Investigation of radially converging electron beams generated by GESA IV

Summary form only given. The pulsed electron beam facility GESA IV generates radially converging beams by means of a cylindrically shaped explosive emission cathode. Along the cylinder axis a rod-shaped target serves as anode of the triode system. In this study, the generation, homogeneity, dynamics, and stability of electron beams in GESA IV are investigated numerically using MAGIC-3D. Thereby, the reflection of electrons at the target is taken into account as well as the magnetic field induced by the current along the target. Various geometrical details of the GESA IV facility are modified to find the optimum parameters. An apparent anode is introduced with diameter exceeding the dimensions of the target. Also, the effect of lamellae placed radially around the target is studied. Although the target current could be enhanced considerably by the presence of the lamellae, the divergence of the beam along the symmetry axis could not be avoided. The numerical findings are discussed and compared with experimental measurements conducted at the GESA IV facility.