• Nuclear Engineering and Technology
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• 제54권2호
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• pp.437-441
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• 2022

In this study, we developed a neutron time-of-flight (nTOF) measurement system for a 1.7-MV tandem proton accelerator with a target covered with 300-nm-thick lithium (Li) layer. With implementation of beam chopping module after its ion source, the accelerator is configured to operate in pulsed-beam mode with a pulse width <50 ns at 20-kHz repetition rate. This enables the gamma flash-type nTOF measurement system to identify the neutron generated with 3-MeV proton beam energy. The nTOF system consists of a 30" cylindrical NaI(Tl) and four stilbene scintillation detectors. The NaI(Tl) scintillator is placed 50 cm from the Li target to measure the time of beam irradiation on the target, and the stilbene detectors are placed 2 and 2.4 m away to measure nTOF at each location. The nTOF system successfully measured the generated neutron energy at irradiated proton energies of 2.6 and 3.0 MeV with an average energy resolution of 15%.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3121-3125
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• 2023

Neutron conversion detectors that use ¹⁰B-enriched boron carbide are feasible alternatives to ³He-based detectors. We prepared boron carbide films at micron-scale thickness using direct-current magnetron sputtering. The structural characteristics of natural B₄C films, including density, roughness, crystallization, and purity, were analyzed using grazing incidence X-ray reflectivity, X-ray diffraction, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and scanning electron microscopy. A beam profile test was conducted to verify the practicality of the ¹⁰B-enriched B₄C neutron conversion layer. A clear profile indicated the high quality of the neutron conversion of the boron carbide layer.

• Journal of Radiation Protection and Research
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• 제41권2호
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• pp.141-147
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• 2016

Background: A project for building a neutron time-of-flight (nTOF) facility is progressing. We expect that the construction will start in early 2016. Before that, a detailed simulation based on the current architectural drawings was performed to optimize the performance of our facility. Materials and Methods: Currently, several parts had been modified or changed from the original design to reflect requirements such as the layout of the electron beam line, shape of the vacuum chamber producing a neutron beam, and the underground layout of the nTOF facility. Detailed analysis for these modifications has been done with MCNP simulation. Results and Discussion: An overview of our photo-neutron source and KAERI nTOF facility were introduced. The numerical simulations for heat deposition, source term, and radiation shielding of KAERI nTOF facility were performed and the results are discussed. Conclusion: We are expecting that the construction of the KAERI nTOF facility will start in early 2016, and these results will be used as basic data.

• Journal of Radiation Protection and Research
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• 제26권3호
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• pp.327-331
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• 2001

The Pohang Neutron Facility based on an electron linac was constructed in order to construct the infrastructure for nuclear data production in Korea. It consists of a 100-MeV electron linac, a water-cooled Ta target, and an 11-m time-of-flight path. We measured the time-of-flight path length, the neutron energy spectra for different water levels inside the moderator, and the neutron total cross sections of polyethylene and copper by the transmission method.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4057-4065
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• 2023

Organic scintillators are widely used for neutron/gamma detection. Pulse shape discrimination algorithms have been commonly used to discriminate the detected radiations. These algorithms have several limits, in particular with plastic scintillator which has lower discrimination ability, compared to liquid scintillator. Recently, machine learning (ML) models have been explored to enhance discrimination performance. Nevertheless, obtaining an accurate ML model or evaluating any discrimination approach requires a reference neutron dataset. The preparation of this is challenging because neutron sources are also gamma-ray emitters. Therefore, this paper proposes a pipeline to prepare clean labeled neutron/gamma datasets acquired by an organic scintillator. The method is mainly based on a Time of Flight setup and Tail-to-Total integral ratio (TTT_ratio) discrimination algorithm. In the presented case, EJ276 plastic scintillator and ²⁵²Cf source were used to implement the acquisition chain. The results showed that this process can identify and remove mislabeled samples in the entire ToF spectrum, including those that contribute to peak values. Furthermore, the process cleans ToF dataset from pile-up events, which can significantly impact experimental results and the conclusions extracted from them.

• 한국방사선학회논문지
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• 제2권1호
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• pp.31-34
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• 2008

The neutron capture spectrum for the light nuclide was very useful to study the nuclear structure. In the present study, the capture gamma-ray from the 27-keV resonance of $^{19}F(n,g)^{20}F$ reaction were measured with an anti-Compton NaI(Tl) spectrometer and the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo institute of technology. A neutron Time-of-Flight method was adopted with a 1.5 ns pulsed neutron source by the $^7Li(p,n)^7Be$ reaction. In the present experiment, a Teflon(($CF_2$)n) sample was used The sample was disk with a diameter of 90mm. The thickness of sample was determined so that reasonable counting rates could be obtained and the correction was not so large for the self-shielding and multiple scattering of neutrons in the sample, and was 5mm. The primary gamma-ray transitions were compared with previous measurement of Kenny.

• 한국방사선학회논문지
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• 제7권3호
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• pp.245-249
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• 2013

천연 탄탈의 중성자포획에 의한 공명에너지를 측정하기 위하여 교토대학의 원자로연구소의 46-MeV 전자선형가속기의 광핵반응에서 발생하는 중성자를 이용하였다. 중성자포획에서 발생되는 즉발감마선을 BGO($Bi_4Ge_3O_{12}$)섬광검출장치로 측정하였다. 검출장치는 탄탈 시료에서 발생되는 즉발감마선을 기하학적으로 모두 측정하도록 만들어져 있으며 측정되어진 전기적 신호를 탄탈의 중성자 공명에너지 동정하는 스펙트럼구성에 사용하였다. 연구에서 사용되어진 중성자의 에너지는 1 ~ 200 eV 영역에 대하여 각각의 공명에너지를 분석하였다. 중성자에너지 측정은 중성자 비행시간법(TOF: Time-of-Flight)을 통하여 측정하였다. 광핵반응을 통한 중성자발생에서는 고에너지영역에서 강한 제동복사선이 발생하므로 수 keV영역 이하 영역의 중성자에너지에 대해서만 중성자공명을 측정하였다. 얻어진 Ta에 대한 중성자 포획 공명에너지 측정결과는 이전의 실험에 의한 측정 결과들 및 ENDF/B-VI와 Mughabghab의 평가된 값들과 비교 및 검토를 하였다. 측정되어진 공명들은 4.28 eV에서 거대 공명들을 측정하였고 그 이상의 에너지 영역의 다른 공명들도 이론에 의해서 계산되어진 값들과 비교하였다. 144.3 eV를 제외한 공명들은 평가값들과 거의 일치하는 경향을 보였다.

• 한국방사선학회논문지
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• 제6권5호
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• pp.403-408
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• 2012

본 연구는 천연 인듐의 중성자폭획 후에 발생된 감마선을 12개의 BGO($Bi_4Ge_3O_{12}$) 섬광검출기로 구성된 검출장치를 이용하여 즉발감마선을 측정하여 중성자공명에 의해서 발생된 감마선을 분석하여 중성자의 에너지 1 ~ 300 eV 영역에 대하여 공명에너지를 분석하였다. 사용되어진 검출장치는 시료에서 발생된 즉발감마선에 대하여 모든 감마선을 측정할 수 있는 기하학적인 구조로 만들어졌다. 중성자원으로는 교토대학의 원자로연구소의 46-MeV 전자선형가속기의 광핵반응에서 발생하는 중성자를 이용하였다. 중성자발생원으로부터 검출기까지의 거리가 $12.7{\pm}0.02m$이므로 광핵반응에서 발생하는 강한 X선의 영향을 고려하여 수 keV영역이하의 중성자에너지에 대하여 중성자공명을 측정하였다. 측정되어진 공명들은 1 eV이상의 에너지 영역에서 거대 공명들을 측정하였고 이들 공명들은 이론에서 알려진 값들과 비교하였다. 본 연구를 통하여 기존에 알려진 거대 공명의 에너지를 확인하였고, 100 eV이상의 에너지 영역에서의 공명에너지들에 대한 평가에 의한 이론값들이 실제로 존재하는 공명임을 실험적으로 확인하였다. 1 keV 이상의 영역에 대하여는 공명이 연속적인 구조를 보이고 있음을 실험적으로 확인했으며 공명에 대하여 통계적인 평가가 있어야함을 알았다. 91.49 eV 공명은 본 연구를 통하여 처음 발견되어진 공명이라 볼 수 있다.

• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1354-1357
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• 2017

Characterization of special nuclear material may be performed using energy spectroscopy of either the neutron or gamma-ray emissions from the sample. Gamma-ray spectroscopy can be performed relatively easily using high-resolution semiconductors such as high-purity germanium. Neutron spectroscopy, by contrast, is a complex inverse problem. Here, results are presented for $^{252}Cf$ and PuBe energy spectra unfolded using a single EJ309 organic scintillator; excellent agreement is observed with the reference spectra. Neutron energy spectroscopy is also possible using a two-plane detector array, whereby time-of-flight kinematics can be used. With this system, energy spectra can also be obtained as a function of position. Spatial-dependent energy spectra are presented for neutron and gamma-ray sources that are in excellent agreement with expectations.

• Nuclear Engineering and Technology
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• 제4권2호
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• pp.116-131
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• 1972

Li$^{7}$ (p, n) Be$^{7}$ 원자핵반응에서 Li target의 두께와 입사양자의 에너지를 적절히 선정하므로써 1-n sec 파동 Van de Graaff 가속도로부터 keV 영역에서의 연속중성자spectrum을 발생시키고 92% 농축된 5mm 두께의 $B^{10}$ 판과 4개의 4＂$\times$3＂ NaI (T1) 발광체로 이루어진 속중성자검출기를 이용 속중성자 비행시간법에 의한 중성자spectrometer 를 제작하였다. 장치의 에너지 분해능은 50 keV에서 0.3%보다 양호하며 신호대잡음비도 개량되었다. 이를 이용하여 몇가지 분석된 단일동위원소의 전단면적을 측정하고 R-matrix 전자계산 code로 분석하였다. 각 공명에 따르는 스핀식와 공명인수들을 찾아내었다.