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. Roberto Passaquieti ILIAS-GW Meeting, Palma, 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.).

3. Roberto Passaquieti ILIAS-GW Meeting, Palma, 25 October 2005 3 –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. C3 Task: Main Activities Ta 2 O 5 coatings, Yamamoto 2003

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

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

6. Roberto Passaquieti 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 mm 3 each). Si thermal expansion coefficient shows two zero crossings at  123K and  17K. Displacement fluctuations of mirror driven by thermal expansion are strongly reduced at these low temperature values. Si relatively high thermal conductivity has also positive effects in reducing mirror thermal lensing

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

8. Roberto Passaquieti ILIAS-GW Meeting, Palma, 25 October 2005 8 EGO Cryogenic Test Facility (CTF) The EGO CTF is placed in a building (~ 450 m 2 ) 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 m 3 ). CTF W N

9. Roberto Passaquieti 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.

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

11. Roberto Passaquieti ILIAS-GW Meeting, Palma, 25 October 2005 11 The EGO-CTF Cryostat The designed cryostat consists 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. 1.2m 2m

12. Roberto Passaquieti ILIAS-GW Meeting, Palma, 25 October 2005 12 The Cryo-Cooler 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. PT410W: Power: 7.2kW @ 50Hz Stage1: 40W @ 25K stage2: 1W @ 4.2K Threshold:0W @ 2.8K Cooling: Liquid Acoust.N: 70dB @1m PT410W: Power: 7.2kW @ 50Hz Stage1: 40W @ 25K stage2: 1W @ 4.2K Threshold:0W @ 2.8K Cooling: Liquid Acoust.N: 70dB @1m PT60W: Power: 3kW @ 50Hz Stage1: 60W @ 80K Cool.Thr.: 0W@ 30K Cooling: Liquid Acoust.N.:70dB @1m PT60W: Power: 3kW @ 50Hz Stage1: 60W @ 80K Cool.Thr.: 0W@ 30K Cooling: Liquid Acoust.N.:70dB @1m

13. Roberto Passaquieti 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.

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

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

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

17. Roberto Passaquieti 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.

18. Roberto Passaquieti 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

19. Roberto Passaquieti 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.

20. Roberto Passaquieti 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.

21. Roberto Passaquieti ILIAS-GW Meeting, Palma, 25 October 2005 21 Extra Stiffness Measurement of Soft Thermal Link 1x1x70 cm Aluminum l=60 cm Set of stripes Test Apparatus Prototype: set of 10+10 brass strips (0.3X0.01X0.00005 m 3 each) Prototype: set of 10+10 brass strips (0.3X0.01X0.00005 m 3 each)

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

23. Roberto Passaquieti 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 (2 nd year deliverable). - Interactions beetwen C1 and C3 tasks have been well clarified and organized.