Plasma losses in high-current plasma configurations due to the ‘inverse skin effect’

Abstract

Experiments on zeta-pinches have shown that the surface layer of the plasma can be ejected towards the walls of the chamber. Phenomena of this type usually develop when the discharge current flowing through the circuit is decreasing, but they can also occur with a rising current when there is recurring discharge ignition.The application of an axial-magnetic field does not prevent the surface layer of the plasma from being ejected towards the chamber walls; it merely limits the rate at which the process occurs.It is shown that the break-up of the plasma sheath is due mainly to a reverse current induced in the surface layer of the pinch. When the discharge current is decreasing, a reverse current is produced by the 'inverse skin effect' [1].It is suggested that plasma losses due to the 'inverse skin effect' may also be observed for certain discharge regimes in theta-pinch, zeta, Tokamak and other systems.

Effect of heat transfer on the penetration of an electromagnetic pulse into a plasma layer and the inverse skin effect

“…In the time interval −13 ≲ ≲ − 8, the field penetrates into the plasma layer, causing its small heating. [5][6][7][8][9][10][11][12]). At time ≲ − 8, plasma is heated less than two times, therefore, penetration of the field takes place in weakly heated plasma.…”

“…The appearance of current on the layer surface in the direction opposite to the acting pulse field at the pulse shutdown is associated with the phenomenon that is called the inverse skin effect (see, for example, refs. [5][6][7][8][9][10][11][12]). Figures 3 and 4a show the presence of the inverse skin effect in the conditions under consideration, when it is necessary to take into account heat transfer.…”

“…In addition, because the heating of electrons occurs in an inhomogeneous field, the particle temperatures are inhomogeneous. [5][6][7][8][9][10][11][12] The change in temperature is accompanied by a change in the conductivity of plasma, which, in turn, qualitatively changes the field distribution.…”

“…Because of these changes, more favourable conditions appear for the inverse skin effect manifestation. [5][6][7][8][9][10][11][12]…”

A plasma lens for the CERN Antiproton Collector scaled from model and experiment

“…The IS occurs in any conductor when the skin depth becomes comparable with the conductor radius and when the current derivative is negative. Only little experimental attention was given to this effect in the past [9,10], although its import ance for a pinched discharge was already pointed out by Haines [8]. A thorough analytical description of the IS of an expanding plasma column is difficult; however, a useful approximation is obtained by considering flux conservation, derived [11].…”