William S. Corak

Measurement and Control of the Level of Low Boiling Liquids

An account is given of a simple, reliable, and generally applicable electrical means for accurately measuring and controlling the level of low boiling‐point liquids. The sensitive elements exhibit at least a fivefold voltage difference for nitrogen and at least a five hundred‐fold difference for helium depending on whether they are in the liquid or the vapor. Heat transfer characteristics for liquid nitrogen are also noted.

A Transfer Device for Low Boiling Liquids

The principles involved in the transfer of low boiling liquids under their own vapor pressures are indicated and calculations are presented for the specific case of the transfer of liquid nitrogen. A convenient device for transferring liquid nitrogen by this procedure is described and its operating characteristics are compared with the calculations.

White Beam Synchrotron X-Ray Topography of Gallium Arsenide

The defect structure of gallium arsenide is being examined using white beam transmission topography. The specimens under examination are cut-and-polished, three inch diameter, single crystal substrates from various suppliers in the “as received” condition. The goal of this continuing program is to first document the existence of various crystallographic defect structures and then to establish their effect on the performance of microwave integrated circuits subsequently fabricated on the wafers. Success in establishing such a correlation might permit the use of an x-ray diffraction measurement to screen incoming material, eliminating marginal substrates and achieving a corresponding increase in yield.