How to get a new accelerator mass spectrometry (AMS) facility running: The chemistry part

How to get a new accelerator mass spectrometry (AMS) facility running: The chemistry part

Merchel, S.; Arnold, M.; Aumaître, G.; Bourlès, D.; Braucher, R.

The AMS business is booming: Many low-energy (< 1 MV) facilities, which are fully dedicated for 14C-analysis, are under construction or in funding status. Additionally, medium-energy accelerators such as the British 5 MV-NEC machine at “SUERC” Glasgow, the French 5 MV-HVEE-machine “ASTER” at Aix-en-Provence [2] and the two German 6 MV-HVEE-machines “DREAMS” at Dresden [3] and “Cologne AMS” at Cologne [4] have been recently installed or are still in testing mode in Central Europe. Of course, these bigger machines need not only experienced physicists and technicians to get them running. It also seems to be advisable to have some experienced scientists around, who knows how to prepare AMS targets for 10Be, 26Al, 36Cl, 41Ca, and 129I measurements.
In contrast to the 14C-community, where e.g. round-robin exercises are routine business, the idea of quality assurance and traceable standards has only been brought up lately for the other cosmogenic radionuclides measurable at medium-energy AMS facilities. Thus, world-wide accepted standards issued by metrology institutes are rare: NIST is selling two kinds of 129I/127I-standards, and the Institute for Reference Materials and Measurements (IRMM) provides one set of 41Ca/40Ca solutions having eight different ratios [5]. Unfortunately, the most commonly used 10Be/9Be standard provided by NIST has been recently sold-out and will not be reissued. Other primary standard-type materials (26Al,36Cl), which are not commercially available, have been prepared by diluting certified activities and subsequent analysis within round-robin exercises [6-8]. After production of big quantities of in-house secondary standards for all nuclides (Tab. 1), cross-calibration versus primary standard-type materials has to be performed [2].

Table 1: Primary and secondary AMS standards in use at ASTER and DREAMS.
Primary standards Secondary (in-house) standards
10Be NIST SRM 4325 (sold-out) NIST SRM 4325 (ASTER)
10Be via 9Be(nth,gamma)10Be (DREAMS)
26Al MB04-A,B,C,D [6] SM-Al-10,11,12,13 [2]
36Cl SM-Cl-11,12,13 [7,8] SM-Cl-11,12,13 [7,8]
41Ca IRMM ERM®-AE701 [5] SM-Ca-10,11,12 [2]
--> SM-Ca-P9,11,13 [2]
129I NIST SRM 3231, Level II SM-I-9,10,11,12

Finally, as commercial 9Be contains intrinsic 10Be up to a level of 4x10-14 [9] sophisticated production of in-house carriers, used as machine blanks and for samples, from Be-containing minerals such as Be2SiO4 originating from deep mines, is needed. After production and measurement of all these materials, the AMS facility is ready for routine measurements.

Acknowledgments: We are grateful to U. Herpers & E. Strub for providing 26Al-activity, to A. Wallner & M. Bichler for performing the neutron-irradiation of 9Be, to C. Varajão for providing Be2SiO4 crystals, and to R.C. Finkel, L. Benedetti, W. Möller, HVEE, the FZD-operator- & AMS-team for great cooperation.

References: [1] S. Freeman et al., NIM B 259 (2007) 66. [2] M. Arnold et al., doi: 10.1016/ j.nimb.2010.02.107. [3] Sh. Akhmadaliev et al., this meeting. [4] M. Klein et al., this meeting. [5] C. Hennessy et al., NIM B 229 (2005) 281. [6] S. Merchel, W. Bremser, NIM B 223–224 (2004) 393. [7] S. Merchel et al. Geochim. Cosmochim. Acta 73 (2009) A871. [8] S. Merchel et al., in prep. for NIM B. [9] S. Merchel et al., NIM B 266 (2008) 4921.

Keywords: accelerator mass spectrometry

  • Poster
    10th European Conference on Accelerators in Applied Research and Technology (ECAART 10), 13.-17.09.2010, Athens, Greece