Virgo-Material “macro” group

M.Punturo

VIRGO-MAT 2

VIRGO-MAT components

• Virgo-MAT is composed by three INFN groups– Firenze/Urbino

• M.Lorenzini, G.Losurdo, F. Martelli, F. Piergiovanni, F.Vetrano

– Perugia• P.Amico, C.Bernardini, L.Gammaitoni, F.Marchesoni, M.Punturo,

F.Travasso, H.Vocca

– Pisa• M. Al-Shourbagy, S.Bigotta, A.Di Lieto, L.Predolin, A.Toncelli,

M.Tonelli

VIRGO-MAT 3

M1 Activities• Advanced materials for mirror substrates

– Michelson-Morley ITF in Perugia (next slide)– Mechanical characterization of the VIRGO Mirror

substrates in Perugia and in the site (Vir-Not-Per-1390-263)– Measurement of substrates for future ITF

• CaF2 substrate (P. Amico et al, Rev.Sci.Instr. 73 (2002), 178-184)

• Monocrystalline Si substrate “Virgo like”

4

M1:Large substrate measurement facility

PZT

PHD

Vacuum Chamber @10-6 mbar

+

+15

-15

x

Hz few n

HV

HV

nm064.1

Locking electronics

Read-out electronics

Pusher

Hz

mL

1210

VIRGO-MAT 5

M2 ActivitiesAdvanced materials and techniques for resonant detectors

• “Support” role:– Long history in measurement of low losses materials– Several infrastructures to measure thermo-mechanical

properties of fibers in Perugia and Firenze, at room temperature and at low temperature (M5 task)

• Two “clamp free” loss angle measurement facilities

• One cryostat under completion

VIRGO-MAT 6

M4 activitiesDevelopment of low loss dielectric coatings for advanced detectors

• Fabry-Perot facility to measure directly thermal noise in thin membranes (see P.Amico report in T1 task)– Coating effect of thin membranes and small mirrors

• Facility to measure the Q of coated membranes realized under the EGO R&D program and delivered to Lyon

VIRGO-MAT 7

M5 activities

• R&D activities for next generation ITF suspension

• Realization of mono-crystalline fibers that could improve the suspension thermal noise at room temperature and at low temperature– Best candidate: silicon fibers/ribbons– Exotic cooling technique: anti-stokes fluorescence

VIRGO-MAT 8

Micro-Pulling-Down furnace in Pisa

VIRGO-MAT 9

Produced mono-crystalline fibers10/03/04 L 4 cm 12/03/04 L 13 cm

16/03/04 L 13 cm

18/03/04 L 17 cm

22/03/04 L 11 cm

25/03/04 L 21 cm

VIRGO-MAT 10

Evaluation of the thermo-elastic contribution

7.026765 104

3.877602 1010

thSiO2 x 300( )

thSi x 300( )

thAl2O3 x 300( )

thSiO2 x 200( )

thSi x 200( )

thAl2O3 x 200( )

10000.1 x0.1 1 10 100 1 10

31 10

10

1 109

1 108

1 107

1 106

1 105

1 104

1 103

Sapphire @ 300K

Sapphire @ 200K

FS @ 300K

Si @ 300K Si @ 200K

FS @ 200K

Thermoelastic loss angle

VIRGO-MAT 11

Particular behavior of Si

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

The

rma

l exp

ansi

on c

oeffi

cie

nt [

K-1]

Temperature [K]

The

rma

l Co

nduc

tivity

[W

m-1 K

-1]

Crystalline Silicon

VIRGO-MAT 12

Magic temperature

105

1011

thSiO2 x 100( )

thSi x 100( )

thSi x 117( )

100000.1 x0.1 1 10 100 1 10

31 10

41 10

11

1 1010

1 109

1 108

1 107

1 106

1 105

FS @ 100K

Si @ 117K

Si @ 100K

VIRGO-MAT 13

How to cool locally?• It is important to cool locally the flexural point

– Cold finger• Easy to implement

• Commercial

• Liquid N2 is enough

• Noisy

– Anti-stokes fluorescence• High difficulties

• Low (?) efficiency

• And the noise?

VIRGO-MAT 14

Anti-Stokes Cooling• To evaluate the temperature distribution along the wire, we

must take in account the thermal conduction/dissipation processes

Laser

T0=300K

T0=300K

Si fiber200m diameter700 mm height

SiO2 clamp, 35mm diameter

VIRGO-MAT 15

ec x( )

x100 200 300

0

0.05

0.1

Thermal conduction mechanisms• Usual thermo-dynamical sign definition• Anti-stokes cooling

Laser

T0=300K

T0=300K

dtPTedq lasas )(

TeT

Te

0)(

0 is the temperature where the efficiency goes to zeroFor ZPLAN we have

0018.0

2595

480

M.T.Murtagh, J.of Non-Crystalline solids 253 (1999) 50-57

VIRGO-MAT 16

Thermal conduction• Conduction law

qk

qk

dtdl

SdTTkdqk

• For each small section we can discretize:

dtdl

STTTTTkdqdqdq jjjjjokikk 11,,

IR Radiation dtSTTTdq

dtSTTTdq

ljjSBr

lSBr

03

03

1

1067.5 8

SB

VIRGO-MAT 17

Differential Equation• The differential equation is, where T=T(t,y)

dtSyTTyTdl

Sdy

y

TyTklPTe

mcTydttTydT lSBlas

Si

03

0 )(1

,

• It is a “bordello” then, I adopted a numerical solution

300

117.517117

T0 t

TNstep 1

2t

TNstep t

Ntime dt0 t dt0 50 100 150 200 250 300

100

150

200

250

300 300

50

Ti

Ntime

10

Ti

5 Ntime

10

Ti Ntime

Nstep 1( ) L0 i L0 0.1 0.2 0.3 0.4 0.5 0.6

50

100

150

200

250

300

VIRGO-MAT 18

Temperature distribution

-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7100

150

200

250

300

Te

mp

era

ture

[K]

Position [m]

T T

1(y)=300-(300-116.928)exp(-8.28 y)

T2(y)= A + B

1y + B

2y2 + B

3y3 + B

4y4

Parameter Value Error-------------------------------------------A 113.52815 1.67763B1 1285.48793 36.89706B2 -3163.21177 234.42451B3 3219.72231 536.33065B4 -1100.03542 399.89429--------------------------------------------

It is not linear and the noise evaluation must take in account it

VIRGO-MAT 19

104

109

P f( )

100000.1 f0.1 1 10 100 1 10

31 10

41 10

9

1 108

1 107

1 106

1 105

1 104

Noise contribution due to optical cooling

• Fundamentally, the optical cooling can introduce a length noise in the interferometer through the cooling laser power fluctuation coupled with the fiber length

• The laser power fluctuation causes a wire length fluctuation filtered by– Thermal conduction process

– Vertical spring behavior of the suspension wire

fP Laser power fluctuation

Optical cooling efficiency

Poc Subtracted power fluctuation

TeT

Te

0)(

VIRGO-MAT 20

… noise evaluation 2

• The integral length fluctuation is given by:

f

ff Tcm

fPTeLfTL

,

• Where Tf is the temperature of the (cooled) flexural point, m the mass of the wire, c(T) is the specific heat and the average expansion coefficient is:

yL

eyTdyyTL

28.8

0

)928.116300(300)(1

• Taking in account also the filtering effect of the thermal conduction:

f

f

c

f Tcm

fPTeL

ffTL

21

1,

cmS

Lc

1

VIRGO-MAT 21

… noise evaluation 3• Taking into account that the loaded wire acts like a spring:

22

0

2220

202

0 0)(

LyLyy

• Considering the (minimal) Vertical to Horizontal coupling:

1 10 100 100010-25

10-24

10-23

10-22

10-21

10-20

10-19

10-18

h(f

) [1

/sq

rt(H

z)]

Frequency [Hz]

Current Virgo Pendulum thermal noise Steel Wire Creep Optical Cooling on high k Pend.Th.Noise FS suspension

VIRGO-MAT 22

M5-Cx: “Classical” cryogenic design • Drawing of a cryogenic payload for the EGO-VIRGO cryogenic facility

– G.Cella, A.Giazotto, R.Passquieti, M.Punturo, F.Richard