DC discharge in low-pressure ethanol vapour

Abstract

In this paper, we present data from experimental studies of the DC breakdown in ethanol vapour at low pressure as well as electrical and optical measurements of DC discharge parameters from low-current to high-current regimes. A Paschen curve and the corresponding distribution of emission intensities at low-current were recorded in the range of pd (pressure x electrode gap) from 0.10 Torr cm to 3.00 Torr cm, covering the region of Paschen minimum. Recorded axial profiles of emitted light from low-current discharge reveal that heavy particles make up a significant part in ethanol vapour breakdown in a wide range of values of pd i.e. E/N, for values E/N>3 kTd they become dominant. Also, we recorded volt-ampere characteristics at working conditions close to the minimum of the Paschen curve, together with spatial profiles of lowcurrent discharge. In the region of transition from normal to abnormal glow, sudden changes of the regime of operation were observed.

Effective ionization coefficients for low current dc discharges in alcohol vapours at low pressure

“…In our earlier papers [32,33] we have presented measurements of breakdown voltages and spatial profiles of low-current dc discharges in alcohol vapours: methanol, ethanol, isopropanol, and n-butanol as well as in water vapour. In our previous papers on alcohols, spatial emission profiles have been used to illustrate the transition between different discharge modes.…”

“…In our previous papers on alcohols, spatial emission profiles have been used to illustrate the transition between different discharge modes. In this paper we start from the axial profiles for the low current diffuse (Steady State Townsend-SST) regime recorded, as described in [32,33] and produce effective ionization coefficients.…”

“…For recordings of light emission, we used a sensitive ICCD camera (Andor IStar DH720-18U-03) equipped with a glass lens that allows us to acquire axial discharge profiles of spectrally integrated emission in the visible range of spectrum, defined by the transparency of the lens and the quantum efficiency of the ICCD photocathode. Adding the optical filters allows us to measure profiles associated with some specific lines [32,33]. Further recordings with optical filters (Hα, CH at 431.2 nm) were done to provide us with additional information on particular processes of excitation [32,33] and even the possibility to obtain absolute spatial profiles of excitation coefficients [35].…”

“…Adding the optical filters allows us to measure profiles associated with some specific lines [32,33]. Further recordings with optical filters (Hα, CH at 431.2 nm) were done to provide us with additional information on particular processes of excitation [32,33] and even the possibility to obtain absolute spatial profiles of excitation coefficients [35]. Profiles of Hα emission proved to be valuable as they show only a small contribution of fast neutrals to excitation [33], which enabled us to extend the range of measurement of effective ionization coefficients to somewhat higher E/N .…”

“…In all cases we operate at pressures well below the vapour pressure (that may drastically change with variation of the temperature), so our pressure and results are not dependent on small variations of the room temperature. A more detailed description of the experimental procedure is given in [32,33].…”