Jungmin Jo
Seoul National University
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Featured researches published by Jungmin Jo.
Review of Scientific Instruments | 2016
Jungmin Jo; MunSeong Cheon; Jun Young Kim; Tongnyeol Rhee; Junghee Kim; Y.J. Shi; M. Isobe; Kunihiro Ogawa; Kyoung-Jae Chung; Y. S. Hwang
Measurements of the time-integrated triton burnup for deuterium plasma in Korea Superconducting Tokamak Advanced Research (KSTAR) have been performed following the simultaneous detection of the d-d and d-t neutrons. The d-d neutrons were measured using a 3He proportional counter, fission chamber, and activated indium sample, whereas the d-t neutrons were detected using activated silicon and copper samples. The triton burnup ratio from KSTAR discharges is found to be in the range 0.01%-0.50% depending on the plasma conditions. The measured burnup ratio is compared with the prompt loss fraction of tritons calculated with the Lorentz orbit code and the classical slowing-down time. The burnup ratio is found to increase as plasma current and classical slowing-down time increase.
Review of Scientific Instruments | 2018
Kunihiro Ogawa; M. Isobe; Takeo Nishitani; Eiji Takada; Hiroki Kawase; Tatsuki Amitani; Neng Pu; Jungmin Jo; MunSeong Cheon; Junghee Kim; Misako Miwa; S. Matsuyama; Isao Murata
The behavior of the 1 MeV triton has been studied in order to understand the alpha particle confinement property in the deuterium operation of toroidal fusion devices. To obtain time evolution of the deuterium-tritium (D-T) neutron emission rate where the secondary DT neutron emission rate is approximately 1012 n/s, we designed two high detection efficiency scintillating fiber (Sci-Fi) detectors: a 1 mm-diameter scintillation fiber-based detector Sci-Fi1 and a 2 mm-diameter scintillation fiber-based detector Sci-Fi2. The test in an accelerator-based neutron generator was performed. The result shows that the directionality of each detector is 15° and 25°, respectively. It is found that detection efficiency for DT neutrons is around 0.23 counts/n cm2 for the Sci-Fi1 detector and is around 1.0 counts/n cm2 for the Sci-Fi2 detector.
Review of Scientific Instruments | 2017
Jungmin Jo; M. S. Cheon; Junghee Kim; YoungHwa An; Seungil Park; Kyoung-Jae Chung; Y. S. Hwang
Feasibility of using conventional photo-multiplier tubes (PMTs) without a scintillator as an ex-vessel radiation detector in a tokamak environment is studied. Basic irradiation tests using standard gamma ray sources and a d-d neutron generator showed that the PMT is responding both to gamma photons and neutrons, possibly due to the direct generation of secondary electrons inside the PMT by the impingement of high energy photons. Because of the selective sensitivity of the PMT to hard x-ray and neutrons in ohmic and neutral beam injected plasmas, respectively, it is shown that the PMT with certain configuration can be utilized either to monitor the fluctuation in the fusion neutron generation rate or to study the behavior of runaway electrons in tokamaks.
Review of Scientific Instruments | 2018
Jungmin Jo; M. S. Cheon; Junghee Kim; Soobin Lim; M. Isobe; Kunihiro Ogawa; T. Nishitani; Seugil Park; Isao Murata; Kyoung-Jae Chung; Y. S. Hwang
In time-resolved measurement for triton burnup in Korea Superconducting Tokamak Advanced Research (KSTAR) deuterium plasmas, an NE213 liquid scintillation detector was installed and operated during the 2017 KSTAR campaign. The detector is composed of an NE213 scintillator (50 mm in diameter and 10 mm in thickness) and a photomultiplier tube (PMT). The PMT anode signal was processed under a data acquisition system which contains a field programmable gate array circuit and pulse processing software that is capable of discriminating gamma-ray and neutron pulse signals. In order to determine an appropriate threshold level for the 14 MeV neutron signal resulting from triton burnup, the NE213 scintillation detector was calibrated by using d-d and d-t neutron generators at the National Fusion Research Institute and Intense 14 MeV Neutron Source Facility, OKTAVIAN, Osaka University, Japan. The detector was installed on KSTAR with a 10 mm thick soft-iron stray magnetic field shield and a radiation shield which consists of 100 mm thick lead blocks and 200 mm thick borated polyethylene blocks. A discrimination range for d-t neutron was determined based on test results from neutron generators and KSTAR. Data points selected from the discrimination range were consistent with the classical triton confinement characteristics. In conclusion, under condition of an input counting rate of 1.9 × 105 counts per second (CPS), the detector is able to measure triton burnup signals up to 500 CPS for various plasma parameters.
Review of Scientific Instruments | 2016
YooSung Kim; Y.J. Shi; Jeong-hun Yang; Seong-Cheol Kim; Young Gi Kim; Jeong-Jeung Dang; Seongmoo Yang; Jungmin Jo; Soo-ghee Oh; Kyoung-Jae Chung; Y. S. Hwang
Electron density profiles of versatile experiment spherical torus plasmas are measured by using a hydrogen line intensity ratio method. A fast-frame visible camera with appropriate bandpass filters is used to detect images of Balmer line intensities. The unique optical system makes it possible to take images of Hα and Hβ radiation simultaneously, with only one camera. The frame rate is 1000 fps and the spatial resolution of the system is about 0.5 cm. One-dimensional local emissivity profiles have been obtained from the toroidal line of sight with viewing dumps. An initial result for the electron density profile is presented and is in reasonable agreement with values measured by a triple Langmuir probe.
Fusion Engineering and Design | 2013
Kyoung-Jae Chung; YoungHwa An; Bong-Ki Jung; Hyunyoung Lee; Jeong-Jeung Dang; Jeong-Hun Lee; Jeong-hun Yang; Jungmin Jo; Da-Hye Choi; Young Gi Kim; Yong-Su Na; Y.S. Hwang
Fusion Engineering and Design | 2015
YoungHwa An; Jeong Won Lee; HyunYeong Lee; JongGab Jo; Bong-Ki Jung; Kyoung-Jae Chung; Young Gi Kim; Jungmin Jo; Jeong-hun Yang; Yong-Su Na; T.S. Hahm; Y.S. Hwang
Fusion Engineering and Design | 2015
Young Gi Kim; Jong Ha Lee; Jeong Won Lee; YoungHwa An; Jeong Jeung Dang; Jungmin Jo; HyunYeong Lee; Kyoung-Jae Chung; Y.S. Hwang; Yong-Su Na
Fusion Engineering and Design | 2014
Yuna Lee; Jeong-Jeung Dang; Jungmin Jo; Kyoung-Jae Chung; Y. S. Hwang; MunSeong Cheon; H.G. Lee; L. Bertalot
Fusion Engineering and Design | 2016
Jungmin Jo; Mun Seong Cheon; Kyoung-Jae Chung; Y. S. Hwang