1. Participants: 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

2. Participants: 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 Cryogenic suspension system for advanced resonant detectors

3. MiniGRAIL Cryogenics cryostat Liquid N 2 77K (-196 ºC) Liquid He 4K (-269 ºC) Dilution refrigerator (10 mK)

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

5. To 50 mK shield To mixing chamber Cryogenics Thermal anchoring suspension To still shield

6. Cryogenics Run 4 Minimum temperatures: T sphere = 80 mK T mc = 20 mK Time dependent heat leak from sphere: 45  W after 6 weeks

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

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

9. 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 The new sphere

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

11. Improvements on the Vibration Isolation System 370 Material  before (mm) f before (Hz) CuAl 1,23703516 CuAl 3,43703516 Cu 5-73703397

12. Improvements on the Vibration Isolation System 370 362 358 Material  before (mm) f before (Hz)  after (mm) f after (Hz) CuAl 1,237035163703516 CuAl 3,437035163623633 Cu 5-737033973583512

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

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

15. Cryogenic run transformer + 2-stage SQUID calibrator

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

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

18. MiniGRAIL sensitivity - run 6 Run 6 T5 K  700 ħ Q10 5 M200 g C1.1 nF V bias 200 V Run 7 T80 mK  100 ħ Q10 6 M400 g C1.5 nF V bias 400 V T eff = 40  K 4 x 10 -22

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