"Impatient" scientists: Accelerator mass spectrometry (AMS)
for the determination of long-lived radionuclides

              

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Introduction

The Ion Beam Center of HZDR has expanded its measurement capability by another highly-sensitive analytical method, accelerator mass spectrometry (AMS), which is used for the determination of long-lived radionuclides.

In contrast to ordinary decay counting, the "impatient" scientists do not wait for the disintegration of a radioactive nucleus. In fact, they determine the not-yet-decayed radionuclides by mass spectrometry, which is much more efficient.

There is a main advantage of using a high-energy accelerator for mass spectrometry: The background and interfering signals, resulting from molecular ions and ions with similar masses e.g. isobars, are nearly completely eliminated. Thus, AMS generally provides much lower detection limits in comparison to conventional mass spectrometry. Our AMS system offers excellent measurement capabilities also for external users.

In contrary to common low-energy AMS facilities in Germany and Europe, which have mainly specialized in radiocarbon analyses (¹⁴C), the HZDR-AMS is the first modern-type facility in the EU that rusn at a terminal voltage of 6 MV. Maximum stability is guaranteed by producing the high-voltage of the accelerator by a high-frequency cascade generator instead of an old-fashioned van-de-Graaff one.

The benefits from using AMS for radiation protection, nuclear safety, nuclear waste, radioecology, phytology, nutrition, toxicology, and pharmacology research are obvious and manifold: Smaller sample sizes, easier and faster sample preparation, higher sample throughput and the redundancy for radiochemistry laboratories will largely reduce costs. Lower detection limits widen applications to shorter and longer time-scales and to sample types that could never been investigated before. Especially in environmental and geosciences, the determination of long-lived cosmogenic radionuclides like 10Be, 26Al, and 36Cl became more and more important. Using these nuclides dating of suddenly occurring prehistoric mass movements, e.g. volcanic eruptions, rock avalanches, tsunamis, meteor impacts, earth quakes and glacier movements, is possible. Additionally, glacier movements and data from ice cores give hints for the reconstruction of historic climate changes and providing information for the validation of climate model predicting future changes.

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Cosmogenic radionuclides One of our first approaches have been the determination of long-lived cosmogenic radionuclides. Right after the installation of the AMS set-up, we started to measure the following nuclides: Later on, we will also focus on other radionuclides, e.g. actinides. We are capable of measuring isotopic ratios as low as 10-16.

nuclide half-life 10Be 1.387 Ma 26Al 0.7 Ma 36Cl 0.301 Ma 41Ca 0.104 Ma 129I 15.7 Ma

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Chemical sample preparation AMS measurements of long-lived radionuclides are only possible if samples are chemically treated, as the original samples (water, rocks etc.) that contain reasonable amounts of radionuclides are too big (100 g - 10 kg). Or in other words, the radionuclide concentrations in the range of sub-ppq are too low to allow an analysis of typical 1 mg-targets. Besides, the chemical separation is doing most of the work reducing the troublesome isobars, and eliminating possible contamination from other sources. For instance, the analysis of cosmogenic 10Be in quartz can only be performed if samples are previously cleaned from atmospherically-produced 10Be. The preparation of 10Be-, 26Al-, and 41Ca-AMS-targets needs the use of large quantities of hydrochloric acid (HCl) and, thus, should be preferably performed in a separated place than 36Cl- und 129I-AMS-target preparation keeping the risk of cross-contamination as low as possible.

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Machine layout

Ions are extracted from two identical hybrid ion sources, which can handle gaseous and solid samples. Each Cs-sputter source is equipped with a 200-sample wheel. On the low-energy (LE) side the ions are separated by an energy-analyser, a 54° electrostatic deflector, and a mass-analyzer, a 90° magnet, equipped with a fast-bouncing system. The tandetron accelerator [Gottdang et al., 2002] contains a gas stripper and active stripper gas regulation. On the high-energy (HE) side, a 90° analysing magnet is followed by a Faraday-Cup for stable isotope measurements. The rare isotopes are detected by a 4-anode gas ionization chamber, after passing a 35° electrostatic deflector and a 30° vertical analysing magnet for further background reduction. For ¹⁰Be and ³⁶Cl measurements a silicon nitride absorber foil (1 µm) can be inserted in the HE-part for post-stripping [Klein et al., 2008].

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Access for external users Of course, we are performing AMS measurements also for external users. Additionally, we offer "in-house-training" for AMS sample preparation in our chemistry labs at HZDR, which are already functional since 2009. If you are interested in setting up your own sample preparation labs, please do not hesitate to contact us for our mentoring programme.
	Thomas Smith, U Bern (CH)	Cornelia Wilske, UFZ Halle	Vasila Sulaymonova, TUBA Freiberg
Guillem Domènech i Surinyach, U Politècnica de Catalunya (E)	Lisa Michel & Rebecca Schmidt, TU Dresden	Angela Landgraf, U Potsdam	Peter Ludwig, TU Munich
Jenny Feige, VERA, U Vienna (A)	Anna Seither, TUBA Freiberg	Aurore Hutzler, CEREGE, Aix-en-Provence (F)	Ines Röhringer, U Bayreuth
Cengiz Yilderim, U & GFZ Potsdam	Maggi Fuchs & Katja Klemm, TUBA Freiberg	Bernhard Kuczeweski, U Cologne	Christoff Andermann, TUBA Freiberg & U Rennes (F)

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References

S. Akhmadaliev, R. Heller, D. Hanf, G. Rugel, S. Merchel, The new 6 MV AMS-facility DREAMS at Dresden, Nucl. Instr. and Meth. in Phys. Res. B 294 (2012) 5-10.

S. Merchel, S. Akhmadaliev, S. Pavetich, G. Rugel, Ungeduldige Forscher träumen mit DREAMS - Bestimmung langlebiger Radionuklide mit Beschleunigermassenspektrometrie, GIT Labor-Fachzeitschrift 56 (2012) 88-90.

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Useful links

Video about ¹⁴C-dating @ GNS, New Zealand (in English)

Animation about ¹⁴C AMS @ ANSTO, Austrailia (in English)

Talk about "Accelerator Mass Spectrometry in Biology and Health Care" (Science on Saturday, LLNL, USA, in English)

Video about ²⁶Al/¹⁰Be-dating of the "Peking Man" @ PRIME Lab, USA (in English)

Cosmogenic nuclides in meteorites and AMS for "German dummies" (in German)

Further information "Cosmic radiation" und "Cosmogenic nuclides" (in German)

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Please contact Silke Merchel for further information or have a look at the following papers:

Further reading particularly with respect to terrestrial produced cosmogenic radionuclides

• Reviews

P. R. Bierman, Rock to sediment – slope to sea with ¹⁰Be – rates of landscape change, Ann. Rev. Earth Planet. Sci. 32 (2004) 215-225.

T. E. Cerling, H. Craig. Geomorphology & in-situ cosmogenic isotopes, Ann. Rev. Earth Planet. Sci. 22 (1994) 273-317.

J. C. Gosse, F. M. Phillips, Terrestrial in situ cosmogenic nuclides: theory and application, Quaternary Science Review 20 (2001) 1475-1560.

S. Ivy-Ochs, M. Schaller, Examining Processes and Rates of Landscape Change with Cosmogenic Radionuclides, In: Radioactivity in the Environment, Chapter 6, 16 (2009) 231-294.

W. Kutschera, Progress in isotope analysis at ultra-trace level by AMS, International Journal of Mass Spectrometry 242 (2005) 145-160.

A. E. Litherland, X-L. Zhao, W. E. Kieser, Mass spectrometry with accelerators, Mass Spectrometry Reviews 30 (2011) 1037-1072.

P. Muzikar, D. Elmore, D.E. Granger, Accelerator mass spectrometry in geologic research, GSA Bulletin 115 (2003) 643-654.

• Chemical separation: ¹⁰Be und ²⁶Al

E. T. Brown, J. M. Edmond, G. M. Raisbeck, F. Yiou, M. D. Kurz, E. J. Brook, Examination of surface exposure ages of Antarctic moraines using in-situ produced ¹⁰Be and ²⁶Al, Geochim. Cosmochim. Acta 55 (1991) 2269-2283.

R. G. Ditchburn. N. E. Whitehead, The separation of ¹⁰Be from silicates, 3^rd Workshop of the South Pacific Environmental Radioactivity Association (1994) 4-7. / expanded description on http://depts.washington.edu/cosmolab/chem.html

C. P. Kohl, K. Nishiizumi, Chemical isolation of quartz for measurement of in-situ-produced cosmogenic nuclides, Geochim. Cosmochim. Acta 56 (1992) 3583-3587.

S. Merchel, U. Herpers, An Update on Radiochemical Separation Techniques for the Determination of Long-Lived Radionuclides via Accelerator Mass Spectrometry, Radiochim. Acta 84 (1999) 215-219.

• Chemical separation: ³⁶Cl

S. Jiang, Y. Lin, H. Zhang, Improvement of the sample preparation method for AMS measurement of ³⁶Cl in natural environment, Nucl. Instr. and Meth. in Phys. Res. B223-224 (2004) 318-322.

S. Merchel, U. Herpers, An Update on Radiochemical Separation Techniques for the Determination of Long-Lived Radionuclides via Accelerator Mass Spectrometry, Radiochim. Acta 84 (1999) 215-219.

J. O. Stone, G. L. Allan, L. K. Fifield, R. G. Cresswell, Cosmogenic chlorine-36 from calcium spallation, Geochim. Cosmochim. Acta 60 (1996) 679-692. / expanded description on http://depts.washington.edu/cosmolab/chem.html

• Accelerator mass spectrometry

R. C. Finkel, M. Suter, AMS in the Earth Sciences: Technique and Applications, Advances in Analytical Geochemistry 1 (1993) 1-114.

S. Merchel, M. Arnold, G. Aumaître, L. Benedetti, D. L. Bourlès, R. Braucher, V. Alfimov, S. P. H. T. Freeman, P. Steier, A. Wallner, Towards more precise ¹⁰Be and ³⁶Cl data from measurements at the 10^-14 level: Influence of sample preparation, Nucl. Instr. and Meth. in Phys. Res. B266 (2008) 4921-4926.

C. Tuniz, J. R. Bird, D. Fink, G. F. Herzog, Accelerator Mass Spectrometry, CRC Press (1998).

• Production rates

J.M. Licciardi, C.L. Denoncourt, R.C. Finkel, Cosmogenic ³⁶Cl production rates from Ca spallation in Iceland, Earth Planet. Sci. Lett. 267 (2008) 365-377.

J. Masarik, K. J. Kim, R. C. Reedy, Numerical simulation of in situ production of terrestrial cosmogenic nuclides, Nucl. Instr. and Meth. in Phys. Res. B259 (2007) 642-645.

K. Nishiizumi, E. L. Winterer, C. P. Kohl, J. Klein, R. Middleton, D. Lal, J. R. Arnold, Cosmic ray production rates of ¹⁰Be and ²⁶Al in quartz from glacially polished rocks, J. Geophys. Res. 94 (1989) 17907-17915.

F. M. Phillips, W. D. Stone, J. T. Fabryka-Martin, An improved approach to calculating low-energy cosmic-ray neutron fluxes near the land/atmosphere interface, Chemical Geology 175 (2001) 689-701.

I. Schimmelpfennig, Sources of in-situ ³⁶Cl in basaltic rocks. Implications for calibration of production rates, Quaternary Geochronology 4 (2009) 441-461.

J. O. Stone, G. L. Allan, L. K. Fifield, R. G. Cresswell, Cosmogenic chlorine-36 from calcium spallation, Geochim. Cosmochim. Acta 60 (1996) 679-692.

J. O. H. Stone, J. M. Evans, L. K. Fifield, G. L. Allan, R. G. Cresswell, Cosmogenic chlorine-36 production in calcite from muons, Geochim. Cosmochim. Acta 62 (1998) 433-454.

• Scaling factors

D. Desilets, M. Zreda, Spatial and temporal distribution of secondary cosmic-ray nucleon intensities and applications to in situ cosmogenic dating, Earth Planet. Sci. Lett. 206 (2003) 21-42.

T. J. Dunai, Scaling factors for production rates of in situ produced cosmogenic nuclides: a critical re-evaluation, Earth Planet. Sci. Lett. 176 (2000) 157-169.  See also comments by Desilets et al. 188 (2001) 283-287 and reply by Dunai 188 (2001) 289-298.

T. J. Dunai, Influence of secular variation of the geomagnetic field on production rates of in situ produced cosmogenic nuclides, Earth Planet. Sci. Lett. 193 (2001) 197-212.

D. Lal, Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models, Earth Planet. Sci. Lett. 104 (1991) 424-439.

J. Masarik, M. Frank, J. M. Schäfer, R. Wieler, Correction of in situ cosmogenic nuclide production rates for geomagnetic field intensity variation during the past 800,000 years, Geochim. Cosmochim. Acta 65 (2001) 2995-3003.

N. A. Lifton, J. W. Bieber, J. M. Clem, M. L. Duldig, P. Evenson, J. E. Humble, R. Pyle, Addressing solar modulation and long-term uncertainties in scaling secondary cosmic rays for in situ cosmogenic nuclide applications, Earth Planet. Sci. Lett. 239 (2005) 140-161.

N. Lifton, D. F. Smart, M. A. Shea, Scaling time-integrated in situ cosmogenic nuclide production rates using a continuous geomagnetic model, Earth Planet. Sci. Lett. 268 (2008) 190-201.

J. S. Pigati, N. A. Lifton, Geomagnetic effects on time-integrated cosmogenic nuclide production with emphasis on in situ ¹⁴C and ¹⁰Be, Earth Planet. Sci. Lett. 226 (2004) 193-205.

J. O. Stone, Air pressure and cosmogenic isotope production, J. Geophys. Res. 105 (2000) 23753-23759.

• House advertising - some of our latest publications ;-)

2013

S. Akhmadaliev, R. Heller, D. Hanf, G. Rugel, S. Merchel, The new 6 MV AMS-facility DREAMS at Dresden, Nucl. Instr. and Meth. in Phys. Res. B 294 (2012) 5-10.

M. Arnold, G. Aumaître, D.L Bourlès, K. Keddadouche, R. Braucher, R.C Finkel, E. Nottoli, L. Benedetti, S. Merchel, The French accelerator mass spectrometry facility ASTER after 4 years: Status and recent developments on ³⁶Cl and ¹²⁹I, Nucl. Instr. and Meth. in Phys. Res. B 294 (2013) 24-28.

D. Hampe, B. Gleisberg, S. Akhmadaliev, G. Rugel, S. Merchel, Determination of ⁴¹Ca with LSC and AMS: method         development, modifications and applications, Journal of Nuclear and Radioanalytical Chemistry 296 (2013) 617-624.   

J. Llorca, J. Roszjar, J.A. Cartwright, A. Bischoff, A. Pack, U. Ott, S. Merchel, G. Rugel, L. Fimiani, P. Ludwig, D. Allepuz, J.V. Casado, The Ksar Ghilane 002 shergottite – the 100^th registered Martian meteorite fragment, Meteorit. Planet. Sci. 48 (2013) 493–513.

R. Zech, I. Röhringer, P. Sosin, H. Kabgov, S. Merchel, S. Akhmadaliev, W. Zech, Late Pleistocene glaciation in the Gisssar Range, Tajikistan, based on ¹⁰Be surface exposure dating, Palaeogeography, Palaeoclimatology,        Palaeoecology 369 (2013) 253-261.

2012

S. Merchel, S. Akhmadaliev, S. Pavetich, G. Rugel, Ungeduldige Forscher träumen mit DREAMS - Bestimmung langlebiger Radionuklide mit Beschleunigermassenspektrometrie, GIT Labor-Fachzeitschrift 56 (2012) 88-90.

S. Merchel, W. Bremser, S. Akhmadaliev, M. Arnold, G. Aumaître, D. L. Bourlès, R. Braucher, M. Caffee, M. Christl, L. K. Fifield, R. C. Finkel, S. P. H. T. Freeman, A. Ruiz-Gómez, P. W. Kubik, M. Martschini, D. H. Rood, S. G. Tims, A. Wallner, K. M. Wilcken, S. Xu, Quality assurance in accelerator mass spectrometry: Results from an international round-robin exercise for ¹⁰Be, Nucl. Instr. and Meth. in Phys. Res. B. 289 (2012) 68-73.

2011

R. Braucher, S. Merchel, J. Borgomano, D.L Bourlès, Production of cosmogenic radionuclides at great depth: A multi element approach, Earth Planet. Sci. Lett. 309 (2001) 1-9.

S. Merchel, W. Bremser, V. Alfimov, M. Arnold, G. Aumaître, L. Benedetti, D. L. Bourlès, M. Caffee, L. K. Fifield, R. C. Finkel, S. P. H. T. Freeman, Y. Matsushi, D. H. Rood, K. Sasa, P. Steier, T. Takahashi, M. Tamari, S. G. Tims, Y. Tosaki,  K. M. Wilcken, S. Xu, Ultra-trace analysis of ³⁶Cl by accelerator mass spectrometry: an interlaboratory study,Anal. Bioanal. Chem. 400 (2011) 3125-3132.

2010

M. Altmaier, U. Herpers, G. Delisle, U. Ott, S. Merchel, Glaciation history of Queen Maud Land (Antarctica) using in-situ produced cosmogenic ¹⁰Be, ²⁶Al and ²¹Ne, Polar Science 4 (2010) 42-61.

M. Arnold , S. Merchel, D.L. Bourlès, R. Braucher, L. Benedetti, R.C. Finkel, G. Aumaître, A. Gottdang, M. Klein, The French accelerator mass spectrometry facility ASTER: Improved performance and developments, Nucl. Instr. and Meth. in Phys. Res. B 268 (2010) 1954-1959.

S. Merchel, L. Benedetti, D.L. Bourlès, R. Braucher, A. Dewald, T. Faestermann, R.C. Finkel, G. Korschinek, J. Masarik, M. Poutivtsev, P. Rochette, G. Rugel, K.-O. Zell, A multi-radionuclide approach for in situ produced terrestrial cosmogenic nuclides: ¹⁰Be, ²⁶Al, ³⁶Cl and ⁴¹Ca from carbonate rocks, Nucl. Instr. and Meth. in Phys. Res. B 268 (2010) 1179-1184.

T. Orlowski, O.Forstner, R. Golser, W. Kutschera, S. Merchel, M. Martschini, A. Priller, P. Steier, C. Vockenhuber, A. Wallner, Comparison of detector systems for the separation of ³⁶Cl and ³⁶S with a 3-MV tandem, Nucl. Instr. and Meth. in Phys. Res. B 268 (2010) 847-850.

P. Steier, R. Golser, W. Kutschera, M. Martschini, S. Merchel, T. Orlowski, A. Priller, C. Vockenhuber, A. Wallner, ³⁶Cl exposure dating with a 3-MV tandem, Nucl. Instr. and Meth. in Phys. Res. B 268 (2010) 744-747.

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