Injection and propagation of multiple relativistic electron beams into preformed plasma channels for high-power x-ray production

A program is presently underway to apply the multiple, high-v/γ relativistic electron beams from the Casino I accelerator to achieve high-power x-ray production via the bremsstrahlung process. The approach seeks to combine the ν/γ = 15, 1.0 MV, 700 kA beams produced by each of the four modules using plasma-channel transport and relativistic beam overlap to maximize the power density and total energy delivered to the x-ray target. Experimental work in the areas of pinch formation, beam injection, wire plasma channel formation, background gas and pressure dependence, beam transport efficiency and repeatability is presented. Recent experiments at the Naval Surface Weapons Center have demonstrated transport of individual 700 kA beams over distances of 71 cm using wire-initiated air-plasma channels. Transport efficiencies of 85% have been achieved at reduced air pressures (75 Torr) based on x-ray measurements at the source and at 71 cm. Results are encouraging and indicate that the plasma-channel multi-beam approach is a viable one for achieving electron-beam power multiplication.