A Conical Ion Diode with Self-Magnetic Insulation of Electrons

Abstract: The results of studying the generation of a gigawatt-power pulsed ion beam formed by a diode in the mode of self-magnetic insulation of electrons are presented. Studies were carried out at the TEMP-4M accelerator in the mode of generating two pulses: the first is negative (500 ns, 150–200 kV) and the second is positive (150 ns, 250–300 kV). The formation of anode plasma occurs during the explosive emission of electrons during the first pulse. To improve the efficiency of generating an ion current, a conical geometry of the diode was proposed in which the electron-drift length exceeds that in the previous diode structures by factor of 2. It was found that the energy efficiency in the conical diode increased to 15–17%, while the ion-beam energy density at the focus increased to 2–3 J/cm²; the beam consisted of protons and carbon ions. The efficiency of suppression of the electron component of the total current in the diode was analyzed and the calculations of the electron-drift duration and ion acceleration were performed. It is shown that in the diode of the new design, efficient plasma formation occurs on the entire working surface of the graphite anode, while the plasma concentration may limit the ion current.