Indigenous Development of Helium Liquefier and Cyclic Refrigerators

Helium liquefaction was achieved, at Cryo-Engineering and Cryo Module Development Section (CCDS) of Raja Ramanna Centre for Advanced Technology, Indore, using a helium liquefier designed and developed with completely indigenous components for the first time in the country on August 14, 2010. This helium liquefier is based on reciprocating type expansion engine and uses cross counter flow type heat exchangers, based on high finned density copper tubes. The cyclic compressor is a four stage air cooled reciprocating type compressor. Its oil removal system is also designed and developed indigenously. Helium gas from commercial cylinders, as well as that recovered from user experiments, is used for liquefying, after passing it through a liquid nitrogen based gas purifier, made locally. 
30K and 10K refrigerators are also designed and developed at CCDS and at present under field trials in different user labs. Time between maintenance and period of continuous operation over which the temperature remains stable strongly depends on the on line oil removal mechanism in the compressor. Fabrication procedures have to be developed, such as development of high quality welding and brazing. Processing of different components is another important parameter to achieve acceptable impurities level during operation. Both the processing of components and leaks, takes substantial fraction of the total time taken for development of cryogenic machinery.