Cooling the ET payloads Fulvio Ricci - PowerPoint Presentation

Slide1

Cooling the ET payloads

Fulvio Ricci

Slide2

Talk outline

Assumptions for cooling the

LF Interferometer

HF Interferometer

the thermal input evaluation and wires for the mirror suspension

Payload Material

for the reaction mass

for the

e.m

. actuators

The thermal links :

material

geometry

mechanical transfer function

thermal resistance

Cooling strategies

LF :

cryo

-fluid vs.

cryo

-generator

Mechanical

vs

boiling noise

HF cooling or heating?

Slide3

Assumptions

Two independent interferometers

Main advantage: commissioning and data taking activity in parallelTwo kinds of attenuator chainsSuperattenuators

with different performances

Cryogenic solution also for the HF interferometer for

Thermal

lensing

compensation

Mirror and coating thermal noise

Slide4

LF Int. and thermal noise

Slide5

HF Int. and thermal noise

Slide6

Payload mechanical Issues

Large

Masses

:

reduces

the

recoils

(

good

for

suspension

thermal

noise

)

increases

the

violin

modes

(

good

for

control

)

reduces

the

vertical

modes

(

not

good

for

control

)

excess

thermal

load

Wires

Length

Increment

reduces

the

pendulum

frequencies

(

good

for

suspension

thermal

noise

)

reduces

the

violin

modes

(

not

good

for

control

)

reduces

the

vertical

modes

(

not

good

for

control

)

Wires

Diameter

Increment

:

increment

of

the

wire

sections

(

good

for

cooling

)

reduces

the

violin

mode

frequencies

(

not

good

for

control

)

reduces

the

dilution

factor

(

not

good

for

suspension

thermal

noise

)

Slide7

7

Ti6Al4V

Si

Material Properties

Slide8

Measuring

in

Rome

the

thermal

conductivity

of

the

links

and the

suspension

wires

Potenza immessa

Conducibilità termica

PT

Cryomech

multistage

sample

CuBe

3

Slide9

Old Silicon sample prepared by

micropulling

Slide10

Slide11

Payload

for

the LF case

.

Payload

Marionette: (Ti6Al4V wire)

d = 3 mm, M

1

: 400 kg, L=2 m T=2 K

Mirror (silicon wire)

dimensions:

diam

45cm, thickness 30cm

(limit of present technology)

d = 3 mm, M

2

: 110 kg, L=2 m T=10 K

(only 18kW in cavity, 600

m

m enough for heat extraction)

Recoil Mass (silicon wire)

d = 3 mm, M

3

: 110 kg L=2 m T

=10 K

Modes: pendulum 0.28 Hz, 0.36 Hz, 0.50Hz

vertical 0.4 Hz (blades), 20 Hz, 26 Hz

violins 33 Hz, 67 Hz, 100 Hz, 200 Hz, …

M

1

M2M3

Coating @ 10 K

Ti:Ta2O5 SiO2 Losses @10K: 3.8 10

-4 5 10-4Standard Coating :

END Mirror: HL(19)HLLINPUT Mirror: HL(8)HLL

Slide12

Payload

Marionette: (Ti6Al4V wire)

d = 3 mm, M

1

: 400 kg, L=2 m T=2 K

Mirror (silicon wire)

dimensions:

diam

45cm, thickness 30cm

(limit of present technology)

d = 8 mm, M

2

: 110 kg, L=2 m T=10 K

Recoil Mass (silicon wire)

d = 5 mm, M

3

: 110 kg L=2 m T=10 K

Modes: pendulum 0.28 Hz, 0.36 Hz, 0.50Hz

vertical 0.4 Hz (blades), 23 Hz, 62 Hz

violins 15.8 Hz, 31.6 Hz, 63.2 Hz, 126.4 Hz, …

M

1

M

2

M

3

Coating @ 10 K

Ti:Ta2O5 SiO2

Losses @10K:

3.8 10-4

5 10-4Standard Coating :END Mirror: HL(19)HLLINPUT Mirror: HL(8)HLL

Payload

for

the HF case.

Slide13

13

Design of a Full Scale Cryogenic Payload

Marionetta

Reaction Mass (MRM)

Ti alloy cable (low thermal

conductivity) Ti-6Al-4V

Marionetta

Mirror silicon Wires

Reaction Mass high conductive wires

Reaction Mass

(Dielectric material)

Silicon mirror

Slide14

Marionette

Epoglass

G11

arms

B

ody

in

amagnetic

Steel (AISI316L

)

Tungsten ( or

CuW

) insert

Epoglass

arms G11 (suitable for

cryo

applications)

Copper plate to clamp the suspension wires and the thermal links

Tungsten

Mass for balancing the marionette

by an electric motor

Slide15

Recoil Mass

To

act

as

cryo

trap

(T

RR

<

T

mirror

)

To

protect

the

mirror from shocks,

from pollution and wire breaks ;

To support the coils

for

mirror

actuationCenter of mass coincident with the mirror one;Suspension plane passing through the center of mass;4 back coils, 1 lateral coil;Lateral (one side)

holes for mirror position monitoring;

Materilas: SS +

Dielectric material for the coils (epoglass);

Design main characteristics

Function

Slide16

Material for the recoil mass:

HF Int.

days

days

Pressure

[mbar]

The evolution of vacuum into the VIRGO tower for old (purple) and new (black) payloads

Old payload

Al reaction mass

New payload

TekaPeek

,

a high vacuum compatible plastic

Alternative suggestion:

Vespel

® Polyimide, an ultra-high vacuum compatible, easily

machined,and

an excellent insulator from DuPont.

Unfortunately

Vespel

outgassing

~5 times higher than that of peek

Slide17

Approximate

outgassing rates to use for choosing vacuum materials or calculating gas loads (All rates are for 1 hour of pumping)

Vacuum MaterialStainless Steel Aluminum

Mild Steel

BrassHigh

Density Ceramic

Pyrex

Vacuum Material

Viton

(Unbaked)

Viton

(Baked)

Outgassing

Rate(torr

liter/sec/cm2)6x10-9 7x10-9 5x10-6 4x10-6 3x10-9 8x10-9Outgassing

Rate(torr

liter/sec/linear cm)8

x 10-7 4 x 10-8

Slide18

18

Outside : Steel AISI316L

Inside:

High density

cermics

tungsten carbide (WC) ceramics

with a density of 15.5 g/cm

3

Safety stops

The length of the RM can be changed according to mirror dimensions

Design

for HF will

integrate the TCS

components

Recoil Mass

High-density ceramics and their manufacture

Yamase

O.: Fuel and Energy, 38 (issue 4), July 1997 , pp. 257-257(1)

Slide19

19

Same kind of Coil

- Magnet System used in

Virgo:

Nb

-Ti wires embedded in a copper matrix

Coil and Magnet Size can be changed according to constraints given by locking.

Electrostatic

actuators

easily adapted

Piero Rapagnani

3/11/2008

Electromagnetic actuators

Slide20

20

Virgo

F7 legs and coils: 84 kg

Marionette (AISI316L): 100 kg

Reaction Mass(Al6063): 60 kg

Mirror (

Suprasil

): 21 kg

Overall payload weight: 181 kg

ET

Marionette (AISI316L+Tungsten+epoglass): 400 kg

Reaction Mass (AISI316L+Peek):

140

kg

Mirror (

Suprasil

for HF, Silicon for LF )

:

110

kg

Overall payload weight:

650

kg

Comparing

the

Payloads

Slide21

21

Design

of

the

cooling

system

Tanks to R. Passaquieti

3

The upper part

is

thermally

insulated

by

thermal

screens

Cryo

-Compatible

Superattenuator

design

Slide22

Thermal Links I

Geometries

A corona of thin beams Long Braids

Slide23

Thermal Links II:

mechanical transfer function measurements at low temperature

Evidence of a negligible influence of braids in the case of the torsion degrees of freedom

Slide24

Pure Materials as aluminum and copper RRR =

rroom temperature /

r

o

where

r

o

resid

. resist. at T~0 K

Thermal Links III

Slide25

Solution for the stationary state

Use of a high purity material

k~2000 W/m/K in the range 1-10 K

Thermal link length 20

m

Thermal difference at the link ends ~ 1K

HF Int. ~ 10 W: ~60 wires r~1 mm

LF Int. ~200

mW

~8 wires r~1 mm

Thermal Links IV

Slide26

Epoglass

LVDT

at low temp

Supercondcting

wires

Solutions from the previous ILIAS experience

VFC

Elastic support

Piezo

actuators

Slide27

27

Reducing

the

vibration

Cooling

mirrors

reduces

all

those

noises

temperature

dependent

.

Vibration

noise

of

the

refrigetation

system (~0.01 - 0.03 mm/(Hz)

1

/

2

)

kept

under

control.

Improved attenuation

is

possible

by controlling

other degrees

of freedom

and adding

a Pt

which

operates@180o

of

phase

The upper part is thermally

insulated by thermal screens

Cryo

-Compatible Mirror suspension design

Slide28

Evaluation for the thermal inputs

(Order of magnitude )

Payload chamber:

φ

∼1.5

m

h~3

m

-4 K shield (25 layers

s.u

.) ~ 0.4 W

- 77 K shield (75 layers s.u.)~35 W

Auxiliary tower:

φ∼1

m

h~2

m

4 K shield (25 layers s.u.) ~ 0.3 W

77 K shield(75 layers s.u.) ~ 27 WCryo trap: φ∼1.2

m L4K~ 100 m (L77K > L4K) 4 K shield (25 layers

s.u.) ~ 10 W77 K shield (75 layers s.u.) ~ 1 kW ( relaxing the thermal input requirement from the hot hole we can

assume L4K~ 50 m) In the

cryotrap

case the

cryofluid

solution seems unavoidable

Slide29

For each test mass we need 2 towers and 2 cryostats :

Assuming a mirror of t~300 mm

f~ 450 mm ( 400 is available already but soon we can hope in silicon slabs of 450 mm in diameter )

m

~ 110kg

The test mass is hosted in an inner cylindrical vacuum chamber

f

~ 1.5

m

h

~ 4

m



external cryostat

f

~ 2

m

h ~ 4.5 m

Cold element tower which includes filters f~ 1.5

m h ~ 4.5 m

Cold box

Vac. Tube

Mirror

4 K

cryo

trap

~ 100m

~ 2

m

~ 1.5m Cryotraps for the vacuum tubes and test mass cryostat

300 K

Slide30

Cryofluid

solution : the boiling problem

( not present in the superfluid case)

Displacement amplitude and frequency spectrum shape depend on the tank material and geometry: typical pressure fluctuation 20

dBa



2 10

-4

Pa.

For example in the case of the GW resonant antenna Explorer

x

rms

~ 10

-10

m

@ 4K

with an evaporation

rate of a liquid Helium

~2 lt/h

E

xample of the noise characteristics of a boiling fluid in cylindrical container

Slide31

Open

points for the discussion

Do we agree to assume still that HF is

a

cryo

detector?

If yes, the operating temperature is defined mainly by the optimization of the heat extraction from the mirror ( max thermal conductivity)

If not, we have to review the thermal noise contribution on the ET-HF

sensitivity curve

The

cooling time

- We

need to reduce it ( up to 1 week per mirror )

- use of the He gas exchange,

a complex solution in a real GW interferometer

- Use a telescopic system to transmit the

refr

. power via solid