STREGA WP2 - Task C3

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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


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

(<

1
W)
.





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

C
1

activities

during

the

last

4
th

year

of

the

project,


also

during

the

first

part

of

the

project

some

activities

are

in

common

between

C
1

and

C
3

task

(investigation

on

sensors

and

actuators,

invstigation

on

material

properties,

noise

studies,

simulation

software,

etc
.
)



ILIAS
-
GW General Meeting R. Passaquieti 5 November 2004

4


Up

to

now

the

C
3

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


ILIAS
-
GW General Meeting R. Passaquieti 5 November 2004

5

Payload Prototype


The

designed

payload

prototype

consists

of

a

silicon

mirror

(
350
mm

diam
.
,

100

mm

thick,

22
kg

weight)

suspended

to

a

silicon

marionette

by

two

couples

of

low

dissipative,

monolithic

silicon

ribbons

(
30
mm

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




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

Thermal expansion coefficient [K
-1
]
Temperature [K]
Thermal Conductivity [W m
-1
K
-1
]

ILIAS
-
GW General Meeting R. Passaquieti 5 November 2004

6

Payload Design and Mechanical FEA

210 Hz


ILIAS
-
GW General Meeting R. Passaquieti 5 November 2004

7

Payload Thermal FEA


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


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



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
,

304
L,

316
,

321
,

304
LN,

316
LN


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
:

18
Ni

(
200
)

series

tested

at

room

temperature

and

100
K

exhibits

ductile

fracture



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



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
)x
10
-
4


Steel

at

77

K,

r

>
1
:


creep

strain=

(
7
.
4
-
30
)x
10
-
4


Steel

at

77

K,

r

<
1
:


creep

strain=

(
0
.
35
-
2
.
7
)x
10
-
4


r

=

stress/yield

strength


Necessity

of

focused

experimental

activity


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
.



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.


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

4
K

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
.
45
m,

depth=
1
.
95

m)
.

CTF

W

N

2m

1.2m


ILIAS
-
GW General Meeting R. Passaquieti 5 November 2004

16

Cryostat Service Structure


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

(


2
H稩
.



Compression/expansion

cycles

are

source

of

low

frequency

excess

noise

(INFN

Roma
1

measurements)
.


the

INFN

Roma
1

group

on

this

item

has

already

achieved

experience

on

the

PTR

noise

reduction

(see

task

C
1
)
.


PT410W:

Power: 7.2kW @ 50Hz

Stage1: 40W @ 25K

stage2: 1W @ 4.2K

Threshold:0W @ 2.8K

Cooling: Liquid

Acoust.N: 70dB @1m


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


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 X


K
X

= 11.4 N/m

3) Rotation around Z

K
ΘZ

= 3.5 N/m

4) Rotation around X

K
ΘX

= 3.0 N/m


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

(C
1

+C
3

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

C
1

task

activity
.

It

has

been

extablished

the

collaboration

with

the

INFN

Roma
1
and

the

Leiden

Univ
.

groups
.





Strong

support

has

been

received

from

EGO
.