Helium Gas Environment Research Articles

Precise Pressure-Temperature Control System for Electrical Measurements down to 4.2 K Using Helium Gas as a Pressure Transmitting Medium

A system in which electric measurements can be performed under a good hydrostatic condition (up to 7 kbar in helium gas environment) and under very precisely controlled temperature has been developed. This system is especially suitable for the very low temperature measurements (down to 4.2 K) where most pressure transmitting materials solidify. The system has been utilized for the measurements of dielectric constant and the spontaneous polarization of a quantum ferroelectric, tris-sarcosine calcium bromide ((CH3NHCH2COOH)3CaBr2; TSCB).

Dynamic Thermal Distortions in an X-ray Mask Membrane During Pulsed X-Ray Exposure

The dynamic thermal distortion for an X-ray mask membrane has been numerically studied with special reference to the effect of elastic waves on its distortion behavior during pulsed X-ray exposure. A partial differential equation governing the dynamic behavior is derived by combining the theory of plane stress and the principle of Hamilton. The calculations based on an implicit finite difference method are performed for a SiN membrane under a 1-bar helium gas environment. Thermal displacement caused by a pulsed X-ray extends in the form of an elastic wave from a terminated rim toward a center. Critical pulse duration is offered in which the displacement in an exposure field does not occur during pulsed X-ray exposure. The peak displacement takes place with a time lag after a pulse exposure.

Safety studies of cryostable superconductor

Superconductors used in a large superconducting magnet system are generally designed to be cryostable. There exists a strong possibility that cryostable conductor will burn out in a helium gas environment should a normal zone be generated from any point of the coil above the liquid helium level. An experiment is set up to investigate the heating of a cryostable conductor in a helium gas environment. Results will be presented and the ultimate safety of a cryostable conductor will be discussed.

Compatibility between several heat resistant alloys and sintered Li2O in static helium gas environment

The reaction of sintered Li2O discs with several commercial heat resistant alloys has been investigated under the conditions of 3.3 × 104Pa (13 atm) static He gas atmosphere in the temperature range of 500 and 750° C. Reaction products were identified by X-ray diffraction analysis to be two phases of Li5FeO4 and LiCrO2. The former was dominant below 650° C and the latter was dominant above 650° C. The activation energies of the reaction were determined by the Arrhenius plots for weight changes and sub-scale thickness measurements. The reactivity of the four Fe-Ni-Cr alloys decreased according to the order of Incoloy 800, 316 SS, Hastelloy X-R and Inconel 600. Grain boundary penetration was observed above 500° C for Incoloy 800, 550° C for 316 SS and 600° C for Inconel 600. There was no grain boundary penetration in Hastelloy X-R.