수필 : 지방사 (地方吏) 10 년

채문식 대한지방행정공제회 1959 地方行政 Vol.8 No.74

평양만 보고는 북한을 알 수 없다

채문식 한국지역사회연구소 1991 지역사회 Vol.10 No.-

S-band 고주파 전자가속기 가속관의 시뮬레이션 및 정밀가공을 통한 공진주파수 최적화

주진식,신승욱,김재현,이수민,채문식,차형기,이남호,이병노 (사)한국방사선산업학회 2018 방사선산업학회지 Vol.12 No.2

High-frequency electron accelerators are widely used in the various radiation equipment such as container inspection device, non-destructive inspection system and radiation therapy. The RF characteristics of S-band (2856 MHz) side-coupled structures for accelerator cavity were measured by using E-antenna (in refection), part of the half cell cavity was found to be out of error bound from resonance frequency, and thus was re-processed. When the error bound of the frequency is within 2 MHz, it can be reduced by using external tuning device. But if the error bound is bigger than 10 MHz, external tuning device cannot be used. In this study, Based on the result of accelerator cavity simulation and the precise machining, accelerating cell part and side-coupling cell were reprocessed to produce accelerator cavity frequency that is fit to purpose.

부분 불소화된 폴리스티렌의 감마선 조사 효과

이병민,심하은,연영흠,남유리,채문식,김재호,임대희,권희정 한국고분자학회 2022 폴리머 Vol.46 No.5

부분 불소화된 폴리스티렌의 감마선 조사 효과에 대해 연구하였다. 폴리스티렌은 방향족 구조로 인해 방사선내성을 가지는 유기 고분자이다. 폴리스티렌의 방사선 내성을 향상하기 위해 부분 불소화된 폴리스티렌을 용액 중합하였다. 부분 불소화된 폴리스티렌의 감마선 조사는 공기 분위기에서 60Co 선원을 이용하여 10 kGy/h의 선량율로수행하였고 감마선 흡수선량은 25, 50, 100, 200, 500 kGy이었다. 원소 함량과 화학 구조, 열적 특성의 변화는 각각퓨리에 변환 적외선 분광법, X-선 광전자 분광법, 열중량 분석, 시차주사열량계를 사용하여 분석하였다. 분석 결과를 바탕으로 폴리플루오로스티렌은 500 kGy의 감마선 흡수선량 조사 후 산화 반응이 가장 적고 열적 특성이 가장우수하였다. 이러한 결과를 바탕으로 부분 불소화된 폴리스티렌이 방사선 내성 응용 분야에 사용이 가능할 것으로판단된다

Performance of an Indium-sealed S-band RF Photoelectron Gun for Time-resolved Electron Diffraction Experiments

김현우,장규하,백인형,이기태,정영욱,남진희,채문식,김미혜,김영찬,왕기영,박선정,한장희,Nikolay A. Vinokurov 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.1

We have developed a one-and-half -cell S-band radio-frequency (RF) photoelectron gun (pho- togun) fed by a coaxial coupler. The RF photogun is dedicated to ultrafast-electron-diraction experiments by generating electron bunches of 3-MeV energy and a-few-pC charge, which is not strict condition compared to those for X-ray free-electron lasers. Brazing of RF cavities is well- developed process for making RF guns or RF accelerators. Sometimes, however, a failure occurs in the brazing process, causing the entire electron gun or accelerating cavity to spoil. Axial-symmetric design of the RF photogun permits indium sealing for cavity cells, a photocathode plate, and a coupling RF part. We rstly report that the indium-sealed RF photogun successfully meets the required performance and long-term stability for ultrafast electron diraction experiments. We have stably operated the RF photogun for more than three years with the electron beam conditions of 3-MeV energy, up-to-10-pC charge, and a repetition rate of 50 Hz. The quantum eciency of the copper photocathode had improved from 106 to 105 depending on vacuum condition from 108 to 5 1010 Torr, respectively. Measured emittance and energy spread of the generated electron beam showed 0.3 mm-mrad and less than 0.25%, respectively, for a bunch charge of 2 pC, which agree well with those obtained by ASTRA simulation.

Material Discrimination Using X-Ray and Neutron

Jaehyun Lee,Jinhyung Park,Jae Yeon Park,채문식,Jungho Mun,Jong Hyun Jung 대한방사선방어학회 2023 방사선방어학회지 Vol.48 No.4

Background: A nondestructive test is commonly used to inspect the surface defects and internal structure of an object without any physical damage. X-rays generated from an electron accelerator or a tube are one of the methods used for nondestructive testing. The high penetration of X-rays through materials with low atomic numbers makes it difficult to discriminate between these materials using X-ray imaging. The interaction characteristics of neutrons with materials can supplement the limitations of X-ray imaging in material discrimination. Materials and Methods: The radiation image acquisition process for air-cargo security inspection equipment using X-rays and neutrons was simulated using a GEometry ANd Tracking (Geant4) simulation toolkit. Radiation images of phantoms composed of 13 materials were obtained, and the R-value, representing the attenuation ratio of neutrons and gamma rays in a material, was calculated from these images. Results and Discussion: The R-values were calculated from the simulated X-ray and neutron images for each phantom and compared with those obtained in the experiments. The R-values obtained from the experiments were higher than those obtained from the simulations. The difference can be due to the following two causes. The first reason is that there are various facilities or equipment in the experimental environment that scatter neutrons, unlike the simulation. The other is the difference in the neutron signal processing. In the simulation, the neutron signal is the sum of the number of neutrons entering the detector. However, in the experiment, the neutron signal was obtained by superimposing the intensities of the neutron signals. Neutron detectors also detect gamma rays, and the neutron signal cannot be clearly distinguished in the process of separating the two types of radiation. Despite these differences, the two results showed similar trends and the viability of using simulation-based radiation images, particularly in the field of security screening. With further research, the simulation-based radiation images can replace ones from experiments and be used in the related fields. Conclusion: The Korea Atomic Energy Research Institute has developed air-cargo security inspection equipment using neutrons and X-rays. Using this equipment, radiation images and Rvalues for various materials were obtained. The equipment was reconstructed, and the R-values were obtained for 13 materials using the Geant4 simulation toolkit. The R-values calculated by experiment and simulation show similar trends. Therefore, we confirmed the feasibility of using the simulation-based radiation image.

리눅스 시스템을 이용한 고속중성자 측정제어

박재연(Jae Yeon Park),문정호,이재현,이재현,채문식,이민웅(MinWoong Lee),이남호 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6

Design of 6 MeV X-Band Electron Linac for Dual-Head Gantry Radiotherapy System

신승욱,이승현,이종철,김휘수,하동협,Mitra Ghergherehchi,채종서,이병노,채문식 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.12

A compact 6 MeV electron linac is being developed at Sungkyunkwan University, in collaboration with the Korea atomic energy research institute (KAERI). The linac will be used as an X-ray source for a dual-head gantry radiotherapy system. X-band technology has been employed to satisfy the size requirement of the dual-head gantry radiotherapy machine. Among the several options available, we selected a pi/2-mode, standing-wave, side-coupled cavity. This choice of radiofrequency (RF) cavity design is intended to enhance the shunt impedance of each cavity in the linac. An optimum structure of the RF cavity with a high-performance design was determined by applying a genetic algorithm during the optimization procedure. This paper describes the detailed design process for a single normal RF cavity and the entire structure, including the RF power coupler and coupling cavity, as well as the beam dynamics results.

Measurement of Characteristic of X-band RF Cavity for 6 MeV Electron Linac

신승욱,이승현,오세영,Donghyup Ha,Mitra Ghergherehchi,채종서,이병노,채문식 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.7

A compact 6 MeV electron linear accelerator (linac), intended to be used as an X-ray source for a dual-head gantry radiotherapy system has been developed. In order to meet the size requirements of the dual-head gantry machine, an X-band radio frequency (RF) technology is used, which facilitates a reduction in the size of the linac, which is nine times smaller than the conventional medical purpose linac using S-band RF technology. Nevertheless, the X-band RF technology requires much higher machining precision and higher-quality surface finish owing to the electrical breakdown phenomena resulting from its small size. After the design was completed, the RF cavity was machined using high-precision machining technology, achieving machining tolerances of ±2 μm, and a surface roughness less than 50 nm. Various RF properties were measured in the fabricated RF cavity by using a network analyzer, and the distribution of the electric field generated in the RF cavity was verified by a bead-pull measurement technique. RF conditioning and beam commissioning experiments were performed, following the fabrication and tuning of the RF cavity.