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This paper describes two kinds of optical cryostats designed and manufactured at Absolut System. The first one makes use of pressurized LN2 for temperature control of a sample holder in the 80 K - 470 K temperature range. An optical window is implemented above the sample holder to allow for rugosity and 3D distortion of heterogeneous semicon sample assemblies on a wafer. The second one makes use of CRYOMECH remote motor type pulse tube cryocoolers for temperature control of the sample holder in the 3 K - 300 K temperature range. In this type of cryostats, particular attention has been paid to reduce the vibrations exported by the cooler. These 4 K ultra low vibration cryostats are used for characterization of samples via optical windows. Both designs will be presented and the performance reported. [ABSTRACT FROM AUTHOR]

The NGST ACTDP cooler features a 5–6 K Joule-Thomson (JT) cooler pre-cooled by a three-stage Pulse Tube (PT) cryocooler. Our design provides remote cooling of ∼60 mW at 5 to 6 K and, optionally, remote cooling at 18 K. The NGST ACTDP cooler is being developed under contract with the Jet Propulsion Laboratory to enable active cooling of instruments including large space telescopes, in particular the Mid InfraRed Instrument (MIRI) of the James Webb Space Telescope (JWST). This paper describes the design of the NGST ACTDP cooler and presents test results, including the integrated tests of the two major subsystems making up the thermal-mechanical cryocooler, the closed loop JT cooler and the PT pre-cooler. Both the JT and PT subsystems have been demonstrated to provide the cooling required for MIRI in laboratory tests using flight like hardware with excess capacity. These tests enable a reliable projection of the total electrical power of the NGST MIRI cooler of 200–296 W for steady state operation under end of life conditions, depending on the margins added to the thermal loads and parasitics. NGST’s design offers a low risk approach to providing cooling of MIRI making maximum use of flight proven hardware. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fuji Electric Group has developed a miniature pulse tube cryocooler (PTC) of U-shaped configuration with a specific cooling capacity of 2W at 70K and requiring 100W of electrical input power. The emphasis has been on compactness, light weight, high performance, high reliability and low cost. This PTC is for commercial applications: for example, semiconductivity and high temperature superconductivity (HTS) devices used in wireless telecommunication systems and imaging sensors. The dimensions of the PTC have been reduced to 246mm wide by 232mm high and a weight of 8.5kg as integral configurations. The linear compressor motor uses two sets of moving coils to drive twin pistons supported by flexure bearings in a dual opposed configuration. The phase shifter, consisting of an inertance tube and reservoir tank, has been optimized. We produced and tested a prototype reduced-cost PTC. The prototype has a cooling capacity greater than 2.5W at 70K with 100W of electrical input power. The vibration of the cold head is less than 2 micrometers (peak to peak) when the hot-end side flange of the expander is fixed. This paper describes in detail its performance including inclination and vibration. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Two small helium liquefiers using 4 K pulse tube cryocooler have been developed and commercialized at Cryomech, Inc. Model PT405 and PT410 pulse tube cryocoolers used for the liquefiers have cooling capacities of 0.5 W and 1.0 W at 4.2 K respectively. One distinctive advantage of the pulse tube liquefiers is efficient precooling of helium gas to be liquefied with the 1st stage heat exchanger and the 2nd stage regenerator of the cold head. The liquefier with the PT405 liquefies helium from room temperature at a rate of 7.2 Liter/day for 4.6 kW power input. The liquefier with the PT410 has a liquefaction rate of 14.0 liter/day for 8.0 kW power input. The helium liquefiers have been used for a few challenging applications to liquefy and re-condense helium. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In order to provide cryogenic cooling for applications that are extremely sensitive to mechanical vibration, Thales Cryogenics has been delivering U-shape pulse tube cryocoolers since 2001. The disadvantage of the U-shape design is that the available regenerator volume is too limited if the application puts constrains on the overall diameter of the cold finger, thus limiting the coolers efficiency. As presented at CEC/ICMC 2003, Thales Cryogenics and CEA/SBT have achieved very good results with a large concentric pulse tube delivering 4W @ 77K driven by a flexure bearing compressor. Furthermore, the same team, together with Air Liquide DTA, developed a very efficient 1W pulse tube cooler for the ESA MPTC project. Based on the experiences obtained with those programs, Thales Cryogenics and CEA/SBT have now developed a small concentric pulse tube that is driven by a flexure bearing compressor. The result is a very compact and reliable cooler, with an efficiency that is nearly doubled compared to the U-shape version with the same overall external diameter dimensions. 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 a comparison with a comparable Stirling cold finger. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A co-axial type pulse tube cryocooler has been fabricated which is applied as a current lead for the superconducting coil. The cryocooler consists of an outer regenerator tube enclosing and thermally insulating a central pulse tube. The connection between the pulse tube and the regenerator was realized at the cold end. This arrangement allows inserting a 16 mm diameter copper rod on the axis of a cryocooler which serves as a current lead. Characterizations of the pulse tube current leads are performed by the numerical analyses and the experiments. The Equivalent Pressure Volume (EPV) method was utilized to obtain optimized refrigeration capacity with four-valve operation mode. The paper also discusses the possibility of applying a pulse tube current lead to the superconducting coils. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Distributed loads are frequently encountered in large deployable structures used in space applications such as optical mirrors, actively cooled sunshades, and on focal plane electronics. One mechanism for providing distributed cooling is via an oscillatory cryocooler such as a pulse-tube that is integrated with a fluid rectification system consisting of check-valves and buffer volumes in order to extract a small amount of continuous flow. This continuous flow allows relatively large loads to be accepted over a long distance with a small temperature difference and has advantages relative to vibration and electrical isolation. Also, it is possible to provide rapid and precise temperature control via modulation of the flow rate. The same working fluid, helium, can be used throughout the entire system, reducing complexity and simplifying the contamination control process. This paper describes steady state and transient modeling results and presents experimental data for a single-stage pulse tube with a rectifying interface that is integrated with a distributed load. The predicted and measured steady state and transient behaviors are compared. The experimental data are used to demonstrate the thermal management concept and illustrate how it can be used for rapid and precise temperature control. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Under contract with the Air Force Research Lab (AFRL), Lockheed Martin has built and tested a 3-stage pulse tube cryocooler which provides cooling at 10K and 75K. The cooler was designed for 200mW cooling at 10K and 8W cooling at 75K. The pulse tube is a simple 3-stage coldhead with no moving parts, driven by a long-life linear flexure-bearing clearance-seal compressor. The coldhead is a robust U-tube arrangement, with all metal seals for long life. Performance data will be presented. Future Air Force and Department of Defense (DoD) satellites will require efficient, low temperature cryocoolers to support space surveillance, missile defense, and other mission applications. The use of Very Long Wave Infrared (VLWIR) focal planes using arsenic doped silicon detectors operating at 10K which can detect to 25 micron wavelength has long been sought as the solution to the mid course missile defense mission. The immaturity of 10K cryocooler technology has impeded the use of VLWIR focal planes in current space payloads. A viable, efficient 10K cryocooler could provide further benefits through the use of on-focal plane readout and signal processing using low temperature superconducting electronics. The resultant smaller apertures produce cheaper, lighter sensors, much easier to host in a space-based system. An efficient, compact 10K cryocooler would provide significant capability improvements to future DoD systems. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A Large heat lift 40 to 80 K Pulse Tube Cooler (LPTC) is currently under development in partnership between AL/DTA, CEA/SBT and THALES Cryogenics. The Engineering Model (EM) foreseen is aiming to provide 2 W of cooling capacity at 50 K for 10°C rejection temperature and for 125 watts input power to the compressor’s motors. Cold finger development models (DM) have been manufactured with an in-line architecture and connected to an off-the-shelf compressor from Thales Cryogenics. In parallel, the compressor motor has been optimized and prototyped. The various trade-offs, performed both on the cold finger and compressor side, during the development phase are presented. This work is funded by the European Space Agency (ESA/ESTEC Contract N°18433/04/NL/AR) in the frame of future Earth Observation instruments development. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Under contract with the Space Dynamics Laboratory, Lockheed Martin’s Advanced Technology Center (LM-ATC) has built and tested the two-stage Engineering Model of a space flight pulse tube cryocooler, which provides simultaneous cooling at 75 K and 130 K. The cryocooler is robust and simple, consisting of a two-stage coldhead with no moving parts, driven by a linear flexure-bearing compressor and powered by a high-efficiency electronic controller that includes ripple suppression and vibration cancellation. A distance of up to one meter separates the coldhead and compressor. The cryocooler was designed to simultaneously provide 0.75 W of cooling at 75 K and 6 W cooling at 130 K while conductively rejecting heat at 313 K. Total system power is 125 W. Performance data is presented, showing excellent cryocooler performance. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Launched on NASA’s Aura spacecraft on July 15, 2004, JPL’s Tropospheric Emission Spectrometer (TES) instrument has completed a successful first year in space and captured a number of important lessons. The instrument contains four focal plane arrays in two separate housings cooled to 65 K by a pair of NGST pulse tube cryocoolers. The instrument includes a two-stage passive cooler to cool the optical bench to 180 K. The cryocooler system design is tightly coupled with the overall thermal control design to maximize performance. Soon after cooling the optical bench and focal planes to their operating temperatures on August 20, 2004, ice contamination of the focal planes led to the need of a decontamination cycle. Ice buildup of cryogenic surfaces led to increased cryocooler heat loads. After six months of successful science operations, plans were developed to increase the optics temperature to 187 K to improve the interferometer optical alignment and obtain higher quality science data. The plan is in place and will be implemented in the near future. This paper provides a general overview of the cryogenic system design and reviews the instrument cryogenic performance over the past year. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Lockheed Martin’s Advanced Technology Center has developed a compact coaxial pulse tube cryocooler for avionics applications. The cooler was designed to deliver in excess of 1W cooling at 77K with a heat rejection temperature of 70°C, and to cool down from ambient temperature in a very short period of time. The cryocooler utilizes our MINI compressor, developed for NASA-GSFC, coupled with a newly-designed coaxial pulse tube designed to approximate the Standard Advanced Dewar Assembly (SADA II) packaging envelope. The cryocooler mass is 1.25 kg. Test data show excellent performance, with cooldown times of less than 6 minutes (coldhead only, with no additional thermal mass attached to the coldhead). Performance data will be shown for a variety of operating conditions. A discussion of low cost pulse tube cryocoolers will also be presented. This cryocooler was developed and tested with Lockheed Martin IRAD funding. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]