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Two-stage Stirling cryocoolers (2ST cooler) produced by Sumitomo Heavy Industries, Ltd. have been launched into orbit on three satellites: the “AKARI (ASTRO-F)” infrared astronomical satellite, JEM/SMILES on ISS, and the “HITOMI (ASTRO-H)” X-ray astronomical satellite. A 2ST cooler compressor has a linear-ball-bearing system as a piston-supporting structure. The linear ball bearing system is a key components to realize a lower drive frequency (15 Hz), a long piston stroke (30 mm). Its typical cooling power is 200 mW at 20 K for the second stage and 1000 mW at 100 K for the first stage, with 90 W electrical input power. During the test of the “HITOMI” engineering model, the energy resolution of the detector was found to be degraded when cryocoolers were in operation. After investigation, it was found that micro vibration from 2STs caused the degradation. The continuum in the vibration spectrum propagated into sub-Kelvin region and generated thermal noise. The continuum has origin in linear ball bearing in the compressor. In the case of “HITOMI”, vibration isolators were introduced to resolve this issue. For future mission, we are required to reduce microvibration of cryocooler itself. Therefore, the piston support mechanism in the compressor was modified from linear ball bearings to triangle shape flexure springs in order to reduce the continuum in vibration spectrum. In order to achieve a long piston stroke (±15 mm), the generated stress could be reduced to 400 MPa (Less than 1/2 of fatigue limit) or less even when the shape of the triangle shape flexure spring was devised and displaced by 15 mm. The typical vibration level has been reduced to 1 × 10−5 Nrms2 / Hz or less at a frequency of 200 Hz or less and 1/10 times or less at 200–600 Hz than that of a compressor with a linear ball bearing system. The cooling power is kept to 260 mW at 20 K, with 90 W electrical input power. This low vibration cooler is expected to be an improved cryogenic system for use in future projects with sub-Kelvin detectors.

Sumitomo Heavy Industries, Ltd. (SHI) developed a high-power Stirling-type pulse tube cryocooler for cooling high-temperature superconductor (HTS) devices, such as superconductor motors, superconducting magnetic energy storage (SMES), and fault current limiters. The experimental results of a prototype pulse tube cryocooler were reported in September 2013. For a U-type expander, the cooling capacity was 151 W at 70 K with a compressor input power of 4 kW. Correspondingly, the coefficient of performance (COP) was about 0.038. However, the efficiency of the cryocooler is required to be COP > 0.1 and it was found that, theoretically, it is difficult to further improve the efficiency of a pulse tube cryocooler because the workflow generated at the hot end of the pulse tube cannot be recovered. Therefore, it was decided to change the expander to a free-piston type from a pulse tube type. A prototype was developed and preliminary experiments were conducted. A cooling capacity of 120 W at 70 K with a compressor input power of 2.15 kW with corresponding COP of 0.056, was obtained. The detailed results are reported in this paper.

Apart from double acting type engines, Stirling engines have either 2 pistons in 2 cylinders or 2 pistons in a single cylinder. Typically, the heater, regenerator and cooler are installed between the 2 pistons. The pulse tube engine, on the other hand, consists of a single piston in a single cylinder, a pulse tube, a heater, a regenerator, a cooler and a second cooler. For this paper, a simple prototype engine that uses air at normal atmospheric pressure as the working gas was fabricated. The oscillating velocity of the working gas in the pulse tube was measured using LDV, and the work flow emitting out of the pulse tube was observed. In addition, the effect of inserting heat storage material in the pulse tube on shaft power and indicated power was examined experimentally. A dramatic increase in the shaft power was achieved.

A low-noise, pulse-tube cryocooler has been developed. It is suitable for cooling variable semiconductor or superconducting devices. The cryocooler's electro-magnetic noise and inclination characteristics are improved, and the cooling capacity is 4.9 W at 77 K with an input power of 800 W. The minimum temperature was less than 49 K. The cooling performance at 77 K was within 5% degradation for all orientations. The low-noise pulse-tube cryocooler was installed in a cryostat designed for a high-Tc SQUID sensor. The electro-magnetic noise was measured by the magnetometer-type SQUID sensor cooled in the cryostat. The noise level was influenced by the direction of the sensor. When the sensor was parallel to the cryocooler cylinder, the white noise was about 300 fT/√Hz and the cyclic noise produced by the cryocooler's magnetic material or mechanical vibration was not observed. When the sensor was vertical to the cylinder, the white noise was about 2 pT/√Hz and the cyclic noise was about 10 pT rms. A real-time magnetocardiography was successfully measured using a high-Tc SQUID magnetometer cooled by the pulse-tube cryocooler. The signal-to-noise ratio was better than the conventional cryocooling system.

The pulse-tube cryocooler is which doesn't need a moving parts in the expansion space and the advantage that said with improvement of reliability by low vibration is given. But it becomes difficult to predict performance of the cryocooler because there is not a piston when we design new cryocooler. In late years, analysis technique by Thermoacoustics theory has been developed as the tool which understood the pulse-tube cryocooler at the overall. Moreover and, as a simple method, Matsubara likens gas in pulse-tube to solid piston, and develops equivalent PV method calculating work in the expansion space. But, as pulse-tube design tool, there are many points to be still not enough. So we select numerical calculation by 3rd order as analysis technique to do design development of pulse-tube cryocooler by this report, and report it because evaluation examined behavior of inside gas by a difference of the phase shifter.

The large capacity handled by the IMT 2000 requires that a high-frequency band of 2 GHz be used. However, raising the frequency results in the occurrence of various problems related to the large volume of data handled, such as increased signal loss, lower signal quality and interference in adjacent frequency bands. It is hoped that substituting a high-temperature superconductor in a place of the existing dielectric filter will reduce insertion loss, noise and high Q values. The authors have applied current technologies for film, microwave and cryocooler to develop a high-temperature superconducting (HTS) filter subsystem for the base stations of mobile telecommunication systems. The new filter has a fractional bandwidth below 1.02% at 1.955 GHz and has a minimum insertion loss at 0.2 dB. A small, highly efficient and long-life pulse-tube cryocooler a with cooling capacity of 0.65 W at 70 K and 60 W compressor input power is used 60 W. The components have been integrated into a subsystem, the external dimensions of which have a total volume of 10.1 L.

Since 2012, a new, compact Gifford-McMahon (GM) cryocooler for cooling superconducting single photon detectors (SSPD) has been developed and reported by Sumitomo Heavy Industries, Ltd. (SHI). Also, it was reported that National Institute of Information and Communications Technology (NICT) developed a multi-channel, conduction-cooled SSPD system. However, the size and power consumption reduction becomes indispensable to apply such a system to the optical communication of AdHoc for a mobile system installed in a vehicle. The objective is to reduce the total height of the expander by 33% relative to the existing RDK-101 GM expander and to reduce the total volume of the compressor unit by 50% relative to the existing CNA-11 compressor. In addition, considering the targeted cooling application, we set the design cooling capacity targets of the first and the second stages 1 W at 60 K and 20 mW at 2.3 K respectively. In 2016, Hiratsuka et al. reported that an oil-free compressor was developed for a 2K GM cryocooler. The cooling performance of a 2K GM expander driven by an experimental unit of the linear compressor was measured. No-load temperature less than 2.1 K and the cooling capacity of 20 mW at 2.3 K were successfully achieved with an electric input power of only 1.1 kW. After that, the compressor capsule and the heat exchanger, etc. were assembled into one enclosure as a compressor unit. The total volume of the compressor unit and electrical box was significantly reduced to about 38 L, which was close to the target of 35 L. Also, the sound noise, vibration characteristics, the effect of the compressor unit inclination and the ambient temperature on the cooling performance, were evaluated. The detailed experimental results are discussed in this paper.

The pulse tube refrigerator does not have moving parts in the cold section and has high reliability. So, it has already been used practically as a cryocooler. However, this type of refrigerator is not developed for residential freezer or air conditioner use. Then, an inertance type refrigerator, which used atmospheric pressure air for the working gas has been developed in order to examine the possibility of the refrigerator for the temperatures around 0 C. In this paper, the effect of inertance dimensions and the regenerator matrix on cool-down characteristic is examined experimentally. Additionally, effects of inertance length on COP and heat loss are analytically examined. As a result, the working gas temperature in the cold head has lowered from room temperature of about 55 C. The gas temperature in the cold head is -32 C.