Arc at Ultrahigh Pressure

Abstract

Most publications presenting the results of studies of high-current pulsed arcs in gases describe the discharges in the vacuum or in gas at low pressure. At the same time, pulsed arcs in gases at high and ultrahigh initial pressures are the relatively poorly studied area of electrophysics. Our investigations of high-current pulsed arcs in super dense gases have revealed a number of characteristic phenomena inherent only for such arcs. Three installations have been developed to carry out the researches in this area: two two-stage electric discharge units with dI/dt—1010 A/s and one with dI/dt—1011 A/s. The two first installations were designed for operation at currents up to 500 kA and initial concentrations of normal molecules and atoms of gas to 3.3 × 1022 cm−3. The PPG-5 plasma generator was designed to operate at current of up to 2 MA and initial concentration of molecules and atoms up to 1022 cm−3. The aim of these studies was generation and diagnostic of the hydrogen and helium plasmas with the charged particles concentration up to 1021 cm−3 and temperature up to 50 eV. The results of the experiments show that the increase of the initial concentration of hydrogen molecules makes it possible to reach the temperature of the central arc zone above 30 eV at concentration of the electrons is 1019 to 1021 cm−3. Since the plasma with such parameters at duration of steady state of ~10 μs is the source of UV and soft X-ray radiation, the diagnostic of these radiations is added to the number of the basic problems. It is determined that increase of the initial gas pressure causes the increase of the electric field intensity in the arc and its contraction . Other important conclusion is that at such initial gas pressures, the increase of the discharge current from 100 to 500 kA and its rise rate from 109 to 1010 A/s leads to the increase of the near-electrode voltage drops. The coefficient of the energy transfer from the arc to gas at initial pressure ≥20 MPa reaches 90%.