Nonlinear studies of axis-encircling electron beam with off-centering and field tapering effects

Summary Form only given, as follows. A self-consistent nonlinear analysis of an axis-encircling electron beam in a vane circuit oscillator has been made. Optimized quantities with respect to energy, current, vane depth, and magnetic field have been determined and compared with experiment. The analysis also includes more realistic parameters, such as the off-centering effect and the tapering of the magnetic field. Three specific sources of off-centering have been identified: (1) an unbalanced magnetic field reversal, (2) a finite-span magnetic transition, and (3) a finite upstream Larmor radius. The effects of these sources of off-centering on an ideal configuration (balanced field reversal, zero-span cusp and constant up- and downstream magnetic fields) have been investigated. For the peniotron mechanism to dominate over the competing negative mass instability, a near-ideal axis-encircling electron beam is required. Tolerances for off-centering effects causing deviation from ideal have been investigated. Magnetic tapering has been investigated both as a realistic experimental parameter and for the purposes of designing an adiabatic compression, which has been shown to reduce the off-centering effect.<>