KAGRA Logbook

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CRY (General)

nobuhiro.kimura - 4:35 Thursday 23 October 2025 (35397)

Regarding the Cooling Status of Duct Shield Cryo-coolers

[Kimura and Yasui]
We have examined the temperature changes over the past few weeks for each cryostat's duct shield cryo-cooler.
Please see attached graphs.
From the graphs:
IX duct shield cryo-cooler BS side:
Temperature increase trend continued but shifted to a decrease about 4 days ago.

EX duct shield cryo-cooler BRT side:
Shows a slow temperature increase trend.
The temperature of the EX duct shield cryo-cooler BRT side has reached a state requiring

IY duct shield cryo-cooler arm side:
Temperature is stable except for a peak about 10 days ago. It appears unrelated to the compressor oil temperature rise.

EY duct shield cryo-cooler arm side:
No particular changes. It also appears unaffected by the cooling water trouble on October 15th.

Images attached to this report

Comments to this report:

nobuhiro.kimura - 21:15 Thursday 23 October 2025 (35402)

EX duct shield cryo-cooler BRT side:
The cold head of the EX BRT-side duct shield cryocooler is showing a gradual temperature rise trend.
Consequently, the temperature of the BRT-side duct shield is also showing a gradual rise trend.
It is necessary to monitor whether the temperature of the BRT-side duct shield reaches 150 K.