Simulation of the Compensation of a High-Current Ion Beam by an Electron Beam in a Cusp Magnetic System

Abstract

The results of 2.5D-simulation of the dynamics of particles of a high-current ion beam moving in a magnetic field of acute-angled geometry (cusp), compensated in charge and current by an electron beam injected along the radius onto the axis from the periphery, uniformly in azimuth, are presented. The influence of own space charge fields and polarization fields on the dynamics of ions is clarified. It is shown that at high densities of the electron and ion beams, the electron beam injected into the cusp together with the ion beam, moving along the magnetic field lines, drags the ion beam away from the axis to the periphery into the region of zero magnetic field. At the exit from the cusp, the electron beam injected along the radius onto the axis drifts along the axis in a uniform magnetic field, while the ion beam performs oscillatory motion by radius in the crossed the electric field of the electron beam space charge and the longitudinal magnetic field.

Acceleration of a High-Current Proton Beam in a Linear Induction Accelerator at Its Compensation by Electron Beams

“…The similar investigation [6], performed for the injection of high-density ion beams with a lower energy of several hundred kiloelectronvolt, which is typical for existing high-current ion sources (for example, [7]), in the absence of an accelerating field, showed that a threshold arises in beam density 10 12 cm -3 , above which transportation is not possible.…”

“…But similarly to simple transportation of the ion beam (see Fig. 2,a and [6]) in the drift region it "inflates" due to its drift in crossed electric and magnetic fields that looks like beam corrugation. So the accelerating field does not allow avoiding the increase of ion beam transverse size.…”

“…At the density of the proton beam n i = 10 10 cm -3 , as well as in the accelerating field absence in a strong magnetic field [6], the following particle dynamics arises. In the radial electric field of space charge and polarization field and the longitudinal external magnetic field the complicated motion of protons occurs.…”

“…However, as in the absence of an accelerating field [6], both compensating electron beams do not allow maintaining the transverse dimensions of the proton beam after acceleration in the cusp and transport in the drift region to the next section.…”

“…In this paper, the case of [6] is studied but in the presence of an accelerating field in the cusp region. The dynamics of a proton beam in the magnetic field of a cusp configuration and in the uniform magnetic field of the drift region with compensation by the axial electron beam, injected into the first half of the cusp, and by the electron beam, injected along the radius into the second half of the cusp, is studied depending on the beam density.…”