Download ppt - Caltech, February 12th1 Virgo central interferometer: commissioning and engineering runs Matteo Barsuglia Laboratoire de lAccelerateur Lineaire, Orsay

Caltech, February 12th 1

Virgo central interferometer:commissioning and engineering runs

Matteo Barsuglia Laboratoire de l’Accelerateur Lineaire, Orsay


Summary

• Introduction

• The central interferometer

• Operation with a simple Michelson

• Operation with a recycled Michelson

• Operation with the full injection system

• E-run programs

• Conclusions


Pisa

Virgo aerial view


Virgo sensitivitySeismic noise

Thermal noise

Shot noise


Virgo optical scheme


The central interferometer (CITF)

BS


CITF: goals

• Test all the tehcnical choice during arm construction:

• Suspensions

• Fully digital control chain

• Output mode-cleaner

• Local controls


Suspensions

Top stage

Last stage

Seismic filters


Suspension Control

Top stage

Lower suspension stages:

• “marionetta” (from upper suspension stage)

• mirror (from “reference mass”)


Control Architecture• Completely digital

• LinxOS

• C or C++

• photodiode-read-out 20 kHz

• Control 10 kHz

Global control (PowerPC platform):• read phd signals• algorithm for lock acquisition• linear locking and alignment

For each suspension

DSP• correction sharing• Resonance compensation• local controls

DAC 20 bits

Photodiodes (powerPC platform):• ADC 16 bits• compression dynamics filters

GPS Timing

DOL’s

DOL’s


Local Controls

Output mode-cleaner

• Completely out of vacuum

• CCD camera

• Coarse system, markers (50 mrad)

• Fine system (laser beam, optical lever)

• Control from marionetta (noise filtering)


Detection system Suspended detection bench

Output mode-cleaner


Operation with a simple Michelson

• Superattenuator controllability

• Hierarchical control

• Digital control chain


• Control robustness


Suspension performances

• No excitation of unwanted degrees of freedom

• High robustness to non stationnary noises

• Passive filtering experiment (see Braccini’s talk)


Michelson locking with top stage

Fast corrections (f > 70 mHz)

Slow corrections (f < 70 mHz)

3.5 mN

Force applied to mirror

No feedback to top stage

with feedback to top stage


Control robustness• Results from E0 run (72 hours) : ITF continuously locked on dark fringe for more than 51h• 1 unexpected loss of locking, duty cycle > 0.98 %

51 hours

unlocked (bright fringe)

locked (dark fringe)


OMC locking on dark fringeTransmitted power

signal

TEM00 TEM00TEM00 TEM00

Contrast improvement ~ 10


Operation with a recycled Michelson

• Lock acquisition

• Frequency stabilization

• Linear alignment


Lock acquisition


The lock acquisition problem

modules storage

North tunnel

• Force needed to stop the mirror (finesse = 250)

• maximum force 40 mN (limited by EM noise)

kg

mFmvmNF 20250sec/110

2

Fv

mmt 250sec/1sec2


Strategy (I) - enlarge the acting time

modules storage

North tunnel

• Use of an antisymetric trigger

> 50 % open

few % close

• Widening the error signal

Pr_B5_ACq(Pr_B5_DC)p


A simulated lock acquisitiontrigger

ITF internal power

Dark fringe speed recycling speed

PR correction WI correction


A real lock acquisition

Correction PR Correction WI

ITF internal power Dark fringe power


Frequency stabilization

• crossover ~ 3 Hz

• very aggressive filtering above 13 Hz


Linear alignment


Linear alignment - results

ugf ~ 5-10 Hz


Operation with injection system


Acquisition detection switch

• Dark fringe control switched from B1p to B1

• Offset between B1p and B1

dark fringe on B1p dark fringe on B1

• Need offset compensation and smooth transition


Optical characterization

• Input power ~ 2 - 2.5 Watts

• Recycled power (maximum) ~ 240 Watts

• Not coupled light ~ 30 %

• Interferometer contrast:

~ 5 10-4 (before OMC) ,

~ 5 10-5 (after OMC)


E4 sensitivity

Alignmentcontrolnoise

Laserfrequency

noise


High frequency noise

Laser frequency noise

Peaks: mirrors + holders


Intermediate range noise

• mode-cleaner mass TF

• no common mode loop


CITF e-run program

• 5 e-runs (september 2001-july 2002)

• 72 hours each

• 8 hours shift

• 4 people in shift (1 ITF, 1 laser/injection, DAQ, 1 learner)

• 12 on call sub-system experts

• central building closed, remote control


Sensitivity evolution during e-runs


Lock robustness during e-runs

E0 1 (local ctrl fail) 98% ~ 51 h E1 1 (local ctrl fail) 85% ~ 27 hE2 3 (2 ctrl software, 1 vacuum) 98% ~ 41 hE3 4 (1 ctrl software, 3 ctrl tuning) 98% ~ 40 hE4 4 (2 ctrl software, 2 injection) 73% ~ 14 h

Run #losses (in ‘normal’ operation) duty cycle longest lock

Normal operation = no experiments, no special conditions, no calibration


Data acquisition during e-runs

• 20 kHz

• 2 writing processes in paralles

• ~ 4 Mbytes/sec

• 1 Tbyes/e-run

• 3 kind of data streams:

• 20 kHz frames

• 50 Hz

• Trend (1 Hz)


Run overview – E4 (July 2002)calibration and other special investigations ~ 7 hours

« stable » operation ~ 61 h 30’

calibration

~ 3 h 30’


Duty Cycle – E4

• Normal operation ~ 61h 30’

• Locked ~ 42h 20’

Duty cycle ~ 73 %

• 6 streams with CITF locked

• longest (5) ~ 14h 30’

• shortest (3) ~ 55’

652 31 4

Duty cycle limited by lock acquisition problems of retroreflected light from ITF to injection system


Investigation groups

• Sources of lock losses

• Suspension motions

• Angular drifts


• Calibration

• Angular noise

• Seismic noise

• Acoustic noise

• Noise gaussianity/stationarity

• Glitches

• Lines identification

• Injection system noise


Lock losses study - example

• burst in the local controls of IB

1 sec


Offset = 1 ·10 -11

Rms = 9 ·10 -12

Offset = 4 ·10 -14

Rms = 1 ·10 -12

Locking accuracy


Conclusions - sensitivity

Solutions for frequency noise• Replace MC suspension

• Add “common mode” loop

• Solution for alignment noise• automatic alignment

• filtering of high frequency noise


Conclusions - I • Technical choices validated

• superattenuators

• “out of vacuum” local controls with CCD cameras

• digital control chain

• output mode-cleaner and detection system

• Lot of experience

• E-runs program very useful for detetector characterisation


Virgo Planning

• Now:

• large mirror installation

• vacuum leak tests

• new MC suspension

• local control improvements


Mirror installation I


Mirror installation II