Design and Fabrication of Vibration-Free Cryostat for Cryocooler-Cooled Superconducting Magnet in CPS

The vibration-free cryostat for a cryocooler directly cooled superconducting magnet is designed, fabricated, and tested for a cryogenic probe station (CPS). A low-temperature superconductor coil has a solenoidal configuration with a copper former which is thermally connected to a cryocooler with 1.5 W refrigeration power at 4.2 K. A pair of current lead, which is composed of a metal element and a high-temperature superconductor element, is employed and cooled by a cryocooler. A sample stage for transient measurement is located in the bore of a superconducting magnet and thermally connected to the cold head of a cryocooler to cool the sample down to liquid helium temperature. No mechanical contact exists between the superconducting magnet and the sample stage in the system. A bellows and mount pads are fabricated to attenuate the transmission of a cryocooler vibration. The structure of the cryostat to support the superconducting magnet and the sample stage has a long thermal path to minimize heat leakage. This paper presents the process of the design, fabrication, and magnet excitation test. The cooling performance of the cryocooler-cooled superconducting magnet is discussed with respect to the thermal resistance along the conduction plate. In addition, the measurement of the vibration in the CPS is presented, and the vibration level is reported.