Focussing properties of a strongly insulated applied Br-proton diode with a preformed anode plasma source

In the paper we describe a magnetically insulated proton diode in extraction geometry developed for the high voltage pulse generator KALIF which produces a 40 kJ proton beam pulse at a power level of greater than 0.65 TW. This is very close to the optimum for the parameters of KALIF and was reached through a high diode coupling efficiency (80%), a high ion production efficiency (90%), and a high beam purity (80-90%). The key elements of the diode are an active proton source based on a thin Ti-hydride film covered by a thin layer of Pd and a strong insulating magnetic field (V_crit/V ≥ 3.0). A microscopic divergence of about 1.0 ° and a total divergence of 1.4 ° for the complete system have been measured. It has been found that an electron limiter at the anode significantly reduces the microscopic divergence of the beam. Focussing to proton power densitites of 1 TW / cm² has been achieved by eliminating most of the chromatic aberrations and by correcting for the spherical aberrations.