Extraction of highly charged Au ions from a multiampere electron beam EBIS at BNL

Abstract

Excellent progress has been made in the operation of the Brookhaven National Laboratory electron beam ion source (EBIS), which is a prototype for an EBIS that could meet requirements for a RHIC preinjector. We have achieved very stable operation of the electron beam at 10 A through the EBIS trap. Ion injection of low charge gold ions from a low energy vacuum ion source [Brown et al., Rev. Sci. Instrum. 65, 1260 (1994)] and subsequent extraction of these ions with most probable charge state Au34+ has been demonstrated with electron beams up to 8 A. The total ion charge for gold measured on current transformer at the EBIS exit was 55 nC after a 30 ms confinement period. This corresponds to ∼85% of the theoretical ion trap capacity and exceeds our goal of 50% neutralization. The collected ion charge is proportional to the electron current and the gold charge state scales with the electron current density. Details of the EBIS configuration, total charge measurements, and time-of-flight spectra are given.