review of ham suspension designs for advanced ligo
DESCRIPTION
Review of HAM Suspension Designs for Advanced LIGO. Norna A Robertson HAM Isolation Requirements Review Caltech, July 11th 2005. HAM Optics- Modecleaner Mirrors. Modecleaner suspension: triple pendulum with two sets of cantilever blades overall length 0.69 m (to optic centre) - PowerPoint PPT PresentationTRANSCRIPT
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Review of HAM Suspension Designs for Advanced LIGO
Norna A Robertson
HAM Isolation Requirements Review
Caltech, July 11th 2005
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HAM Optics- Modecleaner Mirrors
• Modecleaner suspension:• triple pendulum with two sets of
cantilever blades
• overall length 0.69 m (to optic centre)
• optic size 15 cm diam x 7.5 cm thick
• masses ~ 3kg, 3kg, 3kg
• final stage on fused silica fibres• radius 75 micron, length 22 cm
• no reaction chain
• controls prototype built at Caltech and tested at LASTI
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HAM Optics - Recycling Mirrors
• Recycling mirror suspension
• triple pendulum with two sets of cantilever blades
• overall length 0.64 m (to optics centre)
• optic size 26.5 cm diam x 10 cm thick
• masses ~12 kg, 12 kg, 12 kg
• Truncated metal middle mass (c.f. modecleaner)
• final stage on steel wires • radius 140 micron, length 25 cm
• no reaction chain
• detailed design carried out
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HAM requirements - reminder
• Modecleaner (MC)• Long. noise (all sources) 3 x 10^-17 m/rt Hz @ 10 Hz
• Vert. noise (all sources) 3 x 10^-14 m/rt Hz @ 10 Hz
• Recycling mirror (RM)• Long. noise (all sources) 4 x 10^-16 m/rt Hz @ 10 Hz
• Vert. noise (all sources) 2.2 x 10^-13 m/rt Hz @ 10 Hz(assumes coupling 0.0018 from vert. wedge)
• Conclusions• Satisfy MC for seismic isolation - RM should be OK.
• Relaxed requirement for RM allows use of steel wires from suspension thermal noise considerations
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MC Suspension: Transfer Functions
Long. TF at 10 Hz = 1.3 x 10^-5
Assuming current SEI DRD noise level, residual noise = 2.6 x 10^-18 m/rt Hz
Vert TF at 10 Hz = 4.7 x 10^-3
Assuming current SEI DRD noise level, and cross-coupling of 10^-3, residual noise = 9.4 x 10^-19 m/rt Hz
Damping time to 1/e ~10secs
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MC Suspension Thermal Noise(Longitudinal and vertical summed quadratically)
1.E-22
1.E-21
1.E-20
1.E-19
1.E-18
1.E-17
1.E-16
1.E-15
1 10 100 1000
Frequency [Hz]
Dis
pla
cem
ent
[m
/sq
rt(H
z)]
x_steel_22cm_40um
x_silica_22cm_75um
lower curve: silica fibres with radius of 75 micron in the final stage (stress 0.4 GPa)upper curve: steel wire with radius 40 micron in final stage (stress 1.4 GPa, high)Noise at 10 Hz: 1.6 x 10^-18 m/rt Hz (silica)
7.7 x 10^-18 m/rt Hz (steel)
3 x10^-17m/rt Hz
Graph from G Cagnoli
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RM Suspension: Transfer Functions
Long. TF at 10 Hz = 1.8 x 10^-5Assuming current SEI DRD noise level, residual noise = 3.6 x 10^-18 m/rt Hz
Vert. TF at 10 Hz = 4.7 x 10^-3Assuming current SEI DRD noise level, and cross-coupling of 0.0018, residual noise = 1.7 x 10^-18 m/rt Hz
Damping time to 1/e ~10secs
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RM Suspension Thermal Noise(Longitudinal and vertical summed quadratically)
1.E-22
1.E-21
1.E-20
1.E-19
1.E-18
1.E-17
1.E-16
1.E-15
1 10 100 1000
Frequency [Hz]
Dis
pla
cem
ent
[m
/sq
rt(H
z)]
x_steel_05GPa_140um
x_steel_1GPa_100um
x_silica_03GPa_175um
lower curve : silica fibres with radius 175 micron (stress 0.3 GPa)middle curve: steel wires with radius of 100 micron (stress 0.9 GPa)upper curve: steel wires with radius 140 micron (stress 0.5 GPa)Noise at 10 Hz: 1.1 x 10^-18 m/rt Hz (silica)
6.4, 9.4 x 10^-18 m/rt Hz (steel)
4x10^-16 m/rt Hz
Coupling of 0.0018 assumed from vert. to long.
Graph from G Cagnoli
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Backup
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HAM Chambers• Some input into any future re-evaluation of HAM requirements. Consider noise at modecleaner
mirror (long. plus vert.)
• Seismic noise 2.5 x 10-18 m/rt Hz @ 10 Hz ( assuming current SEI DRD noise level)
• Suspension thermal noise also approx. this level. (ref. conceptual design T 010103-03-D)
• c.f. Requirement: long + vert from all sources: 3√2 x 10-17 m/√ Hz @ 10 Hz
• Conclusion: there is scope for re-evaluation of SEI requirements for HAM chamber.
2.5 x 10-18 m/√ Hz @ 10 Hz