• Title/Summary/Keyword: Muon

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Development of a muon detector based on a plastic scintillator and WLS fibers to be used for muon tomography system

  • Chanwoo Park;Kyu Bom Kim;Min Kyu Baek;In-soo Kang;Seongyeon Lee;Yoon Soo Chung;Heejun Chung;Yong Hyun Chung
    • Nuclear Engineering and Technology
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    • v.55 no.3
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    • pp.1009-1014
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    • 2023
  • Muon tomography is a useful method for monitoring special nuclear materials (SNMs) such as spent nuclear fuel inside dry cask storage. Multiple Coulomb scattering of muons can be used to provide information about the 3-dimensional structure and atomic number(Z) of the inner materials. Tomography using muons is less affected by the shielding material and less harmful to health than other measurement methods. We developed a muon detector for muon tomography, which consists of a plastic scintillator, 64 long wavelength-shifting (WLS) fibers attached to the top of the plastic scintillator, and silicon photomultipliers (SiPMs) connected to both ends of each WLS fiber. The muon detector can acquire X and Y positions simultaneously using a position determination algorithm. The design parameters of the muon detector were optimized using DETECT2000 and Geant4 simulations, and a muon detector prototype was built based on the results. Spatial resolution measurement was performed using simulations and experiments to evaluate the feasibility of the muon detector. The experimental results were in good agreement with the simulation results. The muon detector has been confirmed for use in a muon tomography system.

Image reconstruction algorithm for momentum dependent muon scattering tomography

  • JungHyun Bae;Rose Montgomery;Stylianos Chatzidakis
    • Nuclear Engineering and Technology
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    • v.56 no.5
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    • pp.1553-1561
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    • 2024
  • Nondestructive radiography using cosmic ray muons has been used for decades to monitor nuclear reactor and spent nuclear fuel storage. Because nuclear fuel assemblies are highly dense and large, typical radiation probes such as x-rays cannot penetrate these target imaging objects. Although cosmic ray muons are highly penetrative for nuclear fuels as a result of their relatively high energy, the wide application of muon tomography is limited because of naturally low cosmic ray muon flux. This work presents a new image reconstruction algorithm to maximize the utility of cosmic ray muon in tomography applications. Muon momentum information is used to improve imaging resolution, as well as muon scattering angle. In this work, a new convolution was introduced known as M-value, which is a mathematical integration of two measured quantities: scattering angle and momentum. It captures the objects' quantity and density in a way that is easy to use with image reconstruction algorithms. The results demonstrate how to reconstruct images when muon momentum measurements are included in a typical muon scattering tomography algorithm. Using M-value improves muon tomography image resolution by replacing the scattering angle value without increasing computation costs. This new algorithm is projected to be a standard nondestructive radiography technique for spent nuclear fuel and nuclear material management.

Design and characterization of a Muon tomography system for spent nuclear fuel monitoring

  • Park, Chanwoo;Baek, Min Kyu;Kang, In-soo;Lee, Seongyeon;Chung, Heejun;Chung, Yong Hyun
    • Nuclear Engineering and Technology
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    • v.54 no.2
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    • pp.601-607
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    • 2022
  • In recent years, monitoring of spent nuclear fuel inside dry cask storage has become an important area of national security. Muon tomography is a useful method for monitoring spent nuclear fuel because it uses high energy muons that penetrate deep into the target material and provides a 3-D structure of the inner materials. We designed a muon tomography system consisting of four 2-D position sensitive detector and characterized and optimized the system parameters. Each detector, measuring 200 × 200 cm2, consists of a plastic scintillator, wavelength shifting (WLS) fibers and, SiPMs. The reconstructed image is obtained by extracting the intersection of the incoming and outgoing muon tracks using a Point-of-Closest-Approach (PoCA) algorithm. The Geant4 simulation was used to evaluate the performance of the muon tomography system and to optimize the design parameters including the pixel size of the muon detector, the field of view (FOV), and the distance between detectors. Based on the optimized design parameters, the spent fuel assemblies were modeled and the line profile was analyzed to conduct a feasibility study. Line profile analysis confirmed that muon tomography system can monitor nuclear spent fuel in dry storage container.

Feasibility Analysis of Exploring Underground Utilities Using Muon (뮤온 입자를 활용한 지하매설물 탐사 가능성 분석)

  • Seo, Seunghwan;Chung, Moonkyung;Kwak, Kiseok;Kang, Jae Mo
    • Journal of the Korean Geotechnical Society
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    • v.38 no.11
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    • pp.137-147
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    • 2022
  • Various geophysical exploration methods are used to determine the exact location of underground utilities, and many studies have been performed to improve the accuracy. This study analyzed the feasibility of exploring underground utilities through a new exploration method using cosmic ray muon. A prototype of a portable muon detector was manufactured by combining a scintillator and a silicon photomultiplier. Further, a calibration operation was performed on the muon count rate. The ground thickness of the ground model was measured using the muon detector prototype, where the value could be estimated with an error of about 3%, close to the actual. In addition, the theoretical basis for tomography analysis technology was analyzed to utilize the muon detector for exploring underground utilities, and a zenith angle correction method was presented. This study revealed that the technology of exploration using muon can analyze density with high resolution and will be used for exploring underground utilities.

Design of muon production target system for the RAON μSR facility in Korea

  • Jeong, Jae Young;Kim, Jae Chang;Kim, Yonghyun;Pak, Kihong;Kim, Kyungmin;Park, Junesic;Son, Jaebum;Kim, Yong Kyun;Lee, Wonjun;Lee, Ju Hahn
    • Nuclear Engineering and Technology
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    • v.53 no.9
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    • pp.2909-2917
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    • 2021
  • Following the launch of Rare Isotope Science Project in December 2011, a heavy ion accelerator complex in South Korea, named RAON, has since been designed. It includes a muon facility for muon spin rotation, relaxation, and resonance. The facility will be provided with 600 MeV and 100 kW (one-fourth of the maximum power) proton beam. In this study, the graphite target in RAON was designed to have a rotating disk shape and was cooled by radiative heat transfer. This cool-down process has the following advantages: a low-temperature gradient in the target and the absence of a liquid coolant cooling system. Monte Carlo simulations and ANSYS calculations were performed to optimize the target system in a thermally stable condition when the 100 kW proton beam collided with the target. A comparison between the simulation and experimental data was also included in the design process to obtain reliable results. The final design of the target system will be completed within 2020, and its manufacturing is in progress. The manufactured target system will be installed at the RAON in the Sindong area near Daejeon-city in 2021 to carry out verification experiments.

Observation of Periodic and Transient Cosmic Ray Flux Variations by the Daejeon Neutron Monitor and the Seoul muon Detector

  • Oh, Suyeon;Kang, Jeongsoo
    • Journal of Astronomy and Space Sciences
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    • v.30 no.3
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    • pp.175-178
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    • 2013
  • Recently, two instruments of cosmic ray are operating in South Korea. One is Seoul muon detector after October 1999 and the other is Daejeon neutron monitor (Kang et al. 2012) after October 2011. The former consists of four small plastic scintillators and the latter is the standard 18 NM 64 type. In this report, we introduce the characteristics of both instruments. We also analyze the flux variations of cosmic ray such as diurnal variation and Forbush decrease. As the result, the muon flux shows the typical seasonal and diurnal variations. The neutron flux also shows the diurnal variation. The phase which shows the maximum flux in the diurnal variation is around 13-14 local time. We found a Forbush decrease on 7 March 2012 by both instruments. It is also identified by Nagoya multi-direction muon telescope and Oulu neutron monitor. The observation of cosmic ray at Jangbogo station as well as in Korean peninsula can support the important information on space weather in local area. It can also enhance the status of Korea in the international community of cosmic ray experiments.

Beam line design and beam transport calculation for the μSR facility at RAON

  • Pak, Kihong;Park, Junesic;Jeong, Jae Young;Kim, Jae Chang;Kim, Kyungmin;Kim, Yong Hyun;Son, Jaebum;Lee, Ju Hahn;Lee, Wonjun;Kim, Yong Kyun
    • Nuclear Engineering and Technology
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    • v.53 no.10
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    • pp.3344-3351
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    • 2021
  • The Rare Isotope Science Project was launched in 2011 in Korea toward constructing the Rare isotope Accelerator complex for ON line experiments (RAON). RAON will house several experimental systems, including the Muon Spin Rotation/Relaxation/Resonance (μSR) facility in High Energy Experimental Building B. This facility will use 600-MeV protons with a maximum current of 660 pμA and beam power of 400 kW. The key μSR features will facilitate projects related to condensed-matter and nuclear physics. Typical experiments require a few million surface muons fully spin-polarized opposite to their momentum for application to small samples. Here, we describe the design of a muon transport beam line for delivering the requisite muon numbers and the electromagnetic-component specifications in the μSR facility. We determine the beam-line configuration via beam-optics calculations and the transmission efficiency via single-particle tracking simulations. The electromagnet properties, including fringe field effects, are applied for each component in the calculations. The designed surface-muon beamline is 17.3 m long, consisting of 2 solenoids, 2 dipoles affording 70° deflection, 9 quadrupoles, and a Wien filter to eliminate contaminant positrons. The average incident-muon flux and spin rotation angle are estimated as 5.2 × 106 μ+/s and 45°, respectively.

A novel reconstruction algorithm based on density clustering for cosmic-ray muon scattering inspection

  • Hou, Linjun;Zhang, Quanhu;Yang, Jianqing;Cai, Xingfu;Yao, Qingxu;Huo, Yonggang;Chen, Qifan
    • Nuclear Engineering and Technology
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    • v.53 no.7
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    • pp.2348-2356
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    • 2021
  • As a relatively new radiation imaging method, the cosmic-ray muon scattering imaging technology can be used to prevent nuclear smuggling and is of considerable significance to nuclear safety. Proposed in this paper is a new reconstruction algorithm based on density clustering, aiming to improve inspection quality with better performance. Firstly, this new algorithm is introduced in detail. Then in order to eliminate the inequity of the density threshold caused by the heterogeneity of the muon flux in different positions, a new flux correction method is proposed. Finally, three groups of simulation experiments are carried out with the help of Geant4 toolkit to optimize the algorithm parameters, verify the correction method and test the inspection quality under shielded condition, and compare this algorithm with another common inspection algorithm under different conditions. The results show that this algorithm can effectively identify and locate nuclear material with low misjudging and missing rates even when there is shielding and momentum precision is low, and the threshold correcting method is universally effective for density clustering algorithms.

RF heating experiment to verify the design process of graphite target at the RAON µSR facility

  • Jae Young Jeong;Jae Chang Kim;Kihong Pak;Yong Hyun Kim;Yong Kyun Kim;Wonjun Lee;Ju Hahn Lee;Taek Jin Jang
    • Nuclear Engineering and Technology
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    • v.55 no.10
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    • pp.3768-3774
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    • 2023
  • The purpose of the target system for the muon spin rotation, relaxation, and resonance (µSR) facility at the Rare isotope Accelerator complex for ON-line experiments (RAON) is to induce the production of a significant number of surface muons in thermally stable experiments. The manufactured target system was installed at RAON in the Sindong area near Daejeon in 2021. The design was made conservatively with a sufficient margin of safety through ANSYS calculations; however, verification experiments had to be performed on the ANSYS calculations. Because the 600-MeV proton beam has not yet been provided, an alternative way to reproduce the calculation conditions was required. The radio frequency (RF) heating method, which has not yet been applied to the target verification experiment but has several advantages, was used. It was observed that the RF heating method has promise for testing the thermal stability of the target, and whether the target system design process was performed conservatively enough was verified by comparing the RF heating experiments with the ANSYS calculations.