Arc field measurement with a simple experimental arrangement

The electric field of a discharge was measured using a simple device consisting of a three-phase rectifier, an RLC circuit and two arcs of variable length burning in series: the reciprocal movement of the arcs ensured that the total length was constant. Measurements were performed in dry air in the current range from 20 mA to 4 A for pressures between 20 and 150 kPa. It was noted that the voltage-length characteristics of the glow discharges were very close to a linear dependence at lower pressures but exhibited a tendency to become non-linear with increasing pressure. The average zero-length voltage was 367 V at 20 kPa, 346 V at 60 kPa, and 331 V at 100 and 150 kPa. The current dependence of the electric field for i>or approximately=1 A at 100 kPa is well described by the function E=57 i alpha (V cm -1 ); the exponent was found to be pressure-independent between 60 and 150 kPa, where alpha approximately=-0.54. Fields at lower currents reveal a stronger dependence: in the case of 100 kPa, for instance, the exponent is -0.81 while at 60 kPa the characteristic on a log-log plot is quite non-linear. The slope decreases again at the low-current end of the characteristics. The transition boundary between the glow-discharge and arc modes is about 0.3A.