Traveling Wave Amplifier Driven by a Large Diameter Annular Electron Beam in a Disk-Loaded Structure
Technical Report,30 Sep 2014,30 Sep 2015
Univerity of Michigan Ann Arbor United States
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This project studies the viability of a high-power traveling wave tube TWT using a novel disk-on-rod slow-wave structure SWS, which admits a large diameter, high current, annular electron beam. The annular electron beam carries a much higher current than a pencil beam, and the use of SWS allows moderate bandwidth. The gain and bandwidth were studied using analytic theory and simulation. The cold-tube as well as the hot-tube dispersion relation were constructed, from which the Pierce gain parameter, C, and the space charge parameter, QC, are extracted. Two very different methods were used to validate the calculation of C and they yield identical results. The gain was then calculated using Pierce classical theory of TWT based on C and QC, and was spot-checked against simulation results from the ICEPIC, MAGIC and CHRISTINE codes. Fair agreement was observed. The preliminary conclusion is that the disk-on-rod TWT is a viable, high-power extension to the conventional TWT which uses a pencil beam. The most important issue appears to be the excitation of unwanted modes.