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STREGA - WP2-Task C: Design of advanced cryogenic suspensions

STREGA - WP2-Task C: Design of advanced cryogenic suspensions. Year 1 - 2004. C-1:Cryogenic last-stage suspensions (interferometers) (F.Ricci-G.Frossati) Objectives: -Design new suspension elements for the last stage of interferometers.

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STREGA - WP2-Task C: Design of advanced cryogenic suspensions

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  1. STREGA - WP2-Task C: Design of advanced cryogenic suspensions Year 1 - 2004 C-1:Cryogenic last-stage suspensions (interferometers) (F.Ricci-G.Frossati) Objectives: -Design new suspension elements for the last stage of interferometers. -Achieve a low noise remote control of the mirror position using cryogenic sensors -Assemble and test of a full-scale prototype of cryogenic final stage C-2:Cryogenics suspensions for advanced interferometers (G.Frossati-M.Bassan)- Objectives: -Two 1.2 ton spheres with their suspension assembled and measurements of Q and thermal noise at low temperature performed. C-3: Cryogenics suspension system for interferometers (S.Braccini-M.Bassan) Objectives: -The entire apparatus be located in a cryogenic environment; the extra noise coming from the cryogenic system be studied and made negligible. -Full cryogenic suspension be assembled and tested Participants:

  2. STREGA - Task C2 Year 1 - 2004 Cryogenic suspension system for advanced resonant detectors Participants:INFN ROG Leiden University Tasks:- Cool down of Minigrail to 50 mK - Investigation of heat transfer from the mixing chamber to the sphere Deliverables:- Report on mechanical transfer function measurements of cryogenic suspension Participants:

  3. Liquid N2 77K (-196 ºC) Liquid He 4K (-269 ºC) Dilution refrigerator (10 mK) MiniGRAILCryogenics cryostat

  4. still (700 mK) 50 mK plate mixing chamber (10 mK) MiniGRAILCryogenics;The dilution refrigerator

  5. To still shield To 50 mK shield To mixing chamber CryogenicsThermal anchoring suspension

  6. CryogenicsRun 4 Minimum temperatures: Tsphere = 80 mK Tmc = 20 mK Time dependent heat leak from sphere: 45 W after 6 weeks

  7. 1 2 3 4 5 6 7 Attenuation cables + absorbers Vibration Isolation System

  8. 1 2 3 4 5 6 7 Vibration Isolation System Attenuation between mass 1 and 2

  9. The new sphere • Larger diameter (68 cm instead of 65 cm) gives lower frequency and higher mass (1300 kg instead of 1150 kg). • Six holes machined in TIGA positions

  10. Frequency of new sphere about 200 Hz lower Resonance frequencies of bare sphere at 300 K Old sphere New sphere

  11. 370 370 370 370 370 370 370 Improvements on the Vibration Isolation System

  12. 370 370 362 362 358 358 358 Improvements on the Vibration Isolation System

  13. 370 370 362 362 358 358 358 Improvements on the Vibration Isolation System ~ 50 dB

  14. electrode mass (~ 200 g) spring membrane Closed Membrane Capacitive Transducer CuAl6% • Advantages: • Compact design • Easy to make d ~ 30 micro m VBIAS up to 500 V

  15. transformer + 2-stage SQUID calibrator Cryogenic run

  16. exponential fit 3 hour acquisition @ 5K of mode 3 (2943 Hz) Teff = 70 mK

  17. 1.5 x 10-20 MiniGRAIL sensitivity - run 6

  18. 4 x 10-22 MiniGRAIL sensitivity - run 6 Teff = 40 K

  19. MiniGRAIL sensitivity - comparison MiniGRAIL run 6 MiniGRAIL run 7 GEO NAUTILUS/EXPLORER Planned at the end of 2004 AURIGA LIGO S3 Initial target large interferometers

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