Production and investigation of TW proton beams from an annulardiode using strong radial magnetic insulation fields and a preformedanode plasma source

A magnetically insulated proton diode in extraction geometry which has achieved an ion beam power of 0.8 TW and an ion production efficiency of greater than 90% is described. Using a Pd-Ti metal hydride film on the anode surface and diverting part of the generator current through it with the help of plasma opening switches, a proton-rich plasma is preformed on the anode before any voltage occurs across the diode gap. Thus it is possible to apply very strong magnetic insulation, V_c/V_op>3. Ion current and diode voltage simultaneously reach a plateau for 40 ns, resulting in a nearly constant diode impedance for 60 ns. Thus, chromatic aberrations of the diode focusing system are minimized. The microscopic divergence of proton beamlets due to diode effects is determined to be 0.7°. Geometric aberrations of spherical and aspherical anode shape have been determined. The experimental results are compared to simulations with a 2.5 dimensional stationary PIC (particle-incell) code