some advanced virgo developments laser benches suspensions daq/controls b. mours (with slides from...
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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
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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
2010/10/07
32010/10/07
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
2010/10/07
2010/10/07 5
Master laser Nd-YAG
> 30 mW
Y doped fibre: thin fibre design6 x 50WPump diodes
EOM
Noise performances and beam geometry OKPower limited to 100W (Stimulated Brillouin Scattering) coherent additionTowards higher power : SBS threshold x 6Reliability still TBD
Green box
17/11/09 66 www.nufern.com
Examples of deployed systemsCustom 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
17/11/09 7
Beam Dump
Master laser NUFERN
Amplifier~ 100W ~300mW
Power control
Frequency control
Camera
CCD
RIN/Frequency/Beam shape measurements
EOM
17/11/09 8
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
17/11/09 9
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
17/11/09 10
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.
2010/10/07 11
30% power loss in 500 hours : too much, probably due to the transportation accident, being checked by
NUFERN ….
Reliability
2010/10/07 12
MO
1x 300Wdiode
Double pass rod amplifierDichroic
MirrorRod fiberCore diamater up to 80µm
Industrial design: lithography…Proved reliability150 lasers/year (50-300W)
200W
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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)
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Benches seismic isolation
Developments for Virgo+ and AdVirgo
5 Nov 2010
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
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 Riccardo DeSalvo and Alessandro Bertolini
Width profiletop surface, smax = 1.59 GPa
New blade profile (half model)
GAS spring blade
Bi-metal plate
LVDT – voice coil Magic wand
M. DoetsNikhef
GAS as chain element
Could be tested in collaboration with LCGT
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
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, AEIF. 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
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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