Reciprocating motion of magnetically driven arcs in air at low critical atmospheric pressure

Using high-speed photography and an optical-fiber microcomputer system, a series of experimental investigations were performed on the motion of DC short arcs in a transverse magnetic field in air at low critical atmospheric pressure. It is shown that the cold cathode arc runs a long distance forward (ampere´s direction) and backward (retrograde direction) without stop. This phenomenon is called reciprocating motion. The reciprocating motion appears to be of three types: reciprocating motion at high speed, motion at low speed, and motion forward and backward at greatly differing speeds. However, the reciprocating or retrograde phenomenon on hot cathode material has not yet been observed. A model of cathode jets for the arc motion has been developed that can fairly well explain the arc motion direction change and the reciprocating phenomenon.<>