1.Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 2.Spallation Neutron Source Science Center, Dongguan 523803, China 3.State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China 4.State Key Laboratory of Particle Detection and Electronics, China 5.University of Chinese Academy of Sciences, Beijing 100049, China 6.Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China 7.Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413, China 8.Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China 9.Northwest Institute of Nuclear Technology, Xi’an 710024, China 10.Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei 230026, China 11.School of Physics, Beihang University, Beijing 100083, China
Fund Project:Project supported by the National Key R&D Program of China (Grant No. 2016YFA0401604), the National Natural Science Foundation of China (Grant No. 12005115), and the Basic and Applied Basic Research Foundation of Guangdong Province, China (Grant No. 2019A1515110287)
Received Date:02 November 2020
Accepted Date:27 December 2020
Available Online:07 April 2021
Published Online:20 April 2021
Abstract:At present, there exist few proton-beam terminals for the detector calibration in the world. Meanwhile, most of these terminals provide monoenergetic protons. Back-n white neutron source from China Spallation Neutron Source(CSNS) was put into operation in 2018. Based on the white neutron flux ranging from 0.5 eV to 200 MeV from the CSNS Back-n white neutron source, continuous-energy protons involved in a wide energy spectrum can be acquired from the 1H(n, el) reaction. Adopting this method, a new research platform for researches such as proton calibration is realized at CSNS. As hydrogen exists as gas at normal temperature and pressure, in the selecting of the proton-converting target, the hydrogen-rich compounds are preferential considered. Considering the reaction cross sections of the 1H(n, el), 12C(n, p)12B, 12C(n, d)11B, 12C(n, t)10B, 12C(n, 3He)10Be, 12C(n, α)9Be and 1H(n, γ)2H, polyethylene and polypropylene are suitable for serving as targets in this research. Based on a 3U PXIe, digitizers with 1 GSps sampling rate and 12 bit resolution are utilized to digitize and record the output signals of telescopes. The time and amplitude information of each signal are extracted from its recorded waveform. Proton fluxes can be calculated by using the neutron energy spectrum and the cross section of the 1H(n, el) reaction. Using the γ-flash event as the starting time of the time-of-flight (TOF) and the time information of signal in detector as the stopping time, the kinematic energy of each secondary proton can be deduced from the TOF and the angle of the detector. A calibration experiment on three charged particle telescopes, with each telescope consisting of a silicon detector and a CsI(Tl) detector, is carried out on this research platform. The readout methods of the CsI(Tl) detectors in these three telescopes are different. In the calibration experiment, ΔE-E two-dimensional spectra and amplitude-Ep two-dimensional spectra of these telescopes are obtained. Through comparing these particle identification spectra, the SiPM is chosen as the signal readout method for CsI(Tl) detectors in the charged particle telescopes. These researches provide experimental evidence for the construction of the charged particle telescope at Back-n, and also illustrate the feasibility of wide-energy spectrum proton calibration based on the Back-n white neutron source. Keywords:proton calibration/ detector/ 1H(n, el) reaction/ back-n white neutron source
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2.基于反角白光中子源得到的宽能谱次级质子相较于中子与其他核素相互作用产生质子的过程, 1H(n, el)反应的反应截面大. 基于中子与质子的1H(n, el)反应, 可以利用白光中子束流及含1H靶得到反冲质子. 如图2所示, 发生弹性散射时, 反冲质子将会获得动能. 图 21H(n, el)反应示意图 Figure2. Schematic diagram of the 1H(n, el) reaction.