Design and fabrication of a conductively cooled cryostat by cryocooler

In order to measure the superconducting transition temperature, the critical current and the alternating current (ac) loss on short samples of high temperature superconducting (HTS) tape, a conduction cooled cryostat has been designed and built. Two closed-cycle coolers provide cooling with an ultimate sample temperature below 20 K. The main temperature sensors are located on the sample mount (B1), on the CVI cold head (B2), and on the Dakin cold head (B3). Temperature regulation is provided by 50 W of electrical heater that opposes the cooling power from the cold heads. Temperature control feedback is by means of temperature sensors co-located with the heaters on the second stage of the cryocoolers. AC losses on the HTS tape sample were measured at 30 K so that the developed device performance was evaluated. In this paper, the design, fabrication and test results on the conduction cooled cryostat are presented.