Fast proton generation when passing through a gas of high-current electron beam of steep front of current pulse

An effect of the current pulse steepness on the ion acceleration has been investigated in the IMPUL'S accelerator with the following electron beam parameters: the energy 1 MeV, the current 25 kA, the pulse front 10-30 ns. Experiments have been carried out with a drift chamber 10 cm in diameter and 100 cm in length. A dependence of the accelerated proton energy on the gas pressure in the chamber has been measured. It is shown that proton acceleration ceases when the ionization time becomes less than the time required for the current to reach its limiting value. Acceleration interruptions have been observed at a pressure of 0.6 torr instead of 0.2 torr observed before at a front duration of 30 ns. The maximum energy of accelerated protons at a front duration of 10 ns has increased to 3.5 MeV and in a number of cases it has reached 5 MeV at a front duration of 30 ns. Experiments have been carried out with a complex-profile drift chamber to ascertain the effect of limiting currents on the production of a virtual cathode and attendant ion acceleration. The obtained experimental data proved the connection between particle acceleration and the appearance and dynamics of the negative potential well which produces when the electron beam passes through a low pressure gas