Pumping of Induced Gas by an Arc Column.

Results of an investigation of pressure distribution along the positive column of a continuous electric arc confined in a segmented copper tube are presented. Pressure is measured at seven different points, equally spaced, for filling pressures ranging between some 10** minus **2 Torr and several Torr, and for current densities attaining 400 A/cm**2. Three operating rates are differentiated, i. e. : free fall, Intermediate rating, diffusion rating. In free fall conditions, the pressure gradient, as measured, is directed towards the cathode.