ATHENA X-IFU 300 K-50 mK cryochain demonstrator cryostat

In the framework of the ESA X-ray mission ATHENA, scheduled for launch in 2028, an ESA Core Technology Program (CTP) was started in 2016 to build a flight like cryostat demonstrator in parallel with the phase A studies of the ATHENA/X-IFU instrument [1], [2]. As part of this CTP, called the Detector Cooling System (DCS), design, manufacturing and test of a cryostat including existing space coolers will be done. In addition to the validation of thermal performance, a Focal Plan Assembly (FPA) demonstrator using Transition Edge Sensors (TES) detector technology will be also integrated and its performance characterized versus the environment provided by the cryostat. This is a unique opportunity to validate many crucial issues of the cryogenic part of such a sensitive instrument.A dedicated activity within this CTP-DCS is the demonstration of the 300 K–50 mK cooling chain in a Ground System Equipment (GSE) cryostat. The studies are focused on the operation of the space coolers, which is made possible by the use of a ground cooler for cooling cryogenic shields and mechanical supports. Thanks to the modularity of the cryostat, several cooling chains could be tested. In the base line configuration described here, the low temperature stage is the CEA hybrid sorption/ADR 50 mK cooler with thermal interfaces at 4 K and 2 K. 4 K cooling is accomplished by a 4 K Joule-Thomson (JT) cryocooler and its Stirling precooler provided by JAXA. Regarding the 2 K stage, at first a 2 K JT from JAXA will be used. Alternatively, a 2 K JT cooler from RAL could replace the JAXA 2 K JT. In both cases new prototype(s) of a 2 K JT will be implemented, precooled by the EM 15 K pule tube cooler from Air Liquide. This test program is also the opportunity to validate the operation of the cryochain with respect to various requirements, such as time constant and temperature stabilities. This would bring us valuable inputs to integrate the cryochain in DCS cryostat or for the X-IFU phase A studies. This cryochain demonstration is also a critical milestone for the SPICA mission [3]. The design of the cryostat and first thermal validations both before and after integration of the JAXA JT coolers are presented in this paper.     

Development of mechanical cryocoolers for Astro-H/SXS

The Soft X-ray Spectrometer (SXS) is a high-resolution spectrometer with an X-ray micro-calorimeter array onboard the Japanese X-ray astronomy satellite Astro-H, planned for launch in 2013. The micro-calorimeter is operated at cryogenic temperature of 50 mK provided by the Adiabatic Demagnetization Refrigerator (ADR) with a heat sink of 1.3 K liquid helium stored in the SXS Dewar. To extend the liquid helium lifetime to over 3 years in orbit, two types of mechanical cryocoolers are installed: 20 K-class double-staged Stirling (2ST) coolers and a 1 K-class Joule-Thomson (JT) cooler. Improvement of mechanical cryocoolers has been investigated and verified for higher reliability and cooling performance. The engineering model (EM) of upgraded mechanical cryocoolers was fabricated for a long lifetime test. The required cooling power of 200 mW at 20 K for the 2ST cooler and 10 mW at 1.7 K for the JT cooler are achieved by EM test.     

Operating modes and cooling capabilities of the 3-stage ADR developed for the Soft-X-ray Spectrometer instrument on Astro-H

A 3-stage adiabatic demagnetization refrigerator (ADR) (Shirron et al., 2012) is used on the Soft X-ray Spectrometer instrument (Mitsuda et al., 2010) on Astro-H (Takahashi et al., 2010) [3] to cool a 6 × 6 array of X-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system (Fujimoto et al., 2010) consisting of a superfluid helium tank, a 4.5 K Joule–Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes.     

Outgas analysis of mechanical cryocoolers for long lifetime

Mechanical cryocoolers for space applications are required to have high reliability to achieve long-term operation in orbit. ASTRO-H (Hitomi), the 6th Japanese X-ray astronomy mission, has a major scientific instrument onboard—the Soft X-ray Spectrometer (SXS) with several 20K-class two-stage Stirling (2ST) coolers and a 4K-class Joule Thomson (JT) cooler, which must operate for 3 years to ensure the lifetime of liquid helium as a cryogen for cooling of its detectors [1], [2]. Other astronomical missions such as SPICA [3], [4], LiteBIRD [5], and Athena [6] also have top requirements for these mechanical cryocoolers, including a 1K-class JT cooler to be operated for more than 3–5 years with no cryogen system.The reliability and lifetime of mechanical cryocoolers are generally understood to depend on (1) mechanical wear of the piston seal and valve seal, and (2) He working gas contaminated by impurity outgases, mainly H₂O and CO₂ released from the materials in the components of the cryocoolers. The second factor could be critical relative to causing blockage in the JT heat exchanger plumbing and the JT orifice or resulting in blockage in the Stirling regenerator and thereby degrading its performance. Thus, reducing the potential for outgassing in the cryocooler design and fabrication process, and predicting the total amount of outgases in the cryocooler are very important to ensure cryocooler lifetime and cooling performance in orbit.This paper investigates the outgas analysis of the 2ST and the 1K/4K-JT coolers for achieving a long lifetime. First, gas analysis was conducted for the materials and components of the mechanical cryocoolers, focusing on non-metallic materials as impurity gas sources. Then gas analysis of the mechanical wear effect of the piston seal materials and linear ball bearings was investigated. Finally, outgassing from a fully assembled cryocooler was measured to evaluate whether the outgas reduction process works properly to meet the requirement levels.     

In-orbit performance of a helium dewar for the soft X-ray spectrometer onboard ASTRO-H

ASTRO-H was an X-ray astronomy satellite that the Japan Aerospace Exploration Agency (JAXA) developed to study the evolution of the universe and physical phenomena yet to be discovered. The primary scientific instrument of ASTRO-H was the Soft X-ray Spectrometer (SXS). Its detectors were to be cooled to 50 m K using a complex cryogenic system with a multistage adiabatic demagnetization refrigerator (ADR) developed by the National Aeronautics and Space Administration (NASA), and a cryogenic system developed by Sumitomo Heavy Industries, Ltd. (SHI). SHI’s cryogenic system was required to cool the ADR’s heatsink to 1.3 K or less in orbit for three years or longer. To meet these requirements, SHI developed a hybrid cryogenic system consisting of a liquid helium tank, a 4 K Joule-Thomson cooler, and two two-stage Stirling coolers.ASTRO-H was launched from Tanegashima Space Center on February 17, 2016. The initial operation of the SXS cryogenic system in orbit was completed successfully. The cooling performance was as expected and could have exceeded the lifetime requirement of three years.This paper describes results of ground tests, results of top-off filling of superfluid liquid helium just before launch, and cooling performance in orbit.     

Lifetime test and heritage on orbit of coolers for space use

This report describes the results and operating status of ground lifetime testing and achievements on orbit of coolers for space use. Ground lifetime tests of coolers of three types were conducted to demonstrate their long life and reliability. Three single-stage Stirling coolers were tested for 89,016, 71,871 and 68,273 h from 1998, a two-stage Stirling cooler was tested for 72,906 h, and a 4-K class cooler with a two-stage Stirling cooler and a Joule–Thomson cooler was tested for over 2.5 years. After lifetime tests were completed, a few coolers were investigated to determine the cause of the cooling performance degradation. Additionally, the filled gas of the coolers was analyzed. These coolers have shown good results on orbit. Three single-stage Stirling coolers were carried on the X-ray astronomical satellite “SUZAKU” (launched in July 2005), Japanese lunar polar orbiter “KAGUYA” (launched in September 2007), and the Japanese Venus Climate Orbiter “AKATSUKI” (launched in June 2010). Two units of a two-stage Stirling cooler were carried on the infrared astronomical satellite “AKARI” launched in February 2006. A 4-K class cooler was carried on the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) aboard the Japanese Experiment Module (JEM) of the International Space Station (ISS). SMILES was launched in September 2009.     

Development of mechanical cryocoolers for the cooling system of the Soft X-ray Spectrometer onboard Astro-H

Astro-H is the Japanese X-ray astronomy satellite planned for launch in 2014. The Soft X-ray Spectrometer (SXS) onboard Astro-H, is a high energy resolution spectrometer utilizing an X-ray micro-calorimeter array, which is operated at 50 mK by the ADR with the 30-L superfluid liquid helium (LHe). The mechanical cryocoolers, 4 K-class Joule Thomson (JT) cooler and 20 K-class double-staged Stirling (2ST) cooler are key components to achieve a LHe lifetime for over 3 years in orbit (5 years as a goal). Based on the existing cryocoolers onboard Akari (2006) and JEM/SMILES (2009), modifications for higher cooling power and reliability had been investigated. In the present development phase, the Engineering Models (EMs) of these upgraded cryocoolers are fabricated to carry out verification tests for cooling performance, mechanical performance and lifetime. Nominal cooling power of 200 mW at 20 K for the 2ST cooler and 40 mW at 4.5 K for the JT cooler were demonstrated with temperature and power margin. Mechanical performance test for the 2ST cooler units proves tolerability for pyro shock and vibration environment of the Astro-H criteria. Continuous running of the 4 K-class JT cooler combined with the 2ST precooler for lifetime test has achieved over 5000 h without any degradation of cooling performance.     

Optimization of the working fluid for a sorption-based Joule–Thomson cooler

Sorption-based Joule–Thomson coolers operate vibration-free, have a potentially long life time, and cause no electromagnetic interference. Therefore, they are appealing to a wide variety of applications, such as cooling of low-noise amplifiers, superconducting electronics, and optical detectors. The required cooling temperature depends on the device to be cooled and extends into the cryogenic range well below 80 K. This paper presents a generalized methodology for optimization in a sorption-based JT cooler. The analysis is based on the inherent properties of the fluids and the adsorbent. By using this method, the working fluid of a JT cooler driven by a single-stage sorption compressor is optimized for two ranges of cold-tip operating temperatures: 65–160 K and 16–38 K. The optimization method is also extended to two-stage compression and specifically nitrogen and carbon monoxide are considered.     

热声制冷机

热声制冷是微型低温技术潜在的最佳方法。一台声驱动热声制冷机主要包含一个接在中空管道端部的声波发生器和一个在管道内预选位置处放置的热声器件。声波发生器产生的声波在热声效应作用下可在热声器件两端形成温度梯度。介绍了一种基于高效斯特林循环的热声制冷机的基本原理及主要组成。在此基础之上,可通过对各组成部件结构参数的计算、确认,设计出一台热声制冷机。     

斯特林制冷机回热器热损研究

讨论了回热器的各种损失对斯特林制冷机的影响,对斯特林制冷机回热器的结构和丝网填料进行了分析,并模拟分析各种损失的影响.研究表明,回热器的结构、丝网填料对制冷机的性能有重大影响.     

一种复合制冷系统的空间使用可行性分析

半导体制冷器由于材料限制,主要应用于２００ Ｋ 左右的中低温领域。通过低温热管将半导体制冷器热端与辐射制冷器相连,使其热量直接辐射到宇宙空间中,维持２００ Ｋ 温度,将可能使冷端达到接近１００ Ｋ 的空间实用化低温。作者将对这种半导体制冷器／ 热管／ 辐射制冷器的复合制冷系统空间使用的可行性作出简单分析。     

斯特林制冷机用于冰箱技术的发展优势

相对于常用的蒸汽压缩节流制冷冰箱系统,采用逆向斯特林循环自由活塞斯特林制冷机的新型冰箱具有高效率采用"绿色"制冷剂制冷温区广启动电流低制冷量易控等特点,在环保及节能方面具有明显的优势.论文结合自由活塞式斯特林制冷机自身特点,分析其用于小容量家用冰箱以及低温冷柜的优越性;介绍了国外斯特林冰箱的研究进展;展望了这种极具潜力的冰箱制冷系统在我国的发展前景.     

自由活塞斯特林制冷机动力吸振器设计及实验研究

自由活塞斯特林制冷机(FPSC)中动子组件高频运动,产生一定的整机振动力,会影响制冷机工作性能并限制其应用,因此减振技术是FPSC的关键技术之一。本文对一台280 K@300 W斯特林制冷机动力吸振器进行设计,包括减振弹簧型线设计、结构形式选择、三种型号吸振器的质量刚度匹配、模态分析以及扫频验证实验。模拟及实验结果显示,b型吸振器的固有频率设计值、模拟值、实测计算值分别为79.98 Hz、79.56 Hz、80.95 Hz,而实验值为77 Hz,误差分别为3.8%、3.3%、5.1%,质量比约为0.09,满足低振动及轻量化要求,为此,优选b型吸振器作为斯特林制冷机的减振方案。     

Mixed refrigerants for a glass capillary micro cryogenic cooler

Optimized mixed refrigerants are applied in Joule-Thomson (JT) micro cryogenic coolers (MCC) to enhance efficiency. Mixed refrigerants deliver equivalent refrigeration power with much lower pressure ratio and flow rate compared to pure nitrogen refrigerant. To determine the behavior of mixtures in MCCs, the normal boiling points of the components, mixture solubility, and refrigeration loss due to pressure drop on the low-pressure side of the heat exchanger are evaluated. The MCC discussed here was designed to operate at 77 K with the heat exchanger warm end precooled to 240 K by a thermo-electric cooler. An optimized five-component mixed refrigerant was calculated to provide a minimum isothermal enthalpy difference of 1.35 kJ/mol between 77 K and 240 K with a high pressure of 1.6 MPa and a low pressure of 0.1 MPa. Experimentally, a stable temperature of 140 K was achieved with a flow rate of 11 μmol/s. A transient temperature of 76 K was observed.     

Study of a coaxial thermoacoustic-Stirling cooler

A coaxial thermoacoustic-Stirling cooler is built and performance measurements are performed. The cooler uses the acoustic power produced by a linear motor to pump heat through a regenerator from a cold heat exchanger to an ambient one. The cooler incorporates a compact acoustic network to create the traveling-wave phasing necessary for the operation in a Stirling cycle. The network has a coaxial geometry instead of the toroidal one usually used in such systems. The design, construction and performance measurements of the cooler are presented. A measured coefficient of performance relative to Carnot of 25% and a low temperature of −54 °C are achieved by the cooler. This efficiency surpasses the performance of the most efficient standing-wave cooler by almost a factor of two.     

斯特林制冷机在轨工作模式的模拟控制与测量

研制出一套模拟控制与测量装置,模拟斯特林制冷机在轨运行的工作模式,为其在空间应用提高可靠的试验数据。     

A vibration free cryostat using pulse tube cryocooler

This paper introduces a new vibration free cryostat cooled by liquid helium and a 4 K pulse tube cryocooler. The cryogenic device mounts on the sample cooling station which is cooled by liquid helium. The boil off helium is recondensed by the pulse tube cryocooler, thus the cryostat maintains zero boil off. There is no mechanical contact between the cryogenic part of the cryocooler and the sample cooling station. A bellows is used to isolate the vibration which could transfer from the cryocooler flange to the cryostat flange at the room temperature. Any vibrations generated by the operation of the cryocooler are almost entirely isolated from the cryogenic device. The cryostat provides a cooling capacity of 0.65 W at 4.21 K on the sample cooling station while maintaining a vapor pressure of 102 kPa. The sample cooling station has a very stable temperature with oscillations of less than ±3 mK during all the operations. A cryogenic microwave oscillator has been successfully cooled and operated with the cryostat.     

有限元法在辐射制冷器热分析中的应用

辐射制冷器主要为红外探测器提供合适的低温工作条件,是星载红外遥感探测系统的重要组成部分。建立了W型辐射制冷器的有限元模型。利用AN SYS分析软件对辐射制冷器热变形进行了分析,提出了减小2个冷头相对位移的措施,为辐射制冷器的优化设计和红外相机的光学补偿提供了理论依据。     

斯特林制冷系统的电磁兼容设计

海洋水色扫描仪的红外探测器使用斯特林制冷机制冷。本文通过分析水色扫描仪的各种电磁干扰源,提出斯特林制冷系统的电磁兼容设计方法,并给出电磁干扰试验结果。     

Structural analysis of a cryogen-free refrigerator for space

Future X-ray observatories in space, such as European Space Agency's (ESA) X-ray evolving universe spectroscopy (XEUS) mission, will require cooling to the region 10–100 mK to enable the utilisation of advanced cryogenic photon detectors in cryogenic spectrometer instruments. Such missions are envisaged to be completely cryogen-free, replacing the traditional superfluid liquid helium cryostat with a space worthy mechanically cooled system. As part of the Mullard Space Science Laboratory's (MSSL) adiabatic demagnetisation refrigerator (ADR) development programme, we have investigated the construction of a flight cryostat containing a 10 mK ADR (the MSSL double ADR (dADR)) that can be cooled by a single Astrium (formally Matra Marconi Space (MMS)) 4 K mechanical cooler. A proto-type dADR has been constructed and will be flight proven as part of a sounding rocket payload, where the dADR system will be used to cool an array of superconducting tunnel junction (STJ) detectors at the focus of an X-ray telescope.