Abstract: A circuit to power an electron source includes a filament transformer comprising a primary side and a secondary side, a high-voltage transformer coupled to the filament transformer and the electron source, and an alternating current (AC) current limiter coupled in series with the primary side or the secondary side of the filament transformer. The AC current limiter includes a diode bridge and a current-limiting device in the diode bridge.

Abstract: In the particular embodiments described in the specification, a vacuum furnace includes a conveying arrangement for holding four solid metal members with their end faces in closely-spaced relation and an energy beam gun directs energy to the adjacent faces to melt the metal. Metal ejected from the heated surfaces by explosive vaporization of inclusions in the metal is trapped by the adjacent surfaces of the other metal members.

Abstract: A clear optical path is provided in a furnace in which high intensity top surface heating is carried out. The path extends through a viewport to the interior of the furnace chamber. The path extends to a clear metal mirror surface and from the mirror surfaced to other portions of the furnace chamber which are not viewable directly through the viewport.

Abstract: In an electron beam evaporation system utilizing a grid to control electron flow, non-uniformities in vapor density caused by periodic trapping of electrons near the filament due to the magnetic field produced by alternating heater current are substantially reduced either (1) by out-of-phase grid modulation which increases electron flow from the filament at times when the alternating magnetic field operates to trap electrons, (2) by using a high frequency a.c. source for heating the filament thereby to smooth out the effects of the a.c.-produced magnetic field, or (3) by using an auxiliary cathode heated by the bombardment of electrons from a filament spaced from the cathode by a distance which removes the cathode from the magnetic field produced by the a.c. heating of the filament. In one emobodiment, demodulation of vapor density is employed in laser isotope separation to provide a temporally uniform atomic uranium vapor.

Abstract: A level sensor for measurement of the level of molten metal in an electron beam evaporator which operates to sense directly the position of the point or line source of evaporant by detection of radiation such as light emitted therefrom. Compensation is provided for variations in electron beam deflecting magnetic field to avoid interpreting lateral movement of the point or line source from field variations as level changes. Compensation is also provided in the detection circuit for variations in detected light intensity that would otherwise provide an erroneous indication of level change. Detection of further conditions that produce unreliable level sensing and system inhibition in response thereto is provided as a safety feature.