A compact tritium AMS system

Tritium (H-3) is a radioisotope that is extensively utilized in biological and environmental research. For biological research, 3H is generally quanti fied by liquid scintillation counting requiring gram-sized samples and coun ting times of several hours. For environmental research, H-3 is usually qua ntified by He-3 in-growth which requires gram-sized samples and in-growth t imes of several months. In contrast, provisional studies at LLNL's Center f or Accelerator Mass Spectrometry have demonstrated that accelerator mass sp ectrometry (AMS) can be used to quantify 3H in milligram-sized biological s amples with a 100 to 1000-fold improvement in detection limits when compare d to scintillation counting. This increased sensitivity is expected to have great impact on the biological and environmental research community. Howev er, in order to make the 3H AMS technique more broadly accessible, smaller, simpler, and less expensive AMS instrumentation must be developed. To meet this need, a compact, relatively low cost prototype 3H AMS system has been designed and built based on an LLNL ion source/sample changer and an AccSy s Technology radio frequency quadrupole (RFQ) linac. With the prototype sys tem, H-3/H-1 ratios ranging from 1 x 10(-10) to 1 x 10(-13) have be measure d from milligram-sized samples. With improvements in system operation and s ample preparation methodology, the sensitivity limit of the system is expec ted to increase to approximately 1 x 10(-15). (C) 2000 Elsevier Science B.V . All rights reserved.