Publications (19)17.72 Total impact
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Article: Calibration of electron cyclotron emission radiometer for KSTAR.
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ABSTRACT: We developed and installed an electron cyclotron emission radiometer for taking measurements of Korea Superconducting Tokamak Advanced Research (KSTAR) plasma. In order to precisely measure the absolute value of electron temperatures, a calibration measurement of the whole radiometer system was performed, which confirmed that the radiometer has an acceptably linear output signal for changes in input temperature. It was also found that the output power level predicted by a theoretical calculation agrees with that obtained by the calibration measurement. We also showed that the system displays acceptable noise-temperature performance around 0.23 eV.The Review of scientific instruments 10/2010; 81(10):10D916. · 1.52 Impact Factor -
Article: Electron cyclotron emission diagnostics on KSTAR tokamak.
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ABSTRACT: A new electron cyclotron emission (ECE) diagnostics system was installed for the Second Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The new ECE system consists of an ECE collecting optics system, an overmode circular corrugated waveguide system, and 48 channel heterodyne radiometer with the frequency range of 110-162 GHz. During the 2 T operation of the KSTAR tokamak, the electron temperatures as well as its radial profiles at the high field side were measured and sawtooth phenomena were also observed. We also discuss the effect of a window on in situ calibration.The Review of scientific instruments 10/2010; 81(10):10D922. · 1.52 Impact Factor -
Article: Diagnostics for first plasma and development plan on KSTAR
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ABSTRACT: The first plasma with target values of the plasma current and the pulse duration was finally achieved on June 13, 2008 in the Korea Superconducting Tokamak Advanced Research (KSTAR). The diagnostic systems played an important role in achieving successful first plasma operation for the KSTAR tokamak. The employed plasma diagnostic systems for the KSTAR first plasma including the magnetic diagnostics, millimeter-wave interferometer, inspection illuminator, Hα, visible spectrometer, filterscope, and electron cyclotron emission (ECE) radiometer have provided the main plasma parameters, which are essential for the plasma generation, control, and physics understanding. Improvements to the first diagnostic systems and additional diagnostics including an x-ray imaging crystal spectrometer, reflectometer, ECE radiometer, resistive bolometer, and soft x-ray array are scheduled to be added for the next KSTAR experimental campaign in 2009.Review of Scientific Instruments 06/2010; 81(6):063502-063502-6. · 1.37 Impact Factor -
Article: Key features and engineering progress of the KSTAR Tokamak (Invited paper, ICOPS 2003)
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ABSTRACT: The Korea superconducting tokamak advanced research (KSTAR), which is under construction at the National Fusion R&D Center, Korea Basic Science Institute, Daejeon, Korea, has the mission to develop a steady-state capable advanced superconducting tokamak to establish the scientific and technological bases for a fusion reactor. After an intensive R&D program, substantial progress of the KSTAR tokamak engineering had been made on major tokamak structures, superconducting magnets, in-vessel components, diagnostic system, heating system, and power supplies with industrial manufacturers by May 2002. The engineering design has been elaborated to the extent necessary to allow a realistic assessment of its feasibility, performance, and cost. Since May 2003, the project has been in the phase of procurement. The fabrication of main tokamak structure such as vacuum vessel, cryostat, and supporting structures is well progressed. The manufacturing work of superconducting coils is also proceeding favorably. The tokamak assembly started in July 2003 after site preparation and assembly jig. The start of commissioning is scheduled for June 2006. This paper describes the key features and engineering progress of the KSTAR tokamak and elaborates the work currently underway.IEEE Transactions on Plasma Science 05/2004; · 1.17 Impact Factor -
Article: RF-heating and plasma confinement studies in the HANBIT mirror device
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ABSTRACT: HANBIT is a magnetic mirror confinement device. Recently, after finishing the first campaign for the basic system development, it started the second campaign for high-temperature plasma confinement physics study in a mirror configuration. Here, we introduce briefly the HANBIT device and report initial physics experiment results on RF-plasma heating and confinement in the simple mirror configuration. It appears that the discharge characteristics of HANBIT are quite different from those in other mirror devices, and an explanation is presented to clarify the difference.Nuclear Fusion 07/2003; 43(8):686. · 4.09 Impact Factor -
Article: Design and construction of the KSTAR tokamak
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ABSTRACT: The extensive design effort for KSTAR has been focused on two major aspects of the KSTAR project mission - steady-state-operation capability and advanced tokamak physics. The steady state aspect of the mission is reflected in the choice of superconducting magnets, provision of actively cooled in-vessel components, and long pulse current drive and heating systems. The advanced tokamak aspect of the mission is incorporated in the design features associated with flexible plasma shaping, double null divertor and passive stabilizers, internal control coils and a comprehensive set of diagnostics. Substantial progress in engineering has been made on superconducting magnets, the vacuum vessel, plasma facing components and power supplies. The new KSTAR experimental facility with cryogenic system and deionized water cooling and main power systems has been designed, and the construction work is under way for completion in 2004.Nuclear Fusion 05/2002; 41(10):1515. · 4.09 Impact Factor -
Article: Engineering design status of the KSTAR central solenoid structure
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ABSTRACT: The central solenoid (CS) magnet system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device consists of four pairs of segmented CS coils and a CS coil structure. The maximum repulsive force between CS coils is about 12 MN. The functions of the CS structure are to apply preload on the CS coils and to support the repulsive force between CS coils during operation. The designed axial compression of 15 MN at 4.5 K will be applied partly by assembling the preload structure at room temperature with preload of about 13.4 MN and partly by the thermal contraction difference between the CS coils and the structure during cool down. Additional preload will be given by minute adjustment of wedges. The structural analysis of the CS magnet system has been performed to verify the CS structure design reliability.IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor -
Article: Detailed evaluation of insulation stresses in the KSTAR central solenoid
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ABSTRACT: The insulation system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device plays a role of the structural element by binding the conductor jackets as well as breaking the current. The KSTAR Central Solenoid (CS) coils are stacked with four pairs of coils with up-down symmetry. The insulation of the CS coils experiences various stress states, such as tensile, normal compressive, and shear stresses due to applied preload at room temperature, thermal contraction difference during cool-down, and magnetic forces during operation. In particular, the normal tension and shear of the insulation has been a critical issue for magnet design. In this paper, a more detailed model in addition to electromagnetic and global structural analysis will be constructed and analyzed to evaluate the insulation stress. The results may suggest appropriate allowable stress criteria for insulation systems at cryogenic temperature.IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor -
Conference Proceeding: KSTAR vacuum vessel thermal shield analysis
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ABSTRACT: The KSTAR Vacuum vessel thermal shield is composed of multilayer insulation (MLI), cryopanel and supports. One of the major design parameters for the design of thermal shield cryopanel and supports is the eddy current induced during plasma disruption. The eddy current creates joule heating as well as electromagnetic (EM) loads combining with magnetic fields. Since the cryopanel should be maintained at a cryogenic temperature lower than 80 K, even a small amount of joule heating may play an important role in increasing the cyropanel temperature. Also the EM loads are very critical mechanical forces for the design of structure of the thermal shield, especially for the supports. Joule heating and EM loads on the vacuum vessel thermal shield during plasma disruption were calculated to provide the design requirement of the thermal shield. Based on the joule heating and EM loads, the structural and thermal stress analyses were performed for the assessment of the structural robustness of the vacuum vessel thermal shield. It was found that the effect of joule heating on the thermal shield design is minimal, but the EM loads are important for the design of cryopanel as well as supports. The optimal number and size of supports were determined.Fusion Engineering, 2002. 19th Symposium on; 02/2002 -
Conference Proceeding: Structural design and analysis for the KSTAR cryostat
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ABSTRACT: The KSTAR cryostat is a 8.8 m diameter vacuum vessel that provides the necessary thermal barrier between the ambient temperature test cell and the supercritical helium cooled superconducting magnet providing the base pressure of 1×10<sup>-5</sup> torr. The cryostat is a single walled vessel consisting of central cylindrical section and two end closures, a flat base structure with external reinforcements and a dome-shaped lid structure. The base structure has 8 equally spaced support legs anchored on the concrete base. The cryostat vessel design was executed to satisfy the performance and operation requirements. The mechanical penetration components with bellows were designed to restrict the displacements of all kinds of ports due to EM loads and thermal loads within the allowable limits. The major loads considered in this paper for the design of cryostat vessel are the vacuum pressure, the dead weight of vacuum vessel, PFC, and magnet which are total about 400 tons, the electromagnetic load driven by plasma disruption, and seismic loads. Based on these loads, structural analyses were performed. It was found that the maximum stress intensity was below the allowable limit, and that the cryostat vessel had buckling safety of over 5. Based on the results, structural robustness of the cryostat vessel has been proved.Fusion Engineering, 2002. 19th Symposium on; 02/2002 -
Conference Proceeding: Design overview of the KSTAR magnet structures
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ABSTRACT: The magnet structure system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device consists of 16-segmented toroidal field (TF) coil structures encasing each D-shaped TF coil, a central solenoid (CS) structure surrounding 4 pairs of CS coils, modular poloidal field (PF) coil structures supporting each PF coil in 8 or 16 places, and a gravity support. The engineering design of the magnet structures has been conducted with related electromagnetic load calculations and structural analyses for various operation scenarios. A prototype TF coil structure will be fabricated to check the manufacturing feasibility. A prototype magnet supporting post has been fabricated and tested at 80 K up to 15,000 cycles of vertical load under 80 tons. In addition to the magnet structure development, winding and heat treatment of a real-sized prototype TF coil have been finished without any defect such as SAGBO. The fabrication of the coil will be completed by the middle of 2002. As an interface of the magnet system, a cryogenic facility and a current feeder system have been designed.Fusion Engineering, 2002. 19th Symposium on; 02/2002 -
Conference Proceeding: Progress of the KSTAR tokamak engineering
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ABSTRACT: The KSTAR tokamak is under construction with aim of establishing a scientific and technological basis for an attractive fusion reactor. The KSTAR tokamak system consists of a vacuum vessel, magnet systems, in-vessel components, a cryostat, thermal shields, a vacuum pumping system, and ancillary systems. These systems are in the final stage of engineering design and prototype manufacturing with industrial manufacturer's involvement. The extensive structural analyses of the vacuum vessel, cryostat and supporting structures have been performed. The prototype vacuum vessel of a full-scale 62-degree sector has been constructed to verify the overall fundamental characteristics of the developed manufacturing techniques. A prototype TF coil has been wound in D-shape without an internal joint and finished the heat treatment process. For magnet structures, final design modifications and extensive structural analyses have been carried out to maintain mechanical rigidity against electromagnetic forces for various operation scenarios. Substantial progress in engineering has been made on in-vessel components, thermal shields and vacuum pumping system.Fusion Engineering, 2002. 19th Symposium on; 02/2002 -
Article: Electromagnetically induced absorption spectra depending on intensities and detunings of the coupling field in Cs vapour
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ABSTRACT: We have observed electromagnetically induced absorption (EIA) spectra depending on intensities and detunings of the coupling field in the cycling transition (6S1/2, F = 46P3/2, F' = 5) of the Doppler-broadened Cs atomic system. With a weak coupling field, we were able to see an EIA spectrum with a subnatural linewidth. On increasing the intensity of the coupling laser, we found that a transmission dip produced by an electromagnetically induced transparency appeared at the centre of the EIA structure, which is the first time that this has been observed. By detuning the frequency of the coupling laser, we were able to obtain a clear dispersion-like spectrum for blue-side detuning, but we obtained a complicated shape for red-side detuning because of the influences of other hyperfine levels. These results were compared qualitatively with theoretical curves obtained from a simple model.Journal of Physics B Atomic Molecular and Optical Physics 11/2001; 34(23):4801. · 1.88 Impact Factor -
Article: Thermohydraulic design of the KSTAR vacuum vessel
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ABSTRACT: The KSTAR vacuum vessel is designed as a racetrack-shaped double wall configuration with major ports, reinforcing ribs, bellows and a leaf spring style support structure. The vessel will be baked out by hot nitrogen gas and cooled with shielding water during normal operation. The baking/cooling medium will be fed into the double wall through the manifold to bake the vessel at 250 °C within 24 h. The heat-transfer mechanism used for the design is introduced. The heat loads on the non-symmetric vessel during the bakeout produce a non-symmetric thermal expansion that can create high thermal stresses on the support structure and the vacuum vessel interface area with the ports. The 3D temperature distribution and the resulting thermal loads in the vacuum vessel during bakeout are calculated. It is found that the vacuum vessel and its supports are structurally robust based on the thermal stress analyses.Fusion Engineering and Design. -
Article: RF-heating and plasma confinement studies in the HANBIT mirror device
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ABSTRACT: HANBIT is a magnetic mirror confinement device. Recently, with almost finishing the first campaign for the basic system development, it started the second campaign for the high-temperature plasma confinement physics study in mirror configuration. Here, we introduce briefly the HANBIT device and report initial physics experiments results on RF-plasma heating and confinement in the simple mirror configuration. It appears that the discharge characteristics of HANBIT are quite different from those in other mirror devices, and an explanation is presented to clarify the difference. -
Article: Mirror Stabilization Experiments in the Hanbit Mirror Device
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ABSTRACT: The Hanbit device is a magnetic mirror machine which has a central cell, one anchor cell and one plug cell plus associated vacuum chambers. It is about half of the original TARA mirror device from MIT. The Hanbit device has been involved in a series of experiments on stabilization of the MHD flute type mode. Earlier work showed that it was possible to stabilize the m = -1 flute type MHD instability with RF power near the cyclotron resonance. This stability has been attributed to the sideband coupling process. We have now undertaken investigations to see if a divertor and the Kinetic Stabilizer (KS) of R. F. Post can stabilize the MHD instability. Divertors were used previously in experiments on the TARA mirror device and the HIEI mirror device. The Hanbit divertor configuration uses one of the central cell coils with reversed current as the divertor coil and two adjacent coils with increased current to compensate for the field droop and to prevent the field lines from intercepting the bare ICRH antenna. The divertor strongly reduces the m = -1 instability when the null point (x-point) is sufficiently inside the vacuum tank. However, the diverted plasma is directed into a wall and the divertor cannot be used to eliminate impurities. The KS uses microwave produced plasmas on field lines in the cusp tank region. According to the theory, by locating a stabilizing plasma pressure on the field lines at a region with a strong second derivative and large radius in the expanding field region outside the mirrors, the main plasma in the mirror central cell in regions with unfavorable field line curvature can be stabilized. Two coils on the cusp tank are configured to produce expanding field lines with a large positive radius of curvature. A 5-kW 2.45 GHz magnetron is used to produce the stabilizing ECRH plasma pressure in this region. A reduction of instability duration has been observed for high power plasmas. However, for low power plasmas that terminate violently with an m = -1 instability, the KS action makes the duration of the instability longer. Details of both experiments are given. -
Article: Key Features and Progress of the KSTAR Tokamak Engineering
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ABSTRACT: Substantial progress of the KSTAR tokamak engineering has been made on major tokamak structures, superconducting magnets, in-vessel components, diagnostic system, heating system, and power supplies. The engineering design has been elaborated to the extent necessary to allow a realistic assessment of its feasibility, performance, and cost. The prototype fabrication has been carried out to establish the reliable fabrication technologies and to confirm the validation of analyses employed for the KSTAR design. The completion of experimental building with beneficial occupancy for machine assembly was accomplished in Sep. 2002. The construction of special utility such as cryo-plant, de-ionized water-cooling system, and main power station will begin upon completion of building construction. The commissioning, construction, fabrication, and assembly of the whole facility will be going on by the end of 2005. This paper describes the main design features and engineering progress of the KSTAR tokamak, and elaborates the work currently underway. -
Article: Design and construction of the KSTAR tokamak
[show abstract] [hide abstract]
ABSTRACT: The extensive design effort for KSTAR has been focused on two major aspects of the KSTAR project mission — steady-state-operation capability and advanced tokamak physics. The steady state aspect of the mission is reflected in the choice of superconducting magnets, provision of actively cooled in-vessel components, and long pulse current drive and heating systems. The advanced tokamak aspect of the mission is incorporated in the design features associated with flexible plasma shaping, double null divertor and passive stabilizers, internal control coils and a comprehensive set of diagnostics. Substantial progress in engineering has been made on superconducting magnets, the vacuum vessel, plasma facing components and power supplies. The new KSTAR experimental facility with cryogenic system and deionized water cooling and main power systems has been designed, and the construction work is under way for completion in 2004. -
Article: Tokamak field error measurements with an electron beam in KSTAR
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ABSTRACT: It is possible to detect the presence of small field errors in a tokamak with an electron beam. This was demonstrated earlier on T-15 and TEXTOR. This paper discusses the concept, past experience on these tokamaks, calculations for the Korea Superconducting Tokamak Advanced Research (KSTAR) device, an electron beam source, measurement devices for these measurements, and some results. It is shown that small toroidally averaged field errors can be detected by this method. A low voltage electron beam (e-beam) gun and fluorescent screen were mounted in a vertical port and inserted into the vacuum vessel at the end of the KSTAR 2nd campaign plasma experiments. A camera with a narrow field of view was mounted in midplane port in a tube tangent to the field lines at R ∼ 1.3 m and photographed the beam striking the screen. The poloidal field (PF) currents were held constant during the camera exposure period. Many shots with various PF coils energized were made and the deflections of the e-beam were measured. The measurements were made with a camera integration time of 300 ms because of the low light intensity. The results show that there are large field errors that diminish as the PF currents are raised. There appears to be no significant up–down asymmetry for static fields. Measurements with a 7 PF coil scenario with a calculated field null located at e-beam radial position show much larger fields than calculated. KSTAR was constructed with Incoloy 908 conduit using cable-in-conduit conductors (CICC) in 10 of the 14 PF coils and all 16 of the toroidal field (TF) coils. Incoloy 908 has a relative magnetic permeability, μ, of about 10. The field errors appear to be largely due to Incoloy 908.Fusion Engineering and Design.
Top co-authors
Top Journals
Institutions
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2010
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Korea Atomic Energy Research Institute (KAERI)
Taiden, Daejeon, South Korea
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2003
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Korea Basic Science Institute KBSI
Seoul, Seoul, South Korea
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