Operating characteristics of a segmented hollow cathode over a wide pressure range

A segmented hollow cathode has been designed, constructed and operated over a wide pressure range from 1 mbar to 200 mbar to determine optimum operating characteristics for a series of unique applications. The device is designed for use as a plasma source for molecular gas lasers operating in the UV and visible spectra. The cathode consists of 1 mm thick nickel disks and 0.1 mm tungsten foil disk segments stacked alternately, forming a cylindrical geometry on its outer surface and a near-spherical geometry inside. The tungsten foil disk inner diameters vary along the longitudinal axis of the cathode. With this special geometric arrangement one hollow cathode structure is embedded within another. The spacing between the segments (tungsten foil disks) creates one hollow cathode geometry, and the spherical geometry formed by the inner diameter of the segments is a second hollow cavity. This design permits one to operate the device at an expanded pressure range. The device's voltage and current characteristics are studied at different operating pressures and the optimum operating parameters such as pressure, voltage, current, and foil thickness are investigated. Helium, argon or a helium-argon mixture is used as the fill gas throughout the series of experiments.<
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