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Design considerations

Passive attenuation for the LIGO Output mode cleaner; HAM SAS R. DeSalvo, S. Marka, V. Sannibale, A. Takamori, C. Torrie , A. Bertolini. Design considerations. Simplest possible seismic attenuation system. One single stage of passive attenuation Fully UHV compatible

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Design considerations

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  1. Passive attenuation for the LIGO Output mode cleaner;HAM SASR. DeSalvo, S. Marka, V. Sannibale, A. Takamori, C. Torrie , A. Bertolini LIGO-G050178-00-R

  2. Design considerations • Simplest possible seismic attenuation system. • One single stage of passive attenuation • Fully UHV compatible • Suitable for all conceivable options of OMC • Satisfying LIGO and Adv-LIGO requirements for all HAMS • Broadband attenuation performance 50~60 dB • Tidal correction and < mrad alignment incorporated • Earthquake protection incorporated • Upgradeable to active attenuation as reserve of att. power • As inexpensive as possible • Can replace stacks even without replacing optical tables LIGO-G050178-00-R

  3. Results • Expected performance compatible to cumulative performance of all three layers of ad-LIGO active attenuation • Cost of one single layer • Less control complexity than a single layer (passive) • equal complexity, if upgraded, to active attenuation • Suitable to instrument any HAM for any load www.LIGO.caltech.edu/~desalvo/HAM-SAS LIGO-G050178-00-R

  4. Notable characteristic • Horizontal and vertical degree of freedom decoupled LIGO-G050178-00-R

  5. Horizontal attenuation Intermediate (GAS) platform Inverted Pendula Flex joints X Y f Base platform LIGO-G050178-00-R

  6. Illustrating An IP performance Earthquake generator shaking tower LIGO-G050178-00-R

  7. LIGO-G050178-00-R

  8. LIGO-G050178-00-R

  9. Typical IP performance To 10 mHz resonance 60 dB LIGO-G050178-00-R

  10. HAM IP first tests • Preliminary test results • 60 dB achieved without CounterWeight • 1/8 payload (8 times better at full payload) • Further improvement with CW • 80 Hz resonance, reducing attenuation performance, moved above 100 Hz and dampable with eddy currents LIGO-G050178-00-R

  11. A similar IP leg LIGO-G050178-00-R

  12. LIGO-G050178-00-R

  13. Dynamic micro-positioning • LVDT for nanometer positioning memory • Voice coil actuator • Tidal corrections from global controls • milli Watt in-vacuum power LIGO-G050178-00-R

  14. Dynamic micro-positioning • Co-located LVDT actuator units LIGO-G050178-00-R

  15. Static micro-positioning • Remotely actuated springs in all d.o.f. • No standing currents in actuators LIGO-G050178-00-R

  16. Vertical direction, the GAS springs LIGO-G050178-00-R

  17. Vertical direction, the GAS springs Optical bench Intermediate platform GAS springs LIGO-G050178-00-R

  18. Vertical direction, the GAS springs Optical bench Equivalent LVDT/actuator unit implemented LIGO-G050178-00-R

  19. Illustrating a GAS spring performance LIGO-G050178-00-R

  20. LIGO-G050178-00-R

  21. Typical GAS Passive vertical attenuation performance LIGO-G050178-00-R

  22. Low frequency performance • attenuation factors as large as one thousand for frequencies above 3 Hertz for LF-GW-ID • Sizeable attenuation at the micro seismic peak at 150 mHz LIGO-G050178-00-R

  23. Bellow equivalent springs (neutralized by GAS) Two Cantilever GAS springs 350 Kg Payload Load capabilities, DFBS prototype LIGO-G050178-00-R

  24. Complete SAS design for HAMs Existing Optical bench LIGO-G050178-00-R

  25. Transition from LIGO-I to Adv-LIGO • The transition between LIGO and Advanced LIGO is obtained by simply eliminating a number of spacers LIGO-G050178-00-R

  26. SAS design for BSCs LIGO-G050178-00-R

  27. BSC SAS • The HAM-SAS design fits in the BSC and is capable to offload the entire weight • An additional pendulum stage,needed to reach the (lower) level required by the quad suspensions,gives a redundant safety factor in horizontal isolation LIGO-G050178-00-R

  28. HAM and BSC SAS features • SAS is a viable and inexpensive in-vacuum seismic attenuation candidate for Adv-LIGO (60 dB broadband) • One passive layer can potentially replace all three stages of stiff SEI • Upgradeable to active attenuation as reserve of attenuation power • Fully compatible with the SUS system LIGO-G050178-00-R

  29. HAM SAS design status • HAM SAS design for OMC or any other HAM bench is ready for production http://www.ligo.caltech.edu/~desalvo/HAM-SAS and http://www.ligo.caltech.edu/~desalvo/HAM-SAS.doc • Preliminary bidding indicate a cost of ~ 150K$ and production times of the order of three months • Prototyping in LASTI, to validate the design should be considered • Scaling of the design is possible for BSC LIGO-G050178-00-R

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