Anode scattering effects on electron pinch radius in low-impedance REB diodes

The effect of different anode material on the size of very intense pinches is studied from the radial structure of the bremsstrahlung from a tightly pinched relativistic electron beam. Time-dependent data are obtained which point out the influence of scattering by the anode which electrons experience near the pinch axis. The scattering broadens the bremsstrahlung FWHM for pinches with high-Z (80) anodes to 6 mm, compared to 4 mm for low-Z (13) anodes. When anodes composed of low- and high-Z elements in different annular regions are used, translation of backscattered electrons enhances the current density upon the low-Z regions and decreases it upon the high-Z regions.