Title: Materials and Cooling Techniques
1Materials and Cooling Techniques
- G. Frossati, A.de Waard, L.Gottardi and O.Usenko
- Kamerlingh Onnes Laboratory
- Leiden, The Netherlands
ESF exploratory workshop Toward a 3rd
generation European Gravitational Wave
Observatory Perugia, 21-23-Sept. 2005
2Sensitivity
Minimum detectable energy TeffT/?Q 2TN
For a SQUID noise energy of one quantum
Need??0.05 Q2x106 T30 mK
3material properties
- Dissipation is mainly caused by the mobility of
defects - defects freeze out at low temperature
- Q-factor increases with reducing temperature
4H for several spheres
5MiniGRAILCryogenics The dilution refrigerator
6MiniGRAILCryogenics
7Next 33 ton sphere ?
- Project together with the Roma group to be
submitted to INFN
hQL 4x10-24/vHz
hQL4x10-23/vHz
8Cooling from 300K
Fill liquid helium
9Forced flow
MiniGRAIL 1.4 ton N2 1200 L 600 L He
SFERA 33 7 ton 40000 N2 20000 L He !
Use 4 GM cryocoolers For pre-cooling from 300K
to 20K 4 PT410 for cooling to 4K and for the
dilution refrigerator GM600 (Cryomech) 1200W at
250K PT400 60W at 60K and 1W at 4.2k Heat to
remove 70J/gm 2.8x109J Cool-down time 2 weeks
to 4k
10Liquid mixtures of 3He and 4He
11Dilution Refrigeration as an upside-down
evaporation
VAPOR
LIQUID
12Dilution Refrigeration Schematic view
CIRCULATION SYSTEM
? STILL
TMC
? HEAT ABSORPTION REGION
13Pulsed tube dilutionrefrigeratorJoule Thompson
heat exchanger replaces the 1K pot No need for
Helium bath
PTR
50K
4K
JT Heat exchanger
600 mK
60 mK
Mixing Chamber
10 mK
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17Strain sensitivity
MiniGRAIL
?f1000 Hz
?f100 Hz
?f10 Hz
2m CuAl6 sphere