Accelerator mass spectrometry instrumentation

Accelerator mass spectrometry Instrumental technique for direct enumeration of low-level radioactive nuclides. 

Newer instrumental methods of potential utility in organic analysis of environmental and geological biomarkers are compound specific isotope analysis (CSIA) and carbon-14 dating with accelerator mass spectrometry (AMS). CSIA provides the carbon isotope composition of individual... 

Instrumental layouts and developments in AMS are reviewed by Kutschera.195 Today AMS is the most powerful, sensitive and selective mass spectrometric technique for measuring long-lived radionuclides at the level of natural isotopic abundances (10-16 to 10-12). Accelerator mass spectrometry (AMS) allows uranium isotope ratio measurements with an abundance sensitivity for 236U in the range of l(rlo-10 l2.l98J"... 

Acceleration mass spectrometry (AMS) - The precise measurement of isotopic ratios for very low abundance isotopes is beyond the capability of conventional mass spectrometers. In these cases of isotopes at minute trace levels, some 50 mass spectrometers exist worldwide. The tendetrons used for these types of analyses are derived from Van de Graaff-type particle accelerators. These instruments are based on tandem mass spectrometry. 

Instrumentation AMS - Accelerator Mass Spectrometry Radiocarbon Dating Application Authentication Place Italy... 

Because use of mass spectrometry by chemists has increased greatly, most U.S. chemists have access to mass spectrometry facilities at their own institutions to confirm synthesis and support structure elucidations. Heavily used national centers provide more expensive instrumentation and more complex experiments. Most notably, a section of the National High Magnetic Field Laboratory at Florida State University provides state-of-the-art Fourier transform ion cyclotron resonance mass spectrometry. The NSF Arizona Accelerator Mass Spectrometry Laboratory is used primarily to provide radiocarbon measurements. NIH funds a number of national mass spectrometry centers to support biomedical research, including those at Boston University and the Pacific Northwest National Laboratory. 

The book concentrates on the most common instruments nsed in chemical, environmental, biological, and medical research. Less frequently encountered forms of mass spectrometry are not addressed, such as inductively coupled plasma mass spectrometry (ICP-MS) isotope ratio mass spectrometry (IRMS), accelerator mass spectrometry (AMS), proton transfer reaction mass spectrometry (PTRMS), and single-particle laser ablation time-of-flight mass spectrometry (SPLAT). 

In VoL 2 of this handbook, the origin of elements has been discussed in detail. Therefore, the present authors will exclude that part, except for some comments on the importance of particular radionucKdes. In this chapter, the principles and instrumentation of accelerator mass spectrometry (AMS), the key player for detection of cosmological radionucKdes in ultra trace scale, will be discussed in detail. Detailed discussion of all the research works carried out to date with cosmogenic radionuclides is out of scope. Only the detection of million-year half-life radionucKdes in ultra trace concentration will be touched, followed by concise description of the required chemistry. Rather than giving a general description, a few of them have been chosen and described in separate sections. Inductively coupled plasma-mass spectrometry (ICP-MS), thermal ionization mass spectrometry (TIMS), secondary ion mass spectrometry (SIMS), or resonant laser ionization mass spectrometer (RIMS), etc. have also been used for detection of cosmogenic radionucKdes. However, these techniques have much lower sensitivity compared to AMS. Brief discussions on these instruments have been appended at the end of this chapter. This chapter ends with a conclusion. 

Ognibene, T.I, Bench, G., Brown, T.A., Vogel, IS. (2004) The LLNL accelerator mass spectrometry system for biochemical C-measurements. Nuclear Instruments and Methods in Physics Research. Section B, 223-224,12-15. 

FIGURE 20.13 Instrumental diagram of an accelerator mass spectrometry setup, the Vienna Environmental Research Accelerator (VERA). Source Vockenhuber, C, et al. (2003) Accelerator mass spectrometry of heavy long-Uved radionuclides. International Journal of Mass Spectrometry, 223-224,713-732. 

Some AMS investigations have been done in semiconductor research, but concluding from the number of publications, interest seems to have peaked in the 1990s. For instance, the last three proceedings of the International Conference on Accelerator Mass Spectrometry [310-312] did not include any work related to semiconductors. This might well have to do with the improvements SIMS instruments experienced over the last two decades. 

FIGURE 40.21 Comparison of the depth profiles of a copper impurity by trace element accelerator mass spectrometry (TEAMS) and secondary ion mass spectrometry (SIMS). Reprinted from McDaniel, ED, Datar, S.A., Nigam, M., Ravi Prasad, G.V. (2002) Impurity measurements in semiconductor materials using trace element accelerator mass spectrometry. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms, 190 1-A), 826-830. Copyright (2002), with permission from Elsevier Science. 

Fifield, L.K. (2004) Applications of accelerator mass spectrometry advances and innovation. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms, 223-224, AOl-All. 

Knezovich, J., Brown, T., Buchholz, B., Finkel, R., Guilderson, T, Kashgarian, M., Nimz, G., Ognibene, T., Turney, S., Vogel, I, eds. (2007) Accelerator Mass Spectrometry—Proceedings of the Tenth International Conference on Accelerator Mass Spectrometry, Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms, Vol. 259, Elsevier. 

Kirchhoff, J.F., Marble, D.K., Weathers, D.L., McDaniel, ED., Matteson, S., Anthony, J.M., Beavers, R.L., Bennett, T.J. (1994) Fabrication of silicon-based optical components for an ultraclean accelerator mass spectrometry negative ion source. Review of Scientific Instruments, 65, 1570-1574. 

The methodology of accelerator mass spectrometry (AMS) clearly differs from all other approaches to analyzing of atomic mass so far referred to in this book. While ions to be analyzed by a quadmpole analyzer are injected at kinetic energies of about 10 eV, those for a sector instrument at 5-10 keV, and those for TOFs at 15-30 keV, in AMS ions have several MeV. Another unique and key feature of the technique is that the ions experience dramatic changes in kinetic energy and charge state during the experiment. 

Py/GC/MS. pyrolysis, gas chromatography, and mass spectrometry used as a combined technique Py/MS. pyrolysis and mass spectrometry used as a combined technique oa-TOF. orthogonally accelerated time of flight Q. quadrupole field or instrument... 

In Laser Ionization Mass Spectrometry (LIMS, also LAMMA, LAMMS, and LIMA), a vacuum-compatible solid sample is irradiated with short pulses ("10 ns) of ultraviolet laser light. The laser pulse vaporizes a microvolume of material, and a fraction of the vaporized species are ionized and accelerated into a time-of-flight mass spectrometer which measures the signal intensity of the mass-separated ions. The instrument acquires a complete mass spectrum, typically covering the range 0— 250 atomic mass units (amu), with each laser pulse. A survey analysis of the material is performed in this way. The relative intensities of the signals can be converted to concentrations with the use of appropriate standards, and quantitative or semi-quantitative analyses are possible with the use of such standards. 

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