[en] This paper presents the results of numerical simulations of thermal stratification in liquid hydrogen as a cryogenic fluid. The authors used the vorticity-stream function method and correlated the surface temperature with the heat flux, fluid level and time. In addition, the simulation results are compared with experimental data

[en] Minimizing thermal resistances across interfaces is critical for efficient thermal performance of conductively cooled superconducting magnet systems. Thermal conductance measurements have been made for a flexible thermal coupling, designed to accommodate magnet-to-cryocooler and cryocooler-to-shield relative motion, and an interface incorporating Multilam designed as a sliding thermal connector for cryocoolers. Temperature changes were measured across each interface as a function of heat input. Thermal conductances have been calculated for each interface, and the impact of each interface on conductively cooled magnet systems will be discussed

[en] Tests were performed to select a Phase Separator (porous plug) material to be used with the NASA/Stanford University Relativity Mission. The porous plug is used to retain superfluid helium (SFHe) in the 2400 liter tank of the Dewar. Operation of this plug is unique in that it is used to control SFHe temperature, operate over a wide range of flowrate, and provide gas for spacecraft attitude control. This paper summarizes data taken during evaluation of various materials made of sintered stainless. Data was taken during normal and choked flow conditions. Tests were performed on increasing the flowrate capability by using a heater on the downstream side of the plug. Critical breakthrough parameters were determined. These tests led to the selection of a material for use in the Dewar

[en] This paper presents the design and test results of a weir used to measure the flow rate of saturated liquid helium in a two phase helium flow stream. The flow meter requires the presence of saturated vapor to measure the liquid flow rate but does not measure the vapor flow rate. The weir, located at a high point in the flow path, acts as a dam and creates a reservoir of liquid behind it. Liquid helium drains through a notch in the weir. The liquid helium level behind the weir is measured to determine the flow rate. The level increases with flow rate. The unmeasured vapor passes over the top of the weir and mixes with the liquid downstream of the weir. A weir was installed on the outlet of a string of superconducting magnets

[en] Paper describes -20 - +20 V voltage and -4 - +4 A current pulse shaper designed to study critical current in superconductors and processes of heat transfer in helium 2. Pulse minimal duration is 50 ns, time to determine output voltage with 0.025% accuracy at input voltage variation by 1 V constitutes 0.9 mcs

[en] Short communication

[en] Results are presented from measurements of pressure and temperature differences as a function of the flow rate and hydrostatic head for two types of porous plugs for phase separation of superfluid He and He vapor: (1) a plug made of sintered stainless steel, similar to that in the IRAS, IRT, and COBE dewars except for larger pores, and (2) a glass plug with pores of uniform cross section. Results show that a liquid/vapor phase boundary exists at the outer surface of the porous plug for low flows or large hydrostatic heads; as the flow increases or the hydrostatic head decreases, the boundary retreats into the plug. Some hysteresis near the phase boundary retreat was observed in the stainless steel plug. 6 refs

[en] A 1/4-in-diam remotely controlled motorized cryovalve for a spaceborne superfluid-He (SFHe) dewar is described. Special attention is given to the mechanical and electrical requirements for the SFHe control valve, the valve design, the testing/performance evaluation, and applications. It is shown that the design of the cryovalve met all imposed requirements: it seals against SFHe leakage, operates remotely at temperatures below 1.8 K, and survives launch environments. Diagrams are presented for the motor and gearbox drive mechanism of the valve, the spindle and steel-tape drive for lift-arm actuation, the cryovalve test apparatus, and the plumbing schematic for the dewar. 2 refs

[en] A research program to develop a He-3/He-4 solution refrigerator for space applications is underway. The results of the effort to use an electric field as a substitute for gravity to control the He-3/He-4 mixture interface that separates phases in terrestrial units are described. Further, experimental results obtained from an engineering model of a single-cycle dilution refrigerator with a mixing chamber capable of operating in a zero-gravity environment are described. Future research and development plans are outlined, in particular the need to test the operation of a single-cycle as well as a continuously operating dilution refrigerator in space. 12 refs

[en] In relation to the problem of supercooling for ice storage devices, experiments on freezing a relatively large volume of supercooled water is carried out. In the experiment, an experimental method to determine a probability of freezing a large volume of supercooled water with a uniform temperature distribution is introduced. It is accomplished by dividing the water into many smaller droplets. In a statistical analysis, a method to improve an accuracy in a case of having a limited number of experiments is introduced, and the probability of freezing is calculated for each degree of supercooling. The average freezing temperature for the experiment is placed just at the extended region of the other researchers results worked on small droplets. By relating the value with the probability of freezing on various kinds of heat transfer surfaces, the probability of freezing which is independent of the surface is calculated. In this paper it is confirmed to be negligible compared with the one on the surface