Development of Marx adder based solid-state electron gun modulator

Electron guns are indispensable components of accelerators, generating electrons under the application of high voltage. High-voltage pulse modulators provide the pulsed extraction voltage required to produce a pulsed electron beam. A novel solid-state Marx adder-based gun modulator has been developed to drive a test-bench electron gun at the Electron Beam Center (EBC), Mumbai, India. The modulator delivers up to 40 kV, 3 A pulses with a pulse width of 10 μs at a repetition rate of 200 Hz. This work presents the design considerations, analysis, and implementation of the solid-state modulator, with emphasis on addressing the unique non-linear load characteristics of the electron gun. Common-mode chokes are employed innovatively for isolated charging of Marx stages. Development of this modulator is significant from the perspective that it ensures a wide range of control over pulse voltage, pulse repetition rate, and pulse width of electron beam generation for the user. Experimental validation with resistive and electron gun loads is presented in detail in this paper.