Final Acceptance Tests of Helium Refrigerator for Wendelstein 7-X

Following successful installation and commissioning, final acceptance tests were carried out on the helium refrigerator for Wendelstein 7-X.The tests were carried out for the normal operating modes i.e. peak power mode (3.4 K), standard mode(3.9 K), short standby mode (< 10 K) and long standby mode (< 100 K).Besides the normal modes, the transient modes including, cool-down and warm-up, auto interchanging between various modes and the purging modes were tested.In addition, the handling of quench, emergency signals such as cryostat vacuum break,utility failure, alarm and trip signals were checked.