Superfluid experiment in the zero gravity state was performed with a cryostat aboard a sounding rocket S-520. The observation of dynamic behavior of liquid helium (He II), the verification test of a porous-plug phase separator with a controlling heater, the investigation of thermal behavior of superfluid thin film or of a superfluid heat pipe, and the noise test of a cooled FET pre-amplifier for IR detectors were performed. The experiment showed that the initial bulk fluid motions rather quickly damped and a stable liquid containment in the cryostat was realized, and that a very good temperature uniformity was attained throughout the vessel. The porous-plug was found to work as good as the prediction for the zero-g state. The adsorbed film became thicker in the reduced gravity state than on the ground.
Electrical insulators for various types of superconducting magnets are reviewed. Epoxy resins and their composites have been widely used for magnets of radiation resistance up to 1×107Gy (1×109rad). For higher radiation resistant magnets (-1×108Gy) polyimides and their composites should be adopted. Adequate study should be made to select insulators for INTOR magnets which are expected to with-stand 2-5×107Gy. For resin moulded type magnets, epoxy resin impregnants with adequate toughness at cryogenic temperatures should be adopted with vacuum pressure moulding process. Turn layer insulators, ground wall insulators, and spacers between pies are needed for pool boiling type magnets. These insulators are all FRP in their last state. High density FRP with low thermal contraction and high compressive strength have been developed in several countries. They are compared in their properties essential for spacer use. Ground insulators for forced flow type magnets are also reviewed. Voltage withstand test conditions for superconducting magnets are checked. FRP cryostats or dewers have been constructed in several facilities. Some unique cryostats, W type and U type, are introduced.
This paper reviews the recent progress of the small cryocoolers operating near 4K, for the application of small scale superconducting magnets or superconducting devices. The research and development scheme of cryocoolers can be classified into two categories. The first one is related to the investigation of reliability, compactness and cutting costs of the well known cryocooler systems. Stirling or G-M cycle cryocoolers with a J-T loop and small scale claude cycle also belong in this category. The second one is a fundamental approach to the novel refrigeration systems such as a magnetic refrigerator or regenerative cryocoolers which can be cooled down to liquid Helium temperature without J-T loop. A cascade J-T system using gas adsorption compressor is also included.
It is necessary to monitor the liquid-level of superfluid helium (He II) in order to control the refrigeration system of He II. One approach to detect the liquid-level of He II by means of ultrasonic waves is shown in this paper. The experimental results are greatly satisfactory. Heat powers brought into He II bath are below 0.1μW. The measuring error is 1.5%. Other advantage is that this liquid-level meter can be used for any liquid.
Specific heat of dysprosium gallium garnet (DyGaG) single crystal has been measured between 20 and 2K in the magnetic fields up to 5T. From the specific heat and adiabatic demagnetization measurements, the temperature dependence of the entropy in various magnetic fields is determined. It is shown that DyGaG is one of the good materials for magnetic refrigeration between 12 and 2K.
A double acting bellows type liquid helium pump was developed for the cryogenic system of a large thin solenoid magnet. The pump performed the maximum capacity of 900l/hr and the maximum pressure head of 4.4×105Pa while the heat generation in the pump was only 200mW. The fatigue test of the bellows was made prior to the construction of the pump. It endured more than six million pumping cycles in liquid nitrogen temperature. The pulsation of the outlet pressure was largely reduced by use of oil-air cylinder actuation.