Current continuity in dense plasma

The equations of current continuity have been solved for high-density (nion>1012 cm−3) gaseous plasma as a problem associated with electron-beam-controlled electrically excited pulsed laser energy sources. The procedure used first-order numerical approximations to the space and time development of current and potential gradients. The results of a laser plasma study are (a) the total electron current is not very sensitive to electron emission at the cathode because (b) the sheath multiplies both secondary electrons and cathode current by a large factor and adjusts to current requirement set by electron mobility and density in the plasma. Small changes in the sheath thickness and potential drop satisfy the variable-current condition set by gas ionization and ion recombination: I=new=ew (S/α)1/2. The potential drop in the sheath of an STP plasma is 400–2000 V for plasma currents of 1–10 A/cm2, and the sheath thickness is d≃0.003 cm.