High-voltage stability requirement of a DC electron gun for an ERL light-source

Nagai, Ryoji; Hajima, Ryoichi; Iijima, Hokuto; Nishimori, Nobuyuki; Sawamura, Masaru; Kikuzawa, Nobuhiro ; Minehara, Eisuke

A DC electron gun is employed for an electron source of an energy-recovery linac (ERL). The electron beam parameters are fluctuated due to the instability of a high-voltage power supply of the gun. The fluctuations of the electron beam parameters are estimated for the ERL light-source. In the result of the estimation, the bunch length of the electron beam is mainly fluctuated by the instability of the high-voltage power supply. For the bunch length fluctuation of 1% or less, the required high-voltage stability is less than 110. The main part of the instability of the high-voltage is the ripple of the Cockcroft-Walton circuit. The compensation of the ripple utilizing an LC filter is proposed, and the required stability is easily achieved in the preliminary design of the power supply.