Virgo-Material “macro” group
M.Punturo
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
2
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”
VIRGO-MAT
3
M1:Large substrate measurement facility
Pusher
n
Vacuum Chamber @10-6 mbar
1.064m
PZT
Locking electronics
HV
PHD
HV
+15
Read-out electronics
-15
+
x
 L  10 12
m
Hz
  few Hz
 n  
4
M2 Activities
Advanced 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
5
M4 activities
Development 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
6
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
7
Micro-Pulling-Down furnace in Pisa
VIRGO-MAT
8
Produced mono-crystalline fibers
10/03/04 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
9
Evaluation of the thermo-elastic contribution
Thermoelastic loss angle
4
7.026765 10
3
1 10
4
1 10
thSiO2( x  300 )
thSi( x  300 )
1 10
thAl2O3( x  300 )
1 10
5
6
thSiO2( x  200 )
7
1 10
thSi( x  200 )
thAl2O3( x  200 )
8
1 10
9
1 10
3.877602 10
10
1 10
10
0.1
0.1
1
VIRGO-MAT
x
10
100
3
1 10
1000
10
Particular behavior of Si
Crystalline Silicon
6000
-6
-1
Thermal Conductivity [W m K ]
5000
-1
Thermal expansion coefficient [K ]
5x10
-6
-1
4x10
4000
-6
3x10
3000
-6
2x10
-6
2000
0
1000
1x10
-1x10
-6
0
20
40
60
0
80 100 120 140 160 180 200 220 240 260 280 300
Temp erature [K]
VIRGO-MAT
11
Magic temperature
10
5
5
1 10
6
1 10
thSiO2( x  100 )
thSi( x  100 )
7
1 10
8
1 10
thSi( x  117 )
9
1 10
1 10
10
11
1 10
10
11
0.1
0.1
1
10
VIRGO-MAT
x
100
3
1 10
4
1 10
10000
12
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
13
Anti-Stokes Cooling
• To evaluate the temperature distribution along the wire, we
must take in account the thermal conduction/dissipation
processes
SiO2 clamp,
T0=300K
35mm diameter
Si fiber
200m diameter
700 mm height
Laser
T0=300K
VIRGO-MAT
14
Thermal conduction mechanisms
• Usual thermo-dynamical sign definition
• Anti-stokes cooling
T0=300K
dqas  e(T )  Plas  dt
M.T.Murtagh, J.of Non-Crystalline solids 253 (1999) 50-57
e(T ) 
T  0

e
Laser
  T
0 is the temperature where the
efficiency goes to zero 0.1
For ZPLAN we have
 0  48
  2595
  0.0018
T0=300K
ec( x ) 0.05
0
VIRGO-MAT200
100
x
300
15
Thermal conduction
• Conduction law
dqk  k T   dT 
qk
S
 dt
dl
• For each small
section we can
discretize:
dqk  dqk ,i  dqk ,o
S
 k T j  T j 1  T j   T j  T j 1   dt
dl
qk
IR Radiation
dqr     SB  T 3 T0  T   Sl dt
dqr     SB  T j T0  T j  Sl dt
3
VIRGO-MAT
 SB  5.67 10 8
 1
16
Differential Equation
• The differential equation is, where T=T(t,y)
dT  y   T t  dt , y   T0 

 T 
1 
S
  e(T )  Plas   l   k T  y   dy      SB  T  y 3 T0  T  y   Sl dt

mcSi 
dl
 y 

• It is a “bordello” then, I adopted a numerical solution
300
300
300
300
250
250
T
T
T
i
0 t
200
10
Nstep
2
T
Ntime
1
T
 t 200
i
Nstep  t
T
5 Ntime
10
i  Ntime
150
150
100
117.517117 100
0
0
50
100
150
t dt
200
250
300
Ntime dt
50 50
0
0
VIRGO-MAT
0.1
0.2
0.3
i L
0.4
0.5
0.6
( Nstep
17
1 ) L
Temperature distribution
300
T
T1(y)=300-(300-116.928)exp(-8.28 y)
Temperature [K]
250
2
200
150
100
-0.1
3
4
T2(y)= A + B1y + B2y + B3y + B4y
Parameter
Value Error
------------------------------------------A
113.52815
1.67763
B1
1285.48793
36.89706
B2
-3163.21177 234.42451
B3
3219.72231
536.33065
B4
-1100.03542 399.89429
--------------------------------------------
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Position [m]
It is not linear and the noise evaluation
VIRGO-MAT must take in account it
18
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
P f 
e(T ) 
T  0

 oc  P
Laser power fluctuation
10
e
  T
4
1 10
1 10
Optical cooling efficiency
1 10
4
5
6
P ( f )
1 10
Subtracted power fluctuation
1 10
10
VIRGO-MAT
9
1 10
7
8
9
0.1
0.1
1
10
f
100
3
19
1 10
4
1 10
10000
… noise evaluation 2
• The integral length fluctuation is given by:
LT f , f     L 
eT f  P f 
m  cT f 
• 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:
L
1
    T  y dy
L0
T ( y)  300  (300  116.928)  e 8.28 y
• Taking in account also the filtering effect of the thermal
conduction:
e T f  P f 
1
  L
L T f , f 
m  c Tf
1  2f  c 


1 L
c 
 m  c VIRGO-MAT
 S
 
 
20
… noise evaluation 3
• Taking into account that the loaded wire acts like a spring:
y    ( y  L)  0
2
0
-18
y    L  

 02
2
0
  
  2   02
2
2
10
Current Virgo
Pendulum thermal noise
Steel Wire Creep
Optical Cooling on high k
Pend.Th.Noise FS suspension
-19
10
-20
h(f) [1/sqrt(Hz)]
• Considering
the (minimal)
Vertical to
Horizontal
coupling:
10
-21
10
-22
10
-23
10
-24
10
-25
10
1
10
VIRGO-MAT
100
Frequency [Hz]
1000
21
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
VIRGO-MAT
22