Channel spark source for a stable electron beam e.g. an electron gun, has a conical sleeve in the hollow cathode with a gas feed and an adjusted pressure drop to give a large number of shots without loss of beam quality

摘要

The channel spark source assembly, to generate a stable and bundled electron beam (2), has a sleeve (21) in the hollow cathode (1) as an open cone towards the anode (17), away from the trigger plasma side, as a component part of the hollow cathode. The sleeve forms a ring gap (13) with the hollow cathode wall, with a closed end to the dielectric tube (7) and an open end to the channel spark body (11). The end of the hollow cathode ends at a gap from the anode, to give a residual volume with the clear width of the cathode, opening into the ring gap. A gas feed (15) is through or in the hollow cathode wall, to give a dosed gas feed into the interior of the cathode, to set a pressure drop between the hollow cathode outlet and the outlet of the dielectric tube end piece (5). A leakage structure is in the vacuum seal at the trigger plasma side of the hollow cathode, leading to the ring gap, which can also set the pressure drop. The field from a permanent magnet (12) or electromagnet passes wholly through the dielectric tube in sections. The magnets can slide to the longitudinal axis of the dielectric tube, and the axis of the magnetic field can swing to the longitudinal axis.