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45 MeV 양성자 빔을 이용한 중합체 겔 선량계의 특성 평가
봉지혜,김금배,양태건,고인옥,박지애,김경민,정해조,지영훈,권수일 한국물리학회 2012 새물리 Vol.62 No.1
A normoxic polymer gel dosimeter was developed to measure the dosimetric characteristics of a 45 MeV proton beam. The gel dosimeter was synthesized using gelatin, methacrylic acid (MAA),hydroquinon (HQ), tetrakis (THPC) and Distilled water (HPLC) and was poured into an ABS container. The 45 MeV proton beam of the MC-50cyclotron accelerator was used for testing the gel dosimeter, and using a collimator, we exposed the gel dosimeter at a diameter of 12mm and a beam current of 2 nA. For the comparison with the gel dosimeter, 50 films of EBT2 were seriated and exposed to 5 nA for 5sec. The relaxation rate (R2) of the gel dosimeter exposed to the beam was obtained using 3.0T MRI and its dose was analyzed. In the dosimetric range of 0 ~ 15.5 Gy, the correlation coefficient was analyzed. The bragg peak of the proton beam based on the dosimetric changes in the 3.9 ~ 5.3 Gy dosimetric range was found at WED 12.39 mm. The possibility for using the gel dosimeter with films for the dosimetric measurement of a proton beam was confirmed. 정상산소 중합체 겔 선량계를 제작하여 45 MeV 양성자 빔에 대한 선량특성을 측정하였다. 겔 선량계는 젤라틴(Gelatin), 메타크릴산(MAA),히드로퀴논(HQ), 테트라키스(THPC), 증류수(HPLC)를 이용하여 합성하고ABS용기에 넣었다. 겔 선량계는 MC-50 사이클로트론 가속기의 45 MeV 양성자 빔을 사용하였으며 콜리메이터를 이용하여 지름 12 mm, 빔전류 2nA 로 조사하였다. 겔 선량계와의 비교를 위해서 GafchromiⓇ 필름 50장을 연속 배열하여 5 nA로 5 초 동안 조사시켰다. 빔이 조사된겔 선량계는 3.0 T MRI를 이용하여 횡이완률 R2 값을 얻어 선량을분석하였다. 0 ~ 15.5 Gy 선량범위에서 선형상관계수를 구하였다. 3.9 ~ 5.3 Gy 선량 영역에서 선량변화에 따른 양성자 빔의 브래그피이크는 WED 12.39 mm 에서 나타났다. 양성자 빔의 선량 측정에 겔선량계가 필름과 함께 선량분포를 확인하는데 유용하게 사용될 수 있는가능성을 확인하였다.
Feasibility of CBCT Dosimetry for IMRT Using a Normoxic Polymethacrylic-acid Gel Dosimeter
봉지혜,권수일,김금배,김미숙,정해조,지영훈,고인옥,박지애,김경민 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.5
The purpose of this study is to evaluate the availability of cone-beam computed tomography(CBCT) for gel dosimetry. The absorbed dose was analyzed by using intensity-modulated radiation therapy(IMRT) to irradiate several tumor shapes with a calculated dose and several tumor acquiring images with CBCT in order to verify the possibility of reading a dose on the polymer gel dosimeter by means of the CBCT image. The results were compared with those obtained using magnetic resonance imaging(MRI) and CT. The linear correlation coefficients at doses less than 10Gy for the polymer gel dosimeter were 0.967, 0.933 and 0.985 for MRI, CT and CBCT, respectively. The dose profile was symmetric on the basis of the vertical axis in a circular shape, and the uniformity was 2.50% for the MRI and 8.73% for both the CT and the CBCT. In addition, the gradient in the MR image of the gel dosimeter irradiated in an H shape was 109.88 while the gradients of the CT and the CBCT were 71.95 and 14.62, respectively. Based on better image quality, the present study showed that CBCT dosimetry for IMRT could be restrictively performed using a normoxic polymethacrylic-acid gel dosimeter.
백지혜,최성환,이재진,김연한,봉수찬,박영득,곽영실,조경석,황정아,장비호,양태용,황은미,박성홍,박종엽,Baek, Ji-Hye,Choi, Seonghwan,Lee, Jae-Jin,Kim, Yeon-Han,Bong, Su-Chan,Park, Young-Deuk,Kwak, Young-Sil,Cho, Kyung-Suk,Hwang, Junga,Jang, Bi-Ho,Y 한국천문학회 2013 天文學論叢 Vol.28 No.3
We have developed a data integration system for ground-based space weather facilities in Korea Astronomy and Space Science Institute (KASI). The data integration system is necessary to analyze and use ground-based space weather data efficiently, and consists of a server system and data monitoring systems. The server system consists of servers such as data acquisition server or web server, and storage. The data monitoring systems include data collecting and processing applications and data display monitors. With the data integration system we operate the Space Weather Monitoring Lab (SWML) where real-time space weather data are displayed and our ground-based observing facilities are monitored. We expect that this data integration system will be used for the highly efficient processing and analysis of the current and future space weather data at KASI.
조경석,봉수찬,최성환,양희수,김지헌,백지혜,박종엽,임은경,김록순,김수진,김연한,박영득,S.W. Clarke,J. M. Davila,N. Gopalswamy,V. M. Nakariakov,B. Li,R. F. Pinto 한국천문학회 2017 Journal of The Korean Astronomical Society Vol.50 No.5
The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400~nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence ($<$12~min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.
양희수,봉수찬,조경석,최성환,박종엽,김지헌,백지혜,나자경,Mingzhe Sun,Qian Gong 한국천문학회 2018 Journal of The Korean Astronomical Society Vol.51 No.2
In a solar coronagraph, the most important component is an occulter to block the direct light from the disk of the sun Because the intensity of the solar outer corona is $10^{-6}$ to $10^{-10}$ times of that of the solar disk (\ir), it is necessary to minimize scattering at the optical elements and diffraction at the occulter. Using a Fourier optic simulation and a stray light test, we investigated the performance of a compact coronagraph that uses an external truncated-cone occulter without an internal occulter and Lyot stop. In the simulation, the diffracted light was minimized to the order of $7.6\times10^{-10}$ \ir~when the cone angle $\theta_c$ was about $0.39\degree$. The performance of the cone occulter was then tested by experiment. The level of the diffracted light reached the order of $6\times10^{-9}$ \ir~at $\theta_c=0.40\degree$. This is sufficient to observe the outer corona without additional optical elements such as a Lyot stop or inner occulter. We also found the manufacturing tolerance of the cone angle to be $0.05\degree$, the lateral alignment tolerance was $45$\,\um, and the angular alignment tolerance was $0.043\degree$. Our results suggest that the physical size of coronagraphs can be shortened significantly by using a cone occulter.
한국 e-CALLISTO 관측소 자동 관측 시스템 개발
박종엽,최성환,봉수찬,권용준,백지혜,장비호,조경석,문용재,PARK, JONGYEOB,CHOI, SEONGHWAN,BONG, SU-CHAN,KWON, YONGJUN,BAEK, JI-HYE,JANG, BI-HO,CHO, KYUNG-SUK,MOON, YONG-JAE,Monstein, Christian 한국천문학회 2015 天文學論叢 Vol.30 No.3
The e-CALLISTO is a network of CALLISTO (Compact Astronomical Low-frequency, Low-cost Instrument for Spectroscopy in Transportable Observatories) spectrometers which detect solar radio bursts 24 hours a day in frequency range 45-870 MHz. The number of channels per spectrum is 200 and the time resolution of whole spectrum is 0.25 second. The Korean e-CALLISTO station was developed by Korea Astronomy and Space Science Institute (KASI) collaborating with Swiss Federal Institute of Technology Zurich (ETH Zurich) since 2007. In this paper, we report replacement of the tracking mount and development of the control program using Visual C++/MFC. The program can make the tracking mount track the Sun and schedule CALLISTO to start and to finish its observation automatically using the Solar Position Algorithm (SPA). Daily tracking errors (RMSE) are 0.0028 degree in azimuthal axis and 0.0019 degree in elevational axis between 2014 January and 2015 July. We expect that the program can save time and labor to make the observations of solar activity for space weather monitoring, and improve CALLISTO data quality due to the stable and precise tracking methods.