Excitation functions of the proton induced nuclear reactions on natZn up to 40 MeV

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Abstract

We measured the excitation functions of the natZn(p,xn)66,67Ga, natZn(p,pxn)62,65,69mZn, and natZn(p,αxn)61Cu nuclear processes up to 40 MeV by using a stacked-foil activation technique at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences. The results were compared with the earlier reported experimental data and theoretical calculations based on the ALICE-IPPE code. We have given new data points for the formation of the above radionuclides. The present values are in good agreement with some well-measured literature values. Integral yields were also deduced from the measured cross-sections. The reported direct measured thick target yields for the formation of the 66Ga and 67Ga radionuclides at 22 MeV support our deduced yields. The optimum formation of the 66Ga and 61Cu radionuclides with minimum impurities can be obtained at 8–15 MeV and 10–20 MeV energy range, respectively. The yields and decay characteristics of the nuclide 65Zn are suitable for thin layer activation analysis.

Introduction

A wide variety of cyclotrons and accelerators with energy range between 3 and 800 MeV find applications in nuclear medicine especially in technologically advanced countries. They are used for producing radiotracers for applications in diagnosis via the emission tomography as well as the internal radiotherapy. The radionuclide produced at cyclotron with neutron deficient and decay mainly by an electron capture (EC) or a β+ emission is especially suitable for diagnostic studies. The science and technology for the production of radionuclide by using the cyclotron has become a very important feature of the modern nuclear medicine [1]. There are several distinct aspects, specific to the production at a cyclotron, relate to the nuclear reaction data for high current irradiations.

The particle induced activation cross-sections are required to optimize the production routes, i.e. to maximize the yield of the desired product and to minimize the yields of the radioactive impurities. A full knowledge of the excitation function is essential for the optimization of the radionuclide formation, because an accelerated charged particle impinging on a material loses its energy very quickly, instead of using an average cross-section. The production yield of radionuclide in the cyclotron with reasonable accuracy can be deduced from the full excitation function of the nuclear process.

Particles induced activation data on zinc are required in various fields; medical radioisotope production, radiation and shielding in nuclear technology, to follow nuclear wear and/or corrosion using thin layer activation (TLA) analysis, etc. Zinc is an important target material for the production of medically important radioisotopes, 66Ga, 67Ga, 61Cu,62Zn/62Cu, and so on. To develop a proper radiochemical separation of these radioisotopes and to estimate the radiation dose, one should have to acquire the knowledge on the excitation functions of the natZn + p nuclear processes. Few experimental data sets [2], [3], [4], [5], [6], [7] exist both on natural and enriched zinc target. Most of these data are below 30 MeV, but large discrepancies are present among them. No recommended data are reported yet. For efficient and proper production of a radioisotope accurate nuclear data are needed. This work was undertaken to measure the cross-sections for the natZn + p processes up to 40 MeV as a part of systematic studies on proton induced reactions on natural zinc metals.

Section snippets

Experimental technique

The excitation functions of the proton induced reactions on the natural zinc were measured as a function of the proton energy in the range of 4-40 MeV by using a conventional stacked foil activation technique combined with high-resolution gamma-ray spectrometry. A high-purity (99.98%) zinc foil (100 μm thick) with a natural isotopic composition 64Zn 48.6%, 66Zn 27.9%, 67Zn 4.1%, 68Zn 18.8% and 70Zn 0.6%) was used as the target for the irradiation. Monitor foils of copper (100 μm thick) and

Data analysis

Cross-sections for the independent and cumulative formation of several radionuclides in proton-induced activation on natural zinc were measured. The activities of the radioisotopes produced from the target and the monitor foils were measured non-destructively using high-purity germanium (HPGe) gamma-ray spectroscopy. The source-to-detector distance was kept long enough to assure a low dead time and a point-like geometry. The HPGe-detector (EG&G Ortec.) was coupled with a 4096 multi-channel

Results and discussion

The cross-sections for the formation of several radionuclides in the interactions of protons with natural zinc, measured in this work, are presented in Table 2. The total uncertainties are also given. The obtained cross-section data and deduced yields are shown in Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9 together with the literature values and the calculated values of the theoretical model code ALICE-IPPE compiled in MENDL-2P [10].

Conclusion

The new independent and cumulative cross-sections for the natZn(p,x) processes were obtained using stacked foil activation technique. The energy range was covered 4-40 MeV. Our precise data set has broad applications in the field of medical isotope production, for charged particle activation analysis, thin layer activation, estimation of residual activity on the field of radiation safety and radioactive waste management.

The present new excitation function curve for the natZn(p,x) processes agree

Acknowledgements

The author would like to express their sincere thanks to the staffs of the MC50 Cyclotron Laboratories for their cordial help in performing the experiment. This work is partly supported through Project Number M20602000001-06B0200-00110 of the Ministry of Science and Technology (MOST) and through the Science Research Center (SRC) program of the Institute of High Energy Physics, Kyungpook National University.

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