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ABSTRACT: As there is substantial progress in the KSTAR tokamak engineering, all the major structures and sub-systems are under fabrication and in procurement phase. The vacuum vessel, port, cryostat cylinder, lid, and bellows are being rigorously fabricated in the factory. The lower part of the KSTAR such as cryostat base and gravity support has been almost finished in its fabrication. There are also great progresses and significant results in manufacturing of the superconducting magnet, including four Toroidal Field (TF) coils, lower and upper PF7 coils which are the largest Poloidal Field (PF) coils. The TF00 coil, which has been made for test and back-up of the TF magnet system, was successfully tested in the cool-down and current charging. As the fabrications and procurements of major structures have been actively proceeded, assembly works were also launched from Aug. 2003. More detailed description on these status, results, and plans will be described in this paper.
Plasma Science and Technology 10/2006; 6(1):2159. · 0.41 Impact Factor
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H. L. Yang,
K. M. Kim,
H. K. Kim,
W. C. Kim,
S. T. Kim,
N. I. Her,
G. H. Kim,
J. W. Sa,
K. H. Hong,
H. K. Park,
H. T. Kim, C. H. Choi,
J. S. Bak
[show abstract]
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ABSTRACT: Since most of the major components have been finished in fabrications and being delivered to the sitie, the KSTAR is now being vigorously assembled to meet the completion milestone of August 2007. The lower systems of the KSTAR such as the cryostat base, supports, and magnet gravity support were assembled within specifications in early 2004. The 337.5deg sector of the vacuum vessel with thermal shields was also assembled on the tokamak pit in April 2005. Assembly of the sixteen toroidal (TF) magnets also started as the next step, which is expected to be finished in the 1<sup>st</sup> quarter of 2006 according to the site delivery schedule of the last TF magnet. It is estimated that it will take more than one year from delivery of the last TF magnet to the assembly finish. Because the KSTAR is a fully superconducting tokamak, the assembly plan had to cover every consideration and this stemed from the existence of thermal shields, superconducting buslines, joints, and other components which are to be operated at cryogenic temperature. This special requirement resulted in the unique characteristics and features in the assembly engineering. In this paper, details of design features and plans of the KSTAR assembly will be explained. Moreover, recent progress in the assembly will be also reported
Fusion Engineering 2005, Twenty-First IEEE/NPS Symposium on; 10/2005
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ABSTRACT: KSTAR (Korea superconducting tokamak advanced research) has chosen the stainless steel 316LN as main material for the magnet structure. Two welding methods such as GTAW (gas tungsten arc welding) and EBW (electron beam welding) have applied to achieve proper weld condition and good weld properties. In order to determine the strength and toughness of stainless steel 316LN at low temperature, mechanical tests were carried out at 4 K, 77 K, and room temperature. The weld joint specimens are successfully produced without weld defects. Also yield strength and fracture toughness at 4 K satisfy the structural design criteria
Fusion Engineering 2005, Twenty-First IEEE/NPS Symposium on; 10/2005
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ABSTRACT: The poloidal field magnet system of the KSTAR consists of three pairs of coils using the cable-in-conduit conductors cooled by forced super-critical helium. The conductor of PF5 is Nb<sub>3</sub>Sn superconductor with Incoloy 908 conduit, and that of PF6 and PF7 is NbTi superconductor with SS 316LN. The PF coils are self-supporting with regard to radial loads, and they are arranged symmetrically with respect to the equatorial plane. PF5 coil is connected to the TF coil structure at eight points by hinges, while PF6 and PF7 coils are connected at sixteen points by flexible plates to allow relative radial movements. In order to investigate the structural integrity, structural analysis has been conducted including buckling and fatigue analyses. The major design loads are dead weight, assembly loads, thermal load due to cool down, and electromagnetic loads under the critical load conditions. It is found that the PF magnet structures can safely withstand all operating conditions. In addition, AISI 316LN can be substituted for JJ1 as the material of the PF coil structures.
IEEE Transactions on Appiled Superconductivity 07/2004; · 1.04 Impact Factor
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J.S. Bak, C.H. Choi,
H.L. Yang,
J.W. Sa,
H.K. Kim,
B.C. Kim,
N.I. Her,
K. Kim,
Y.S. Kim,
W.C. Kim,
Y.M. Park,
Y.K. Oh,
M. Kwon,
G.S. Lee,
K.S.T.A.R. Team
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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
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G.S. Lee,
J. Kim,
S.M. Hwang,
C.S. Chang,
H.Y. Chang,
M.H. Cho,
B.H. Choi,
K. Kim,
K.W. Cho,
S. Cho, [......],
K.M. Young,
J. Schultz,
P.W. Wang,
L. Sevier,
M.D. Carter,
P.M. Ryan,
D.W. Swain,
D.N. Hill,
W.M. Nevins,
B.J. Braams
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ABSTRACT: The Korea Superconducting Tokamak Advanced Research (KSTAR) project is the major effort of the national fusion programme of the Republic of Korea. Its aim is to develop a steady state capable advanced superconducting tokamak to establish a scientific and technological basis for an attractive fusion reactor. The major parameters of the tokamak are: major radius 1.8 m, minor radius 0.5 m, toroidal field 3.5 T and plasma current 2 MA, with a strongly shaped plasma cross-section and double null divertor. The initial pulse length provided by the poloidal magnet system is 20 s, but the pulse length can be increased to 300 s through non-inductive current drive. The plasma heating and current drive system consists of neutral beams, ion cyclotron waves, lower hybrid waves and electron cyclotron waves for flexible profile control in advanced tokamak operating modes. A comprehensive set of diagnostics is planned for plasma control, performance evaluation and physics understanding. The project has completed its conceptual design and moved to the engineering design and construction phase. The target date for the first plasma is 2002.
Nuclear Fusion 05/2002; 40(3Y):575. · 4.09 Impact Factor
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G.S. Lee,
M. Kwon,
C.J. Doh,
B.G. Hong,
K. Kim,
M.H. Cho,
W. Namkung,
C.S. Chang,
Y.C. Kim,
J.Y. Kim, [......],
J.B. Kim,
H.J. Ahn,
D.S. Kim,
J.H. Lee,
Y.W. Lee,
Y.S. Hwang,
S.H. Hong,
K.-H. Chung,
D.-I. Choi,
KSTAR Team
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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
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ABSTRACT: The Korea Superconducting Tokamak Advanced Research (KSTAR) Project has been in progress since 1996. Major parameters of the KSTAR tokamak are: major radius 1.8 m, minor radius 0.5 m, toroidal field 3.5 Tesla. The KSTAR device has a fully CICC type superconducting coil system. Cooling of the superconducting coil is forced cooling by supercritical helium using a low temperature SHE circulation system at 4.5 K. The total cold mass is around 380 tons and required cooling capacity is 10 kW in base-line operation mode and 12 kW in up-graded operation mode at 4.5 K. © 2002 American Institute of Physics.
AIP Conference Proceedings. 05/2002; 613(1):55-59.
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ABSTRACT: Several types of Lorenz forces and Joule heating generated in the magnet system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device have been studied numerically and analytically. We have examined 225 plasma equilibrium states to calculate the maximum magnetic forces and to determine which equilibrium state(s) generate such forces. The obtained results are used as input for structural analysis. A precompression should be applied to the eight-segmented central solenoid (CS) coil assembly to prevent free motion of each coil due to attractive and repulsive forces during operation. We have also evaluated the maximum values of the vertical and lateral forces for each of the CS coils and poloidal field coils and also for the entire CS coil stack. The in-plane force due to toroidal field (TF) coil charging and the out-of-plane force due to interaction of the TF coil current with the poloidal field have been computed. The Joule heating on the TF structure due to plasma disruption has also been calculated.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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ABSTRACT: The current feeder system consisting of superconducting (SC) bus-lines, SC bus-line interface terminal, and current leads is used as the current transmission system for the KSTAR SC coils. The current lead system consists of 11 pairs of vapor-cooled leads for the PF coils and a pair of leads for the TF coils. The PF coils are operated at full currents only during a portion of the entire time. The heat loads of current leads in idle mode, when it carries no current, depend quite strongly on the using material. We have measured the heat load and temperature profile when the overload current was charged in 200 A optimum brass lead. Also, the current feeder system requires a long bus-line that must supply a large amount of current from a current lead to SC coils. We have designed a SC bus-line with NbTi cable-in-conduit conductor (CICC) to reduce Joule heating loss. The CICC is cooled with forced-flow supercritical helium (SHe). The bus-line requires higher reliability and safety than those of the SC coils of the KSTAR. The KSTAR bus-line has been designed to have an independent vacuum space and consist of SHe return and 60 K thermal shield line for shielding. To connect the bus-line with a cryostat of the KSTAR and current lead box, we have developed a prototype SC bus-line interface terminal.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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Y.K. Oh, C.H. Choi,
J.W. Sa,
K.-I. You,
D.K. Lee,
M. Kwon,
G.S. Lee,
H.J. Ahn,
T.H. Kwon,
J.S. Lee,
Y.W. Lee,
S.C. Lee,
C.D. Hong
[show abstract]
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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
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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
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ABSTRACT: The toroidal field (TF) magnet system of Korea Superconducting Tokamak Advanced Research (KSTAR) device consists of 16 superconducting coils enclosed in steel cases. The TF cases are wedged along the inboard straight legs to sustain in-plane centering forces. The inter-coil structures contain adjustable shear keys and conical bolts to provide pre-loading in toroidal direction and to resist in-plane and out-of-plane forces, which are the most critical loads on the TF magnet system. For effective cooling of the TF case, a pad-type cooling channel has been designed to ensure structural and thermal stability. In order to investigate the structural integrity and to increase the structural reliability of the KSTAR magnet system, structural analyses have been conducted. From the analysis results, it has been found that the TF magnet structure can safely withstand the reference scenario operations.
IEEE Transactions on Appiled Superconductivity 04/2002; · 1.04 Impact Factor
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N.I. Her,
S. Cho,
J.W. Sa,
K.H. Im,
G.H. Hong,
G.H. Kim,
J.Y. Park,
H.K. Kim,
B.C. Kim,
I.K. Yu,
D.L. Kim,
W.C. Kim,
Y.K. Oh, C.H. Choi,
J.S. Bak,
M. Kwon,
G.S. Lee,
J.H. Kim,
H.J. Ahn
[show abstract]
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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
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Y.K. Oh, C.H. Choi,
J.W. Sa,
H.J. Ahn,
K.J. Cho,
Y.M. Park,
Y.S. Kim,
K. Kim,
D.K. Lee,
S. Cho,
N.I. Her,
M. Kwon,
J.S. Bak,
G.S. Lee
[show abstract]
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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
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ABSTRACT: In this paper, for the first time, we report high quality CVD hafnium oxynitride (HfOxNy) MOSFETs with conventional self-aligned poly-Si gate. These CVD HfOxNy films deposited using TDEAH (Tetrakisdiethylamino hafnium, C<sub>16</sub>H<sub>40</sub>N<sub>4</sub>Hf) and NH<sub>3</sub> remain amorphous after 900∼950°C annealing. Compared to HfO<sub>2</sub>, HfOxNy exhibits reduced leakage current by 2∼3 orders of magnitude, excellent boron penetration immunity, superior thermal stability of both EOT and leakage current after high temperature annealing, and excellent reliability.
Electron Devices Meeting, 2002. IEDM '02. International; 02/2002
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ABSTRACT: In this paper we present a capacitor charging power supply (CCPS) using a series-resonant three-level inverter topology to improve voltage regulation and use semiconductor switches having low blocking voltage capability such as MOSFETs. This inverter can be operated with two modes, full power mode (FPM) and half power mode (HPM). In FPM inverter supplies the high frequency step up transformer with full DC-link voltage(V<sub>DC</sub>) and in HPM with half DC-link voltage(V<sub>DC</sub>/2). HPM switching method will be adopted when CCPS output voltage reaches the preset target value and operates in refresh mode-charge is maintained on the capacitor. In this topology each semiconductor devices blocks a half of the DC-link voltage, for example we can use the 250 V semiconductor switch when designing 500 V DC-link voltage inverter system without considering the margin. A 15 kW, 30 kV CCPS has been built and tested for an electric precipitator application. The CCPS operates from an input voltage of 500 VDC and has a variable output voltage between 10 to 30 kV and 1 kHz repetition rate at 44 nF capacitive load. A resonant frequency of 67.9 kHz was selected and a voltage regulation of 0.83% has been achieved through the use of half power mode without using the forced cut off the switch current. The theory of operation, circuit topology and test results are given.
Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers; 02/2001
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ABSTRACT: In this paper, for the first time, we present a detailed
evaluation of physical and electrical properties of CVD TaN as a
potential gate electrode material for sub-100 nm MOS device
applications. Our results show that CVD TaN films deposited using TBTDET
(tertbutylimidoirisdiethylamido tantalum) exhibit excellent thermal
stability with underlying ultra thin SiO<sub>2</sub> up to 1000°C
and extremely stable work function (5eV@800-1000°C) suitable for
p-MOS device applications. Compared to PVD TaN, MOS devices with CVD TaN
gate electrode show desirable work function for p-MOS devices, excellent
stability of gate oxide thickness, leakage current, and interface
properties during high-temperature annealing, and superior gate
dielectric TDDB reliability. These results suggest that CVD TaN can be
used as the gate electrode on ultra thin gate oxide in self-aligned
gate-first CMOS processing
Electron Devices Meeting, 2001. IEDM Technical Digest. International; 02/2001
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ABSTRACT: A model parameter extraction system, called APEX (advanced model
parameter extractor), is described. APEX provides the
knowledge-assistant algorithm, which leads an optimizer to find optimal
parameters automatically, and it also provides useful environments to
obtain DC and AC parameters which guarantee good agreement with C-V data
and the inverter chain delay, as well as I-V data. The experimental
results using APEX show that optimal DC and AC parameter sets, including
temperature parameters at different temperatures, can be easily and
accurately obtained for the various sizes of transistors within a
reasonable time
Circuits and Systems, 1993., ISCAS '93, 1993 IEEE International Symposium on; 06/1993
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ABSTRACT: The authors propose an iterative learning control method using the
relative degree of a system for precise tracking control of a class of
nonlinear systems over a finite time interval. The class of nonlinear
systems, in which the iterative learning control is applied, can be
extended by using the proposed method. A sufficient condition is derived
for guaranteeing a uniform convergence to the desired output. The
results obtained for a class of nonlinear systems are shown to be a
generalization of the existing results for linear time-invariant
systems. To show the effectiveness of the proposed method, tracking
control of a single-link manipulator driven directly by a brushless DC
motor is studied
Decision and Control, 1992., Proceedings of the 31st IEEE Conference on; 02/1992
