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.