UCLA

A lanthanum hexaboride hollow cathode using argon gas has been built as a prototype for the eventual development of a hollow cathode that operates with lithium. The cathode with a 0.12 inch orifice diameter is well operated at discharge currents of 10 to 50 A, keeper currents of 0.1 to 2.5 A, and argon gas flow rate of 10 sccm (standard cubic centimeter per minute) to 25 sccm. The electron density at a position 7.9 cm away from the orifice has a peak value of 5.2*1012 cm-3 under 15 sccm argon gas flow rate and 24.4 A discharge current. The electron density at a position of 2.5 cm away from the orifice with 10 sccm argon gas flow rate, and 10.1 A discharge current, has a peak density value 1.12*1012 cm-3 and Maxwellian distribution of electron temperature centered at 3.5 eV. The discharge voltage becomes smaller with higher argon gas flow rate at one regulated discharge current in the region of 15 to 40 A. At discharge current of 10 A, the discharge voltage stays approximately the same for all gas flow rates from 10 sccm to 25 sccm.