STREGA-C3 Cryogenic Seismic Isolation

1. STREGA-C3 Cryogenic Seismic Isolation Roberto Passaquieti Dipartimento di Fisica “E. Fermi” Università di Pisa INFN sezione di Pisa ILIAS-GW Annual General Meeting , Palma de Mallorca 24-25 October 2005

2. STREGA-C3 Task: Description • The aim of C3 task is to realize a full anti-seismic cryogenic suspension system (cryostat+suspension) performing like a Virgo Superattenuator (SA). • Main Actions: • to design a cryo-compatible suspension prototype; • to install the prototype into a cryogenic environment; • to investigate and reduce the extra noise induced by the refrigerator. • To achieve such results it is foreseen the merging with the activities of C1 task; especially from the 4th year (1997) of the STREGA project (investigation on sensors and actuators; material properties; noise studies; simulation; etc.). ILIAS-GW Meeting, Palma, 25 October 2005

3. C3 Task: Main Activities • Design and FEA of a Si test payload intended for a 1:1 scale measurement of the Si mirror Q down to ~ 5K with/without coating. • Investigations on high compliance thermal links at room temperature. • Assembly of a small suspension prototype (SAS) at room temperature. • Contribution to the realization of the EGO cryogenic test facility(CTF). • Design of a full scale cryogenic suspension prototype. Ta2O5 coatings,Yamamoto 2003 ILIAS-GW Meeting, Palma, 25 October 2005

4. Task C3: 5 Years Implementation Plan 2004 2008 Budget: ~18.4 k€ ILIAS-GW Meeting, Palma, 25 October 2005

5. Task C3: 13-30 Month Timetable ILIAS-GW Meeting, Palma, 25 October 2005

6. Si Payload Prototype: Design • The designed test payload consists of a Si mirror (350mm diam., 100 mm thick) suspended to a Si marionette by two couples of monolithic silicon ribbons (300 x 30 x 0.8 mm3 each). • Si thermal expansion coefficientshows two zero crossings at 123K and 17K. • Displacement fluctuations of mirror driven by thermal expansionare strongly reduced at these low temperature values. • Si relatively high thermal conductivity has also positive effects in reducing mirror thermal lensing ILIAS-GW Meeting, Palma, 25 October 2005

7. Si Payload: Design and FEA ILIAS-GW Meeting, Palma, 25 October 2005

8. The EGO CTF is placed in a building (~ 450 m2) at the mid of the West arm of the Virgo interferometer. The EGO CTF cryostat has an inner 4K chamber able to contain a test payload with one anti-seismic filter stage. It will be suspended over a pit in the ground floor (13.8 x 5.45 x 1.95 m3). EGO Cryogenic Test Facility (CTF) W N CTF ILIAS-GW Meeting, Palma, 25 October 2005

9. Status of Works at the EGO-CTF • The EGO-CTF infrastructure works are quite advanced: • the pit on the ground is completed; • the cryostat suspension structure is assembled; • the computer room and the laboratories are foreseen to be delivered by the mid of next November. ILIAS-GW Meeting, Palma, 25 October 2005

10. Cryostat Support and Service Structures ILIAS-GW Meeting, Palma, 25 October 2005

11. The EGO-CTF Cryostat • The designed cryostatconsists of an external vacuum-proof steel cylindrical vessel (2.6m height, 1.4 m diameter). • Inside the room temperature vessel there are two nested super-insulated Al chambers which are foreseen to reach their thermal equilibrium respectively at about 80K and 4K. • The 4K chamber will host the payload; it has an height of 2m and a diameter of 1.2m. 2m 1.2m ILIAS-GW Meeting, Palma, 25 October 2005

12. The Cryo-Cooler PT410W: Power: 7.2kW @ 50Hz Stage1: 40W @ 25K stage2: 1W @ 4.2K Threshold:0W @ 2.8K Cooling: Liquid Acoust.N: 70dB @1m • The EGO-CTF cryo-cooling system is initially based on two pulse tube refrigerators (PTR). • The Pulse Tube Refrigerator essentially achieves criogenic temperature by expanding high pressure He gas to low pressure ( 2Hz). • Compression/expansion cycles are source of low frequency excess noise. • The INFN Pisa group (C3) will collaborate with the INFN Roma1 group (C1) that has already achieved experience on the PTR noise reduction. PT60W: Power: 3kW @ 50Hz Stage1: 60W @ 80K Cool.Thr.: 0W@ 30K Cooling: Liquid Acoust.N.:70dB @1m ILIAS-GW Meeting, Palma, 25 October 2005

13. Status of the EGO-CTF Cryostat. • Cryomech Pt and compressors, are already purchased. • The EGO-CTF infrastructure are being completed • The last version of the cryostat design was ready from February 2005. • The cryostat has been already built. • Assembly and vacuum leak tests are being performed in the delivering workshop (Cryoanlagenbau) in Germany. ILIAS-GW Meeting, Palma, 25 October 2005

14. The EGO-CTF Cryostat The AISI 316L external vessel The 2 AL, super-insulated, inner vessels ILIAS-GW Meeting, Palma, 25 October 2005

15. The EGO-CTF Cryostat ILIAS-GW Meeting, Palma, 25 October 2005

16. The EGO-CTF Cryostat ILIAS-GW Meeting, Palma, 25 October 2005

17. Cryogenic SA Design: Components • SA functional blocks: • Filters • Blades • Magnets for anti-springs • Dampers • Sensors: LVDT, accelerometers • Actuators: coils+magnets • Cables • Motors • Adhesives • Need to be tested for cryogenics. ILIAS-GW Meeting, Palma, 25 October 2005

18. Cryogenic SA Design: Materials • Suitable materials: • 300-series austenitic steels: 304, 304L, 316, 321, 304LN, 316LN • OFHC copper and deoxidized copper • Al alloys: 6061, 6063, 1100 • Titanium, Niobium • Invar • Kapton, mylar • quartz • Not recommended (undergo ductile to brittle transition): • martensitic steels • carbon steels • rubbers, plastics, Teflon • Maraging: 18Ni (200) series, already tested at room temperature down to 100K, exhibit ductile fracture ILIAS-GW Meeting, Palma, 25 October 2005

19. Suspension Prototype Assembly • A small scale suspension prototype (SAS) is being assembled at the Pisa INFN laboratories. • It exhibits less cryogenic incompatible items (no magnets, no glue, no viton) and could be used at 4 K with minor modifications • Foreseen Activities: room temperature tests on • blades, • sensors, • actuators. ILIAS-GW Meeting, Palma, 25 October 2005

20. Investigations for a Cryogenic SA • List of Investigations: • Selection of material for thermal links; measurement of the link stiffness down to cryogenic temperatures; measurement of the link thermal impedance. • Quality factor measurement of damping materials at low temperatures. • Definition of mechanical and thermal behavior of materials for filter components; test of a full assembled filter at cryogenic temperature. • Dimensioning of the electric cables, keeping into account the heat conduction and dissipation. • Test of the LVDT sensors and accelerometers at cryogenic temperatures. • Qualification of cryogenic motors and traslators. • Qualification of the pulse tubes from the point of view of their vibrations; design of a vibration attenuation system. ILIAS-GW Meeting, Palma, 25 October 2005

21. 1x1x70 cm Aluminum l=60 cm Set of stripes Extra Stiffness Measurement of Soft Thermal Link Test Apparatus Prototype: set of 10+10 brass strips (0.3X0.01X0.00005 m3 each) ILIAS-GW Meeting, Palma, 25 October 2005

22. Cryogenic SA Prototype: Preliminary Design ILIAS-GW Meeting, Palma, 25 October 2005

23. Conclusions • The first year plan was fulfilled:a Si payload prototype was designed and its FEA was performed. • A small scale suspension prototype is being installed at the Pisa INF laboratory. • The EGO CTF is being delivered together with its cryostat. • The work done on the jellifish prototype need to be extended at low temperature. • The design of the cryogenic SA prototype and its cryostat is started. A preliminary design has been delivered (2nd year deliverable). • Interactions beetwen C1 and C3 tasks have been well clarified and organized. ILIAS-GW Meeting, Palma, 25 October 2005