• Applied Science and Convergence Technology
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• v.24 no.4
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• pp.84-89
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• 2015

The base pressure and outgassing rate of a mild steel chamber were measured and compared to those of a stainless steel chamber. A combined sputter-ion and non-evaporable getter pump with a nominal pumping speed of 490 l/s generated the base pressure of $2.7{\times}10^{-11}$ mbar in the mild steel chamber and $1.2{\times}10^{-10}$ mbar in the stainless steel chamber. The rate-of-rise measurements show that the mild steel has an extremely low outgassing rate of $2.6{\times}10^{-13}$ mbar $ls^{-1}cm^{-2}$, which is about one-order of magnitude smaller than the outgassing rate of the stainless steels. Vacuum annealing of the mild steel at $850^{\circ}C$ reduced the outgassing rate further to $8.8{\times}10^{-14}$ mbar $ls^{-1}cm^{-2}$, which was comparable to the outgassing rate of a heat treated stainless steel for extreme-high vacuum use.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.70.1-70.1
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• 2015

The facility for RAON superconducting heavy-ion accelerator at a beam power of up to 400 kW will be produced rare isotopes with two electron cyclotron resonance (ECR) ion sources. Highly charged ions generated by the ECR ion source will be injected to a superconducting LINAC to accelerate them up to 200 MeV/u. During the acceleration of the heavy ions, a good vacuum system is required to avoid beam loss due to interaction with residual gases. Therefore ultra-high vacuum (UHV) is required to (i) limit beam losses, (ii) keep the radiation induced within safe levels, and (iii) prevent contamination of superconducting cavities by residual gas. In this work, a RAON vacuum design for all the accelerator system will be presented along with Monte Carlo simulation of vacuum levels in order to validate the vacuum hardware configuration, which is needed to meet the baseline requirements.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1566-1570
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• 2007

[ $SF_6$ ] gas circuit breakers are widely used for short circuit current interruption in EHV(Extra High Voltage) or UHV(Ultra High Voltage) power systems. To develop $SF_6$ gas circuit breakers, the arc resistance value is necessary to compare experimental results to numerical ones. The arc resistance value can be obtained from a breaking test with a $SF_6$ gas circuit breaker. The direct testing or synthetic testing facility is widely used to verify the breaking ability for $SF_6$ gas circuit breakers. We employed the simplified synthetic testing facility to test a $SF_6$ gas circuit breaker prototype. The arc resistance characteristic was measured and calculated under the various experimental conditions. This arc resistance value can be used for verifying the numerical results from arc simulation in a circuit breakers.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.3
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• pp.157-171
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• 1994

A scanning tunneling microscope has been built, which can resolve atomic arrangements of conductors and semiconductors in ultra high vacuum below $10^{-11}$ Torr. Its background and operational principles are reviewed and the guide lines in building the scanning tunneling microscope are shown. The results of measurements for highly oriented pyrolytic graphite and Si(111) surface are presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.3
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• pp.139-144
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• 2005

[ $SF_6$ ] gas circuit breakers are widely used short circuit current interruption in EHV or UHV power system. For a $SF_6$ gas circuit breaker development, the $SF_6$ gas velocity measurement is necessary during $SF_6$ circuit breaker's trip operation. Small-gap flashover characteristics are used for this measurement. So, small-gap measuring system which will be used to develope GCB should be developed. This study shows the characteristic analysis and experimental results of small-gap measuring system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.776-779
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• 2001

The main objective of this paper is to design and mechanical strength analysis of UHV(Ultra High Voltage) suspension insulator. One of the important properties required for suspension insulators is mechanical strength under tensile load. The cement and porcelain part are express according to change of pin head type an aspect mechanical stress. These insulators are designed and produced by using the computer analysis of mechanical, electrical and electrical stresses together with the technical know-how accumulated from long years of study into every respect of insulators.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.447-450
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• 2002

Recently polymeric insulators and arresters are being used for outdoor high voltage applications. Polymeric insulators for transmission line have significant advantages over porcelain and glass insulators, especially for ultra-high voltage(UHV) transmission lines. Their advantages are light weight, vandalism resistance and hydrophobicity. Polymeric insulator kind are a relatively new technology, but their expected life is still unknown. In this paper, the material property for polymeric insulating material such as silicone rubber and EPBM is investigated by cross-link time and the relation between tracking resistance and W resistance is analyzed by IEC 60587 and W aging experiment.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.475-477
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• 2002

본 논문에서는 765kV 송전선로의 일부구간에서 발생되고 있는 풍소음의 대책으로 개발된 저풍소음 도체를 소개하고 이 도체방식을 개발하기 위해 수행된 전기환경장해 및 풍소음 저감 영향에 대한 시험결과를 제시하고 있다. 저풍소음 도체는 우수한 풍소음 저감기능을 가지면서도 기존 전선에 비해 추가적인 전기환경 문제가 발생되지 않아야 하는데, 기존 전선과 달리 전선 주위에 돌기부가 있어서 전계 집중에 따른 환경장해 발생의 우려가 있다. 이러한 이유 때문에 전기환경 모의시험설비인 코로나 케이지를 이용한 코로나 발생 특성 시험을 수행하여 환경설계기준 만족 여부를 확인하였으며, 실규모 시험선로를 이용한 장기 실증시험을 실시하여 송전선로 주변에서 실제 발생 가능한 라디오 장해와 같은 전기환경 장해량에 대한 평가를 실시하여 풍소음 저감효과와 환경설계기준에 만족하는 결과를 얻을 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.63-69
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• 1994

The Ultrahigh Vacuum Electron Cyclotron Resonance Chemical Vapor Deposition(UHV-ECRCVD) system whose base pressure is 1${\times}10^{9}$ torr has been constructed. In-situ cleaning prior to the epitaxial growth was carried out at 56$0^{\circ}C$ by ECR generated uniform hydrogen plasma whose density is $10^{10}/cm{3}$. The natural oxide was effectively removed without damage by applying positive DC bias(+10V) to the substrate. RHEED(Reflection High Energy Electron Diffraction) analysis has been used to confirm the removal of the surgace oxide and the streaky 2$\times$1 reconstruction of the Si surface, and the suppression of the substrate damage is anaylized by X-TEM(cross-sectional Transmission Electron Microscopy). Surface cleaning technique by ECR hydrogen plasma confirmed good quality epitaxial growth at low temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.173.2-173.2
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• 2014

Thin nitride thin films were synthesized by reactive radio-frequency magnetron sputtering in the ultra high vacuum (UHV) chamber. To control the characteristics of thin films, tin nitride thin films were obtained various argon and nitrogen gas mixtures, especially low nitrogen gas ratios. Tin nitride thin films were analyzed with alpha step, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and 4 point probe measurement. The result of alpha step and SEM showed that the thickness of thin nitride thin films were decreased with increasing nitrogen gas ratios. The metallic tin structure was decreased and the amorphous tin nitride structure were observed by XRD with higher nitrogen gas ratios. The oxidation state of tin and nitride were studied with high resolution Sn 3d and N 1s XP spectra.