Commissioning results of the jt-60sa cryogenic system.

The JT-60SA cryogenic system is the French voluntary contribution f to the joint European - Japanese project JT-60SA, a superconducting tokamak currently under assembly in QST Fusion Institute in Naka, Japan. The cryoplant was manufactured in Europe and installed in Japan by Air Liquide Advanced Technologies (AL-aT). After one year of commissioning, the acceptance tests were successfully completed in October 2016. The cryogenic system with an equivalent refrigerant power of 9,5 kW at 4,5 K, supplies different cryogenic users at various temperatures: the superconducting magnets at 4,4 K, the current leads at 50 K , the thermal shields at 80 K and the diverter cryo-pumps at 3,7 K. The major challenge of the commissioning was the demonstration of the pulse operation as the cyclic plasma operation induces large variation of thermal loads to the distribution and refrigeration cold boxes. A thermal damper of 7 m3 mitigates the pulsed heat loads simulated by heaters. An adaptive control of the pressure was successfully tested on the cold compressor and the downstream cryogenic valve to the return LP line. The commissioning results are reported detailing the main operating modes.