Development of a helium recondensing cryostat

Abstract

The present paper illustrates a case study in the progress of ongoing research work to develope a 100 litre Helium cryostat with in-situ recondensing facility. The cryostat with a cryocooler sock comprises 46 components assembled in an optimal sequence. Cryostat development involved thermal load estimation, mechanical design, fabrication of components and sub-assemblies. The cryostat deploys a two stage Gifford McMahon cryocooler with appropriate cooling capacities available on 1st and 2nd stage. The thermal load due to the cryostat assembly is estimated as 34 W and 300 mW for 1st and 2nd stage of the cryocooler respectively. Experimental trials are conducted for testing of the cryostat with recondensing cryocooler. The first no load trial in vacuum produced unsatisfactory results. Appropriate modifications are carried out in the assembly which resulted in no load temperatures of 51.95 K on 1st stage and 3.43 K on 2nd stage. At a heater load of 0.448 W, the 2nd stage stabilized at 4.21 K while 1st stage temperature stabilized at 52.47 K without any heater load on 1st stage. Temperature increased from 51.95 K to 52.47 K for 1st stage showing 0.448 W cooling capacity available at 2nd stage for recondensation at 1 bar pressure. The paper highlights these modifications towards successful development of the Helium recondensing cryostat.