STREGA-C3 Cryogenic Seismic Isolation

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

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.).


– 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

Ta2O5 coatings, Yamamoto 2003Ta2O5 coatings, Yamamoto 2003


Task C3: 5 Years Implementation Plan

20042004 20082008

Budget: ~18.4 k€Budget: ~18.4 k€


Task C3: 13-30 Month Timetable


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 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

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300-1x10-6

0

1x10-6

2x10-6

3x10-6

4x10-6

5x10-6

0

1000

2000

3000

4000

5000

6000

Ther

mal

exp

ansi

on c

oeffi

cien

t [K

-1]

Temperature [K]

The

rmal

Con

duct

ivity

[W m

-1 K

-1]


Si Payload: Design and FEA


EGO Cryogenic Test Facility (CTF)

• 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).

CTFW N


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.


Cryostat Support and Service Structures


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


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


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.


The AISI 316L external vesselThe AISI 316L external vessel The 2 AL, super-insulated, inner vessels

The 2 AL, super-insulated, inner vessels



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.


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


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.


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.


Extra Stiffness Measurement of Soft Thermal Link

1x1x70 cm Aluminum

l=60 cm

Set of stripes

Test ApparatusTest Apparatus

Prototype:

set of 10+10 brass strips (0.3X0.01X0.00005 m3 each)

Prototype:

set of 10+10 brass strips (0.3X0.01X0.00005 m3 each)


Cryogenic SA Prototype: Preliminary Design


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.

STREGA-C3 Cryogenic Seismic Isolation

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