Post on 01-Jan-2016
LCGT CryogenicsStatus Report
2010.09.26
KEK
T.Suzuki
2010 Oct.- 2013 Mar.Cryostat
Vac. Chamber(Mirror Tank + SAS type-A) + Cryoshields + Insulator 2 sets
Vac. Chamber(Mirror Tank + SAS type-A) Partly equipped Cryoshields + Insulator 2 sets
Duct with cryoshield 8 sets
CryocoolersPTC 2-stage for CryostatPTC single or 2-stage for cryoshield
300K Suspension -> Task of Vibration Isolation
Within the budget
Gate valve Gate valve
VacuumDuct (300K)
VacuumDuct (300K)
Cryogenic Duct Cryogenic Duct
SAS
LASER BEAMMirror Al2O3 crystal250x150 30kg
Cryostat/Mirror Tank
Cryostats: End x 2 + Center x 2
(T. Uchiyama)
LCGT Cryogenics Ultra low vibration cryocooler system
ÅEPulse tube cryocooler (PTC) +vibration isolatorÅETwo stage pulse tube with remote valve.ÅEWarmside of the cold head and the valve are tighten
to the ground separately.ÅEA vibration reduction stage (VRS) is fixed in the vacuum
chamber, which is also tighten to the ground.ÅEWarmside of the cold head and the vacuumchamber
are connectedby a soft bellows.ÅEThe VRS and the cold stage of the cold head of the PTC
are linked by flexible heat links made of thin wire bundle.ÅEThe rms amplitude of the second stage of the VRS
reduced to 50nmfromthe original amplitude of the2nd stage of PTC. (z-direction, vertical)
ÅEHorizontal directions are reduced to sub-micrometerrms amplitudes.
( Developed by KEK and SHI )
Vacuum for LCGT・ Optics of the interferometer must operate in a high vacuum because of sensing an extremely small signal. No optical window is required in the main cavity.・ All components have a common vacuum space and should reduce outgassing from their surfaces.・ Generally, metal surfaces have much smaller rate of outgassing than organic materials at 300K. ・ A surface with low temperature also have a very small rate of outgassing. ・ Super Insulator (SI) is effective thermal insulation for cryogenic parts. SI consists of 20~30 layers of aluminized polyester films.
: emissivity1- : reflectivity
Straight pipe <<1
6 baffles -> 99.4% reduction
Baffles for stopping thermal radiation
Quiet Cooling in vacuum
SASSeismic Attenuation Syatem
(T. Uchiyama)Image of Cryostat (Side view)
(T. Uchiyama)Image of Cryostat (Bottom View)
Thermal insulation of cryostatNon-organic materials
Partial use of SI
Use of SI
Select materials with smaller outgassingDehydrationImprove pumping + stop absorbing H2O
Ultra-high vacuum for 300K and 20K
Tolerable outgassing.
Influence of outgassing from SI is negligible.
Protect Cryogenic contamination of mirrors.
Metal surface with low and stable . Stop 300K radiation through gaps of the insulator.
* Required vacuum from interferometer* Time limit for designing* Construction, money
Requirements for Cryocooler System
• Cooling power– Pulse tube cryocooler(PTC) 1W or more around
5K for cryostat– PTC 80W at 80K for duct shield
• Low vibration– At least as the same vibration level as the Kamiok
a ground motion– Same or similar vibration isolator used for CLIO co
oler.
• Maintenance– On site service available– Response time < 24 hours
Cryocooler of CLIO
Vibration Reduction
Stage
HeatLink
VRSCold Stage
Schedule for first 3 years
Atotsu
Mozumi
Center x 2
Two sets of cryostat for both ends.Two sets of vacuum tank with partial cryoshield for center.