Relativistic Electron Beam Transport Research Articles

GradBFocusing and Deposition of Relativistic Electron Beams

$\ensuremath{\nabla}B$ transport, bunching, and focusing of relativistic electron beams give power deposition levels which may provide the absorbed fluxes of 100 TW/${\mathrm{cm}}^{2}$ believed necessary to drive breakeven inertial-confinement-fusion targets. Predicted depositions in excess of 100 (TW/g)/MA are presented here. These levels are up to two orders of magnitude higher than those previously calculated and appear to meet the absorbed-flux requirement.

Relativistic-electron-beam/target interaction in plasma channels

A model describing the transport of relativistic electron beams in plasma channels and their subsequent interaction with solid targets is developed and applied to single-beam and multiple-beam configurations. For single beams the targets consist of planar tantalum foils and, in some cases, cusp fields on the transmission side of the foils are employed to improve beam/target coupling efficiency. In the multi-beam configurations, several beams are arranged in wagon-wheel fashion so as to converge upon cylindrical targets, consisting of either hollow tantalum or solid graphite cylinders, located at the hub. For 0.3-cm beam radii that are less than or equal to the channel radii, mean specific power depositions up to about 17 TW/g per MA of injected beam current are obtained for single beams; 12-beam results are typically an order-of-magnitude less. The corresponding enhancements are up to five times the collisional stopping power for either single or multiple beams. Substantial improvement is predicted for the multi-beam interaction should future channel technology permit transport at higher current densities in smaller channels.

Field-Enhanced REB Deposition and Bremsstrahlung Production

Recently developed models are employed to describe the interaction of a high-current relativistic electron beam with planar gold foils in the presence of macroscopic electromagnetic fields. It is shown that, under certain conditions, azimuthal magnetic fields which-either penetrate into the foil and/or exist on the transmission side of the foil can significantly enhance the specific power deposited in the foil over that which would be deposited for diode fields alone. Similar field effects suggest methods for improving the external conversion efficiencies, softening the spectra and focusing the source intensities of flash X-ray facilities. Finally, preliminary results are shown from a new trajectory-field model for self-consistent relativistic electron beam transport.

Transport of Intense Relativistic Electron Beams in azPinch

We have demonstrated efficient guidance and transport of high-$\frac{\ensuremath{\nu}}{\ensuremath{\gamma}}$ electron beams along a $z$ pinch. Pinch currents substantially smaller than the beam current are sufficient to contain and propagate the beam. The data suggest single-particle motion of beam electrons in the pinch magnetic field. Numerical calculations of possible trajectories correlate with observed beam expansion and corroborate the single-particle analysis.