Validation of accelerated ageing of Thales rotary Stirling cryocoolers for the estimation of MTTF – RM2 Stirling Cryocooler
Most of the time, the cryocoolers are one of the components dimensioning the lifetime of cooled IR detectors, its reliability is thus one of its most important parameters. This parameter has to increase in order to answer market needs. To do this, the data for identifying the weakest element determining cooler reliability has to be collected. Yet, data collection based on field return are hardly usable due to lack of information. A method for identifying the improvement in reliability has then to be set up which can be used even without field return. This paper describes the resulting method followed by Thales Cryogénie SAS and its application to RM2 coolers. 1- A database has been built from extensive expertizes of RM2 failures occurring in accelerate ageing. Failure modes have been identified and corrective actions achieved. 2- Specific changes have been introduced to improve efficiency. The link between efficiency and reliability will be described in this paper. The work on the two axes – weak spots for cooler reliability and efficiency – permitted us to increase in a drastic way the MTTF of the RM2 cooler. Huge improvements in RM2 reliability are actually proven by both field return and reliability monitoring. These figures will be discussed in the paper.
J.M. Cauquil, C. Seguineau, J.-Y. Martin (Thales Cryogénie SAS France)
T. Benschop (Thales Cryogenics B.V. Netherlands)