• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.180-180
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• 2000

Plasma source ion implantation is a new doping technique for the formation of shallow junction with the merits of high dose rate, low-cost and minimal wafer charging damage. In plasma source ion implantation process, the wafer is placed directly in the plasma of the appropriate dopant ions. Negative pulse bias is applied to the wafer, causing the dopant ions to be accelerated toward the wafer and implanted below the surface. In this work, inductively couples plasma was generated by anodized Al antenna that was located inside the vacuum chamber. The outside wall of Al chamber was surrounded by Nd-Fe-B permanent magnets to confine the plasma and to enhance the uniformity. Before implantation, the wafer was pre-sputtered using DC bias of 300B in Ar plasma in order to eliminate the native oxide. After cleaning, B2H6 (5%)/H2 plasma and negative pulse bias of -1kV to 5 kV were used to form shallow p+/n junction at the boron dose of 1$\times$1015 to 5$\times$1016 #/cm2. The as-implanted samples were annealed at 90$0^{\circ}C$, 95$0^{\circ}C$ and 100$0^{\circ}C$during various annealing time with rapid thermal process. After annealing, the sheet resistance and the junction depth were measured with four point probe and secondary ion mass spectroscopy, respectively. The doping uniformity was also investigated. In addition, the electrical characteristics were measured for Schottky diode with a current-voltage meter.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.106.1-106.1
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• 2013

When strong static magnetic field is applied to the TMP, it is expected that the presence of the magnetic field might retard the velocity of the blades which results in the change of the pumping speed of the TMP. However, such effect of the magnetic field on the TMP has not been well characterized. Thus, under the strong magnetic field, monitoring pumping speed as well as generated heat, pressure, and vibration of the TMP may be an important issue to understand the magnetic field tolerance of the TMP and the development of magnetic shielding technique for the key components of the pump. For this purpose, magnetic field generation system to the vertical direction by a circular current source was firstly designed and suggested [K. Baik et al., 44th Annual Conf. KVS, 22(1), 153, (2012)]. In the current study, another magnetic field generation systems are presented to apply the magnetic field to the horizontal and radial directions by the rectangular current sources and the permanent magnets respectively. Such systems were made to generate at least 50 Gauss of magnetic field along the vertical direction and at least 25 Gauss of magnetic field along the horizontal or radial direction. Current study introduces the evaluation system of the magnetic field along the vertical, horizontal, and radial directions and presents the measured experimental results of the magnetic field when such systems are combined with the equipment where TMP will be installed.

• Smart Structures and Systems
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• v.7 no.5
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• pp.379-392
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• 2011

This paper presents a multi-functional system, consisting of a magnetorheological (MR) damper and an electromagnetic induction (EMI) device, and its applications in stay cables. The proposed system is capable of offering multiple functions: (1) mitigating excessive vibrations of cables, (2) estimating cable tension, and (3) harvesting energy for wireless sensors used health monitoring of cable-stayed bridges. In the proposed system, the EMI device, consisting of permanent magnets and a solenoid coil, can converts vibration energy into electrical energy (i.e., induced emf); hence, it acts as an energy harvesting system. Moreover, the cable tension can be estimated by using the emf signals obtained from the EMI device. In addition, the MR damper, whose damping property is controlled by the harvested energy from the EMI device, can effectively reduce excessive cable vibrations. In this study, the multi-functionality of the proposed system is experimentally evaluated by conducting a shaking table test as well as a full-scale stay cable in a laboratory setting. In the shaking table experiment, the energy harvesting capability of the EMI device for wireless sensor nodes is investigated. The performance on the cable tension estimation and the vibration mitigation are evaluated using the full-scale cable test setup. The test results show that the proposed system can sufficiently generate and store the electricity for operating a wireless sensor node twice per day, significantly alleviate vibration of a stay cable (by providing about 20% larger damping compared to the passive optimal case), and estimate the cable tension accurately within a 2.5% error.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.366-371
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• 1995

High performance magnetic materials are characterized by the combination of outstanding magnetic properties and optimized microstructures, e.g., nanocrystalline composites of multilayers and small particle systems. The characteristic parameters of the hysteresis loops of these materials vary over more than a factor of $10^{6}$ with optimum values for the coercive field of several Tesla and permeabilities of $10^{6}$. Within the framework of the computational micromagnetism (nanomagnetism) using the finite element method the upper and lower bounds of the coercive field of different types of grain ensembles and multilayers have been determined. For the case of nanocrystalline composites the role of grain size, exchange and dipolar coupling between grains and the degree of grain alignment will be discusses in detail. It is shown that the largest coercivities are obtained for exchange decoupled grains, whereas remanence enhancing requires exchange coupled grains below 20 nm. For composite permanent magnets based on $Nd_{2}Fe_{14}B$ with an amount of ~ 50% soft $\alpha$-Fe-phase coercivities of ${\mu}_{0}H_{c}=0.75\;T$, a remanence of 1.5 T and an energy product of $400\;kJ/m^{3}$ is expected. In nanocrystalline systems the temperature dependence of the coercivity is well described by the relation ${\mu}_{0}H_{c}=(2\;K_{1}/M_{s}){\alpha}-N_{eff}{\mu}_{0}M_{s}$, where the microstructural parameters $\alpha$ and $N_{eff}$ take care of the short-range perturbations of the anisotropy and $N_{eff}$ is related to the long-range dipolar interactions. $N_{eff}$ is found to follow a logarithmic grain size size dependence ${\mu}_{0}H_{c}=(2\;K_{1}/M_{s}){\alpha}-N_{eff}(\beta1nD){\mu}_{0}M_{s}$. Several trends how to achieve the ideal situation $\alpha$->1 and $N_{eff}$->1->0 will be discussed.

• Resources Recycling
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• v.27 no.6
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• pp.11-22
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• 2018

Magnetic separators has been used in the mining and the recycling fields in general, and is still applied in wide variety of fields. It is classified into the equipments for separating coarse ferrous scrap from non-ferrous materials and the equipments for concentrating fine ferromagnetic particles below 3mm. Magnetic separation equipments for concentrating fine materials also falls into two categories of low intensity and high intensity magnetic separators. The former is used for ferromagnetic materials but also paramagnetic materials of high magnetic susceptibility, and the latter for paramagnetic materials of lower magnetic susceptibility. Both low and high intensity magnetic separators could be utilized either dry and wet. Recently, the High gradient magnetic separators(HGMS) used in the range of less than 0.7 tesla has been gradually replaced by the magnetic separator made of rare earth permanent magnets commercialized in the 1980s. In addition, the expansion of nanotechnology in terms of synthetic magnetic materials in the environmental and biological fields is expected to contribute positively to the development of magnetic separation technology.

• 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 Korean Vacuum Society
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• v.10 no.4
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• pp.431-439
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• 2001

In this paper, the a-Diamond films were synthesized using filtered vacuum arc source (FVAS), FVAS was composed of a torus structure with bending angle of 60 degree. The radius of torus was 266 mm, the radius of plasma duct was 80 mm and the total length was 600 mm. The magnet parts were composed of one permanent magnet and five solenoid magnets. The plasma duct was electrically isolated from the ground so that a bias voltage could be applied. The baffles inside plasma duct were installed in order to prevent the recoil effect of macro-particles. Cathode was made of graphite with 80 mm in diameter. The effects of solenoid magnet on plasma extraction were investigated by computer simulation and experiment using Taguchi's methode. The source and extraction magnet affected the arc stabilization. The extraction beam current was maximized with low value of the source magnet current and high value of the filtering magnet current. The beam current density was 3.2 mA/$\textrm{cm}^2$ and average deposition rate was 5 $\AA$/sec when the currents of arc discharge, source, extraction, bending, deflection and outlet magnet were 30 A, 1 A, 3 A, 5 A, 5 A, and 5 A, respectively. The beam current density and the efficiency of beam transportation were increased with the positive bias voltage of the plasma duct.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.18-22
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• 2017

The purpose of this study was to present an improved method of dose modulation over the increase of build-up for existing 6 MV photon beam. Two neodymium permanent magnets with a strength of 0.5 T (Tesla) were applied with a magnetic field perpendicular to the photon beam. The effects of dose on build-up region with or without the magnetic field were measured according to the magnet-to-magnet distance (MMS) and the magnet-to-surface distance (MSD). For MMS = 6 cm and MSD = 2.5 cm, $D_{0mm}$, $D_{2mm}$, $D_{5mm}$, and $D_{10mm}$ showed improved doses of 6.8 %, 14.6 %, 6.9 %, and 2.1 %, respectively, as compared with 6 MV open beam. In this study, the device with low strength magnetic field can be applied directly to the outside of the human body when the target volume located close to the skin is delivered with radiation. It is expected that the method of build-up modulation using a low strength magnetic field will be feasible in the clinical applications.

• Journal of Korean Society of Disaster and Security
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• v.11 no.2
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• pp.53-60
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• 2018

To diagnosis the local damages of the steel plates, magnetic flux leakage (MFL) method that is known as a adaptable non-destructive evaluation (NDE) method for continuum ferromagnetic members was applied in this study. To analysis the sensitivity according to thickness of steel plate in MFL method based damage diagnosis, several steel plate specimens that have different thickness were prepared and three depths of artificial damage were formed to the each specimens. To measured the MFL signals, a MFL sensor head that have a constant magnetization intensity were fabricated using a hall sensor and a magnetization yoke using permanent magnets. The magnetic flux signals obtained by using MFL sensor head were improved through a series of signal processing methods. The capability of local damage detection was verified from the measured MFL signals from each damage points. And, the peak to peak values (P-P value) extracted from the detected MFL signals from each thickness specimen were compared each other to analysis the MFL based local damage detection sensitivity according to the thickness of steel plate.