Generation of pulsed proton beams in a vacuum diode with a passive anode

The paper presents the results of a study of a pulsed proton beam generated of in a diode with a metal anode (stainless steel, titanium, and copper) operating in bipolar-pulse mode. The experiments were carried out on the TEMP-6 accelerator (250-300 kV, 120 ns) with a focusing diode geometry in a mode of self-magnetic insulation of electrons. For analysis of the ion beam parameters, we used the infrared imaging diagnostics of the beam energy density (spatial resolution of 2 mm) and the time-of-flight diagnostics of the beam compositions (time resolution 1 ns). It was found that with continuous supply of hydrogen into a hollow anode (with holes on the working surface) and a hydrogen pressure in the diode chamber of 30-80 mPa, the proton content in the beam exceeds 80%. An increase in the first pulse duration leads to an increase in the ion current density up to 100 A/ cm2 and the energy density at the focus up to 3 J/cm2. We analyzed various mechanisms of proton beam generation: ions acceleration from the gas plasma in the plasma erosion mode; ions acceleration from the explosive emission plasma of a metal anode the near-surface layer of which is saturated with metal hydrides (anode material). It was found that hydrogen embrittlement of the near-surface layer of the anode occurs during the injection of hydrogen, and during the explosive emission of electrons, part of the material is sprayed in the form of finely dispersed clusters.

Automated summary

This paper presents the results of a study on pulsed proton beam generation using a diode with metal anodes. The experiment analyzed the ion beam parameters through infrared imaging and time-of-flight diagnostics. It was found that continuous supply of hydrogen into a hollow anode and specific hydrogen pressure in the diode chamber resulted in a proton content of over 80% in the beam. Increasing the pulse duration led to higher ion current density and energy density at the focus. Various mechanisms of proton beam generation were examined, including ions acceleration from gas plasma and explosive emission plasma from metal anodes.