In the recent years Thales Cryogenics has achieved good cryogenic performance results with its one Watt and four watt pulse-tube coolers operating around 80 K, which are currently in full serial production. These coolers consist of compressors that are based on well-proven and highly reliable flexure bearing technology, and pulse-tube cold fingers that are based on a CEA/SBT design. This design has been further optimised by Thales. In 2007 Thales has developed and tested the even more powerful LPT9710 coaxial pulse tube cooler that has proven to produce a cooling power of at least 15 W at 80 K. Advantage of a pulse-tube cooler in this cooling range is the absence of a relative high moving mass, present in a Stirling cooler with similar performance. This moving mass results in high forces and consequently high induced vibration levels at the cold finger mounting position and has a negative impact on cooler reliability. The LPT9710 is a cost effective, low vibration, and very high efficiency pulse-tube cooler that is able to reach high cooling powers and low temperatures with a single stage cooler. Temperatures down to 40K have been measured, without optimisation for this operating temperature range. This paper describes the trade-offs that have been considered in the design phases of the compressor and the pulse tube. Design optimisations of the complete pulse-tube cooler will be presented as well. An overview of the test results, the status of the qualification program and the resulting specification of this pulse-tube cooler will be given. The high cooler efficiency will be outlined in more detail and will be compared to other split-Stirling and coaxial pulse-tube coolers. Finally, future development areas that have been made available by this new compressor and pulse tube will be discussed.
W.L. van de Groep, J.C. Mullié, D.W.J. Willems, T. Benschop