Monitoring of chemical processes for 10Be and 26Al AMS target preparation
Dr Jan Kameník1, Prof. Jan Kučera1
1Nuclear Physics Institute Of The Czech Academy Of Sciences, Husinec-Řež, Czech Republic
The first AMS laboratory in the Czech Republic has been under construction since 2018. Since mid-2021, it hosts a multi-isotope low energy AMS system MILEA (Ionplus AG, Switzerland) and several chemical laboratories. For optimization of chemical procedures for target preparation prior to ¹⁰Be and ²⁶Al AMS measurement, methods for monitoring of Be and Al behavior during chemical procedures were proposed. For monitoring of beryllium, radioactive ⁷Be, a gamma-ray emitter with a half-live of 53.2 days, was employed as a tracer. For aluminium, a suitable radioactive tracer is unavailable. Therefore, its monitoring was based on determination of Al by instrumental neutron activation analysis (INAA).
All experiments were performed in an established radiochemical laboratory. Carrier free ⁷Be tracer was obtained from a proton irradiated metallic Li target using ion-exchange separation with cation exchange resin. The Li target originated from a fast neutrons generator operated by Nuclear Physics Institute (NPI). Aluminum was determined in separated aliquots by INAA based on gamma-spectrometric determination of ²⁸Al radionuclide with a half-live of 2.2 min formed during irradiation of stable ²⁷Al with thermal neutrons from research reactor LVR15 (operated by Centrum výzkumu Řež).
Two established methods for Be and Al targets preparation were selected for testing of separation of both elements from precipitation and solid specimens. The first method was based on a combination of precipitation steps with ion-exchange chromatography separation by strongly acidic cation and strongly basic anion exchange resins [1,2]. The second method utilized extraction-chromatography separation using a combination of WBEC and AC resins (Triskem International, France)  without the need of the precipitation steps. The test indicated that both methods were able to separate Be and Al fractions well. The most critical part in term of separation yields were precipitation steps for both Be and Al. About 50% and 65% of original Be and Al was lost, respectively. Perhaps better control of pH can help in increasing of the overall separation yield. Chromatographic processes were efficient, some improvements could be expected from better control of the flow rate. It was confirmed that the proposed monitoring can help in optimization and development of new chemical procedures for preparation of ¹⁰Be and ²⁶Al AMS targets.
Acknowledgment: The work was supported by MEYS Czech Republic (project No. CZ.02.1.01 /0.0/0.0/16_019/0000728).
1. Granger, D. E., Fabel, D., Palmer, A. N. (2001) Pliocene−Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmogenic ²⁶Al and ¹⁰Be in Mammoth Cave sediments. Geological Society of America Bulletin 113(7), 825–836.
2. Zhou, W., et al. (2014) The last 130 ka precipitation reconstruction from Chinese loess ¹⁰Be. J Geophys Res Solid Earth 119, 191–197.
3. Binnie, S. A., et al. (2015) Separation of Be and Al for AMS using single-step column chromatography. Nucl Instrum Methods in Phys Res B 361, 397–401.
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