Measurement of the Neutron Energy Spectra by Using Organic Scintillators at the Beam Dump of the 100-MeV Proton Linear A
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Measurement of the Neutron Energy Spectra by Using Organic Scintillators at the Beam Dump of the 100-MeV Proton Linear Accelerator in the KOMAC D.-H. Kim Department of Nuclear Engineering, Seoul National University, Seoul 08826, Korea and Korea Multi-Purpose Accelerator Complex, KAERI, Gyeongju 38180, Korea
Soobin Lim and Jae-Hyung Park Department of Nuclear Engineering, Seoul National University, Seoul 08826, Korea
Jeong-Jeung Dang, Pilsoo Lee, Han-Sung Kim and Hyeok-Jung Kwon Korea Multi-Purpose Accelerator Complex, KAERI, Gyeongju 38180, Korea
Kyoung-Jae Chung∗ and Y. S. Hwang Department of Nuclear Engineering, Seoul National University, Seoul 08826, Korea (Received 8 January 2020; revised 25 March 2020; accepted 26 March 2020) This paper presents the experimental results of neutron spectra measurements with organic scintillators at the copper beam dump of the 100-MeV proton linear accelerator in the Korea MultiPurpose Accelerator Complex (KOMAC). For the measurement of the fast neutrons generated by the proton-copper nuclear reaction, two organic scintillators made of a stilbene crystal and liquid EJ-309 combined with photomultipliers and fast digitizers were utilized. Both detectors were installed inside radiation shielding structures facing the conical-shaped 100-MeV proton beam dump. The neutron transport was calculated using two Monte-Carlo codes, MCNP6 and GEANT4, with a proper physical model and a nuclear data library, along with the appropriate consideration of the detailed geometrical factors in the vicinity of the beam-dump and the neutron detectors. Each pulse signal measured in the detectors was analyzed to identify whether it was induced by a neutron or a gamma-ray in a mixed radiation field by using pulse shape discrimination technique. For operation of beam current of 5 mA and duty of 0.2%, the neutron yield was measured to be approximately 9.0E+10 n/s, which was 23% smaller than the numerically estimated value. In addition, both the measured and the estimated neutron energy spectra were compared. Keywords: White neutron source, Proton accelerator, Organic scintillator, Monte-Carlo calculation, Neutron energy spectrum DOI: 10.3938/jkps.77.414
I. INTRODUCTION The proton linear accelerator at the Korea MultiPurpose Accelerator Complex (KOMAC) has been in operation since 2013 for proton. A white neutron source is a recent interest as a useful application of a secondary particle beam. Especially, industrial demand for the testing of cosmic-ray-induced radiation damage has been on the rise [1, 2]. White neutron spectra can be achieved by colliding a high-energy proton beam with any material. Figure 1 shows the KOMAC layout and the conicalshaped copper beam dump for generating white neutrons ∗ E-mail:
at the end of a 100-MeV proton beamline. The upcoming fast neutron facility is being prepared not only by implementation of a neutron target station but also by the introduction of fast neutron diagnostics at the KOMAC [3]. In other white neutron source facilities, the neutron activation technique is the
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