Comparison of commercial, spherical powder and wire bundle tungsten ionizers

Conference · Fri Mar 15 04:00:00 EST 1963

OSTI ID:4876109

Kuskevics, G.; Thompson, B. L.

Cesium ionization on different porous tungsten structures was measured in terms of neutral fraction, critical temperature, and flow rate in a regular laboratory test chamber environment in the 10/sup -6/ torr range. These structures included 3/16 in. commerical sintered ionizers with about 2micron average pore diameter, spherical powder ionizers of 6-micron effective pore diameter and, 12- and 6-micron diameter wire bundle ionizers. Conductance was measured at room temperature with nitrogen and at operating temperature with cesium vapor. The neutral fraction was obtained by a surface ionization probe measurement at 15 deg to the beam axis. Critical temperatures were derived from the ion current versus ionizer temperature curves. The ion current was measured at a liquid-nitrogen-cooled, grooved current collector which had two grids to suppress secondar electrons. The ionizer temperature was measured with a sheathed tungsten--ruthenium alloy thermocouple. Ion current and neutral fraction were plotted as log j or log alpha versus 1/T. The directly heated ionizers could be operated up to 1500 deg C. In general the performance of ionizers improved with time of operation. During this conditioning time the critical temperature and neutral fraction shifted to lower values. The best critical temperatures for all tungsten ionizers in the 10/sup -6/ torr residual gas pressure at current densities between 1 and 20 ma/cm/sup 2/ were within 100 deg K of Langmuir's data for solid tungsten. Since the surface was not clean the critical temperature had a considerable spread. Neutral fractions for commercial sintered, spherical powder, and fine wire bundle ionizers ranged from 0.1 to 5 percent, but were considerably higher for coarse wire bundle ionizers. (auth)

• Research Organization: Electro-Optical Systems, Pasadena, CA (United States)
• Sponsoring Organization: Sponsor not identified
• NSA Number: NSA-17-035270
• OSTI ID: 4876109
• Report Number(s): CONF-10--45; Preprint--63016
• Country of Publication: United States
• Language: English

Related Subjects

CESIUM
CONFIGURATION
COOLING
CURRENTS
ELECTRIC CONDUCTIVITY
ELECTRONS
GENERAL AND MISCELLANEOUS
HEATING
ION BEAMS
IONIZATION
IONS
LOW TEMPERATURE
MEASURED VALUES
NITROGEN
PERFORMANCE
POROSITY
POWDERS
PRESSURE
RUTHENIUM ALLOYS
SINTERING
SPHERES
SURFACES
TEMPERATURE
THERMOCOUPLES
TUNGSTEN
TUNGSTEN ALLOYS
VAPORS
WIRES