1. STREGA WP2 - Task C3 Roberto Passaquieti Dipartimento di Fisica E. Fermi Università di Pisa INFN sezione di Pisa ILIAS-GW GENERAL MEETING, Orsay 5 November 2004

2. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 2 STREGA: WP2-C3 Task Task description: to design an anti-seismic suspension system performing like a Virgo Superattenuator and also able of removing from its payload the power absorbed from the impinging laser beam (< 1W). –Objectives: to assembly and test a cryo-compatible suspension system prototype, to install this system into a cryogenic environment, to investigate the extra noise from the cryogenic apparatus and to reduce it to a negligible value. To reach such objectives it is foreseen the merging with task C1 activities during the last 4th year of the project, also during the first part of the project some activities are in common between C1 and C3 task (investigation on sensors and actuators, invstigation on material properties, noise studies, simulation software, etc.)

3. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 3 C3 Task Collaborators (Virgo Cryo-Network) Acernese F., INFN & University Federico II, Napoli Babusci D., LNF INFN, Frascati Barone F., INFN Napoli & University of Salerno Barsuglia M., LAL-Orsay IN2P3/CNRS Bizouard M.A., LAL-Orsay IN2P3/CNRS Brisson V., LAL-Orsay IN2P3/CNRS Braccini S., INFN Pisa Bradaschia C., INFN Pisa Brocco L., INFN & University La Sapienza, Roma Calloni E., INFN & University Federico II, Napoli Cattuto C., INFN Perugia Cavalier F., LAL-Orsay IN2P3/CNRS Cella G, INFN & University of Pisa Cuoco E., INFN Firenze/Urbino Dattilo V., EGO Davier M., LAL-Orsay IN2P3/CNRS DeWaard A., Leiden University, Leiden, The Netherlands De Rosa R., INFN & University Federico II, Napoli Di Fiore L., INFN Napoli Di Virgilio A., INFN Pisa Dominici P., INFN Firenze/Urbino Eleuteri A., INFN & University Federico II, Napoli Ferrante I., INFN Pisa Fidecaro F., INFN Pisa Frasca S., INFN & University La Sapienza, Roma Frasconi F., INFN Pisa & EGO Frossati G., Leiden University, Leiden, The Netherlands Gammaitoni L., INFN Perugia Gennai A., INFN Pisa Giazotto A., INFN Pisa Giordano G., LNF INFN, Frascati Guidi G., INFN Firenze/Urbino Hello P., LAL-Orsay IN2P3/CNRS La Penna P., EGO Losurdo G., INFN Firenze/Urbino Majorana E., INFN Pisa Marchesoni F., INFN Perugia Martelli F., INFN Firenze/Urbino Mazzoni M., INFN Firenze/Urbino Milano L., INFN & University Federico II, Napoli Palomba C., INFN Roma Passaquieti R., INFN & University of Pisa Passuello D., INFN Pisa Perniola B., INFN Firenze/Urbino Punturo M., INFN Perugia Puppo P., INFN Roma Rapagnani P., INFN & University La Sapienza, Roma Ricci F., INFN & University La Sapienza, Roma Stanga R., INFN Firenze/Urbino Vetrano F., INFN Firenze/Urbino Vicere' A., INFN Firenze/Urbino Vocca H., INFN Perugia

4. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 4 Up to now the C3 activities have concerned the following points: –design and thermo-mechanical FEA of a mono-crystalline silicon payload prototype ( INFN Pisa, EGO ) –assembly of a small scale suspension system at room temperature ( INFN Pisa) –preliminary investigation on material properties at low temperature, –preliminary investigation on sensors and actuators – –design and realization of a cryogenic test facility at the EGO site ( INFN Pisa, Leiden Univ., EGO) : –one large cryostat capable to contain a test payload and one anti-seismic mechanical filter –one small cryostat for devices and material properties tests, –tests on high compliance and high thermal conductivity metal strips (INFN Pisa) C3 Task - Main Activities

5. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 5 Payload Prototype The designed payload prototype consists of a silicon mirror (350mm diam., 100 mm thick, 22kg weight) suspended to a silicon marionette by two couples of low dissipative, monolithic silicon ribbons (30mm x 0.8 mm x 300 mm). Silicon peculiarity: –thermal expansion coefficient shows two zero crossings at 123K and 17K. Mirror displacement fluctuations driven by thermal expansion tend to be negligible nearby these low temperature values. Its relatively high thermal conductivity has also the positive effect of reducing mirror thermal lensing

6. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 6 Payload Design and Mechanical FEA 210 Hz

7. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 7 Payload Thermal FEA

8. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 8 COLD FINGER Very Soft Joints Cryostat COLD FINGER Two alternative solutions to mirror heat extraction problem

9. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 9 Superattenuator Components Superattenuator functional blocks: Filters Blades Magnets for anti-springs Dampers Sensors: LVDT Actuators: coils+magnets Cabling Motors Adhesives Start of the investigation on material cryo compatibility

10. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 10 Cryogenic Properties of SA Materials Suitable materials: ferritic steels with 5-9 Ni 300-series austenitic steels: 304, 304L, 316, 321, 304LN, 316LN stable austenitic alloys: Fe-Ni-Cr-N alloys, Fe-Mn-Cr-N alloys and Inconel 908 OFHC copper and deoxidized copper Al alloys: 6061, 6063, 1100 titanium, niobium Invar Kapton, mylar quartz Not recommended: martensitic steels (undergo ductile to brittle transition) carbon steels rubbers, plastics, Teflon Maraging: 18Ni (200) series tested at room temperature and 100K exhibits ductile fracture

11. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 11 Test of Assembled Filter at 77 K and 4.2 K Thermal contraction: Thumb rule: some mm/m contraction for metal rods between 300 and 4 K Problems: misalignments, increased strain Most contraction occurs between 300 and 77 K: significant test of assembled filter at liquid nitrogen temperature

12. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 12 Cryogenic Creep Creep can be significant at cryogenic temperature Cu, Al, etc No validity of simple extrapolation from room temperature according to Arrhenius process with activation energy depending on temperature. Steel at 20 K, r>1 creep strain= (0.9-16)x10 -4 Steel at 77 K, r >1: creep strain= (7.4-30)x10 -4 Steel at 77 K, r <1: creep strain= (0.35-2.7)x10 -4 r = stress/yield strength Necessity of focused experimental activity

13. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 13 List of Investigations on Suspension Materials Selection of material for heat links and thermal conductivity measurement Definition of mechanical and thermal behavior of materials for filter components; test of an assembled filter at 77 K and at 4.2 K Quality factor of damping material at low temperatures, in case dampers will be used Dimensioning of power and signal cabling keeping into account the heat transported by conduction and the heat produced by Joule dissipation Test of LVDTs and accelerometers at cryogenic temperatures Qualification of cryogenic motors in the working conditions of VIRGO Test of adhesive strength and effect on quality factor of mirrors at low temperatures Cryogenic creep: impact on blades material and suspensions in general; long term test. A small cryostat is going to be insatalled in Cascina and it will allow to carry on some of these investigations.

14. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 14 Suspension Prototype Assembly A small scale suspension prototype (LIGO SAS) is going to be assembled at the Pisa INFN laboratories. This system is valid for both strategies. It has less cryogenic incompatible items (no magnets, no glue, no viton,…..) and could be used at 4 K with minor modifications Short term activity: –room temperature tests on –blades –sensors –actuators –thermal links –measurement of chain TF. Long term activity: –replica of the tests into a cryogenic environment.

15. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 15 EGO Cryogenic Test Facility The INFN Pisa and Leiden groups are participating to the EGO CTF birth. This facility will be able to host a cryo-suspension system The EGO CTF will consist essentially of a large cryostat with an inner 4K chamber able to contain a test payload with one anti-seismic filter stage, and one additional small cryostat for material properties studies. It is placed at the mid of the West arm of the Virgo interferometer. The large cryostat will be suspended over a pit in the ground floor (length=13.8 m, width=5.45m, depth=1.95 m). CTF W N 2m 1.2m

16. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 16 Cryostat Service Structure

17. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 17 The Cryo-Cooler The EGO-CTF cryo-cooling system is initially based on pulse tube refrigerators (PTR). The PTR essentially achieves criogenic temperature by expanding high pressure He gas to low pressure ( 2Hz). Compression/expansion cycles are source of low frequency excess noise (INFN Roma1 measurements). the INFN Roma1 group on this item has already achieved experience on the PTR noise reduction (see task C1). 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

18. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 18 Jellyfish Prototype Working Principle: –Superattenuator filters coupled with high compliance and thermal conductivity metal strips not degrading the isolation performance in all d.o.f. Al / Cu ~1 m ~ 40 cm 1 cm 30 cm

19. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 19 Performed Test 1x1x70 cm Aluminum l=60 cm Set of stripes Negligible stiffness, negligible effects on Q (measured) Enough thermal conductivity at 4 K (on paper) Test Apparatus 1) Parallel to Y K Y = 2.4 N/m 2) Parallel to XK X = 11.4 N/m 3) Rotation around ZK ΘZ = 3.5 N/m 4) Rotation around XK ΘX = 3.0 N/m

20. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 20 C3 Task Timetable

21. ILIAS-GW General Meeting R. Passaquieti 5 November 2004 21 Conclusions -A payload prototype has been designed and a preliminary thermo-mechanical FEA has been performed (C1 +C3 tasks) (Deliv. January 2005). -The activity of the Pisa group at the EGO cryogenic facility will allow the build up of the necessary expertise to design a superattenuator cryogenic test facility. -A small scale suspension prototype is going to be installed at INFN Pisa lab. -The work done on the jellifish prototype has already produced some positive preliminary results. -The experimental activity started at the INFN Pisa lab has had many points of interaction with the C1 task activity. It has been extablished the collaboration with the INFN Roma1and the Leiden Univ. groups. Strong support has been received from EGO.