The role of resonance radiation in the propagation of a positive pre-breakdown ionization wave in long discharge tubes

The work is devoted to calculating the flux of resonance photons towards the boundary of a cylindrical discharge tube of a finite size during the propagation of a pre-breakdown ionization wave of positive polarity. A cylindrical discharge tube of finite dimensions with argon at the pressure of p=1 Torr is considered. The propagation mechanisms of metastable and resonance atoms are compared. For the considered discharge conditions, the space-time distributions of metastable and resonance atoms are calculated. The manuscript presents a technique for calculating the flux of resonance photons onto the discharge tube wall with the account of the radiation trapping. It is shown that for the studied conditions the photon flux density towards the longitudinal boundary of the tube ahead of the ionization wave can reach 1013 cm-2s-1. The obtained results allow describing the appearance of seed electrons ahead of the positive ionization wavefront during its propagation due to the electron photoemission from the discharge tube wall.

Influence of contraction of a cesium pulse-periodic discharge on its luminous efficacy and spectral properties

The paper presents the results of a study of pulse-periodic discharge cesium lighting lamps with discharge tubes 5 mm in diameter and an interelectrode distance of 55 and 22 mm. The cesium pressure varied from 10 to 750 Torr at a constant triangular current pulse with an amplitude of 80 A. It is shown that the maximum of the luminous efficacy (~ 65 lm/W) corresponds to a pressure of ~ 130 Torr. It was found that a discharge column in the long tube at a pressure of ~ 300 Torr contracted into a bright pinch with a diameter close to that of the electrodes (2 mm). The pinch was localized along the surface of the tube and moves randomly on it. Contraction leads to a repeated increase in the luminous efficacy with pressure up to ~ 70 lm/W. Wall stabilization limits the plasma temperature on the axis of the pinch (it was found from the recombination continuum) to the level of 6000 – 6500 K. The column in short tube is localized along the axis of the tube over the entire power range. The temperature in it quickly rises to 13000-– 14000 K after the maximum of the luminous efficacy.

Electric Breakdown in Long Discharge Tubes at Low Pressure (Review)

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.

A Study on modification of Aircraft Platform for Air Quality Measurement in Korea

<p>The aircraft measurement for air quality is able to fly in three dimensions within the planetary boundary layer of inland and sea. In this study, the Beechcraft B1900D was modified to build a unique aircraft measurement platform for the measurement of particulate matter and gas. This aircraft has a maximum takeoff weight of 7,765kg and this aircraft is loaded with various air quality measurement equipment. The contents of aircraft modification are as follows. The installed contents for air quality measurement are aircraft aerosol inlets, trace gas inlets, discharge tubes, AIMMS-30, and pylon adapter. The power supply of the measurement equipment replaced the generating capacity of starter generators from 300A to 400A (at DC 28V). In addition, this aircraft was installed on the time synchronization and network system of measurement equipment (HR-ToF-AMS, PTR-ToF-MS, CIMS, etc). Currently, the air quality scientists in Korea have been investigating on long-range transport or local large point sources.</p>