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Prototype Quadruple Pendulum Update – Part 1
Norna Robertson and Calum TorrieUniversity of Glasgow
for the GEO 600 suspension team
LSC Meeting, Hanford, 14 August 2001Sus/Isol Working Group Session
LIGO-G010291-00-Z
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Baseline Design for Adv. LIGO suspensions
Fused silica ribbons suspending 40 kg sapphire mirror – lowest mass in quadruple pendulum
Quadruple pendulum incorporating 3 stages of enhanced vertical isolation using blades
local control sensors/actuators or eddy current damping on top mass
overall length ~ 2 m all locally controlled freqs. in range ~0.4 - 5.5
Hz global control above 0.01 Hz, split between 3
controllers on 3 lowest stages, acting against quad. reaction pendulum
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Mechanical Design – first steps
Design of prototype all-metal quadruple pendulum and reaction pendulum and Bosch support frame carried out in Glasgow (Torrie et al): masses (top to bottom) 15, 15, 16, 30 kg.
Penultimate mass aluminium with central hole and lowest mass aluminium with steel insets, to mimic silica and sapphire respectively (with same dimensions). Upper masses designed to incorporate blades.
Autocad diagrams produced, and parts procured. Some preassembly carried out in Glasgow, excluding blades (due to late delivery). Parts sent to MIT late June
Calum Torrie and Norna Robertson spent ~1 month at MIT June/July
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Mechanical Design of Quadruple Suspension – Autocad Diagrams
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Autocad Diagrams contd.
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Autocad diagrams contd.
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Autocad Diagrams contd.
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Autocad Diagrams contd.
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Autocad Diagrams contd.
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Bosch Frame
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Top Blades
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Top and Second Mass
Top mass before its blades were loaded
Second mass after its blades were loaded
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Methods of Wire Attachments
steel clamp for blade
barrels with grooves- part of second mass
penultimate mass
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Penultimate and Final Masses
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Top Mass with Local Controls
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General Views
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Assembly on Vacuum Platform
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The Happy Parent
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Lessons Learned So Far
Design of upper masses incorporating blades requires modifying to strengthen
Method of putting grooves in clamps, and of tightening clamps, requires care
Method of adjusting tilt in masses with blades: top mass adjustment worked well, extend to next mass
Experience in assembling masses, preparing wire lengths with jigs, installing blades, adjusting, disassembling etc. important
Bosch frame structure works well for prototyping Handling these sizes of masses non trivial –
moving to larger masses will involve specialist lifting and handling equipment
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Thanks
Many people contributed to the assembly of the quads at various times:Dan Mason, Ken Mason, Richard Mittleman, Michael Perreur-Lloyd, Janeen Romie, Virginio Sannibale, Phil Willems ……..
and invaluable technical assistance from Myron MacInnis and Fred Miller
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Future Work
mode frequencies active damping - impulse responses transfer functions eddy current damping global control feedback design, engineering issues for next
prototype