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Some Advanced Virgo Developments Laser Benches suspensions DAQ/Controls

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. Pre Stabilized Laser for AdV. Reminder : Main requests : Virgo quality (noise, reliability ), 200W power

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Some Advanced Virgo Developments Laser Benches suspensions DAQ/Controls

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  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. PreStabilized Laser for AdV • Reminder : • Main requests: Virgoquality (noise, reliability), 200W power • presentreference solution : LIGO-like DPSS • Preparation of a change-request for a fiber laser solution • Cheaper, smaller, better • Remainingchoices • Thinfiber (NUFERN) • Rod fiber (EOLITE) • Amplifier or Injected laser

  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 heatloss • Maintenance

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

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

  7. RIN/Frequency/Beamshapemeasurements Master laser EOM NUFERN Amplifier Beam Dump ~ 100W ~300mW Power control Camera CCD Frequency control

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

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

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

  11. Reliability 30% power loss in 500 hours : toomuch, probably due to the transportation accident, beingchecked by NUFERN ….

  12. Double passrod amplifier Dichroic MO Rod fiber Corediamater up to 80µm Mirror 1x 300W diode 200W Industrial design: lithography… Provedreliability 150 lasers/year (50-300W)

  13. Tentative planning for ROD laser • Eoliteproduces a (140W) test laser for Virgo, • To betested as single and double passamp, 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)

  14. Benches seismic isolation Developments for Virgo+ and AdVirgo

  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. New blade profile (half model) top surface, smax = 1.59 GPa bottom surface, smax = 1.45 GPa Geometric anti-spring development • GAS filter development • Features • Simplicity of design, reduced number of components (< 50 kg) • Bakeable at 200oC • 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 RiccardoDeSalvo and Alessandro Bertolini • Width profile

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

  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 A. Bertolini, AEI F. Mul, Nikhef • 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

  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

  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

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