• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.586-586
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• 2012

The vuv spectrometer for ITER main plasma measurement is designed as a five-channel spectral system. To develop and verify the design, a two-channel prototype system was fabricated with No. 3 (14.4-31.8 nm) and No. 4 (29.0-60.0 nm) among the five channels. For test of the prototype system, a hollow cathode lamp is used as a light source. The system is composed of a collimating mirror to collect the light from source to slit, and two holographic diffraction gratings with toroidal geometry to diffract and also to collimate the light from the common slit to detectors. The overall system performance was verified by comparing the measured spectral resolutions with the calculated spectral resolutions. And we also have developed liquid jet target system. This study is about a neutron generator, which is designed to overcome many of the limitations of traditional beam-target neutron generators by utilizing a liquid target. One of the most critical aspects of the beam-target neutron generator is the target integrity under the beam exposure. A liquid target can be a good solution to overcome damage to the target such as target erosion and depletion of hydrogen isotopes in the active layer, especially for the ones operating at high neutron fluxes and maintained relatively thin with no need for water cooling. In this study, liquid target containing hydrogen has been developed and tested.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.145-145
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• 2011

Recently, multi-hole electrode RF capacitively coupled plasma discharge is being used in the deposition of microcrystalline silicon for thin film solar cell to increase the speed of deposition. To make efficient multi-hole electrode RF capacitively coupled plasma discharge, the hole diameter is to be designed concerning the plasma parameters. In past studies, the relationship between plasma parameters such as pressures and gas species, and hole diameter for efficient plasma density enhancement is experimentally shown. In the presentation, the relationship between plasma deriving frequency and hole diameter for efficient multi-hole electrode RF capacitively coupled plasma discharge is shown. In usual capacitively coupled plasma discharge, plasma parameter, such as plasma density, plasma impedence and plasma temperature, change as frequency increases. Because of the change, the optimum hole diameter of the multi-hole electrode RF capacitively coupled plasma for high density plasma is thought to be modified when the plasma deriving frequency changes. To see the frequency effect on the multi-hole RF capacitively coupled plasma is discharged and one of its electrode is changed from a plane electrode to a variety of multi-hole electrodes with different hole diameters. The discharge is derived by RF power source with various frequency and the plasma parameter is measured with RF compensated single Langmuir probe. The shrinkage of the hole diameter for efficient discharge is observed as the plasma deriving frequency increases.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.48-53
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• 2003

The high temperature melting test for nonflammable wastes using a plasma torch was conducted. The AP-200L hollow cathode type plasma torch was installed at the pilot plasma melting furnace in NETEC. The surrogates were prepared to simulate concrete, soil and their mixture with steel. The experimental conditions such as feeding rate, the distance between melts surface and torch nozzle, torch rotation speed, gas flow rate and pressure in the furnace were decided. Basic parameters such as temperatures of cooling waters, off-gas and torch power were measured. The vitrified samples were analyzed by SEM/EDS.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.155.2-155.2
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• 2011

We present development of the calibration system for IGRINS (the Immersion GRating Infrared Spectrograph). We mainly use Th-Ar and U hollow cathode lamp as the spectral calibration source and telluric features can be used additionally. For the flat source, we selected a 3000K tungsten halogen lamp with 2 inch integrating sphere. From Light Tools simulation, the result flat image through calibration optics satisfied <1% flatness error requirement. We also present mechanical design of calibration box that will be attached on the IGRINS dewar. Three moving stages are designed to perform switching mechanism between all of the observing modes - target observation, flat, precision RV measurement, and spectro-polarimetric observation.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.445-445
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• 2010

전자빔 플라즈마는 전자 소스 부분, 전자 가속 부분, 전자빔 플라즈마 생성 부분으로 구성되어 있다. Hollow cathode형태의 전극과 anode역할을 하는 안쪽 그리드로 DC방전을 일으켜 전자를 발생시키고 안쪽 그리드와 바깥쪽 그리드 사이의 전압차이로 전자를 가속시킨다. 가속된 전자는 중성 가스와 비탄성 충돌을 하게 되어 플라즈마가 생성이 된다. 이러한 방식으로 생성된 전자빔 플라즈마는 플라즈마 형성 공간에 전기장이 없어 전자가 에너지를 얻을 수 없으며, 중성가스와 비탄성 충돌로 인해 에너지를 쉽게 잃기 때문에 전자 온도가 낮게 유지가 된다. 일반적으로 바깥쪽 그리드는 접지를 시켜 전자빔 플라즈마를 발생시키지만, DC 전원을 연결하여 양의 전압을 걸어주면 전자빔 플라즈마의 밀도는 크게 변하지 않고 전자 온도가 급격히 상승하게 된다. Ar 전자빔 플라즈마의 경우 바깥쪽 그리드가 접지에 연결되었을 경우 전자 온도는 0.5eV 정도인 것에 비해 바깥쪽 그리드에 20V DC전압을 걸어주면 전자 온도가 1eV 정도로 크게 증가를 한다. 그 이유는 바깥쪽 그리드 전압의 영향으로 전자빔 플라즈마 전위가 상승하게 되고 그 결과 높은 에너지를 가진 전자가 플라즈마 전위에 갇히게 되기 때문이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.146-147
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• 2011

Processing a large area substrate for liquid crystal display (LCD) or solar panel applications in a capacitively coupled plasma (CCP) reactor is becoming increasingly challenging because of the size of the substrate size is no longer negligible compared to the wavelength of the applied radio frequency (RF) power. The situation is even worse when the driving frequency is increased to the Very High Frequency (VHF) range. When the substrate size is still smaller than 1/8 of the wavelength, one can obtain reasonably uniform process results by utilizing with methods such as tailoring the precursor gas distribution by adjustingthrough shower head hole distribution or hole size modification, locally adjusting the distance between the substrate and the electrode, and shaping shower head holes to modulate the hollow cathode effect modifying theand plasma density distribution by shaping shower head holes to adjust the follow cathode effect. At higher frequencies, such as 40 MHz for Gen 8.5 (2.2 m${\times}$2.6 m substrate), these methods are not effective, because the substrate is large enough that first node of the standing wave appears within the substrate. In such a case, the plasma discharge cannot be sustained at the node and results in an extremely non-uniform process. At Applied Materials, we have studied several methods of modifying the standing wave pattern to adjusting improve process non-uniformity for a Gen 8.5 size CCP reactor operating in the VHF range. First, we used magnetic materials (ferrite) to modify wave propagation. We placed ferrite blocks along two opposing edges of the powered electrode. This changes the boundary condition for electro-magnetic waves, and as a result, the standing wave pattern is significantly stretched towards the ferrite lined edges. In conjunction with a phase modulation technique, we have seen improvement in process uniformity. Another method involves feeding 40 MHz from four feed points near the four corners of the electrode. The phase between each feed points are dynamically adjusted to modify the resulting interference pattern, which in turn modulate the plasma distribution in time and affect the process uniformity. We achieved process uniformity of <20% with this method. A third method involves using two frequencies. In this case 40 MHz is used in a supplementary manner to improve the performance of 13 MHz process. Even at 13 MHz, the RF electric field falls off around the corners and edges on a Gen 8.5 substrate. Although, the conventional methods mentioned above improve the uniformity, they have limitations, and they cannot compensate especially as the applied power is increased, which causes the wavelength becomes shorter. 40 MHz is used to overcome such limitations. 13 MHz is applied at the center, and 40 MHz at the four corners. By modulating the interference between the signals from the four feed points, we found that 40 MHz power is preferentially channeled towards the edges and corners. We will discuss an innovative method of controlling 40 MHz to achieve this effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.254-254
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• 2013

마그네트론 스퍼터링은 그 단순한 구조로 인하여 신뢰성과 확장성이 높은 기술이다, 이로 인해 DLC, ITO 등의 산업 분야에서 많이 사용하는 박막 공정 기술이다. 하지만 인듐과 같은 희토류 금속의 가격이 최근 상승함에 따라 나타난 낮은 타겟 효율성의 문제와 낮은 파워 밀도로 인한 기판의 추가적인 bias 추가에 따른 비용상승, 그리고 reactive 스퍼터링 시 낮은 증착률 등의 문제점들 또한 존재한다. 이러한 단점들을 해결하기 위해 많은 연구들이 이루어 졌으며, 높은 파워 밀도를 위해 High power Impulse Plasma Magnetron Sputtering (HIPIMS) 기술과 타겟 사용률을 높이기 위한 High Target Utilization Sputtering (HITUS) 등의 기술 등이 개발되었다. 본 연구에서는 직류 전원을 사용한 High density Plasma Sputtering System (HIPASS)이라 명하는 고밀도 원거리 플라즈마 소스를 이용한 스퍼터링 이용해 증착한 박막의 특성을 연구 하였다. Hollow cathode discharge에서 발생한 고밀도 플라즈마가 외부 유도 자장 코일에 의하여 타겟 표면까지 도달하게 되며, 스퍼터링 타겟의 고전압 bias에 의해 플라즈마 이온들이 가속이 이루어져 스퍼터링 공정이 이루어 지게 된다. 본 연구의 공정에서 타겟 사용 효율은 최대 90%까지 이며, 원거리 플라즈마 소스에서의 이온으로 스퍼터링을 실시함으로 인해 스퍼터링 전압과 전류의 독립적인 조절이 가능 하다. 본 연구에서 HIPASS을 이용하여 기판에 추가적인 전압 인가 없이 Ti 타겟과 아르곤/질소 혼합가스를 사용하여 TiN 박막을 증착 하였다. TiN의 증착률은 약 44 nm/min였으며, 이 박막의 XRD 분석 결과 TiN (111), (200), (220) 면들이 관찰이 되었다. 높은 스퍼터링 입자 에너지에서 증착 된 TiN 박막에서 우선적으로 나타나는(200)과 (220) 면들이, 본 실험에서는 기판에 추가적인 전압인가 없이도 우선방위 성장을 보였다. 이 박막의 micro-hardness 측정 결과 약 34.7 GPa이며, 이는 UBM 이나 HIPIMS에서 보여주는 결과에 준하거나 그 이상의 수치이다. 이와 같은 결과는 본 연구에서 사용한 HIPASS 증착 공정이 높은 스퍼터링 입자 에너지를 가지기에 고밀도의 TiN 박막이 증착 된 결과로 볼 수 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.540-543
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• 2011

This work is devoted to an experimental investigation on conceptual design of dual consecutive stage micro plasma thruster (${\mu}PT$). Optimization study on the thruster configuration has been performed for various electrode gap distances from 1 mm to 2 mm and the hole diameter from 0.3 mm to 2 mm depending on desired operating conditions and corresponding nozzle design requirement. The operation of ${\mu}PT$ at low pressure from $10^{-1}$ Torr to $10^{-4}$ Torr and at various argon flow rates ranging from 5 sccm to 300 sccm has been studied to understand the physic of plasma and the gas dynamics in details. The specific impulse can reach up to 3000-4000 seconds at low power consumptions from 1 to 5 W. Image of exhaust plume from ${\mu}PT$ will be provided and electrical characteristics is also mentioned in this paper.

• Journal of the Korean Chemical Society
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• v.38 no.1
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• pp.34-40
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• 1994

First observation of uranium using a diode laser was published recently. The experiment was performed by the optogalvanic spectroscopy using diode lasers. A laser source causes the current change in a hollow cathode discharge lamp when metal atoms in plasma absorb the diode laser light. The optogalvanic signal is collected by detecting the current change. This work is the extended investigation of our previous research, the uranium detection using a diode laser. New electronic transitions of uranium and thorium in 775∼850 nm were investigated using diode lasers. In addition, the Rb(Ⅰ) optogalvanic spectra at 780.02 nm and 794.76 nm were studied. The Rb(Ⅰ) spectrum at 780.02 nm showed the isotopic features and hyperfine splittings. This work provides a key idea that the diode lasers are useful in the specrochemical analysis of the radioactive actinides that have a rich spectrum with transitions which can be easily reached with AlGaAs diode lasers. Also, this study shows that the diode lasers can be an important tool to find the spectroscopic parameters of actinides and rare earth elements which have not known.

• Analytical Science and Technology
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• v.11 no.1
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• pp.1-7
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• 1998

This study focuses on developing a controlling and analyzing software for the portable atomic emission spectrometer equipped with an electrothermal vaporizer(ETV) that can perform the in-situ trace analysis of heavy metal ions dissolved in water. The software works well for a notebook PC and it is exclusively developed for the real time analysis with a line filter and a photomultiplier light detector. The program is designed to operate under Windows 95 environment and either Korean or English can be used as a main language. The Delphi 2.0 language software is mainly used for programing. The program is designed to make a calibration curve and the system users can get the analytical data in a short time. And a final report can be generated without having difficulties. This software can be easily modified for other analytical atomic spectrometers.