A 132 GHz gyrotron, operating at fundamental harmonic, is designed for the 200 MHz DNP-NMR experiment. In this article, the design of high quality electron beam source is presented. 2.5 dimensional code EGUN and 3 dimensional code CST-Particle Studio are used in the design and optimization of electron gun. The design of electron beam source is performed for a band of magnetic field values at the emitter surface and cavity center which is necessary for the frequency tunabilty of 2-3 GHz needed in DNP/NMR experiments. The results confirm the axial and transverse velocity spreads around 1% and 2.2% and a pitch factor of 1.5. The parametric analyses are also performed for the various electrical parameters such as emitter voltage, anode voltage, emitter magnetic field, etc.
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