Some Advanced Virgo Developments

Laser Benches suspensions DAQ/Controls

B. Mours (with slides from Alain Brillet & Jo Van de Brand)LCGT-Virgo meetingNovember 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

2010/10/07

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

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)

14

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 profile

top 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

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