J.C. Davis

LLNL/UC AMS facility and research program

Abstract The Lawrence Livermore National Laboratory (LLNL) and the University of California (UC) now have in operation a large AMS spectrometer built as part of a new multiuser laboratory centered on an FN tandem. AMS measurements are expected to use half of the beam time of the accelerator. LLNL use of AMS is in research on consequences of energy usage. Examples include global warming, geophysical site characterization, radiation biology and dosimetry, and study of mutagenic and carcinogenic processes. UC research activities are in clinical applications, archaeology and anthropology, oceanography, and geophysical and geochemical research. Access is also possible for researchers outside the UC system. The technological focus of the laboratory is on achieving high rates of sample throughput, unattended operation, and advances in sample preparation methods. Because of the expected growth in the research programs and the other obligations of the present accelerator, we are designing a follow-on dedicated facility for only AMS and microprobe analysis that will contain at least two accelerators with multiple spectrometers.

The new LLNL AMS spectrometer

Abstract The multi-user tandem laboratory at Lawrence Livermore is a new facility dedicated to AMS and a variety of other ion-beam analysis techniques. The AMS spectrometer design aims and implementation are presented here, and present performance and planned improvements are discussed.

Application of AMS to the biomedical sciences

Abstract Radio-isotopic tracers are a useful tool in numerous areas of biomedical research, including metabolism, pharmacokinetics, and the detailed study of biomolecular interactions. Accelerator mass spectrometry was suggested as a tool for the biomedical sciences shortly after its invention, but few attempts to use its sensitivity in such research have been reported. We have examined some of the strengths and limitations of the technique and find that AMS has a sensitivity advantage over decay-counting for the long-lived radio-isotopes and for shorter-lived, common radiotracers. The advantage can be translated into the use of much smaller sample sizes and much lower radio-isotope concentrations, both of which present new opportunities for biochemical tracing and human research. New approaches to separation and preparation of the material to be assayed for radio-tracers will be developed to take advantage of the sensitivity and specificity. Most biochemical laboratories have used radioactive isotopes as tracers and their facilities have been contaminated with unacceptably high levels of these tracers. Careful protocols and/or new facilities are required to prevent contamination of the AMS samples.

Accelerator mass spectrometry in the biomedical sciences: applications in low-exposure biomedical and environmental dosimetry☆

Abstract We are utilizing accelerator mass spectrometry as a sensitive detector for tracking the disposition of radioisotopically labeled molecules in the biomedical sciences. These applications have shown the effectiveness of AMS as a tool to quantify biologically important molecules at extremely low levels. For example, AMS is being used to determine the amount of carcinogen covalently bound to animal DNA (DNA adduct) at levels relevent to human exposure. Detection sensitivities are 1 carcinogen molecule bound in 1011 to 1012 DNA bases, depending on the specific activity of the radiolabeled carcinogen. Studies have been undertaken in our laboratory utilizing heterocyclic amine food-borne carcinogens and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent environmental carcinogen, to study the metabolism of carcinogens at low doses. In addition, AMS is being used to detect the presence of rare proteins (mutant forms of protamine) in human sperm. Approximately l per 106 sperm analyzed contain the rare form of the protamine. Protamine isolated from this small number of cells is being analyzed by AMS, following 14C labeling. Thus, AMS can be used to verify the identity of an extremely small amount of biological material. Furthermore, an additional improvement of 2 orders of magnitude in the sensitivity of biomedical tracer studies is suggested by preliminary work with bacterial hosts depleted in radiocarbon. Other problems in the life sciences where detection sensitivity or sample sizes are limitations should also benefit from AMS. Studies are underway to measure the molecular targeting of cancer chemotherapeutics in human tissue and to pursue applications for receptor biology. We are also applying other candidate isotopes, such as 3 H (double labeling with 14 C) and 41 Ca (bone absorption) to problems in biology. The detection of 36 Cl and 26 Al have applications for determination of human neutron exposure and understanding neurological toxicity, respectively. The results described here with 14 C-labeled molecules coupled with new isotope applications clearly show AMS technology to be an important new tool for the biomedical sciences community.

The LLNL ion source — past, present and future

Abstract The Multi-user Tandem Laboratory (MTL) at LLNL is a general purpose laboratory for analysis using ion beam techniques. Our initial interest in AMS was for large throughput with modest precision. Toward this goal, we purchased a prototype GIC spherical ionizer source with a 60 sample cassette changer. The source has been extensively modified to increase reliability and to adapt it for AMS operation. The sample changing mechanism was completely rebuilt, pumping was increased in critical areas, electrical stress has been reduced in areas where failures were frequent and protection of insulators from cesium vapor has been increased. We are limiting the divergence to 20 mrad to match the present injection system and are only able to get about 50 μA of stable carbon beam in this configuration. Details of failures, changes to date and planned improvements will be discussed.

AMS beyond 2000

Abstract Extrapolation of developments in accelerator mass spectrometry since the 1990 conference in Paris tempts one to predict the future of the technology. The rapid expansion of biomedical applications of AMS has required not just development of high throughput spectrometers but demonstration of very short experimental cycles, typically a week or less. Such short cycles then make possible the virtual decoupling of sophisticated sample preparation methodologies from the spectrometer itself, imposing greater need for spectrometer availability and reliability. Established research uses of AMS in archaeology and the geosciences will benefit greatly from these developments and be modified by them. The future appears to hold a mix of proliferation of independent, discipline-dependent sample preparation labs, of large numbers of relatively inexpensive optimized spectrometers, and of steady pressure for capability, reliability, and throughput upgrades of the large multi-isotope laboratories.

LLNL multi-user tandem laboratory

Abstract The Physics Department at Lawrence Livermore National Laboratory (LLNL) is building a new tandem Van de Graaff laboratory for nuclear physics and applied physics and technology programs. The laboratory has been funded by a coalition of users including several LLNL divisions, Sandia National Laboratories Livermore, and the University of California. The tandem is the former University of Washington injector FN. The accelerator is upgraded with a Pelletron charging system, Dowlish spiral inclined field beam tubes and SF 6 insulation. The laboratory incorporates several novel design concepts. Initial operation will be in June, 1987 with full operation in October, 1987. Design features, radiological controls, computer assisted operation, and experimental facilities of the laboratory are discussed.

Technical and Policy Issues of Counterterrorism—A Primer for Physicists

No longer threatened by a rival superpower, the US now faces the growing danger of clandestine terrorist groups. Effectively countering terrorists requires that physicists actively contribute to the nation’s defense.

Iraq's Secret Nuclear Weapons Program

The inspections of Iraq mandated by the United Nations as a cease‐fire condition at the end of the Gulf War in February 1991 have revealed a clandestine nuclear materials production and weapons design program of unexpected size and sophistication. The total value of that program, in terms of equipment and personnel deployed between 1981 and 1991, may be on the order of

A dedicated AMS facility for 3H and 14C

5‐10 billion. The program employed an estimated 7000 scientists and 20 000 workers.