Design study of compact EBIS for light-ion production using low-energy hollow electron beams

Abstract

A new compact electron-beam ion source (EBIS) with a low-energy hollow electron beam has been designed to produce ions for use in heavy-ion therapy. Numerical analyses of the electron beam using the three-dimensional particle-in-cell method determine the appropriate shape of the inner electrodes to realize a compact size and a sufficient number of confined ions for heavy-ion therapy. The analyses also show that the undesirable instability of the hollow electron beam is mitigated by the reflection mode with an electron repeller. Experimental tests were performed on the assembled EBIS to assess the validity of its design. The results of an electron-beam test show that the electrodes have been designed appropriately. Additionally, the results of an ion-beam test show that ions can be produced and confined in the newly developed compact EBIS and the number of extracted ions is just shy of the target value, showing the prospects of modifications aimed at realizing a compact EBIS specialized for the production of ions used in heavy-ion therapy.