On the low-energy high-current electron beam profile controlled using ferromagnetic insertions

We report on the results of investigation of the energy density distribution over the cross section of a low-energy (10–30 keV) high-current (up to 25 kA) electron beam transported in the plasma channel in a guiding magnetic field. Beam focusing and energy density redistribution in the beam cross section are carried out using hollow cylindrical insertions prepared from a ferromagnetic steel (magnetic-field concentrators) and installed behind a foil collector (made of nonmagnetic stainless steel of thickness 200 $\mu$m). The energy density distribution is measured by an infrared imager; for this purpose, the concentrator is moved aside by an electromagnet during the pause (about 1 s) between a beam pulse and the instant of thermogram recording. The experiments confirm the possibility of improving the beam homogeneity in the cross section by using magnetic field concentrators. The results of measurements are in satisfactory agreement with the earlier results of calculations.