april 27th, 2006 piero rapagnani – infn roma ilias cryogenic payloads and cooling systems (towards...
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April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Cryogenic payloads and cooling systems Cryogenic payloads and cooling systems (towards a third generation interferometer)(towards a third generation interferometer)
part I:part I: An Interferometer at An Interferometer at Cryogenic TemperaturesCryogenic Temperatures
Piero RapagnaniPiero RapagnaniI.N.F.N. Sezione di Roma I.N.F.N. Sezione di Roma
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Test masses and suspensions thermal noise reduces at low temperature:Test masses and suspensions thermal noise reduces at low temperature:
Thermoelastic noise both of the mirror substrates and coatings decrease:Thermoelastic noise both of the mirror substrates and coatings decrease:
Thermal expansion rate Thermal expansion rate decreases at low temperature; decreases at low temperature;
Mechanical Q of some materials increases at low temperatureMechanical Q of some materials increases at low temperature
@ @ intint
Thermal lensing:Thermal lensing: Thermal conductivity increases and consequently reduces thermal Thermal conductivity increases and consequently reduces thermal
gradients on the coating;gradients on the coating; Refraction index variation with temperature is very small at low Refraction index variation with temperature is very small at low
temperature; temperature;
Why cool the mirrors?Why cool the mirrors?
Tx >∝< 2
22 Tx >∝<
QT
x >∝< 2
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
R&D on CryogenicsR&D on Cryogenics
1) Study of the refrigeration system
- noise
- refrigeration power
2) Suspension compatibility: thermal conduction and acoustic quality factor Q measurements
3) Sensors at low temperatures
- accelerometers and position sensing devices
- actuators
Liquid heliumRefrigeratorsHybrid system
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Issues to cool the mirrorsIssues to cool the mirrors Refrigeration system:Refrigeration system:
• The The injected mechanical noise must be negligibleinjected mechanical noise must be negligible, the , the sensitivity must be preserved:sensitivity must be preserved:
Good mechanical isolation between the Good mechanical isolation between the mirror mirror and the cooling system; and the cooling system;
• Cooling time of the mirror as low as possibleCooling time of the mirror as low as possible::
Good thermal couplings;Good thermal couplings;
High refrigeration power;High refrigeration power; Suspension system compatible with good mechanical and Suspension system compatible with good mechanical and
thermal couplings: thermal couplings:
• Thermal conductivities change with temperature;Thermal conductivities change with temperature;• Mechanical quality factor Q;Mechanical quality factor Q;
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Cryogenic fluids and G.W. DetectorsCryogenic fluids and G.W. Detectors
The first cryogenic antenna in the world 1974-1980: The first cryogenic antenna in the world 1974-1980: M=20 kg, T =4 K , M=20 kg, T =4 K , ~ 5 kHz ~ 5 kHz
No excess noise
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
The second cryogenic antenna of the Rome group The second cryogenic antenna of the Rome group -1978: -1978: M~ 400 kg, T =4 K , M~ 400 kg, T =4 K , ~ 1.8 kHz ~ 1.8 kHz
Excess noise in the first phase of operation:Due to suspension system!!
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Advantage of the Advantage of the superfluid liquid superfluid liquid Helium:Helium:
the the transition transition
Data from the AntennaEXPLORERinstalled at CERN
He phase transition to superfluid
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
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• The current technique to cool down a Resonant Antenna requires “Heavy Work” and several weeks• Detector duty cycle: less than 1 month.
VIRGO
• For an interferometric antenna 6 masses to be cooled. • To preserve the duty cycle this “heavy work” must be done in parallel.....
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
In a BIG Laboratory,large Cryogenic Facilities are possible
The example of LHC at CERN:
Technologies are available, but are VERY expensive and require extensive manpower
The Cryogenic Distribution Line (QRL) for the LHC (Large Hadron Collider). Each of the eight ~3.2 km QRL sectors is feeding Helium at different temperatures and pressures to the local cooling loops of the strings of superconducting magnets operating in superfluid helium below 2 K. With an overall length of 25.8 km the QRL has a very critical cost to performance ratio.
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
An alternative way to cool down without liquid helium: An alternative way to cool down without liquid helium: the new generation of Cryocoolersthe new generation of Cryocoolers
First stage
Second stage
Suitable for applications that require efficient operation:
No moving parts in cold head. Minimal vibration, low acoustic noise, reliability.
High efficiency: 2 to 3 times higher efficiency than GM cryocoolers for loads temperatures between 55 and 120 K.
• A Pulse Tube Refrigerator (PTR) or "G-M style" pulse tube cryocooler, is a variant of a Gifford-McMahon (GM) cryocooler.
• PTR operate at low frequencies, typically <5 Hz.
• Used a conventional oil-flooded G-M compressor and a valve set near the cold head to convert the continuous flow of helium to a low frequency pressure wave.
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
A possible solutionA possible solutionPassive vibrational Passive vibrational isolation system for isolation system for the heat linkthe heat link
Long heat linkLong heat link Part of the Part of the
refrigerating power refrigerating power absorbed by the absorbed by the isolatorsisolators
Attenuation of the Attenuation of the refrigerating powerrefrigerating power
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Our solutionOur solution
Active vibration isolation system for the heat link
Shorter heat linkShorter heat link Refrigerating Refrigerating
power preservedpower preserved
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Q from refrigerator
Q from laser beam
Mirror Reaction Mass: Thermal Shield at ~ 4K
Marionetta Reaction Mass: Thermal Shield at ~ 4K
High Efficiency Thermal Links
Vacuum Chamber and Cryostat Thermal Shields
Silicon Monolithic Wire
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
Q from refrigerator
Q from laser beam
Mirror Reaction Mass: Thermal Shield at ~ 4K
Marionetta Reaction Mass: Thermal Shield at ~ 4K
High Efficiency Thermal Links
Vacuum Chamber and Cryostat Thermal Shields
Silicon Monolithic Wire
Rough Estimates give Tmirror ~ 10 K
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
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Q from Superfluid Helium Reservoir
Q from laser beam
Mirror Reaction Mass: Thermal Shield at ~ 1.5 K
Marionetta Reaction Mass: Thermal Shield at ~ 1.5 K
High Efficiency Thermal Links
Vacuum Chamber and Cryostat Thermal Shields
Silicon Monolithic Wire
A hybrid system usingSuperfluid Helium could
allow to reach T ~ 1.5 K
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Thermal Links:Many Materials andComposites available
Thermal behaviorat low temperaturesmust be tested
April 27th, 2006April 27th, 2006 Piero Rapagnani – INFN RomaPiero Rapagnani – INFN Roma
ILIASILIAS
The short/medium term future:The short/medium term future:The Cryogenic Suspension Test The Cryogenic Suspension Test
FacilityFacilityStill non investigated Problems:
Thermal link (T ~ 4 K)
Cryogenic (T~ 50 K)Suspension Elements