Measurement of the potential gradients for wall-stabilized ares in sulphur hexafluoride and nitrogen

Boundary conditions in wall-stabilized arc columns

“…The wall assembly, which has been described elsewhere (Gozna and Richards 1967), comprised eight stainless-steel disks of 8 mm thickness separated by aluminium silicate insulating disks of 1 mm thickness. This was cooled by transformer oil to maintain high interelectrode resistances ( > 10 MQ).…”

“…For later capacitive measurements of the effective boundary-layer thickness the frequency of the sweep circuit was increased to the range 5-50 kc/s. The main arc current was drawn either from a filtered constant-current d.c. power supply or from the capacitative decay circuit of Gozna and Richards (1967), with a maximum of 50 A in either case. Initial disk current-voltage characteristics using the d.c. supply had a 300 cis modulation due to the remaining ripple in the filtered output and revealed the slight pulsations in the arc diameter.…”

“…Stainless steel was chosen in preference to the more usual copper because it had previously been found that t Now at School of Electrical Engineering, University of Sydney, New South Wales, Australia. the arc products formed in SF6 gave rise to an insulating layer of copper fluoride and sulphides (Gozna and Richards 1967). Even so, only very small currents could be drawn from the plasma column to the disks, and it is shown that this is due to the inherent difference between the plasma boundaries in SF6 and in other gases, due to the high electron-attachment energy of free fluorine.…”

“…Wall-stabilization of cylindrical arc columns has been widely adopted for studies of highpressure gas discharges (Maecker 1964, Kimblin and Edels 1966, Gozna and Richards 1967. The absence of convective heat losses in the outer boundary regions simplifies the theoretical analysis and has permitted experimental measurement of the transport properties of gases at high temperatures (Maecker 1964).…”

Wall‐stabilized argon arcs at medium pressure

“…The axial potential gradient of the arc plasma was measured by measuring the floating potential of each disk [6]. This method enables one to readily realize the arc condition L/Rs 2 10, and is effective in measuring high arc currents; in our experiment, the arc current exceeds 40 A for the 10-mm hole and 20 A for the 7-mm and 5-mm holes, This disk potential method, however, acompanies large errors if insulation resistance between disk and electrode is small compared to am resistance [7]. This insulation resistance depends on resistance of the disk-and electrodecooling waters and hence, in our experiment, the water paths between disks and between disk and electrode was lengthened as much as possible; the impedance between two measuring points was more than 5 MC2 even during the disk potential measurement.…”