1. Some Advanced Virgo Developments Laser Benches suspensions DAQ/Controls B. Mours (with slides from Alain Brillet & Jo Van de Brand) LCGT-Virgo meeting November 5, 2010

2. Pre Stabilized Laser for AdV Reminder :  Main requests: Virgo quality (noise, reliability), 200W power  present reference solution : LIGO-like DPSS Preparation of a change-request for a fiber laser solution  Cheaper, smaller, better Remaining choices  Thin fiber (NUFERN)  Rod fiber (EOLITE) »Amplifier or Injected laser 2010/10/072

3. 3 LZH-LIGO Laser: Nd-SSL

4. Pros and Cons Pro:  Extrapolation of present lasers  Developped in 2009 for LIGO, known performances Con:  Large and expensive  Inefficient  Thermal management problems »32x45W diodes  > 1 kW heat loss  Maintenance 2010/10/074

5. 5 Master laser Nd-YAG > 30 mW Y doped fibre: thin fibre design 6 x 50W Pump diodes EOM Noise performances and beam geometry OK Power limited to 100W (Stimulated Brillouin Scattering)  coherent addition Towards higher power : SBS threshold x 6 Reliability still TBD Green box

6. 17/11/096 6 www.nufern.com Examples of deployed systems Custom rack mounted 120W fiber lasers (32 units deployed with one customer) Nufern Proprietary Eight x100W fiber lasers Example of 2x 1kW fiber lasers deployed with one customer 16x 150W PM Amplifiers deployed with one customer

7. 17/11/097 Beam Dump Master laser NUFERN Amplifier ~ 100W ~300mW Power control Frequency control Camera CCD RIN/Frequency/Beam shape measurements EOM

8. 17/11/098 Relative Intensity Noise control Unity Gain Frequency (UGF): 30 kHz The servo loop UGF can be improved Blue curve: -Noise floor at -165dB/√Hz between 20Hz and 1kHz - Noise floor close to shot noise 10 -8 10 -9 10 -6

9. 17/11/099 Frequency noise UGF : ~200 kHz Noise floor at 6.10 -3 Hz /√Hz, not limited by the power amplifier Limitation: a 500 ns delay coming from the fibre amplifier. Solution: a phase corrector 10 -2

10. 17/11/0910 Contrast ~ 95% Beam shape and matching measurement Evaluation of beam geometry : contrast in reflection from a high quality symmetric Fabry-Perot cavity Blue curve: power reflected by the cavity as a function of the laser frequency Absence of Amplified Spontaneous Emission Absence of residual pump power Result independent of the output power, between 3W and 100W.

11. 2010/10/0711 30% power loss in 500 hours : too much, probably due to the transportation accident, being checked by NUFERN …. Reliability

12. 2010/10/0712 MO 1x 300W diode Double pass rod amplifier Dichroic Mirror Rod fiber Core diamater up to 80µm Industrial design: lithography… Proved reliability 150 lasers/year (50-300W) 200W

13. Tentative planning for ROD laser Eolite produces a (140W) test laser for Virgo,  To be tested as single and double pass amp, and as injected laser  Delivery 12/2010 Spring 2011: choice of the final 200W solution 30 + 100 k€ Fall 2011: delivery of the first 200W laser 350 k€ End 2011: retrofit of the prototype as a 200W laser. 350 k€ (ARTEMIS-EOLITE program) 13

14. Benches seismic isolation Developments for Virgo+ and AdVirgo 5 Nov 201014

15. External Injection Bench suspension  Needed to reduce  Beam jitter noise  Diffused light noise  Seismic attenuation filters  Inverted pendula  GAS filters  Installation in 2011? F. Mul, Nikhef

16. Geometric anti-spring development  GAS filter development  Features  Simplicity of design, reduced number of components (< 50 kg)  Bakeable at 200 o C  No body or cross-bar resonances  Improved thermal stability  Fast construction, assembly and tuning, wide range of loads  Active control possible (e.g. EMAS control) due to integrated LVDT and voice coil, vertical ID  Excellent attenuation performance (80 dB above 10 Hz)  Applications  SAS systems  Suspension chains: with Riccardo DeSalvo and Alessandro Bertolini  Width profile bottom surface,  max = 1.45 GPa top surface,  max = 1.59 GPa New blade profile (half model)

17. GAS spring blade Bi-metal plate LVDT – voice coilMagic wand M. Doets Nikhef GAS as chain element Could be tested in collaboration with LCGT

18. Possible GAS filters use: MSAT for recycling cavities  Could solve space issue for recycling cavities  Folded cavities with reduced requirements  Still a proposal under evaluation among other solutions

19. IB and DB suspension  Attenuation  Horizontal: IP and wires  127 dB (1 fm/rtHz) at 10 Hz  Vertical: GAS springs  3 sets of 2 blades  Vertical – horizontal coupling  1% yields 1 pm/rtHz residual vertical  Easily handled by GAS  No wands needed  Criteria and procedure needed  GAS systems  Short IP legs  Input  Optical paths  Control issues A. Bertolini, AEI F. Mul, Nikhef

20. New DAQ electronic for Virgo+ New timing system  Distribute GPS time to all electronic modules »Optical fiber distribution (between racks)  Local clock generation »Low jitter  VSR2 stability: »6 Months of data »all samples within +- 0.2µs »No sensitive to reboot New control system based on Linux PCs  More CPU cycles, Flexibility  Connection with other PC/ADC/DAC using optical fibers New ADC boards Remark: DAQ software used also for LIGO-Virgo online analysis 20

21. 21 ADC7674 board 16 differential channels 800kHz sampling rate  Enable digital demodulation like for the OMC, or LVDTs 18 bits; Noise floor:  100nV/sqrt(Hz) without whitening  30nV/sqrt(Hz) with on board whitening 4 DSPs for filtering and down sampling Absolute GPS timing Optical fiber output to PCs Cost: 2kEuros/boards