cooling the et payloads fulvio ricci. talk outline assumptions for cooling the lf interferometer hf...
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Cooling the ET payloads
Fulvio Ricci
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?
Assumptions Two independent interferometers
Main advantage: commissioning and data taking activity in parallel
Two kinds of attenuator chains Superattenuators with different performances
Cryogenic solution also for the HF interferometer for Thermal lensing compensation
Mirror and coating thermal noise
LF Int. and thermal noise
HF Int. and thermal noise
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 )
7
4
. 0 /
0. 0
10
3 3Ti6Al4V
Ti6Al4V
Ti6Al4V
Ti6Al4V
Mechanical @ 2 K
Density 44532 1 kg m
Young Modulus Y 127 Pa
Poisson Ratio 4 3
Loss Angle
Young Mo
G
4 3
/ / . 0 /
0.0 / /
( ) 8.8 10 0
3Ti6Al4V Ti6Al4V Ti6Al4V
Ti6Al4V
dulus gradient:
1 Y dY dT 46 1 1 K
Thermal @ 2 K
Specific Heat C 7 J kg K
up to 3 K
Heat Conductivity
C T T
0.14 / /
.7 0 / /
Ti6Al4V
3Ti6Al4V
K W m K
Thermal Expansion 1 1 m m K
Ti6Al4V
2.3315 0 /
189
3 3si
si
Mechanical @ 10 K
Density 1 kg m
Young Modulus(100) Y 132 GPa (100)
GPa (111)
Poisson Ra
9
5
0.22
10
/ / 7.7 0 /
0.276 / /
si
si
si si si
si
tio
Loss Angle
Young Modulus gradient (100):
1 Y dY dT 1 1 K
Thermal @ 10 K
Specific Heat C J kg K
10
2330 / /
4.85 0 / /
-6 -1
si
si
Thermo-Optic coef dn/ dT @ 30K: 5.8 10 K
Heat Conductivity K W m K
Thermal Expansion 1 m m K
Si
Material Properties
Measuring in Rome the thermal conductivity of the links and the suspension wires
Potenza immessa
Conducibilità termica
PT Cryomech multistage
sample CuBe3
Old Silicon sample prepared by micropulling
Payload for the LF case.PAYLOADMARIONETTE: (TI6AL4V WIRE)d = 3 mm, M1: 400 kg, L=2 m T=2 KMIRROR (SILICON WIRE) dimensions: diam 45cm, thickness 30cm (limit of present technology)d = 3 mm, M2: 110 kg, L=2 m T=10 K (only 18kW in cavity, 600 mm enough for heat extraction)RECOIL MASS (SILICON WIRE)d = 3 mm, M3: 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 Hzviolins 33 Hz, 67 Hz, 100 Hz, 200 Hz, …
M1
M2
M3
COATING @ 10 K Ti:Ta2O5 SiO2
Losses @10K: 3.8 10-4 5 10-4
Standard Coating :
END Mirror: HL(19)HLL
INPUT Mirror: HL(8)HLL
PAYLOADMARIONETTE: (TI6AL4V WIRE)d = 3 mm, M1: 400 kg, L=2 m T=2 KMIRROR (SILICON WIRE) dimensions: diam 45cm, thickness 30cm (limit of present technology)d = 8 mm, M2: 110 kg, L=2 m T=10 KRECOIL MASS (SILICON WIRE)d = 5 mm, M3: 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 Hzviolins 15.8 Hz, 31.6 Hz, 63.2 Hz, 126.4 Hz, …
M1
M2
M3
COATING @ 10 K Ti:Ta2O5 SiO2
Losses @10K: 3.8 10-4 5 10-4
Standard Coating :
END Mirror: HL(19)HLL
INPUT Mirror: HL(8)HLL
Payload for the HF case.
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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
Marionette
Epoglass G11 arms
•Body 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 marionetteby an electric motor
Recoil Mass
To act as cryo trap (TRR < Tmirror)
To protect the mirror from shocks, from pollution and wire breaks ;
To support the coils for mirror actuation
• Center 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
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
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 MaterialViton (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
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Outside : Steel AISI316LInside: High density cermics tungsten carbide (WC) ceramics with a density of 15.5 g/cm3
Safety stops
The length of the RM can be changed according to mirror dimensions
Design for HF will integrate the TCS components
Recoil MassHigh-density ceramics and their manufactureYamase O.: Fuel and Energy, 38 (issue 4), July 1997 , pp. 257-257(1)
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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 Rapagnani3/11/2008
Electromagnetic actuators
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Virgoo F7 legs and coils: 84 kgo Marionette (AISI316L): 100
kg o Reaction Mass(Al6063): 60
kgo Mirror (Suprasil): 21 kg
o Overall payload weight: 181 kg
ETo Marionette
(AISI316L+Tungsten+epoglass): 400 kg
o Reaction Mass (AISI316L+Peek): 140 kg
o Mirror (Suprasil for HF, Silicon for LF ): 110 kg
o Overall payload weight: 650 kg
Comparing the Payloads
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Design of the cooling system
Tanks to R. Passaquieti
3
•The upper part is thermally insulated by thermal screens
Cryo-Compatible Superattenuator design
Thermal Links I
Geometries
A corona of thin beamsLong Braids
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
Pure Materials as aluminum and copper RRR = rroom temperature / ro where ro resid. resist. at T~0 K
Thermal Links III
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
Epoglass
LVDT at low temp
Supercondcting wires
Solutions from the previous ILIAS experience
Elastic support
Piezo actuators
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
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 W
Cryo trap: φ∼1.2 m L4K~ 100 m (L77K > L4K)- 4 K shield (25 layers s.u.) ~ 10 W-77 K shield (75 layers s.u.) ~ 1 kW ( relaxing the thermal input requirement from the hot hole we canassume L4K~ 50 m)
In the cryotrap case the cryofluid solution seems unavoidable
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
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 xrms ~ 10-10 m @ 4K with an evaporation rate of a liquid Helium ~2 lt/h Example of the noise characteristics of a boiling
fluid in cylindrical container
Open points for the discussionDo 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