LCGT Cryogenics Status Report KEK T.Suzuki

2010 Oct 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 Cryocoolers PTC 2-stage for Cryostat PTC single or 2-stage for cryoshield 300K Suspension -> Task of Vibration Isolation Within the budget

Gate valve Vacuum Duct (300K) Vacuum Duct (300K) Cryogenic Duct SAS LASER BEAM Mirror Al 2 O 3 crystal  250x150 30kg Cryostat/Mirror Tank Cryostats: End x 2 + Center x 2 (T. Uchiyama)

LCGT Cryogenics 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.  : emissivity 1-  : reflectivity Straight pipe  <<1 6 baffles -> 99.4% reduction Baffles for stopping thermal radiation Quiet Cooling in vacuum SAS Seismic Attenuation Syatem

(T. Uchiyama) Image of Cryostat (Side view)

(T. Uchiyama) Image of Cryostat(Bottom View)

Thermal insulation of cryostat Non-organic materials Partial use of SI Use of SI Select materials with smaller outgassing Dehydration Improve pumping ＋ stop absorbing H 2 O 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 Kamioka ground motion –Same or similar vibration isolator used for CLIO cooler. Maintenance –On site service available –Response time < 24 hours

Cryocooler of CLIO Vibration Reduction Stage Heat Link VRS Cold 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.