Ion beam enhancement in 236UO− measurement by AMS using Si powder as the binder

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2019-10, Vol.456, p.218-221
• Main Authors: Kazi, Z.H., Charles, C.R.J., Zhao, X.L., Cornett, R.J., Kieser, W.E.
• Format: Article
• Language: English
• Subjects: AMS; AMS target; Silicon; U-236; UO− current
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2019.04.006

UO− has so far been the ion of choice for 236U measurement by AMS, but high and stable ionization efficiency for UO− production has been difficult to obtain with some models of Cs+ sputter ion sources. We have experienced considerable difficulties in producing sustainable UO− current even at 10 nA levels using the SO-110B source at A. E. Lalonde AMS Laboratory, University of Ottawa. This source is presently not configured for delivering Cs+ sputter beams at levels greater than 0.5 mA reliably, while ∼1.5 mA is reported to be needed for producing steady UO− currents in the 150–300 nA range. Various tests were undertaken to increase and stabilize the UO− current using the SO-110B source in its present configuration. The test included the addition of several fine powders as binders, including Al, C, Ta, Si, and SiC, to uranium oxide to form the sputter target. Si and Ta + Si were found to provide a significant enhancement to the UO− current production, which enabled us to carry on the 236U measurement using UO− with the existing ion source, although the achieved enhancement is still far short of the 150–300 nA UO− current reported elsewhere.