Thales Cryogenics has been working on high reliability cryocoolers since 1997. During this period two cooler series have been developed, the LSF91xx series for cooling powers up to 3W at 80K and the LSF93xx series for cooling powers up to 8W at 80K. As a result of several design improvements, it was possible to decrease the length and mass of our flexure-bearing coolers. These improvements have been applied in the new LSF95xx series. With the length and mass reduction, the LSF95xx complies with the SADA II specification with respect to envelope and mass. Based on this, being the first manufacturer offering a full flexure-bearing supported cooler that fits within the SADA II envelope, Thales Cryogenics has been selected in several new (military) programs with their LSF coolers. By using a moving magnet configuration in all our flexure-bearing coolers, the risk with respect to contamination problems due to out-gassing have been diminished because the coils are not part of the helium circuit. Furthermore, all connections in the LSF95xx are laser-welded, which means that there is no additional locking required inside the cooler. By using a different magnet design, no magnet segments have to be glued together, which decreases the risk of out-gassing and increases the robustness even more. This paper describes the trade-offs that have been considered in the design phase, and gives a detailed overview of the test results, the status of the qualification program and the resulting specification of the LSF95xx cooler series.
J.C. Mullié, P.C. Bruins, T. Benschop, M. Meijers
THALES Cryogenics B.V. Eindhoven, The Netherlands