• Nuclear Engineering and Technology
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• v.36 no.4
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• pp.357-363
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• 2004

A prototype long pulse ion source was developed, and the beam extraction experiments of the ion source were carried out at the Neutral Beam Test Stand (NBTS) of the Korea Superconducting Tokamak Advanced Research (KSTAR). The ion source consists of a magnetic bucket plasma generator, with multi-pole cusp fields, and a set of tetrode accelerators with circular apertures. Design requirements for the ion source were a 120kV/65A deuterium beam and a 300 s pulse length. Arc discharges of the plasma generator were controlled by using the emission-limited mode, in turn controlled by the applied heating voltage of the cathode filaments. Stable and efficient arc plasmas with a maximum arc power of 100 kW were produced using the constant power mode operation of an arc power supply. A maximum ion density of $8.3{\times}10^{11}\;cm^{-3}$ was obtained by using electrostatic probes, and an optimum arc efficiency of 0.46 A/kW was estimated. The accelerating and decelerating voltages were applied repeatedly, using the re-triggering mode operation of the high voltage switches during a beam pulse, when beam disruptions occurred. The decelerating voltage was always applied prior to the accelerating voltage, to suppress effectively the back-streaming electrons produced at the time of an initial beam formation, by the pre-programmed fast-switch control system. A maximum beam power of 0.9 MW (i.e. $70\;kV{\times}12.5\;A$) with hydrogen was measured for a pulse duration of 0.8 s. Optimum beam perveance, deduced from the ratio of the gradient grid current to the total beam current, was $0.7\;{\mu}perv$. Stable beams for a long pulse duration of $5{\sim}10\;s$ were tested at low accelerating voltages.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.48-55
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• 2003

The design and analysis of a three-phase 6/8 structure SRM(switched reluctance motor) art described. The range of the stator ole arc and the rotor pole arc of the motor we analyzed in the linear region. The optimum range of the stator pole arc and the turn-off angle of the main switches in the power converter are given with the 2-D finite element electro-magnetic field calculation of the motor and the nonlinear simulation. Test results of the prototype are discussed. This type is good for high efficiency drive because the drive circuit is simple and current density and copper loss of the winding are law.

• Journal of Welding and Joining
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• v.17 no.1
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• pp.116-123
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• 1999

The $CO_2$ welding with 100% $CO_2$ shielding gas is commonly used because of its cost and efficiency. Arc phenomena of the $CO_2$ welding is influenced by various factors such as chemical compositions of welding wire, shielding gas, welding condition and welding power source etc. In this study, arc phenomena is investigated by using two type of FCW(titania type, semi-metal type). Then, the welding quality and optimum welding condition can be selected. From this study, the following results were obtained; 1) In low current range(140A), FCW up to welding voltage(22V) resulted in a typical short circuit transfer. 2) In high current range(320A), the arc stability in titania FCW of a typical globular transfer is better than that of semi-metal FCW.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.869-875
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• 2009

The purpose of this paper is to investigate the optimal condition of the syngas production by reforming of propane using Gliding arc plasma reformer. The gliding arc plasma reformer in 3 phases has been newly designed and developed with a quick starting and fast response time. It can be applicable to the various types of fuels (Hydrocarbons $C_xH_y$), and it has a high conversion rate of fuels and high production of hydrogen. The parametric screening studies were carried out according to the changes of a steam feed amount i.e., steam/carbon ratio, total gas flow rate and input electric power. The optimum operating conditions were S/C ratio 2.8, total gas flow rate of 14 L/min and input electric power of 2.4 kW. The result of optimum operating conditions showed the 55 % $H_2$, 14 % CO, 15 % $CO_2$, 10 % $C_3H_8$ and 4 % $CH_4$. Also, $C_3H_8$ conversion, $H_2$ yield and $H_2$ selectivity were 90 %, 42 %, 15 %, respectively. The energy efficiency and specific energy requirements were 37 % and 334 kJ/mol respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.240-240
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• 2011

The first neutral beam injector (NBI-1) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. A first long pulse ion source (LPIS-1) has been installed on the NBI-1 for an auxiliary heating and current drive of KSTAR core plasmas. Performance of ion and neutral beam extractions in the LPIS-1 was investigated initially on the KSTAR NBI-1 system, prior to the neutral beam injection into the main plasmas. The ion source consists of a JAEA magnetic bucket plasma generator with multi-pole cusp fields and a set of KAERI prototype-III tetrode accelerators with circular apertures. The inner volume of plasma generator and accelerator column in the LPIS-1 is approximately 123 liters. Final design requirements for the ion source were a 120 kV/ 65 A deuterium beam and a 300 s pulse length. The extraction of ion beams was initiated by the formation of arc plasmas in the LPIS-1, called as an arc-beam extraction method. A stable ion beam extraction of LPIS-1 has been achieved up to an 100 kV/42 A for a 4 s pulse length and an 80 kV/25 A for a 14 s pulse length. Optimum beam perveance of 1.21 microperv has been found at an accelerating voltage of 80 kV. Neutralization efficiency has been measured by using a water flow calorimetry (WFC) method of calorimeter and an operation of bending magnet. The full-energy species of ion beams have been detected by using the diagnostic method of optical multichannel analyzer (OMA). An arc efficiency of the LPIS was 0.6~1.1 A/kW depending on the operating conditions of arc discharge.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.92-97
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• 2008

In welding of thin plate, some defects such as melt through and unmelted zone occur easily at welding start, however there is a limited study on those problems. Therefore the effects of start block and arc length on melt through and unmelted zone at start were investigated in this study. When start block height was lower than base metal, there was melt through at start. And when the height was even with base metal, no unmelted zone existed. Unmelted zone was increased as start block height increased from 0mm to 0.5mm. However unmelted zone was not much changed as the height increasing from 0.5mm to 1.0mm. When gap existed between start block and base metal, melt through occurred. However, unmelted zone was increased as the contact force of start block on base metal was increased from 0kgf to 7.5kgf. And when arc length was decreased from 3.8mm to 3.0mm, unmelted zone was decreased. It was concluded that the optimum condition to prevent melt through and to minimize unmelted zone would be with start block height 0.25mm, contact force 3.0kgf, and arc length 3.4mm. This optimum condition was applied to the mass production line and resulted in satisfied outcome.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.68-70
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• 2004

In this paper we develop an adaptive interface between video compression and transission protocols to handle QoS fluctuations that are common to mobile communication systems. We consider various generic design alternatives for QoS adaptation and identify 'QoS negotiation' as the most promissing. This method gives the best possibilities to obtain system-wide efficiency. To handle the indued system complexity we apply a design philosophy (called ARC) that separates implementation dependencies by introducing QoS interfaces between system modules. In the ARC phlosophy the implementation details are hidden in the subsystems. To assure efficient adaptation, the QoS must be negotiated between modules. We select the QoS parameters that are both necessary and sufficient for efficient negotiation between the video encoder and protocol modules. We describe the relation between the QoS parameters at the interface and the internal parameters of common video coding methods and protocol elements. Furthermore, we describe a negotiation procedure that allows a system-wide optimum to emerge.

• Journal of the Korean institute of surface engineering
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• v.26 no.4
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• pp.192-202
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• 1993

The characteristics of the high-performance ceramic coatings fabricated on the optimum processings con-ditions for the atmospheric plasma spraying are evaluated by various material tests and analyses. The opti-mum processing parameters for the plasma spraying are determined by using the two-level orthogonal arrays of fractional factorial testing method as a statistical approach. Material tests for the coating specimens are carried out to evaluate microstructure, hardness, adhesion strength, and deposition efficiency. The properties of Al2O3-13%TiO2 coating are discussed with regard to the effective processings parameters. The decarburization effects of WC-12%Co coating is examined by XRD analysis in terms of the arc power and the secondary gas species. The hardness of Al2O2-13%TiO2 coating is increased with the arc power and shows the maximum value at around 40 lpm of Ar gas flowrate, which appears to be the most critical parame-ter on the deposition efficiency. For reducing the decarburization of WC-12%Co coating, the injection of inert He gas instead of reactive H2 gas as a secondary gas is more effective than the dropping of arc power to lessen the plasma enthalpy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.77-78
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• 2006

In order to increase the efficiency of LED, transparent electrodes should be also developed. also suitable anti-reflection coating (ARC) is necessary for practical device applications. In our paper, Al-doped ZnO (AZO) films were fabricated by sputtering on GaP substrate(wavelength:620nm). Choosing optimum substrate temperature and sputtering rate, high quality AZO films were formed. We confirmed that the surface and electrical properties, which implemented using the methods of AFM, Hall measurement. The properties of AZO thin films especially depended on the thickness. We presumed that the change of the increase the external quantum efficiency of LED according to the AZO thin film of thickness.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.269-269
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• 2012

A new ion source has been designed, fabricated, and installed at the NBTS (Neutral Beam Test Stand) at the KAERI (Korea Atomic Energy Research Institute) site. The goalis to provide a 100 keV, 2MW deuterium neutral beam injection as an auxiliary heating of KSTAR (Korea Super Tokamak Advanced Research). To cope with power demand, an ion current of 50 A is required considering the beam power loss and neutralization efficiency. The new ion source consists of a magnetic cusp bucket plasma generator and a set of tetrode accelerators with circular copper apertures. The plasma generator for the new ion source has the same design concept as the modified JAEA multi-cusp plasma generator for the KSTAR prototype ion source. The dimensions of the plasma generator are a cross section of $59{\times}25cm^2$ with a 32.5 cm depth. The anode has azimuthal arrays of Nd-Fe permanent magnets (3.4 kG at surface) in the bucket and an electron dump, which makes 9 cusp lines including the electron dump. The discharge properties were investigated preliminarily to enhance the efficiency of the beam extraction. The discharge of the new ion source was mainly controlled by a constant power mode of operation. The discharge of the plasma generator was initiated by the support of primary electrons emitted from the cathode, consisting of 12 tungsten filaments with a hair-pin type (diameter = 2.0 mm). The arc discharge of the new ion source was achieved easily up to an arc power of 80 kW (80 V/1000 A) with hydrogen gas. The 80 kW capacity seems sufficient for the arc power supply to attain the goal of arc efficiency (beam extracted current/discharge input power = 0.8 A/kW). The accelerator of the new ion source consists of four grids: plasma grid (G1), gradient grid (G2), suppressor grid (G3), and ground grid (G4). Each grid has 280 EA circular apertures. The performance tests of the new ion source accelerator were also finished including accelerator conditioning. A hydrogen ion beam was successfully extracted up to 100 keV /60 A. The optimum perveance is defined where the beam divergence is at a minimum was also investigated experimentally. The optimum hydrogen beam perveance is over $2.3{\mu}P$ at 60 keV, and the beam divergence angle is below $1.0^{\circ}$. Thus, the new ion source is expected to be capable of extracting more than a 5 MW deuterium ion beam power at 100 keV. This ion source can deliver ~2 MW of neutral beam power to KSTAR tokamak plasma for the 2012 campaign.