Electric Breakdown in Long Discharge Tubes at Low Pressure (Review)
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Electric Breakdown in Long Discharge Tubes at Low Pressure (Review) Yu. Z. Ionikh* St. Petersburg State University, St. Petersburg, 199034 Russia *e-mail: [email protected] Received March 19, 2020; revised April 9, 2020; accepted April 10, 2020
Abstract—The review is devoted to studies of the processes and mechanisms of ignition of a glow discharge in tubes whose length significantly exceeds their diameter (long discharge tubes) at low pressures (~10 Torr and lower) and moderate voltage rise rates (~1 kV/μs and lower). The electric field in such tubes before a breakdown is substantially nonuniform. Therefore, a breakdown occurs after an ionization wave (or waves) passes through the discharge gap at a speed of ~105–107 cm/s. This makes the characteristics of the breakdown in long tubes significantly different from the breakdown between large and closely spaced electrodes, where the electric field is uniform before the breakdown and where the Townsend or, under strong overvoltage, streamer mechanism is realized. On the other hand, the nature of these processes is very different from those occurring in nanosecond discharges, which arise at voltages with a steepness of ~1 kV/ns and higher and are associated with high-speed (~109 cm/s) ionization waves. The review is based on the materials of experimental and computational works published from 1938 to 2020. Breakdown processes, optical and electrical characteristics of the discharge gap during breakdown, and the influence of the external circuit parameters and external actions (shielding and illumination by external sources of visible radiation) are analyzed. DOI: 10.1134/S1063780X20100049
CONTENTS 1. Introduction 2. Ionization waves 2.1. Fast waves 2.2. Pre-breakdown (slow) waves 3. Study of breakdown in long tubes under low pressure 3.1. Early works (until 1960) 3.2. Works of the 1960–1980s 3.3. Works of the 1990s and later 4. Manifestation of the wave nature of the breakdown upon discharge ignition in long tubes 4.1. Electrical signals in the discharge circuit 4.2. The effect of shielding on the breakdown 4.3. Breakdown voltage 4.4. “Memory effect” of the discharge gap 4.5. Initiation of breakdown by visible radiation 4.6. Breakdown in a tube with an ungrounded electrode 4.7. Radiation spectrum of the ionization wave 4.8. The discharge after the passage of the ionization wave 5. Conclusions References
1. INTRODUCTION 1. Сylindrical discharge tubes with a length much greater than the diameter (“long” discharge tubes) began to be used in the 1850s in the experiments of J. Plücker and H. Geissler at the University of Bonn [1]. Using a mercury pump created by Geissler, a stable reproducible low-pressure discharge in the tube was obtained, which was later called glow discharge. The term “Geissler” is used now for discharge tubes with a capillary insert (Fig. 1). Until recently, they were used as standard spectral sources. Plücker, experimenting with the created tubes, discovered cathode rays. In the subsequent works of J. Hittorf and W. Crookes, but un
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