External forces from heat links in cryogenic suspensions D1, ICRR, Univ. Tokyo Takanori Sekiguchi.
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Transcript of External forces from heat links in cryogenic suspensions D1, ICRR, Univ. Tokyo Takanori Sekiguchi.
![Page 1: External forces from heat links in cryogenic suspensions D1, ICRR, Univ. Tokyo Takanori Sekiguchi.](https://reader036.fdocuments.in/reader036/viewer/2022062401/5a4d1b917f8b9ab0599c1601/html5/thumbnails/1.jpg)
External forces from heat links in cryogenic
suspensionsD1, ICRR, Univ. Tokyo
Takanori Sekiguchi
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About this Talk
2012/5/15
Estimate seismic noise introduced from heat links. Discuss how to achieve cooling and seismic isolation at
the same time.
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Attenuate seismic noise
Cool down test masses
Basic Requirement forTest Mass Suspension
in KAGRA
2012/5/15
Test Mass Displacement< 3 x 10-20 m/√Hz @ 10 Hz
Mirror Temp. ~ 20 K
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Seismic Attenuation System for KAGRA Test Mass
2012/5/15
~14 m
Seismic vibration transmits to the mirror in two different paths
1. From the top through the attenuation chain
2. From the wall of the cryostat through heat links
①
②
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Heat transferred via pure aluminum heat links.
Cryogenics
2012/5/15
We need 1 mm, L=1 m heat links Φ x 7~8
Thermal simulationDone by Y. Sakakibara
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Mechanical Property of Heat Links
2012/5/15
A heat link works as a soft spring (f0~10 mHz)
with violin modes above ~1 Hz
FEM Simulation Done by Y. Aso, (JGW-G1000108)
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Estimation of Seismic Noise via Heat Links
2012/5/157
Simulation Tool: 3-D rigid-body model simulationT. Sekiguchi, Master Thesis (JGW-P1200770)
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Calculation Result
2012/5/158
①
②
Polluting detector sensitivity above 10 Hz !!
* Assuming 1% couplingfrom vertical
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To Make Matters Worse ..
2012/5/159
There is no guarantee that the wall inside the cryostat is vibrating at the same level as the ground.
???
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Vibration of the Shield inside the Cryostat in CLIO
2012/5/1510
10-100 times larger !!
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K. Yamamoto et al, J. Phys.: Conf. Ser. 32 418 (2006)
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In Worse Case
2012/5/1511
①
②* Assuming 1% couplingfrom vertical
If the attachment point of heat links is vibrating at the same level as cryostat vibration in CLIO..
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Improved Design
2012/5/1512
Add one more “cushion” between the cryostat and mirror
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After Improving Wiring
2012/5/1513GWADW 2012
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After Improving Wiring
2012/5/1514
Several peaks exceed the target sensitivity, but the flour level is OK.
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Further Improvement
2012/5/1515
Suppress the cryostat vibration passively/actively. Put additional filters between suspension and cryostat.
Add vertical springs for test mass suspension.
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Effect on Angular Motion
2012/5/1516
SAS is very soft in yaw motion (~ 10 mHz). Torque from heat links may excite low
frequency angular motion.
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Asymmetry
2012/5/1517
Symmetric wiring does not subject any torque. Assume two kinds of asymmetry:
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1. Different attachment point (~1cm)2. Different stiffness (50%)
4HeatLink dk
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Effect on Angular Motion
2012/5/1518
RMS: 0.5 radμ
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Not small, but can be controlled
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Seismic noise introduced from the heat links can easily affect the detector sensitivity above 10 Hz.
One needs careful wiring of heat links, and further improvement of suspensions may be necessary.
The amplitude of the low-frequency mirror yaw motion excited by the heat links would be within acceptable level.
Summary
2012/5/15
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The END
2012/5/15
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GWADW 2012 21 2012/5/15
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Appendices
2012/5/15
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Seismic Noise Attenuation
Mirror Temp. < 20 K
Requirement for KAGRA Test-Mass
Suspensions
2012/5/15
KAGRA Design SensitivityTest Mass Displacement
< 3 x 10-20 m/√Hz @ 10 Hz