The properties of a proton source developed for use in a pulsed high power magnetically insulated ion diode have been determined. The source is created from a sliding gas discharge on the surface of a thin double layer of TiH and Pd deposited on an insulating substrate. By driving a short (<20 ns) high current pulse through the metal films hydrogen is released from the Ti store and a multichannel electrical breakdown is created in the desorbed gas layer. The uniformity of this breakdown depends on the capacitance per area of the multilayer setup. It has been found that the breakdown always occurs after the same areal gas density has been released. The density as well as the temperature of the plasma depend on a continuous influx of hydrogen from the reservoir and on the expansion. The electron temperature decreased from up to 12 early in the pulse to less than 3 eV late in the pulse. Over a distance of 1 mm the plasma density falls from 1017at the surface to 1015cm−3. The plasma expansion is stopped by a strong magnetic field parallel to the surface; however, the neutral hydrogen density increased with increasing magnetic field. Carbon ions are the most important contaminant of the hydrogen plasma. However, their fraction is smaller than 10%. ©1995 American Institute of Physics.