Beam Propagation Experimental Study.
MISSION RESEARCH CORP ALBUQUERQUE NM
Pagination or Media Count:
A program of extensively diagnosed experiments to investigate the physics of intense relativistic electron beam propagation in low density air is in progress using beam generators. The primary objectives of this research are the rate of erosion of the head of the beam, and to investigate resistive instabilities, such as the hose and hollowing modes, that limit the transport of beam energy over significant distances. The tasks of delineating the pressure range for maximum energy transport and measuring the temporal evolution of the current density profile of the beam produced by the FX-100 have been accomplished. Maximum energy transport measured calorimetrically of the FX-100 beam about 1.5 MeV, 40 kA, 120 ns occurred at 0.3-0.5 Torr air pressure. This air pressure window for maximum energy transport was defined by loss of the tail of the beam at high pressures and by erosion of the beam head at low pressures. Propagation in the window was characterized by a high degree of current neutralization about 80 or more, by intense light emission, suggestive of strong avalanche breakdown, and by the onset of a virulent hollowing instability that resulted in as much as 80 of the beam current being carried in a thin annular shell at a radius about twice the Bennett radius characterizing the initially injected current distribution.
- Particle Accelerators