Production of pulsed proton beams from an ion diode insulated with radial magnetic fields

Characteristics required to focus proton beams onto one point in the axis have been experimentally studied by using an annular magnetically insulated diode with radial magnetic fields powered from a pulsed power supply. The diode perveance was reduced to less than 1/15, showing the effect of electron insulation with the magnetic fields. The experimental result on deflection of the emitted beam orbit did not agree well with single-particle orbit calculation. Proton beams of 400A with an energy of 460keV were obtained at 150mm downstream from the anode surface. The beam divergence angle exceeding 60 was derived from the total ion current propagating along the diode axis. The diode efficiency was estimated to be 25%. The space charge neutrality of the beam was limited to 60%, suggesting the necessity to increase charge neutrality for good focusing. (author)