Breakdown delay times for subnanosecond gas discharges at pressures below one atmosphere

Jordan E. Chaparro, William Justis, Hermann G. Krompholz, Lynn L. Hatfield, Andreas A. Neuber

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


With a RADAN 303-A pulser (a rise time of 150 ps and a maximum voltage of 150 kV into matched load), fast breakdown in argon and air is investigated. An oil-filled coaxial transmission line is coupled with a lens to a biconical section and a radial millimeter-size gap operated at subatmospheric pressure. Diagnostics include capacitive voltage dividers which allow the determination of voltage across and current through the gap with a temporal resolution defined by the digitizer (20 Gs/s, 6 GHz) used. A scintillator-photomultiplier combination with different metal absorber foils and a temporal resolution of 2 ns is used as X-ray detector to obtain a rough energy spectrum of the X-rays and electrons in the range of 10-150 keV. Discharges are characterized by runaway electrons over much of the pressure range, with a strong excitation and ionization layer at the cathode surface, and ldquofree-fallrdquo conditions with negligible gaseous ionization for the rest of the gap. High-energy electrons (> 60 keV) are observed up to atmospheric pressure. Time-to-breakdown curves versus pressure have been measured for different applied voltage rise times. They resemble Paschen curves with a steep increase toward low pressure and a slow increase toward high pressure. The major experimental findings and particularly the time-to-breakdown curves are confirmed using simple force-equation modeling. Monte Carlo calculations simulating collisional ionizations and developing electron avalanches in three dimensions have been used to verify and explain the experimental results.

Original languageEnglish
Pages (from-to)2505-2511
Number of pages7
JournalIEEE Transactions on Plasma Science
Issue number5 PART 3
StatePublished - 2008


  • Anodes
  • Breakdown voltage
  • Delay
  • Discharges
  • Electric breakdown
  • Gas discharges
  • High overvoltages
  • Ionization
  • Runaway electrons
  • Subnanosecond regime
  • Voltage measurement


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