Operating Experience with a High Current Cs+1 Injector for Heavy Ion Fusion

The construction and assembly of a Cs ion injector consisting of a pulsed source and 3 pulsed drift tubes has been complete since April, 1980. The measurement program, underway since then to characterize the beam, has been interspersed with the development of diagnostic equipment. The Cs contact ionization source and each of the 3 drift tubes are driven by 500 kV Marx generators. The injector has been operated reliably at 300 kV/stage at a repetition rate of 1 pulse/4 sec. About 105 pulses have been accumulated. The space charge limited diode and drift tube acceleration system were designed with the aid of the EGUN code of Herrmannsfeldt. Measurements of the beam envelope have been made by means of a movable biased charge collector. Good agreement with the EGUN calculation is found. Measurements of the beam emittance have been made at the exit of the third drift tube. The normalized emittance ¿ ¿N = 2 x 10-6 ¿ m-rad is of better optical quality than that required for further acceleration and transport in a Heavy Ion Fusion (HIF) Induction Linac Driver.