Alessio RocchiINFN Roma Tor Vergata
Thermal Compensation System for Virgo+
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Thermal Lensing
• Observed in Virgo through reduction of the sidebands gain.
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
0 2000 4000 6000 8000 1 104 1.2 104 1.4 104 1.6 104 1.8 104 2 104 2.2 104 2.4 1040
0.005
0.01
0.015
0.02
0.0250.021
0
wi t1( )
ni t2( )
WI ta( )
NI ta( )
256000 t1 t2 ta
ITMs absorptions evaluated through coupled thermal-modal FEM with Ansys
Red and blue curves experimental frequency shifts
WI (7.8±1.1) ppm NI (2.3±0.3) ppm
ITMs effective absorptions
0 2000 4000 6000 8000 1 104 1.2 104 1.4 104 1.6 104 1.8 104 2 104 2.2 104 2.4 1040
0.005
0.01
0.015
0.02
0.0250.021
1.719 106
wi t1( )
ni t2( )
256000 t1 t2 ta
WI
NI
green and pink FEM results
Errors come from dependency of the model from uncertainty on elastic parameters dependency on temperature
Time span ~25000sec
f (
Hz)
New measurement by M. Punturo, NI absorption ~ 4.5
ppm
0.025
0
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Thermal lensing evaluation
-350
-300
-250
-200
-150
-100
-50
0
50
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16
P=7W, Grec=40, F=50, Abs=7.7ppmP=7W, Grec=40, F=50, Abs=1.25ppmP=25W, Grec=19, F=150, Abs=1.25ppmP=25W, Grec=35, F=150, Abs=1.25ppmP=25W, Grec=40, F=50, Abs=1.25ppmP=25W, Grec=40, F=50, Abs=7.7ppm
OP
D (
nm)
Radial Distance (m)
Beausoleil analitycal solution
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Thermal Compensation System
• TCS for Virgo+: annular heating of ITMs with dc CO2 laser• “Annular” profile
– from simulations: reasonable parameters to compensate inner radius~2.5 cm, outer radius~11÷14 cm
Desirable properties:• It is easily adaptable as new understanding of the ITF is realized• It does not require a significant vacuum incursion to install as this would
lead to significant down time to the instrument
Two phases installation:1. Feb 2008, system without power stabilization control loop2. May-June 2008, installation of the power stabilization control loop
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
TCS Power requirements
Virgo on WI mirror (absorption 7.7ppm) ~1.8 W
Virgo (nominal absorption) ~0.4 W
Virgo on WI mirror (absorption 7.7ppm, Plas=25W) ~6.2 W
Virgo (nominal absorption, Plas=25W) ~1.3 W
Virgo+, (F=150, Grec=19) (nominal absorption) ~1.5 W
Virgo+ (F=150, Grec=35) (nominal absorption) ~2.8 W
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Optical layout
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
TCS optical bench
Oven
Optical benches positioning
Acoustic enclosure
WI tower
NI tower
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Final design of the Optical Imaging System
P. La Penna & E. Genin
250
mm
100% efficiency
Single axicon to get the “annular” profile
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Two large in-vacuumsteering mirrors (=190mm)
Positioning controlled manually in all DOFs
Remotely controlled via steppingmotors in angular DOFs and onetranslation
UHV ZnSe viewportDN100CFClear aperture 90mm
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
CO2 Laser AOM
Beam Dump
Schematic view
Beam Dump
Power Meter
L1 L2
L3
L4
L5
AXICON
/2waveplate Polarizer
Components in the blue box are used for laser power stabilization, will be installed by mid 2008
To in-vacumm steering mirror
Aiming LaserLX
Laser output power control
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Tests in Tor Vergata Labs before installation on Virgo
• Measure the RIN of the laser– So we can have an estimate of the injected noise in
the first phase installation
• Check the efficiency of the Optical Imaging System
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Preliminary designof the first in-vacuum mirror
Material: Aluminum
T. Zelenova
~80
0mm
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Exploring different designs for the in-vacuum optics holders, with T. Zelenova
226Hz
252Hz
537Hz
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
f0=537Hz
Unloaded
Loaded with mirror (2kg)
f0=375Hz
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Error signal generation• E. Calloni & M. Laval demonstrated that Phase camera 0 + DarkF tools to
“measure” TCS • Pine-hole photodiodes error signal generation• Phase camera 1 an upgraded tool to understand sidebands and TCS
B5
P1
P2
Pin-hole mirror
Photodiodes
Signal = P1-P2
This is only one error signal, but two are needed. Investigating the possibility to use the signal from B2
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
CO2 laser power stabilization
20W CO2 Laser
AOMPD
PD
Critical components
*DP
AreaRIN
inc
New LASY-20S from Access Laser Co, pre-stabilized, temperature tuned (no line hops)
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Evaluation of TCS noise injected in Virgo+, if RIN is stabilized @ 3×10-7/√Hz, flat over the frequency range 10 Hz to 1000 Hz, TCS power=1.5W.
Noise budget
10 100 1 1031 10 24
1 10 23
1 10 22
1 10 21
1 1021
1024
ztot ( )
z1 ( )
z ( )
zrad ( )
Sh2 fv2( )
Sh fv( )
100010 fv2 fv
Virgo+ sensitivity (without monolithic suspensions)Virgo+ sensitivity (with monolithic suspensions)TotalFlexuralThermoelastic+ThermorefractiveRadiation pressure
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Building and validating the FE model
Comparison with analytical solutionBeausoleil (LIGO-P020026-00-D)
0
0,1
0,2
0,3
0,4
0,5
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16
Analytical Solution (Beausoleil)Ansys - surf151
Tem
pera
ture
(K
)
Radial distance (m)
Max difference ~ 0.3%
Difference is 0.55Hzless than 0.01%
• DRUM MODE
• ANSYS FEM f= 5584.15 Hz
• Experimental value f= 5584.7 Hz
A. Rocchi - 24.10.2007 LSC-Virgo Meeting
Possible optical layout
AXICON