Precision of intense electron beams transported in vacuum by applied magnetic field

Measurements of the spatial distribution of the beam current density in the GESA-facilities [1] shows that the current density oscillates in time although the total beam current is stable. To investigate the nature of these oscillations results from different diagnostics for current and power density measurements have been analyzed (Faraday cups, small metal plates, x-ray detectors, etc.). It was found that oscillations of the beam current density are due to spatial movement (rotation) of the whole beam. The amplitude and appearance of this beam precision strongly depends on magnitude and distribution of the applied magnetic field and also on the target material. The onset of oscillations occurred several |us after the beginning of the pulse. The time of oscillations onset depends on the target material. The period of the oscillation is practically independent of the magnetic field magnitude and distribution and target material, and is always equal to about 1.5 µs. In this paper we discuss the results of current density and x-ray measurements and the possible reasons for the appearance of beam precision during the pulse.