Collaborative Research:AMS Ion Source Development at University of California, Irvine, Woods Hole Oceanographic Institution, University of Arizona, and National Electrostatics Corp

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

EAR-0324752 Roberts Laboratories at University of California at Irvine, Woods Hole Oceanographic Institution, and University of Arizona use accelerator mass spectrometry (AMS) to measure cosmogenic isotopes, primarily 14C, supporting research at the parent institutions plus numerous external researchers. The demand for these analyses comes from many scientific fields, including: geology, archaeology, physics, geography, oceanography, atmospheric sciences, hydrology, biology, art history, forensic sciences and engineering. A reliable and stable ion source for converting samples of interest into intense beams of negative ions is absolutely critical to the overall performance of an AMS spectrometer. The three AMS laboratories collaborating in this proposal currently use four versions of the MC-SNICS Cs sputter ion source, built by National Electrostatics Corp (NEC) of Middleton, WI. We will collaborate with NEC in a 2-year program to modify the ion source for increased output, better reliability, and improved serviceability. Low source output, poor reliability, and time required for source maintenance are currently the largest causes of delay and poor measurement quality for users of AMS laboratories worldwide. Work at UC Irvine will concentrate on changes to the Cs feed and to the Cs and negative ion geometries aimed at increasing output and improving reliability. Woods Hole will investigate active pumping of the source and other vacuum improvements for increased output, and will redesign the ion source extraction region for improved reliability. Arizona will implement improved internal mounting arrangements for the Cs ionizer assembly and focusing electrodes, plus changes to sample alignment procedures leading to reduced servicing down time. A full suite of the modifications initially developed at each laboratory will then be evaluated, and an optimal set will be incorporated in the sources at the three institutions and in new sources produced by NEC. The results will be passed on to the AMS community at large, to allow the many disciplines using AMS to reap the scientific benefits resulting from improved measurement quality due to better source performance.