**Cooling Time Reduction with DLCTo increase cool down by radiation, form black coating with Diamond Like Carbon on outer surface of the payload and inner surface of 8K shield. S.KoikeTM : Test MassRM : Recoil MassIM : Intermediate Mass

ET-meeting, 22th Oct. 2013 N. KIMURA/KEK

1/2 size dummy payload was suspended inside cryostat No.3Thermal radiation was examined(without any heat links)Cooling from room temperature

Half Size Dummy Cryo-payload Experiment with KAGRA cryostatsModel Payloads designed and made byR. Kobayashi, S. Koike(KEK)Spare of CLIO mirror2013.6.24 CEC/ICMC (Anchorage, Alaska)Yusuke Sakakibara*

2013.6.24 CEC/ICMC (Anchorage, Alaska)Yusuke Sakakibara

ET-meeting, 22th Oct. 2013 N. KIMURA/KEK

ResultsEffect of High Emissivity Coating for Cooling Time of the Payload isConfirmed.Consistent with calculation!EmissivitySapphire: 0.5 Platform: 0.3*(T/300K)IM: 0.4*(T/300K)2013.6.24 CEC/ICMC (Anchorage, Alaska)Yusuke Sakakibara*

2013.6.24 CEC/ICMC (Anchorage, Alaska)Yusuke Sakakibara

Heat Load Response Test *****Pulse tube cryocoolersPulse tube cryocoolersPulse tube cryocoolersHeater and thermometerSapphire mirrorCooling test in Toshiba

Result of Heat Load Response @ 8K Radiation Shield*****Cooling test in Toshiba 2 W~ 5 ppm0 W ~0 ppm10 W ~25 ppm5 W ~ 12.5 ppmMirror OperationScatted light power is 4 W @400 kW beam powerwhen scattered loss on the mirror surface is 10 ppm.It is confirmed that 25 ppm (10 W) @400 kW of scattered loss is acceptable as heat load for the cryocoolers via the 8 K radiation shield.

******This is result of his calculation. The horizontal axis is time. The vertical axis is the temperature. These thin lines are the result without DLC coating. These thick lines are temperature with DLC coating. So, initial cooling time with is almost half ! OK fine. But this calculation should be checked experimentally.*OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector.

*OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector.

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