status of thermal compensation in virgo
DESCRIPTION
Status of thermal compensation in Virgo. Roma Tor Vergata LIGO-G070350-00-Z. Thermal Lensing. Observed in Virgo through reduction of the sidebands gain. Difference is ~ 0.3%. Building and validating the FE model. Comparison with analytical solution Beausoleil ( LIGO-P020026-00-D ). - PowerPoint PPT PresentationTRANSCRIPT
Roma Tor Vergata
LIGO-G070350-00-Z
Status of thermal compensation in Virgo
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
Thermal Lensing
• Observed in Virgo through reduction of the sidebands gain.
A. Rocchi - 24.05.2007 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)
Difference is ~ 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 - 24.05.2007 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
Evaluating the losses of the ITMs
Red and blue curves experimental frequency shifts
WI 7.70 ppm NI 2.30 ppm
ITMs effective losses
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
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
Thermal Lensing
-100
-80
-60
-40
-20
0
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16
OPL - WIOPL - NI
OP
L va
riatio
n (
nm
)
Radial distance (m)
Current Thermal lensing
-140
-120
-100
-80
-60
-40
-20
0
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16
OPL - G35OPL - G19
OP
L va
riatio
n (
nm
)
Radial distance (m)
Thermal lensing in Virgo+,Plas=25W; Finesse=150(nominal losses)
Parameters as in R. Flaminio VIR-NOT-EGO-1390-324
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
TL Compensation• Different solutions already investigated (LIGO):
– Heating ring– Shielded heating ring– CO2 laser
• Proposed TCS for Virgo+: annular heating of ITMs with dc CO2 laser
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
• “Annular” profile
– from simulations: reasonable parameters to compensate inner radius~2.5 cm, outer radius~14 cm
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
TCS Power requirements
Virgo now on WI mirror (losses 7.70ppm)
~1.8 W
Virgo (nominal losses) ~0.4 W
Virgo+ (Grec=19)
(nominal losses)~1.5 W
Virgo+ (Grec=35)
(nominal losses)~2.8 W
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
Possible optical layout
AXICON
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
10 100 1 1031 10 28
1 10 27
1 10 26
1 10 25
1 10 24
1 10 23
1 10 22
1 10 21
1 10 20
1 1020
0
ztot ( )
z1 ( )
z ( )
zrad ( )
Sh fv( )
1 10310 fv
Evaluation of TCS noise injected in Virgo+, if RIN is stabilized @ 3×10-7/√Hz.
All sources taken into account.
TotalFlexuralThermoelastic+ThermorefractiveRadiation pressure
Noise budget
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
How to reduce TCS noise1. The obvious: reduce RIN
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
How to reduce TCS noise1. The obvious: reduce RIN
2. Shine both ITMs with the same laser• Noise cancellation is complete only if the power injected on
the ITMs is exactly the same
CO2 Laser
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
How to reduce TCS noise1. The obvious: reduce RIN2. Shine both ITMs with the same laser
• Noise cancellation is complete only if the power injected on the ITMs is exactly the same
3. Shine both sides of the ITMs (credit to P. Willems)
10 100 1 1031 10 29
1 10 28
1 10 27
1 10 26
1 10 25
1 10 24
1 10 23
1 10 22
1 10 21
1 10 20
1 1020
0
ztotc ( )
z1c ( )
zc ( )
zradc ( )
Sh fv( )
1 10310 fv
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
10 100 1 1031 10 26
1 10 25
1 10 24
1 10 23
1 10 22
1 10 21
1 1021
0
Sh fv( )
ztotc ( )
ztot ( )
1 10310 fv
Noise reduction
TCS laser shines:1. Front face of the ITM2. Both faces of the ITM
Total noise reduced by a factor of 5
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
Front heating
Front & back heating
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
-500
-400
-300
-200
-100
0
100
0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16
Front heatingFront & back heating
OP
L d
iffe
ren
ce fr
om
cen
tre
(nm
)
Radial distance (m)
No change in the qualityof the compensation
matters doesn’t
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
Reaction mass temperature field
Front heating Front & back heating
A. Rocchi - 24.05.2007 LSC-Virgo Meeting
Virgo path toward TCSPossible strategy for TCS implementation:
•First step:–Install TCS on Virgo after the Science Run–Time scale: system ready by December 2007/January 2008
•Second step:–TCS for Virgo+, stabilized CO2 laser, improved projector(?)–Time scale: TCS ready by half 2008
A. Rocchi - 24.05.2007 LSC-Virgo Meeting