Speaker
Description
KAGRA was the world's first to introduce a cryogenic mirror system, but various problems have become apparent as actual operation progresses. For example, the low-temperature pipes called Duct Shields, installed at the beam tube connections before and after the main cryostat and maintaining a temperature of around 100K, have proven to be extremely important not only for reducing the incidence of thermal radiation onto the mirror, which was their original purpose, but also as a trap for adsorbing residual gases. However, it has been found that the deterioration of cooling performance due to long-term operation of the pulse tube cryocooler leads to significant problems with residual gas release and mirror contamination. In this presentation, we will share an overview of KAGRA's cryogenic system and the experiences learned here, aiming to apply them to Einstein Telescope.