A helium cryogenics system for the superconducting heavy-ion linear accelerator (SRILAC) has been introduced at the RIKEN Nishina Center. The SRILAC contains a total of 10 superconducting quarter-wave-length resonators made of pure niobium materials installed in 3 cryomodules; which realizes the beam energy upgrade of the existing room-temperature linear accelerator. The refrigerator, a HELIAL MF manufactured by Air Liquide, has successfully accomplished a cooling capacity of about 730 W and a sufficient helium pressure stability with a fluctuation less than ±0.4 kPa. The cryogenic system started operation in October 2019, and the SRILAC has been supplying beams to experiments since June 2020, along with a stable operation of the cryogenics system. This article provides an overview of the cryomodule and the helium cryogenics system as well as the operational status of the helium cryogenics system.

The validation of the Linear IFMIF Prototype Accelerator (LIPAc) has been conducted in Rokkasho Fusion Institute of QST as a collaboration between the EU and Japan under the Broader Approach agreement for fusion energy research and development. In LIPAc, the test of the superconducting RF (SRF) accelerator has also been planned, and the cryogenic system was manufactured and installed in Rokkasho to produce liquid helium for cooling down the SRF Linac. This article describes the details of this cryogenic system for LIPAc, its installation in Rokkasho and the operation test result.

The JT-60SA cryogenic system with a refrigeration capacity of 9.5 kW at 4.5 K consists of Refrigerator Cold Box (RCB) and Auxiliary Cold Box(ACB). The RCB provides cold helium to the ACB, high-temperature superconductor current leads, and an 80 K thermal shield. The ACB supplies supercritical helium at 4.4 K / 0.5 MPa by cold helium circulation pumps to a superconducting magnet system through the heat exchangers in a liquid helium tank. In a tokamak type fusion device, superconducting coils, CS and EF, are operated as dynamically controlling their transport currents to sustain plasma operation. Hence the heat load variations caused by AC losses could disturb the operation of the cryogenic system. The JT-60SA cryogenic system has an active control mechanism to mitigate a substantial dynamic of heat load for the stable operation of the warm helium compressors and turbines. During the commissioning of the cryogenic system, the active control mechanism demonstrated a stable operation of the cryogenic system. A cool-down operation of the cryogenic system started in October 2020. This paper reports the specifications of the cryogenic system, a result from a control test for variable heat load, and thermal analysis result at toroidal field coil operation.