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![Page 1: Thermal Noise performance of advanced gravitational wave detector suspensions Alan Cumming, on behalf of the University of Glasgow Suspension Team 5 th.](https://reader035.fdocuments.in/reader035/viewer/2022062423/5697bfc61a28abf838ca730e/html5/thumbnails/1.jpg)
Thermal Noise performance of advanced gravitational wave detector
suspensions
Alan Cumming, on behalf of the University of Glasgow Suspension Team
5th April 2011
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Overview
• Silica suspension design for aLIGO
• Prototype aLIGO suspension
• Thermal noise performance and loss modelling
• Current status
• Future work
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aLIGO Monolithic Silica Stage
Steel wires
Penultimate mass
‘Ear’
Silica fibres
End/input test mass
‘Ear’
Requirement: 10-19m/Hz @ 10Hz
Upper metal masses (22kg
masses)
Blade springs
Lower Monolithic silica stage
(40kg masses)
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Prototype Suspension, MIT
• Laser pulled silica fibres
4
A. Heptonstall et al., Rev. Sci. Inst. 82, 011301 (2011) Fibres laser welded to ears
Complete suspension
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5
Ear
FibreNeck
Stock Weld
Finite Element Analysis
• Use FEA to predict energy stored in the suspension elements and the dissipation dilution, D
elastic
total
E
ED
A. Cumming et al., Class. Quant. Grav., 215012, 2009,A. Cumming et al., Class. Quant. Grav., in preparation,
2011.
Ear Horn
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Modelling the suspension loss
6
• Internal friction described by the mechanical loss of the system • For a suspension this originates from various different mechanisms in the fibre ends:
• Modelling with FEA gives
Surface loss, surf
Bulk loss, bulk
Weld loss, weld
Thermoelastic loss, th
weldbulksurfthtotal
1 D
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Modelling comparison with measured
A. Cumming et al., Class. Quant. Grav., in preparation, 2011
• Measurement of horizontal noise difficult
• Modelling compared by predicting loss of violin modes
of suspension fibres
• Measured on MIT prototype suspension
• Gives good confidence in modelling technique
Violin mode FEA Frequency (Hz)
Measured
Frequency (Hz)
Projected loss from
FEA model Measured loss
Fundamental 511 511,520 1.50 x 10-9 1.61 x 10-9
1st harmonic 1017 1020 1.75 x 10-9 2.16 x 10-9
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aLIGO Final Stage Noise (Single Test Mass)
10-19m/Hz @ 10Hz
A. Cumming et al., Class. Quant. Grav., in preparation, 2011
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99
Current status and future work
• Suspension design for aLIGO now finalised
• Preparation for the start of manufacture of production suspensions for first installations into the LIGO instruments is currently ongoing
• First installations timetabled for summer 2011
• Studies already ongoing on methods to further increase sensitivity for enhancements to aLIGO using the FEA modelling techniques
• Application of modelling to future third generation detectors using different materials and possibly cooled to cryogenic temperatures
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11
Thermal Noise Model
22224
22 4
ototalo
totaloB
m
Tkx
hornweldfibretotal
1
D
• Use the following loss terms to model the welds, ear horns and fibres
n totalelastic
n2
totalelastic
21
totalelastic
1
E
E
E
E
E
E
2
2
ticthermoelas1
YC
YTo
d
h s 8surface
77.011bulk 102.1 f
7weld 108.5
A.M. Gretarsson et al., Phys. Rev. A, 2000 G. Cagnoli and P.A. Willems, Phys. Rev. B, 2002P.A. Willems, T020003-00M.Barton et al., T080091-00-KA. Heptonstall et al., Phys. Lett. A, 354, 2006A. Heptonstall et al., Class. Quant. Grav, 035013, 2010