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IVEC 2002 |
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IVEC Summary, Session 14, Guns II
Session chairperson and summary author: Gun-Sik Park
This session is highlighted with two reports on the axis-encircling electron gun(or cusp gun) and two reports on the magnetron-injection-gun(MIG). Jeon et al. from Seoul National University, Korea reported the analysis of axis-encircling electron beam using a single cusp magnetic field where the rotation of electron beam before the magnetic cusp is included. From the analysis, the minimum relative position between the cathode and magnetic cusp is found for the low-velocity-spread operation. The analysis was compared with the egun simulation showing a good agreement. Also the measurement using a pinhole was in a reasonable agreement with the estimation. The beam voltage and current used are 30kV and 1A respectively. Gallagher et al. from Northrop Grumman Corporation reported a high power cusp electron gun operated at the beam voltage of 70kV and beam current of 8A. Their gun design is unique where the beam passes through the field reversal while it is still converging. A reduced beam scalloping and less sensitivity to dimensional tolerance could be achieved. The estimated axial velocity spread of the higher power cusp gun was estimated less than 10% with the velocity ratio of 1.5. Anderson et al. from MIT and Felch from CPI reported the emission uniformity study of gyrotron MIG cathode. Their concern of mode competition in gyrotrons due to nonuniform emission of electrons from the thermionic cathode led them to investigate the uniformity of the cathode. Here they described the uniformity in terms of the work function of the emitter. They measured the work function spread by measuring the electron beam current by assuming a distribution for the work function. Yeh et al. from Southern Taiwan University of Technology, Taiwan reported a mechanically tunable MIG gun. This tunable gun is controlled by adjusting the axial position of the center electrode. The center electrode consists of fixed and movable electrode. This gun was developed for the gyro-TWT experiment operated at the beam voltage of 93.6kV and beam current of 3A. The beam current and the velocity ratio are simulated and measured while various parameters such as magnetic field, compression ration, cathode temperature and relative position of the center electrode.
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