Experimental realization of nearly steady-state toroidal electron plasmas

Electron plasmas with densities of 5x10(6) cm(-3) are trapped in the Lawrence Non-neutral Torus II (LNT II) for times exceeding 1 s. LNT II is a high aspect ratio (R(0)/a greater than or similar to 10) partially toroidal trap (270 degrees arc, B(0)=670 G). The m=1 diocotron mode is launched and detected using isolated segments of a fully sectored conducting boundary and its frequency is used to determine the total trapped charge as a function of time. The observed confinement time (approximate to 3 s) approaches the theoretical limit (approximate to 6 s) set by the magnetic pumping transport mechanism of Crooks and O'Neil [Phys. Plasmas 3, 2533 (1996)]. We also present equilibrium modeling and numerical simulations of the toroidal m=1 mode constrained by experimental data. Future work includes the identification of the dominant transport mechanisms via confinement scaling experiments and measurement of the m=2 mode frequency and development of a strategy for making a transition to fully toroidal confinement.