Disrupting high-pressure, current-carrying filaments using cross-field injection of laser ablation plasmas

In a magnetized plasma, laser-irradiated targets may be used to produce localized, expanding plasmas. Such laser-produced plasmas (LPP's) share characteristics with injected fuel pellets in tokamak plasmas: localized high pressure, can become polarized and move via ExB motion. Pellet injection has recently been demonstrated to mitigate the intensity of edge-localized modes [1]. We present results of a basic plasma physics experiment to study the disruption of a high-pressure, current-carrying filament. The experiments are performed on UCLA's Large Plasma Device (LAPD). This is a linear device with $L$=17m, $d$=60cm, $B_{0}=$750G, $n_{e}$=$2\times10^{12}$cm$^{-3}$, $T_{e}$=6eV,$T_{i}\approx$1eV, H$^{+}$). The LPP is produced by a pulsed (8ns, 1J) Nd:YAG laser ablation of a carbon target. The current is produced using a $LaB_{6}$ cathode, with $T_{e}=20$eV, $n\approx 4\times 10^{12}$cm$^{-3}$, yielding cross-field dimensions $h=0.9c/\omega_{pi}$ and $w=3.8c/\omega_{pe}$ for a H plasma, and a Lundquist number $S=8\times 10^{3}$ Using probes and a 1Hz experiment repetition, maps of the plasma potential, electron temperature, magnetic fields (and derived currents), and induced current-sheet oscillations are presented as the current is disrupted.