Transcript Commissioning STATUS

Virgo Commissioning progress
ILIAS, Nov 13th 2006
Matteo Barsuglia
on behalf of the Commissioning Team
1
Outline

July-August

Main problem: thermal lensing

Main activities:

Lock acquisition improvements & automatic alignment

Noise hunting: recover good sensitivity after the shutdown

Thermal lensing

Data takings: WSR-1 (Sept 8th-11th)

Upgrades (September-October)

Faraday isolation optimization

Acoustic isolation laser laboratory

Matching improvements

Actuators noise reduction

Detection Brewster replacement

Frequency noise  see Matt’s talk

WSR-5 (last week-end)

Future steps
2
Thermal lensing
Still the main concern (Lock acquisition long
and more difficult / Noise couplings?)

20 min
Why?

Absorption in the input mirrors seems
to be part of the problem (x4-x10
with respect to the design)

Also thermal lensing in the Faraday?

Dynamics of the fields inside the
interferometer not understood

Simulation ongoing (Finesse, darkF,
Matlab)

Diagnostics through optical spectrum
analyzer

Phase camera in a few months

Thermal compensation in > 1 year
3
Thermal lensing: last week results/1
4
Thermal sensing: last week results/2
20 min
6.7 W input: old matching
5
Thermal sensing: last week results/2
6.7 W input
Matching
activity
20 min
6.7 W input: old matching
Stored power
increase ~
10%
100 sec
6
Thermal sensing: last week results/2
6.7 W input
Matching
activity
20 min
6.7 W input: old matching
Stored power
increase ~
10%
100 sec
5.4 W input
Laser power
reduction
(19%)
7
Thermal sensing: last week results/2
6.7 W input
Matching
activity
20 min
6.7 W input: old matching
Stored power
increase ~
10%
100 sec
5.4 W input
Laser power
reduction
(19%)
5 W input
Stored power
reduction ~ 10%
Laser power
reduction
(25%)
8
Automatic alignment

14 d.o.f. controlled

8 with high gain (~3 Hz), 6 with low gain (~10 mHz)

Power recycling automatic alignment critical during lock acquisition

8 wavefront signals, 6 DC signals (common end mirrors, NI, WI)

Future steps: better filtering, enlarge BW, find demodulated signal for common end
9
WSR-1 sensitivity
WSR-1
C7
C7
WSR-1
10
WSR-1 noise budget
11
Faraday isolation optimization

Faraday isolation ~ 100, expected 10,000

Small key Allen found attached to the rotator  isolation 10,000 in air

In vacuum isolation ~ 1000

Remote adjustment planned

Some signals improved – no clear improvements in the sensitivity
Power recycling
alignment
12
Brewster detection replacement
Detection
Brewster
window

B1 sensitive to detection Brewster vibrations

Wrong Brewster – too small (80 mm instead
110 mm)

New window installed in October

New tests on going
13
Acoustic enclosure laser lab
to the
vacuum
chamber
14
Acoustic enclosure laser lab

Actenuation 3-4 for both benches

Less than expected  try to find
shortcuts

Problems with turbulent air flux

Temporary solved using apertures
(final solution: silenced door)
15
Clapping tests detection lab

Actions planned for detection bench and end benches
16
Noise at high frequency

Oscillator phase noise OK

Shot noise


Almost at the measured value

Difference with design

Stored power 300 W
(500W design)

T_OMC = 0.8 (1 design)

Calibration: ~ 40%
uncertainty
Frequency noise
 See Matt’s talk
17
Control noises
18
Power recycling noise

BW ~ 40 Hz, cut-off 200 Hz

Power recycling coupling changes by
factor 10

Mechanism not understood
Actions:

Understand the coupling mechanism

Switch to B2

Understand the noise of the error
signal (B2_3f_ACp)
19
B2_3f error signal / switch to B2

B2_3f limited by read-out noise from ~ 50-100 Hz

~50 mW when ITF locked ~70 mW during lock acquisition - max power

B2_3f signals strongly depressed by the use of the 3rd harmonics demodulation

B2 gives a better SNR (1st harmonic demodulation)

Switch already tried but never worked for long time periods
20
Actuators noise
DSP
Emphasis
DeEmphasis
G
DAC
CoilDriver
21
Detection bench noise/2

Transfer function zBenchITF output

Several structures already present in
the ITF output excited
C7
22
Detection bench noise
Actuators
noise
C7
23
WSR-5 sensitivity
C7
24
Sensitivity to weather conditions
Red curve: 2.7 Mpc -(wind+sea)
Red curve = 2.7 Mpc-(wind+sea)
25
Suspension improvements
Use 4 locking signals for the
position control of 4 mirrors
in the beam direction
WE
1.
2.
LVDT
ACC
+
GOALS:
reduce use of noisy sensors
do not use ACC where tilt
dominates with no reinjection
of seismic noise
WI
PR
NI
NE
BS
f
3f
I
CARM
I
PRCL
DARM
f
MICH I,Q
26
Future steps

Noise hunting

B2 switch – power recycling control noise improvements

Detection bench actuators noise reduction

Diffused light mitigation



Detection bench

External injection bench
Mirror centering/coils balancing
Suspension control improvements

Global inverted pendulum suspension control

Vertical inertial damping

New SSFS (common mode servo) board

Acoustic isolation detection laboratory and end benches

Continue WSR program (data taking each ~3 weeks)

Long run (a few months) before end of S5
27