Characterization of a compact filament-driven multicusp ion source for low energy time-of-flight Rutherford backscattering spectrometry application

Abstract

Because of the limited pulse height energy resolution of a detector, conventional Rutherford backscattering spectrometry ͑RBS͒ requires an energy of the incident ␣ particle to be in the MeV region. At Chiang Mai University we have researched the possibility of utilizing a 280 keV nanosecond pulse of helium ions for RBS applications. We have chosen a compact filament-driven multicusp ion source of 2.6 cm in diameter and 8 cm in length being investigated for the time-of-flight RBS applications. In this article, we present the general ion source performance using helium, nitrogen, and argon for generating the discharge plasma. The general ion source characteristics have been measured and analyzed. The measurements also include the extractable ion current and the ion beam emittance. We have performed beam extraction calculations with a computer simulation code KOBRA. Results of the measurements and calculations will be presented and discussed.