The type of system investigated used the Claude cycle for the production of refrigeration at 4.4K. Temperatures at this level are suitable for numerous applications of superconductivity. A distinguishing feature of the equipment under development is the use of high-speed dynamic compressors and turboalternators, in which all rotating parts are suspended on self-acting gas bearings. Such a system avoids sliding contact and wear during operation and avoids the contamination problems associated with oil lubricated compressors used in conventional cryogenic refrigerators. The work described was directed finally to the development of a system consisting of three cryogenic turboalternators, six helium centrifugal compressor stages, and a cryogenic heat exchanger with seven heat exchanger modules. Work was limited to the turboalternators and heat exchangers. A cryogenic turboalternator was developed and successfully tested to temperatures in the range of 80 to 100K.