Installation of hybrid ion source on the 1-MV LLNL BioAMS spectrometer

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 294; pp. 311 - 314
• Main Authors: Ognibene, T.J., Salazar, G.A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2013
• Subjects: AMS; Beam interactions; Bouncing; Carbon; CO2 gas; Dynamical systems; Electric potential; Graphite; Ion sources; Isotope ratios; Moving-wire; PARTICLE ACCELERATORS; Spectrometers; Ion sources; CO2 gas; Moving-wire; AMS; Graphite; graphite; moving-wire; ion sources
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2011.11.029

A second ion source was recently installed onto the LLNL 1-MV AMS spectrometer, which is dedicated to the quantification of 14C and 3H within biochemical samples. This source is unique among the other LLNL cesium sputter ion sources in that it can ionize both gaseous and solid samples. Also, the injection beam line has been designed to directly measure 14C/12C isotope ratios without the need for electrostatic bouncing. Preliminary tests show that this source can ionize transient CO2 gas pulses containing less than 1μg carbon with approximately 1.5% efficiency. We demonstrate that the measured 14C/12C isotope ratio is largely unaffected by small drifts in the argon stripper gas density. We also determine that a tandem accelerating voltage of 670kV enables the highest 14C transmission through the system. Finally, we describe a series of performance tests using solid graphite targets spanning nearly 3 orders in magnitude dynamic range and compare the results to our other ion source.