With miniature high operating temperature cryocoolers becoming commonplace, there is an increasing importance of accurate determination of the thermal properties of infrared dewars such as heat load and thermal mass, as well as an increasing challenge to obtaining these properties. Especially in the case where operating temperature in the application is far from liquid nitrogen temperature, such as with HOT detectors, the use of the various known methods should be carefully evaluated. Inconsistencies in results between the various available methods, such as nitrogen boil-off, multi-slope warm-up calorimetry, and theoretical thermal modelling will be discussed, and the work being done at Thales Cryogenics to resolve these inconsistencies is presented.
With the achievements made in the last decade with respect to reliability and cryogenic performance, the use of Stirling and Pulse Tube cryocoolers for new application areas has become viable. Thales Cryogenics has been challenged by its customers to deliver robust and compact solutions for a variety of applications. The test approaches within the Thales Environmental Test Lab – a center of excellence within the Netherlands – have been refined significantly, departing from the classical robustness testing principles, which typically consist of submitting the product to an environment with a compressed energy allocation - shorter time duration and higher PSD levels. An overview is given of recent activities at Thales Cryogenics regarding the development and testing of linear Stirling cryocoolers for extreme environmental conditions. A novel cooler will be presented that has been developed specifically for operation in high ambient temperature conditions. In addition, an overview will be given of ongoing test and development activities regarding coolers for operation under severe mechanical loads. Design aspects, margin philosophy, test plans (including robustness testing) and test results will be presented.
In recent years, several space cryocooler developments have been performed in parallel at Thales Cryogenics. On one end of the spectrum are research programmes such as the ESA-funded 30-50 K system developed in cooperation with CEA and Absolut System and the LPT6510 cooler developed in cooperation with Absolut System. On the other end of the spectrum are commercial designs adapted for space applications, such as the LPT9310 commercial coolers delivered for JPL’s ECOSTRESS instrument and the LSF9199/30 SADA-compatible cooler delivered for various space programmes at Sofradir. In this paper, an overview is presented of the latest developments regarding these coolers. Initial performance results of the 30-50K cooler are discussed, pending developments for the LPT6510 cooler are presented, and the synergies between COTS and space are reviewed, such as design principles from space coolers being applied to an upgraded variant of the COTS LPT9310, as well as design principles from COTS coolers being applied to the LPT6510 for improved manufacturability.
The low-frequency pulse-tube cryocooler has been a workhorse for large heat lift applications. However, the highfrequency
pulse tube has to date not seen the widespread use in tactical infrared applications that Stirling cryocoolers
have had, despite significant advantages in terms of exported vibrations and lifetime.
Thales Cryogenics has produced large series of high-frequency pulse-tube cryocoolers for non-infrared applications
since 2005. However, the use of Thales pulse-tube cryocoolers for infrared sensing has to date largely been limited to
high-end space applications.
In this paper, the performances of existing available off-the-shelf pulse-tube cryocoolers are examined versus typical
tactical infrared requirements. A comparison is made on efficiency, power density, reliability, and cost. An outlook is
given on future developments that could bring the pulse-tube into the mainstream for tactical infrared applications.
During the 2015 SPIE-DSS conference, Thales Cryogenics presented new miniature cryocoolers for high operating
temperatures. In this paper, an update is given regarding the qualification programme performed on these new products.
Integration aspects are discussed, including an in-depth examination of the influence of the dewar cold finger on sizing
and performance of the cryocooler.
The UP8197 will be placed in the reference frame of the Thales product range of high-reliability linear cryocoolers,
while the rotary solution will be considered as the most compact solution in the Thales portfolio.
Compatibility of the cryocoolers design with new and existing 1/4” dewar designs is examined, and potential future
developments are presented.
In recent years there has been a drive towards miniaturized cooled IDCA solutions for low-power, low-mass, low-size products (SWaP). To support this drive, coolers are developed optimized for high-temperature, low heat load dewar-detector assemblies. In this paper, Thales Cryogenics development activities supporting SWaP are presented. Design choices are discussed and compared to various key requirements. Trade-off analysis results are presented on drive voltage, cold finger definition (length, material, diameter and sealing concept), and other interface considerations, including cold finger definition. In parallel with linear and rotary cooler options, designs for small-size high-efficiency drive electronics based on state-of-the-art architectures are presented.
In a Stirling-type pulse-tube cooler with a dual-opposed piston compressor, the residual vibration exported by the cooler is primarily a result of residual imbalances between compressor motors. Using an electronic feedback loop  and driving compressor motors in a master-slave configuration, the exported force from the compressor can be regulated to negligible levels. This has been demonstrated in a multitude of commercial applications  as well as in space applications. In a novel application of the same electronic feedback technology, the residual exported forces resulting from the motion of the free moving displacer of a Stirling cold finger are compensated, by using the linear dual-opposed piston compressor as an active balancer. Theoretical analysis of this is provided, measurements are presented on different cooler types, and the effect of integration aspects - hard mount versus suspended – is discussed. The effect on exported vibration as well as power efficiency is discussed and compared between Stirling and pulse-tube type coolers. Currently available off-the-shelf hardware, the CDE7232, is presented and future developments are discussed.