Since 2005 Thales Cryogenics has been producing coaxial pulse-tube coolers under CEA license for applications that are very sensitive for mechanical vibrations and require a long lifetime. In order to optimize the existing baseline design of the coaxial pulse tube to its customers needs, Thales Cryogenics has been working on several of the critical elements inside the pulse tube. This optimization should lead to a wider application of these pulse-tube coolers into high-end civil applications. This paper describes the work carried out on the optimization of the heat exchangers at the cold tip, the warm end and the buffer including irreversible heat losses caused by disruptions of the gas flow. Moreover, the heat exchange of warm end gas to the surroundings has been investigated. Also, the sensitivity to internal contamination has been tested. Results will enable a design optimization of the whole range of coaxial pulse-tube coolers, varying from 1 and 4 W at 80 K to pulse-tube coolers of more than 12 W cooling power at 80 K. In this paper, test result, trade-offs and benefits of the new design will be discussed and evaluated.
W. van de Groep, J. Mullié, T. Benschop, F. van Wordragen, D. Willems