Gas-discharge electron gun using cold cathode

摘要

The gun has a cathode with a bottom, emitting, concave surface located above an anode ring. The bore of the anode ring has a vertical convex profile with a region (I) opposite the negative glow plasma. Surface region (I) has a hole leading to a channel used to measure the gas pressure. Region (I) tapers downwards so the focal point of the electron beam is kept at a constant height. At the lower end of region (I) is a ring channel for feeding gas into the discharge zone, and a bush surrounding the focal point of the beam. The bore of the bush is larger than the dia. of the beam at the focal point of the latter. The distance of the upper part of the bush from the ring channel is smaller than the average free path length of the gas molecules travelling towards the cathode. Increased power output and improved stability of the gas discharge are obtd.