Subtraction Method for an Effective Quasi-monoenergetic Neutron Beam by Using Continuous Energy Spectra
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Subtraction Method for an Effective Quasi-monoenergetic Neutron Beam by Using Continuous Energy Spectra Eun Jin In, Kyung Joo Min, Sang-In Bak∗ and Do Yoon Kim Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea
Cheolmin Ham, Chungbo Shim, Yujie Zhou and Seung-Woo Hong† Department of Physics, Sungkyunkwan University, Suwon 16419, Korea
Tae-Sun Park Department of Physics, Sungkyunkwan University, Suwon 16419, Korea and Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon 34126, Korea
Jae Won Shin Department of Physics, Soogsil University, Seoul 06978, Korea
V. N. Bhoraskar Department of Physics, S.P. Pune University, Pune 411007, India and Department of Physics, Sungkyunkwan University, Suwon 16419, Korea (Received 21 August 2020; revised 14 September 2020; accepted 21 September 2020) The cross sections of 89 Y(n, 3n)87m,87g Y and 209 Bi(n, 4n)206 Bi reactions at a neutron energy of 30 MeV are measured by making use of neutron beams of continuous energy spectra and a subtraction method. By impinging proton beams of 30 and 35 MeV to a thick beryllium target, neutron beams of continuous and broad energy spectra are produced and are guided to Y and Bi sample targets. The difference between the two neutron spectra generated by two neighboring proton energies is found to be peaked in a narrow energy range and thus can be regarded as quasi-monoenergetic, which can be used to extract (n, xn) cross sections. The uncertainty in the neutron fluence is reduced by analyzing the activities of aluminum and niobium reference samples placed on top of the Y and Bi samples. The use of a subtraction method by employing neutron beams of continuous energy spectra gives us the 89 Y(n, 3n)87m,87g Y and 209 Bi(n, 4n)206 Bi cross sections in fair agreement with the existing experimental data and nuclear data libraries. Keywords: neutron activation analysis, (n, xn) cross section, DOI: 10.3938/jkps.77.740
I. INTRODUCTION Accurate (n, xn) cross sections of 89 Y and 209 Bi isotopes induced by high energy neutrons are needed for the development of fast reactors and accelerator driven systems [1], where yttrium is used as one of the structural materials [2, 3] and bismuth can be used as a coolant in the form of lead-bismuth eutectic [4]. There are, however, only a few experimental data for the reactions 89 Y(n, 3n)87m,87g Y [5–7] and 209 Bi(n, 4n)206 Bi [8– 13], and the existing cross sections have large uncertain∗ Present address: Korea Institute of Nuclear Safety, Daejeon 34142, Korea † E-mail: [email protected]
pISSN:0374-4884/eISSN:1976-8524
89 Y, 209 Bi
ties and inconsistence among the data. The (n, xn) cross sections are usually measured with quasi mono-energetic neutron beams produced by bombarding proton beams on a thin lithium or beryllium target [7,9–12,14–16]. In this work, however, we make use of neutron beams of continuous energy spectra coupled with a subtraction method. Our experiments were conducted with the MC-50 cyclotron [17] at the Korea Institute of Radiological and Medical Science
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