On the Hollow Cathode for an Oxygen Discharge

An old Kaufman ion thruster was remade to operate by using oxygen as working gas. A simple device was designed to protect its hollow cathode from direct exposing to the oxygen environment. The cathode has a small diameter and long insulator tube on its downstream end (at keeper electrode). When it is attached to the discharge chamber, the lead tube is located between the cathode and the discharge chamber. If the cathode used xenon as working gas, oxygen could be used in the discharge chamber. The hollow cathode discharge occurs in usual sequence and a main discharge started by applying a slightly higher voltage between the cathode and discharge chamber. The cathode works well in the oxygen discharge without oxidation. A new small scale line cusp ion source is also studied, which will be used with the hollow cathode in order to improve ionization efficiency. A stable operation was obtained in a reasonable magnet configuration.