and mechanical loss aSi coatings using novel ECR ion beam deposition
Brownian thermal noise associated with the multilayer mirror coatings continues to limit the sensitivity of GW detectors within their most sensitive frequency band. Currently these coatings are fabricated using ion beam deposition (IBD), delivering sub-ppm-level optical absorption and ppm-level scatter. However, further reductions in mechanical dissipation will be essential to fully exploit planned upgrades to Advanced LIGO, e.g. squeezing. Researchers at UWS and UoG have developed a new generation of IBD. The ion source uses electron cyclotron resonance (ECR) within a λ/4 microwave (2.4GHz) cavity to produce an ultra-clean (filament-free) plasma and incorporates a gridless extraction supplying ion energies up to 15keV. Initial results of aSi films show optical absorption of 20ppm at 1550nm for a λ/4 stack (tenfold reduction) with an upper limit on the mechanical loss of 1.2e-4 (factor of 2 reduction over Ta2O5). Details of heated substrate deposition (up to 500C) are also presented.
MrDavid Vine(SUPA, University of the West of Scotland)
Dynamics of Fiber Amplifiers in the Context of Gravitational Wave Detectors’ Laser Sources
After the first direct detection of gravitational waves, the GW community faces the challenge of improving the frequency range and sensitivity of the next generation of GWDs. Two approaches to achieve it are the power scaling of laser sources and the use of cryogenically cooled crystalline silicon-based optical components, which requires the operation at longer wavelength. These improvements need new concepts of laser sources that are not totally defined yet. Fiber amplifiers in Master Oscillator Power Amplifier (MOPA) configuration are demonstrating to be good candidates to meet the requirements of the next generation of GWDs. In this work we study the non-linear processes of gain and temporal dynamics in Er-doped, Yb-doped and Er:Yb-codoped fiber amplifiers with the aim of developing single-frequency, high-power fiber sources at 1μm and 1.5μm with long-term stability. The study of the amplifier dynamics also provides valuable information to realize stabilization loops.
MrOmar de Varona(LaserZentrum Hannover)
Electromagnetic Derivation of Thermal Noise in Grating Reflectors
Coating thermal noise is known to be a crucial limitation of future gravitational wave detectors’ sensitivity. As a potential solution for this issue is given by replacing conventional multilayer based optical components by monolithic crystalline grating reflectors. In this contribution thermal noise in grating reflectors is directly related to the electromagnetic field distribution in these structures. The presented results enable the physical understanding of noise processes in grating reflectors and provide the possibility for a targeted optimization of the structure parameters for minimized thermal noise in the future.
Stefanie Kroker(Braunschweig University of Technology, Physikalisch-Technische Bundesanstalt)
Environment at the underground GW detector KAGRA
KAGRA is an interferometric gravitational-wave (GW) detector with 3-km arms in Japan.
One of the main features of KAGRA is that it is constructed underground of the mountain.
The underground has been considered to be suitable for the GW detectors since the environmental noise, such as seismic noise, is smaller.
On the other hand, there are several problems characteristic in underground, such as spring water.
In this poster, we will explain the current situation inside the KAGRA tunnel, using the environmental data took at the KAGRA site, such as seismic level, humidity, temperature, and so on.
Factors pertaining to the strength of four-fiber monolithic silica test mass suspensions.
The diameter of the silica fibers used in the 40 kg quasi-monolithic aLIGO test mass suspensions was chosen as d = 400 µm to keep the bounce frequency below 10 Hz, and the violin mode frequencies above 500 Hz. For further improvement of detector performance at low-frequency reducing the vertical bounce mode frequency (linearly proportional to the fiber diameter) would be beneficial. A. Heptonstall et al suggested that the fiber diameter can be reduced to 288 µm; this thickness is sufficient to give a fiber strength three times larger than the static load in aLIGO suspension (still providing a reasonable safety margin). We analyze the strength of welded 4-fiber suspension. The additional factors such as strength of welded joints or stock misalignments may limit the suspension strength. The fiber's thickness is one of the few competitive limiting factors. In such case the fiber's diameter can be made near 300 µm and the full suspension strength should not be significantly affected.
DrKirill Tokmakov(University of Strathclyde, Glasgow, UK.)
FINESSE 2.1 - with Multimode Squeezing
FINESSE is a free and open source frequency domain modelling software for optical experiments. FINESSE and its Python wrapper PyKat are used in commissioning and design of gravitational wave detectors. We have recently enabled for modelling of multimode squeezing and parametric instability. The parametric instability model has successfully been tested against first experimental results. Further we announce a web page for learning gravitational wave laser interferometry, FINESSE and PyKat. The material is available in HTML and IPython/Jupyter Notebook formats, and is thought to serve as both self-study material for beginners as well as reference material for experienced users.
MrDaniel Toyra(University of Birmingham)
High power fibered electro-optics components
We want to design a fibered electro-optic modulator and a fibered Faraday isolator able to withstand power greater than 100W. The aim of such components would be to simplify the path between the laser, possibly a fiber laser, and the under vacuum injection bench. By doing that we will reduce in particular the beam jitter noise.
The main difficulty is about the fiber itself: how to keep a good beam quality (TEM00, polarization, noises...) while avoiding all the non linear effects that appear in fibers for such densities of power?
Here we present an active method to keep a stable injection and avoid the noises coming from a misalignment between the input beam and the fiber. The error signal that we use is generated by a scan of the input of the fiber.
We also present the investigations on a Large Mode Area fiber. Especially the compromise that has to be found between the quality of the output beam and the power that can be reach before facing Stimulated Brillouin Scattering.
Matthieu Gosselin(EGO, European Gravitational Observatory)
Indium bond research for crystalline cryogenic suspensions
Pure indium bonds to itself and non-metallic substrates like fused silica with comparable ease. Its vacuum compatibility, thermal conductivity , malleability and low mechanical loss [2,3] and low melt point also make it a good candidate for use in cryogenic systems. Currently it is proposed for use in the sapphire KAGRA suspensions  as well as a possibility for the silicon interfaces of the future ET detector . This poster explains two approaches to achieve strong, low noise indium bonds. One using layers of indium nanometres thick evaporated onto silicon substrates and bonded at the Institute for Gravitational Research in Glasgow. A second approach uses inductive heating of indium foil between sapphire substrates with the aim of bonding suspensions in a detector in-situ, conducted in part at the ICRR in Tokyo, Japan.
MsMargot Phelps(Institute for Gravitational Research, University of Glasgow)
Installation of Input Mode Cleaner of iKAGRA
I installed Input Mode Cleaner(IMC) in iKAGRA and did mode-matching for IMC using two lens. IMC is a big triangle cavity.
MrShogo Kambara(University of Toyama)
Investigation of Suspension Upgrades for the Advanced LIGO Gravitational Wave Detector
To increase the sensitivity of the current interferometric gravitational wave detectors,
an upgrade plan for the US based detectors, or “Advanced LIGO (aLIGO),” is being
studied. As part of this upgrade, changing the mass, stress, and length of the suspension for
the mirrors in the interferometers is considered to improve noise sources. From the previous
year’s Matlab modeling result, the higher stress in the fibre and the longer last stage showed
improvements in the detector’s sensitivity. Since the last stage of the suspension is held by
fused silica fibres, which have very low loss to minimise suspension thermal noise, one of the
challenges for this upgrade will be producing thinner and longer fibres that can hold the test
mass safely. In this report, the impact laser stabilisation on fused silica fibres’ geometry and
strength is being investigated to allow further improvements on fibre production to achieve
Kyung Ha Lee(University of Glasgow)
Large band low frequency sensors based on Watt’s linkage for future generations of interferometric detectors
We present a compact and light low frequency sensor based on a horizontal folded pendulum mechanical design. The device can be used as an inertial sensor for the control system of seismic attenuators of present and future gravitational wave detectors.
The instrument has been developed by the Applied Physics Group of the University of Salerno while the readout, control electronics and software by the INFN Pisa Group.
Laser power stabilization for future gravitational wave detectors
The fundamental limit of all future generation of interferometric gravitational wave detectors, namely quantum radiation pressure noise and photon shot noise, can only be reached with an improved laser power stability. The traditional active power stabilization schemes have also a fundamental limit set by the quantum noise (shot noise) in the sensing process which is bound by technical limitations of the maximal detectable power. In this poster we study a new scheme for power stabilization in which power fluctuations are transferred to another observable, the phase of the light field. The great advantage of such a scheme is to use the full beam power in the transfer process, and hence not be limited by the relative shot noise in the sensing process used by the traditional schemes. We present different experimental setups and also their sensitivity to detect relative power fluctuations of 10-9/sqrt(Hz).
MsMarina Trad Nery(Albert Einstein Institute)
New OSEM results using a displacement-doubling prism-based flag
The suspension systems for future Gravitational Wave (GW) detectors require an improved level of immunity to sources of mechanical perturbation of their suspended test-masses. The displacement sensors used to mitigate such perturbations (OSEMs) need to be upgraded for improving their performance in frequency range < 1 Hz. The conceptual design of displacement shadow sensors utilising a ‘displacement doubling prism’  is presented.
Reference: 1. N.A. Lockerbie, Nucl. Instrum. Meth. A, 741 (2014) 192–195.
DrNicholas Lockerbie(University of Strathclyde)
Optical levitation of a mirror
An optomechanical device reaching the standard quantum limit (SQL) of a force measurement plays a prominent roll for studying quantum mechanics. To prepare such a device, a mechanical oscillator well isolated from the environment is essential for the reduction of thermal disturbances. Here we propose an optical levitation of a mirror with two vertical Fabry-Perot cavities linearly aligned. We show the stability of the system and demonstrate the feasibility of reaching the SQL with this system.
DrYuta Michimura(Department of Physics, University of Tokyo)
Photoelasticity of Silicon and its temperature dependence
The photoelastic coefficients p11-p12 and p44 of silicon for light of a wavelength of 1550 nm was measured using a rotating quarter wave plate polarimeter. The results p11-p12 = (-0.1139±0.0014) and p44 = (-0.0501±0.0014) for room temperature agree well with previously published data for various wavelengths. Additional measurements for the temperature dependence of the p11-p12 coefficients were done using a similar setup combined with a cryostat allowing sample temperatures down to about 10 K. The measurements show a temperature dependence with a maximum deviation of about 10% relative to the room temperature value.
Rene Glaser(FSU Jena / IFK / TTP)
Reduction of quantum noise for gravitational wave detector KAGRA (I)
The design sensitivity of bKAGRA is limited by quantum noise for almost all the observation frequency band. As the first detection of gravitational waves by Advanced LIGO shows, it would be especially important to improve the sensitivity around 100 Hz, where radiation pressure noise would be dominant. To reduce radiation pressure noise and beat the standard quantum limit, a method where the ponderomotively-squeezed output field from the interferometer is detected with homodyne detection was proposed.
For the demonstration of the technique to reduce radiation pressure noise, an experiment with a cavity which has a milligram-scale suspended mirror as a end test mass is ongoing in our laboratory. In this presentation, overview and current status of the experiment are presented. Especially, a new method of intensity stabilization of light for the reduction of classical radiation pressure noise below quantum radiation pressure noise is presented.
MrYutaro Enomoto(ICRR, University of Tokyo)
Reduction of quantum noise for gravitational wave detector KAGRA (II)
In KAGRA, a ponderomotive squeezing technique with a homodyne detection is going to be used for reducing radiation pressure noise. For demonstrating the reduction technique, at first, radiation pressure noise should be observed in wide frequency range. For that purpose, the high finesse Fabry-Perot cavity with a suspended tiny mirror is used for enhancing radiation pressure noise. However, when the intracivity power increases, an angular instability generated by radiation pressure can occur in the cavity depending on the geometry of the cavity. For circumventing the angular instability of the cavity, an angular control system using radiation pressure itself was invented. It was confirmed experimentally that the cavity consisting a suspended 23-mg mirror was unstable without the angular control system under high intracavity power condition. Moreover, with the same intracavity power condition, it was also proved that, using the angular control system, the cavity could be operated stably.
Reduction of Seismic Coupling Noise for TOBA
TOBA(TOrsion-Bar Antenna) is a gravitational wave detector using a torsion pendulum. The resonant frequency of torsional motion is ~1mHz, therefore it is sensitive to gravitational waves at lower frequency band (0.1-10Hz) even on the ground. Two prototype TOBAs were developed and they achieved strain sensitivity h ~ 1e-8/rtHz @0.1Hz - 1e-10/rtHz @5Hz. One of the dominant noise sources for them was seismic noise, especially coupling noise from translational seismic motion to test mass rotation. In order to improve the sensitivity and detect gravitational waves, it is indispensable to reduce this coupling noise. Here we show the specified five coupling routes and reduction methods for them.
Tomofumi Shimoda(University of Tokyo)
Reduction of Virgo Low Frequency environmental magnetic noise
Mitigation works recently done in AdVirgo aiming to a reduction of low frequency magnetic noise pollution in experimental sensible areas.
Silicate bonding extends to the photonics industry
Silicate Bonding has been used to assemble fused silica suspensions with low mechanical loss in quasi-monolithic optical systems for space missions aimed at tests of GR and in ground-based GW detectors. The technique also has broader applications including the construction of compound optical systems capable of withstanding high laser powers. Study of the optical properties of components assembled using this technique is thus of interest. We report on the bonding of phosphate glass and the measurement of some of the properties of the bond: optical index,thickness, reflectance and Light Induced Damage Threshold (LIDT). The measured reflectance at 532nm is below 0.3% while the LIDT at 1535nm is 650MW/cm^2 (6.5J/cm^2 ). Both these values are in line with the usual requirements for high power lasers which opens the way to promising applications. Future work should focus on extending the measurements and bonding other materials for applications in photonics such as YAG or sapphire.
MrGregoire Lacaille(Gooch and Housego)
The input optics for iKAGRA
In this poster, the summary of the input optics for the iKAGRA(initial KAGRA) will be reported.
The iKAGRA operation was done in March and April in 2016. The input optics for iKAGRA includes the PSL(pre-stabilized laser), the IMC (input mode cleaner), IFI (input Faraday isolator) and IMMT(input mode matching telescope). In this poster mainly the PSL and the IMC will be reported.
Thermal conductivity of bonded materials for future generation gravitational wave observatories
Future generations of gravitational wave detectors plan to use cryogenics in order to further reduce thermal noise associated with the mirror test masses and their suspensions. Characterising the thermal conductivity of the candidate materials for these mirror suspension systems (e.g. single-crystal silicon and sapphire), and quantifying the optimum heat flow through compatible bonding techniques for these materials, is therefore crucial. Preliminary results are presented here for hydroxide catalysis bonded silicon (100) samples of combined dimension 5x5x40mm. These results show a lower limit for the thermal conductivity of the bond at the level of 0.059 W/m/K. Studies will continue in order to better evaluate the thermal conductivity of hydroxide catalysis bonds, and investigate methods by which it may be optimised.
MrsMariela Masso Reid(Institute for Gravitational Research/University of Glasgow)
Thermo-refractive noise measurement in the Advanced Virgo Output Mode Cleaner
The Advanced Virgo OMC is composed of two monolithic cavities placed in
series. The light is resonating in the fused silica substrate, which
yields a length noise bounded by thermo-refractive noise.
After introducing the specifications on the OMC length noise, tests and
results of length-noise measurements at the level of the thermo-refractive-noise will be presented.
We will also discuss the impact of the thermo-refractive noise on future detectors.
Thermoelastic damping in silicon and metallic discs: the mode-dependent branching effect
For mechanical resonators in the acoustic band, thermo-elastic noise can be the dominant contribution to the thermal noise spectrum. Silicon membranes show a prominent thermoelastic peak below few kHz; silicon is widely used in precision applications and it represents a suitable solution for the test masses of future cryogenic GW detectors. We measured with GeNS the thermoelastic loss in a set of silicon disk samples, and found a dependancy of the loss angle upon the normal mode geometry. This behavior is deduced from the general theory in free disks but, to our knowledge, it was not yet shown in experiments. We also demonstrated that this feature is seen in homogeneous CuBe disks, proving that it is not related to the silicon anisotropy. We present the results of our measurements and a new theoretical approach exploiting the entropy increase; eventually, the mode-dependent loss is explained in terms of the ratio among dilatation energy and total elastic energy.
TOBA: a Low-frequency Gravitational-Wave Antenna
We are developing a new-type of gravitational-wave antenna, named TOBA (TOrsion-Bar Antenna). I will present the current status of our reaesch activities.
Prof.Masaki Ando(University of Tokyo)
Trade-offs for squeezed light injection in a non-perfect world
Emil Schreiber(Albert Einstein Institute Hannover)
Twin Signal Recycling for the Einstein Telescope
The Einstein Telescope (ET) is a third-generation gravitational wave observatory with a target sensitivity of more than an order of magnitude higher than the current advanced detectors. ET will be located underground,consisting of three nested detectors, each of which is composed of two interferometers in xylophone configuration. In this poster we revisit the technique of Twin Signal Recycling (TSR), which leads to simultaneous resonant enhancement of both the upper and the lower signal sidebands. A comparison of this technique for a futuristic GEO-HF with arm cavities and ET-LF is also discussed here. For the latter, a preliminary attempt at a broadband reduction in quantum noise limited sensitivity by use of frequency dependent squeezing has been simulated using the numerical interferometer simulation package Finesse. The benefits of both these techniques are weighed by measuring the quantum noise limited sensitivity of ET-LF detuned signal recycling with twin signal recycled ET-LF.
MsVaishali Adya(Leibniz Universität Hannover / AEI)
Ultra-quiet Mirror Suspensions for the Glasgow Sagnac Speed Meter
The main goal of the Glasgow Sagnac Speed Meter is to show reduced back action noise compared to a Michelson interferometer with equivalent parameters. In order to ensure limitation by back action noise the input test masses of the two triangular arm cavities are chosen to be 1g mirrors. To achieve the necessary isolation from seismic motion all optics need to be suspended by multi-cascaded pendulums. This poster presents the different suspension designs used in this proof of concept experiment and highlights the challenges for the 1g mirror suspensions.
MrJan-Simon Hennig(University of Glasgow)
Vibration Isolation System for KAGRA: Overview and Results in the First Operation
KAGRA is a Japanese interferometric gravitational-wave telescope with an arm length of 3 km. Main features of KAGRA are 1) placing underground and 2) cooling down mirrors to cryogenic temperature. The test operation with room temperature is over in April 2016.
We achieve vibration isolation of mirrors with long multistage suspension systems called seismic attenuation systems (SAS.) Each stage has functions to lower its resonant frequency. Because the whole of suspension system has to be operated with the interferometer, its control system becomes very complicated. I report an overview of KAGRA's vibration isolation systems and results of suspension performance in the first operation.