The history and general principle of Stirling Engine are briefly discussed. The several points of problem regarding this engine at the present stage and the future applicational probability are shown. This short report is written basing on the author's visit to Philips Res. Lab. at Eindhoven about 4 years ago.
This article introduces the cryogenic power cable, especially its thermal and electrical insulations. These are important matters on the reliability of cryogenic cables. Thermal insulating methods for cables are similar to general cryogenic vesseles. However the length of the cable makes some troubles in evacuation, formation, etc. The applications of thermal insulating methods are discussed with the examples of several plants. Electrical insulating materials at low temperature have been researched in these few years. Solid materials have no reliability because of thermal cracks. Polyethylene paper laminated insulation impregnated with liquid nitrogen has good performance for liquid nitrogen cooled cable. For the superconductive cable, supercritical helium impregnated tape-type insulator seems promissing as electrical insulating methods.
A concentric double solenoid magnet, which can generate a magnetic field up to 10T, is constructed with V3Ga, Nb3Sn, Nb-Ti materials. The Nb3Sn tape of the least current density is put on the extreme parts of the inner solenoid to avoid the magnetic instability due to perpendicular field. The magnet quenches regularly at the limit of current capacity in both solenoids. It is observed, as expected, that the influence of magnetization in the internal solenoid is important on field distribution even by charging only the external solenoid. The residual field and the field distribution at increase or decrease of current are measured on the axis at several conditions, charging only the external solenoid, only the internal solenoid or the both.
For the condensation of 3He into 3He/4He dilution refrigerator, two types of 1K heat exchanger operated by 4He evaporation were designed. One is a disk type and the other is a coaxial counter-flow type heat exchanger. Each exchanger consists of a flow limiting impedance, a sintered copper heat exchanger, and a buffer volume for pumped liquid 4He. No moving part is included in the system. The exchanger is continuously supplied with liquid 4He through the impedance. Sufficient thermal exchange areas for 3He and 4He were obtained in a space of a few cubic centimeters by the use of sintered copper sponges. The small buffer volume for pumped liquid 4He, which forms the 4He-outlet of the exchanger, is useful to stabilize the temperature of the exchanger for an abrupt injection of heat load. The exchanger can absorb approximately 10mW for molar flow rate of 2×10-4 moles/sec of 4He. Therefore it is suitable as a 1K heat exchanger for a dilution refrigerator which has a maximum 3He circulation rate of 10-4 moles/sec. As the exchanger requires a small spacing in the vacuum jacket of the dilution refrigerator, it will be useful for shortening the vertical length of the refrigerator.