• Applied Science and Convergence Technology
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• v.27 no.4
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• pp.65-69
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• 2018

We studied the critical pressure characteristics of an anode type ion beam source driven by both charge repulsion and diffusion mechanism. The critical pressure $P_{crit}$ of the diffusion type ion beam source was linearly decreased from 2.5 mTorr to 0.5 mTorr when the gas injection was varied in 3~10 sccm, while the $P_{crit}$ of the charge repulsion ion beam source was remained at 3.5 mTorr. At the gas injection of 10 sccm, the range of having normal beam shape in the charge repulsion ion beam source was about 6.4 times wider than that in the diffusion type ion beam source. An impurity of Fe 2p (KE = 776.68 eV) of 12.88 at. % was observed from the glass surface treated with the abnormal beam of the charge repulsion type ion beam source. The body temperature of the diffusion type ion beam source was observed to increase rapidly at the rate of $1.9^{\circ}C/min$ for 30 minutes and to vary slowly at the rate of $0.1^{\circ}C/min$ for 200 minutes for an abnormal beam and normal beam, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.383-388
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• 2011

The cold hollow cathode gas ion source is under development for multi aperture focused ion beam (FIB) system. In this paper, we describe the cold hollow cathode ion source design and the general ion source performance using Ar gas. The glow discharge characteristics and the ion beam current density at various operation conditions are investigated. This ion source can generate maximum ion beam current density of approximately 120 mA/$cm^2$ at ion beam potential of 10 kV. In order to effectively transport the energetic ions generated from the ion source to the multi-aperture focused ion beam(FIB) system, the einzel lens system for ion beam focusing is designed and evaluated. The ions ejected from the ion source can be forced to move near parallel to the beam axis by adjusting the potentials of the einzel lenses.

• Advances in materials Research
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• v.6 no.1
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• pp.27-43
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• 2017

The transient thermo-mechanical behavior of a simply-supported beam made of a functionally graded material (FGM) under the effect of a moving heat source is investigated. The FGM consists of a ceramic part (on the top), which is the hot side of the beam as the heat source motion takes place along this side, and a metal part (in the bottom), which is considered the cold side. Grading is in the transverse direction, with the properties being temperature-dependent. The main steps of the thermo-elastic modeling included deriving the partial differential equations for the temperatures and deflections in time and space, transforming them into ordinary differential equations using Laplace transformation, and finally using the inverse Laplace transformation to find the solutions. The effects of different parameters on the thermo-mechanical behavior of the beam are investigated, such as the convection coefficient and the heat source intensity and speed. The results show that temperatures, and hence the deflections and stresses increase with less heat convection from the beam surface, higher heat source intensity and low speeds.

• 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.

• Journal of the Optical Society of Korea
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• v.14 no.2
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• pp.127-130
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• 2010

We have developed an efficient electron beam (e-beam) source, a microcolumn, that can be used as a source module for of microscopy and its applications. To obtain a low operating voltage, a very sharp cold field electron emitter was developed by electrochemically etching a tungsten wire. Laser diffraction was used for the fabrication of high-quality electron lenses and for their precise alignment. The measurement of the e-beam currents, and SEM images captured by the microcolumn confirmed the potential of the device as a very good e-beam source.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.494-499
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• 2004

A ion source using inductively coupled plasma has been tested in order to test its feasibility as a high brightness ion source for focused ion beam. When operating the ion source with filter magentas in front of plasma electrode for a negative ion source, lower remittances are expected. Extracted beam remittances are measured with an Allison-type scanning device for various plasma parameters and extraction conditions. The normalized omittance has been measured to be around 0.2$\pi$mmmrad with beam currents of up to 0.55 ㎃. In particular, noting that multicusp magnets have a role in decreasing the remittance as well as increasing plasma discharge efficiency, transverse magnetic field has been confirmed to be a useful tool fur decreasing remittance via electron energy control.

• 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 Journal of the Acoustical Society of Korea
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• v.18 no.7
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• pp.75-79
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• 1999

The beam patterns of source array and changes in the far-field signatures are compared and analyzed each other in order to identify the seismic capability affected by the misfired source at the multi-channel seismic source array. In the primary pulse amplitude of far-field signature, the 66% of seismic capacity are sustained if approximately 40% of source are misfired among whole gun volume. When the sources with the same distances are misfired at the 154㎐, the beam width of the long- and wide-array which is identical regardless of arraying pattern. The beam width has a tendency to narrow now from 41 to 34 according to increase the volume of misfired source at the long-array beam pattern. Therefore, the source array of small volume are suitable for the shallow seismic survey because of producing adequate beam patterns with narrow beam width.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1600-1609
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• 2017

The accelerator-driven subcritical system (ADS) is driven by a neutron source from spallation reactions introduced by the injected proton beam. Part of the neutron source has energy as high as a few hundred MeV to a few GeV. The effects of high-energy source neutrons ($E_n$ > 20 MeV) are usually approximated by energy cut-off treatment in practical core calculations, which can overestimate the predicted proton beam current in the ADS design. This article intends to quantize this effect and propose a way to solve this problem. To evaluate the effects of high-energy neutrons in the subcritical core, two models are established aiming to cover the features of current experimental facilities and industrial-scale ADS in the future. The results show that high-energy neutrons with $E_n$ > 20 MeV are of small fraction (2.6%) in the neutron source, but their contribution to the source efficiency is about 23% for the large scale ADS. Based on this, a neutron source efficiency correction factor is proposed. Tests show that the new correction method works well in the ADS calculation. This method can effectively improve the accuracy of the prediction of the proton beam current.

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.17-21
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• 2010

Currently miniaturized electron-optical columns find their way into electron beam lithography systems. For better lithography process, it is required to make smaller spot size and longer working distance. But, the micro-columns of the multi-beam lithography system suffer from chromatic and spherical aberration, even when the electron beam is exactly on the symmetric axis of the micro-column. The off-axis error of the electron emitting source is expected to become worse with increasing off-axis distance of the focusing spot. Especially the electron beams far from the system optical axis have a non-negligible asymmetric intensity distribution in the micro-column. In this paper, the effect of the off-axis e-beam source is analyzed. To analyze this effect is to introduce a micro-column model of which the e-beam emitting source is aligned with the center of the electron beam by shifting them perpendicular to the system optical axis. The presented solution can be used to analysis the performance of the multi-electron-beam system. The performance parameters, such as the working distances and the focusing position are obtained by the computational simulations as a function of the off-axis distance of the emitting source.