Status of Advanced Virgo Jo van den Brand, Nikhef and VU University Amsterdam, jo@nikhef.nl KAGRA International Workshop, Taiwan, May 22, 2017
Advanced Virgo Virgo is a European collaboration with about 280 members Advanced Virgo (AdV): upgrade of the Virgo interferometric detector Participation by scientists from France, Italy, The Netherlands, Poland, Hungary, Spain • 20 laboratories, about 280 authors APC Paris INFN Perugia LAPP Annecy Nijmegen − − − ARTEMIS Nice INFN Pisa LKB Paris RMKI Budapest − − − − EGO Cascina INFN Roma La Sapienza LMA Lyon Univ. of Valencia − − − − INFN Firenze-Urbino INFN Roma Tor Vergata Nikhef Amsterdam − − − INFN Genova INFN Trento-Padova POLGRAW(Poland) − − − INFN Napoli LAL Orsay – ESPCI Paris RADBOUD Uni. − − − Funding approved in Dec 2009 • 21.8 ME CNRS and INFN • 3.5 ME Nikhef in kind contribution Goal: be part of the international network of 2nd generation detectors Short-term goal: join the O2 run in 2017 6 European countries 2
Advanced Virgo Dedication There was a dedication ceremony for Advanced Virgo on February 20, 2017 3
Advanced Virgo Dedication Fulvio Ricci has been leading Virgo through interesting times. Giovanni Losurdo is project leader of Advanced Virgo. Project will end on the day that Virgo joins O2 4
Advanced Virgo design Advanced Virgo features many improvements with respect to Virgo and Virgo+ For 2017 • Larger beam • Heavier mirrors • Higher quality optics • Thermal control of aberrations • Stray light control • Improved vacuum For the period 2018 to 2019 • 200 W laser • Squeezing • Signal recycling • Newtonian noise subtraction 5
Sensitivity targets Advanced Virgo features many improvements with respect to Virgo and Virgo+ Phase 1: Configuration similar to Virgo+ Phase 2: Configuration for best sensitivity Virgo+ Phasing decided to increase the chance to reduce the time gap with LIGO Early configuration Late configuration 6
What was achieved so far … 7
What was achieved so far … Substantial infrastructure work MAIN HALL, SPRING 2013 FALL 2013 8
Extreme mirror technology Mirrors were realized that feature low losses, low absorption, and low scattering properties Features: - 42 kg, 35 cm x , 20 cm thick - Flatness < 0.5 nm rms - Micro-roughness: 0.1 nm rms - Optical absorption < 0.5 ppm 9
Extreme mirror technology “Coating of the mirrors at LMA Features: - 42 kg, 35 cm x , 20 cm thick - Flatness < 0.5 nm rms - Micro-roughness: 0.1 nm rms - Optical absorption < 0.5 ppm 10
Payloads Payloads are designed to suspend both optics and baffles 11
Superattenuators No principal changes, but significant refurbishing 12
Suspended benches All photodiodes are isolated to minimize effects from scattered light 13
Vibration isolation systems to host sensors Multi-stage vibration isolation systems (6 + 1) were produced for Advanced Virgo. In addition, 7 pre- isolators have been designed, produced and delivered to KAGRA One blade failure due hydrogen embrittlement in maraging steel spring blades
Instrumentation contributions to Advanced Virgo Optical systems for linear alignment, vibration isolation, IMC and phase camera’s, etc. Detection bench
Instrumentation contributions to Advanced Virgo Optical systems for linear alignment, vibration isolation, IMC and phase camera’s, etc. Detection bench
Optical sensors Linear alignment sensors and phase camera’s have been designed and fabricated at Nikhef. All sensors have been installed, and commissioning is ongoing. Part of Thermal Compensation System Imaging of cavity fields • Reference beam from carrier AOM shift by 80 MHz • Interferometer output Combine on beam splitter • Image carrier and side-bands f1 = 6.270 777 MHz Phase camera f2 = 56.436 993 MHz f3 = 8.361 036 MHz f4 = 131.686 317 MHz f5 = 22.38 MHz • Amplitude and phase CO 2 laser for adaptive Reference beam High speed imaging of HOM Sample beam corrections of HOM Correct aberrations with CO2 lasers • Digital demodulation 14 bit ADCs at 500 MSPS Xilinks Virtex-7 FPGA
Extensive baffling Baffles are applied to minimize scattered light 18
Thermal compensation system TCS is applied to compensate thermal induced optical aberrations 19
Thermal compensation system TCS uses CO2 laser beams incident on compensation plates near input test masses 20
Vacuum system Biggest ultra-high vacuum system in Europe 21
Vacuum system The pressure in the vacuum system was lowered by applying cryogenic vacuum links 22
Advanced Virgo project logistics Project was completed within budget on August 2016, but schedule slipped by about 9 months w.r.t. TDR (2012). Project performance: sensitivity improvement to be determined soon Fellowships: To reduce performance/schedule risk (at the expense of budget risk), part of project contingency turned into contracts/fellowships upon Council authorization 23
Issues The Advanced Virgo project had to overcome a few hurdles 24
Issues encountered during construction Broken superattenuator blades, and broken monolithic suspensions 25
Antispring blades Mirrors were realized that feature low losses, low absorption, and low scattering properties System for vertical vibration isolation • Made of a special steel (maraging) studied to prevent creep • In use since ~15 years 13 blades broken (out of about 350) Cause identified: hydrogen embrittlement • Due to excess H concentration in the bulk Risk mitigation: all the blades showing possible defects in the protective Ni coating have been replaced • About 40% of the total Incurred project delay about several months 26
Filter stage of a Virgo superattenuator Damaged maraging steel spring blades 27
Monolithic suspensions Test masses to be suspended with thin fused silica fibers to reduce suspension thermal noise Technology already used successfully by Virgo in 2011 28
Monolithic suspensions In AdV: several failures occurred, when mirrors were suspended in vacuum Technology already used successfully by Virgo in 2011 29
Multi-front investigation into monolithic suspensions Materials, design, procedures, … were reviewed and studied Meanwhile, test masses were suspended with steel wires in order not to stop the commissioning Suspension with steel wires leads to a loss of sensitivity at low frequency 30
Design sensitivity for Virgo’s initial phase Assuming a loss angle ! = 10 %& the BNS range will be limited to 45 Mpc, while BBH range will be limited to 202 Mpc All four test masses are suspended with steel wires 31
Design sensitivity for Virgo’s initial phase All four test masses are suspended with steel wires 32
Design sensitivity for Virgo’s initial phase Sensitivity with steel wires still compatible with the goal for early phase All four test masses are suspended with steel wires 33
Culprit: contamination generated in the scroll pumps Weak design of the evacuation and venting system (a single line was employed) Origin of monolithic suspension failures found in fall 2016 Failures could be reproduced in test facility Risk mitigation plan has been defined • Detailed implementation plan being prepared • Will be put in place after O2 34
Risk reduction plan Improvement of the vacuum pumping/venting system has been studied in collaboration with experts from CERN, DESY, and INFN Venting system • Separate piping for evacuation and venting • Mechanical shields to avoid direct venting flux towards the fibers • Replacement of scroll pumps with different ones Installation of “fiber guards” as additional safety 35
Where are we? 36
Where are we? The interferometer is stably and reproducibly locked on the dark fringe 37
Noise budget Shot noise limited at high frequencies, while low frequency noise needs to be understood Blue curve: measured noise; green curve: total understood noise 38
Commissioning run C8 Engineering run took place from May 5 to 7 to test long-term stability, and effectivity of automation Longest lock stretch about 6 hours BNS range 3-5 Mpc Science mode duty cycle about 84% 39
Commissioning run C8 Coupling between various degrees of freedom, e.g. MICH and DARM 40
Commissioning Intense commissioning program is ongoing 41
Noise hunting Coupling between various degrees of freedom, e.g. MICH and DARM 42
Noise hunting Some spectral structure strongly correlate with bench motion, e.g. SIB2 43
Next steps 44
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