Progress in AMS measurements at the LLNL spectrometer. [Accelerator Mass Spectroscopy (AMS)]

Conference · Sat Jun 01 04:00:00 EDT 1991

OSTI ID:5610250

Southon, J R; Vogel, J S; Trumbore, S E; Davis, J C; Roberts, M L; Caffee, M; Finkel, R; Proctor, I D; Heikkinen, D W; Berno, A J; Hornady, R S

The AMS measurement program at LLNL began in earnest in late 1989, and has initially concentrated on {sup 14}C measurements for biomedical and geoscience applications. We have now begun measurements on {sup 10}Be and {sup 36}Cl, are presently testing the spectrometer performance for {sup 26}Al and {sup 3}H, and will begin tests on {sup 7}Be, {sup 41}Ca and {sup 129}I within the next few months. Our laboratory has a strong biomedical AMS program of {sup 14}C tracer measurements involving large numbers of samples (sometimes hundreds in a single experiment) at {sup 14}C concentrations which are typically .5--5 times Modern, but are occasionally highly enriched. The sample preparation techniques required for high throughput and low cross-contamination for this work are discussed elsewhere. Similar demands are placed on the AMS measurement system, and in particular on the ion source. Modifications to our GIC 846 ion source, described below, allow us to run biomedical and geoscience or archaeological samples in the same source wheel with no adverse effects. The source has a capacity for 60 samples (about 45 unknown) in a single wheel and provides currents of 30--60{mu}A of C{sup {minus}} from hydrogen-reduced graphite. These currents and sample capacity provide high throughput for both biomedical and other measurements: the AMS system can be started up, tuned, and a wheel of carbon samples measured to 1--1.5% in under a day; and 2 biomedical wheels can be measured per day without difficulty. We report on the present status of the Lawrence Livermore AMS spectrometer, including sample throughput and progress towards routine 1% measurement capability for {sup 14}C, first results on other isotopes, and experience with a multi-sample high intensity ion source. 5 refs.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5610250
• Report Number(s): UCRL-JC-107498; CONF-9105225--1; ON: DE91015112
• Country of Publication: United States
• Language: English

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47 OTHER INSTRUMENTATION
ALKALINE EARTH ISOTOPES
BERYLLIUM 10
BERYLLIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
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CHLORINE 36
CHLORINE ISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
EVEN-EVEN NUCLEI
ION SOURCES
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LIGHT NUCLEI
MASS SPECTROMETERS
MASS SPECTROSCOPY
MEASURING INSTRUMENTS
NUCLEI
ODD-ODD NUCLEI
PERFORMANCE TESTING
RADIOISOTOPES
SPECTROMETERS
SPECTROSCOPY
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YEARS LIVING RADIOISOTOPES