A novel scheme of the zero-liquid-helium-consumption cryostat for superconducting wigglers

For a superconducting wiggler, its superconducting state is usually maintained by liquid helium at atmospheric pressure. Any heat load will vaporize the expensive liquid helium. Therefore, the cryostat, which can decrease the liquid helium consumption, has been pursued by researchers. However, the development of the 4.2 K liquid helium cryostat is a systematic project that depends on lots of key technologies, for instance, the cryocooler, the current lead, the heat insulation, the heat transfer, etc. In this paper, based on the previous investigations of the cryostat, some existing problems are summarized. For the superconducting wiggler at the High Energy Photon Source Test Facility (HPES-TF), a novel design scheme for its cryostat was put forward. In the scheme, the mechanical structure is simpler, the vacuum chamber is set at ambient temperature, and the excess cooling capacity is larger in theory. In the experiment, the superconducting magnet was charged with a current of 320 A, and the electron beam was set at 250 mA. The zero liquid helium consumption was realized with an excess cooling capacity of 0.65 W. The scheme is proven to be feasible and can be used as another typical solution for the superconducting wiggler cryostat in the future.