DC vacuum breakdown in an external magnetic field

Abstract

The subject of the present theoretical and experimental investigations is the effect of the external magnetic field induction on dark current and a possibility of breakdown. The generalization of the Fowler-Nordheim equation makes it possible to take into account the influence of a magnetic field parallel to the cathode surface on the field emission current. The reduction in the breakdown voltage due to the increment in electron-impact ionization was theoretical predicted.Experimentally shown that the presence of a magnetic field about a tenth as a large as the cutoff magnetic field [18] reduces the breakdown voltage by 10% to 20% for practically all cathodes no matter what their surface treatment.

Field emission with relativistic effects in a magnetic field

“…It should be noted that the field enhancement factor is usually of about 30 ÷ 140 in such experiments [23]. Then we can find from (12) that in the case (6) the transmission coefficient reduction is less than 0.015%, which is consistent with the previously obtained results [15,10]. The transmission coefficient decreases by 0.1%, 5% and 50% when cB is equal to 0.1 E, 0.5 E and 0.9 E respectively.…”

“…Equation (10) is the transmission coefficient obtained by Fowler and Nordheim [7]. At the same time, we note that the second and the last terms of the expression (which do not contain the speed of light c) are the correction to the expression for the transmission coefficient obtained by Fowler and Nordheim and can be obtained from their calculations.…”

“…The experiments on suppression of vacuum breakdowns by a magnetic field have been carried out at CERN and IAP NASU with field values of E = 144 M V /m, B = 0.5 T and E = 100 M V /m, B = 0.33 T respectively [10]. It should be noted that the field enhancement factor is usually of about 30 ÷ 140 in such experiments [23].…”

“…Various options for increasing the breakdown resistance in the accelerator's structural materials were considered in literature. Metal surface modification [8], surface conditioning [9], and application of a magnetic field [10] are among them. This paper concerns suppression of field electron emission current by an external magnetic field which is parallel to a metal surface.…”

“…Influence of the magnetic field on the emission current has been previously theoretically studied in [11,12,13,14,15,16]. Blatt F.J. [11] considered field emission from a plain surface of a metal in an external magnetic field perpendicular to it.…”