Transient evolution and steady-state emission from passively mode-locked lasers

Abstract

Computer simulations have been performed for the Toroidal Cusp Experiment (TCX), a plasma device built and operated at the University of California, Los Angeles. TCX is a toroidal MacKenzie machine with an external magnetic field provided by 48 magnetic cusps arranged in poloidal rings. A transformer generates a toroidal electric field which causes a current to flow in the plasma. Experimentally, the following parameters are observed in hydrogen: n e = 2 X 10 13 cm" 3 , T e = 10 -20 eV, Tj= 40 -110 eV. The toroidal current is carried mostly by the ions. A computer model of TCX has been developed, using a twoand-one-half-dimensional electromagnetic particle code. Basically, the simulation results (the electrons are restrained by the magnetic cusp fields, the ions are free to move, there is ion heating, and a relatively large fraction of the current is ion current) agree with those of the experiment and are explained by simple physical theoretical arguments. These provide the scalings observed in the simulation model.