Side-extraction-type secondary-emission electron gun using wire ion plasma source

Summary form only given, as follows. A wire ion plasma source (WIPS) is a compact ion source, which consists of a central thin wire anode and a grounded coaxial cathode. The cathode also acts as a vacuum chamber. The configuration allows the initiation of low-pressure gas discharge only by applying voltage of several hundreds on the anode by virtue of the geometrical electron confinement. A secondary emission electron gun is set beside the WIPS. The electrode set in the gun is highly negative-biased. Ions extracted from the WISP through a grid are accelerated toward the electrode and they collide on its surface with high kinetic energy, which corresponds to the electrode bias voltage. By collision of ions, secondary electrons are emitted from the electrode surface. The emitted electrons are then accelerated toward the extraction window and form a very wide electron beam. The extraction window is set on the side orthogonal to the ion extraction grid and is on earth potential. In this configuration, the accelerating potential distribution is considerably different from that of the plane parallel electrode configuration and it affects the extraction of the electron beam. Therefore, the loci of electrons and the current distribution of beam at the extraction window are computed and compared with the experimental results.