• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.723-724
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• 2004

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.935-940
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• 1998

The Korea Superconducting Tokamak Research (KSTAR) tokamak will have 6 MW of radio-frequency (rf) heating in the ion cyclotron range of frequencies (ICRF). The response of the antenna to the heat loads is analyzed and the resulting stresses in the Faraday shield during the normal operation is calculated. Various heat loading conditions including in the analyzes are the heat loads from the plasma, the ripple-trapped beam particles and the rf loss.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.1078-1079
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.178-178
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• 2007

• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.180-180
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• 2007

• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.179-179
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• 2007

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.201-208
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• 2001

The high power RF transmission line components are required for transmitting MW level RF power continuously in RF heating and current drive system which heat the plasma and produce plasma current in fusion reactor The liquid stub and phase shifter is proposed as the superior to the conventional stub and phase shifter. Experimental results show that they are reliable and easy to operate compared to the conventional stub and phase shifter. There is no distortion of reflected power during the raising of the liquid level. RF breakdown voltage is over 40kV. Temperature increment of the liquid is expected not to be severe. These results verify that the liquid stub and phase shifter can be used reliably in the high power continuous RF facilities.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.319-319
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• 2011

KSTAR ICRF 안테나 장치에서 외곽 플라즈마 밀도분포는 고주파 출력이 내부로 전달되는 효율을 위해 중요하게 다루어 진다. 따라서 1.5T의 자기장에서 플라즈마에 간섭없이 0~$10^{14}/cm^3$의 외곽 플라즈마 밀도분포를 측정할 수 있는 Q-band 대역의 x-mode 반사계가 필요 하였다. 헬리콘 플라즈마는 $10^{13}/cm^3$ 이상의 높은 플라즈마 밀도를 수 kW 이내의 rf power와, 수 MHz 대역의 고주파원을 사용하여 높은 에너지 효율로 얻을 수 있다. 이때 높은 플라즈마 밀도는 외곽 플라즈마 밀도 와 비슷하여 제작한 반사계를 테스트 할 수 있다. 본 연구에서는 x-mode microwave 반사계를 제작하고, 1kW rf power와 10MHz 고주파원으로 헬리콘 플라즈마를 생성하여 정전 탐침으로 진단하였고, 반사계의 Q-band대역의 주파수를 가변 하여 반사되어 나오는 마이크로파의 beat 주파수를 통해 밀도 분포를 얻어서 정전탐침과 비교 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.323-323
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• 2010

핵융합 플라즈마에서 연료 주입과 불순물 제거는 매우 중요한 과제로서 이를 해결하기 위한 방법으로 Glow Discharge Cleaning, ICRF Wall Conditioning과 같은 방법들을 이용한다. 최근 중국의 EAST 토카막 등에서 이러한 방법보다 보다 간소하고 효과적인 방법의 일환으로 수십에서 수백 kHZ의 HF 대역의 교류전원을 이용하여 플라즈마를 발생하고 이를 토카막 벽면의 Wall Conditioning에 적용하는 방법을 시도했다. 본 연구는 이러한 HF 플라즈마를 KSTAR 토카막 Wall Conditioning에 걱용하기 위한 예비 실험으로 선형 플라즈마 발생장치에 30kHZ 2kW급의 HF 파워를 이용하여 플라즈마를 발생하였다. 운전 압력에 따라 전압과 전류 특성을 파악하고 Langmuir probe를 이용하여 플라즈마 밀도와 온도들의 parameter를 측정하였다. 본 발표에서는 구체적인 플라즈마 발생장치를 소개하고 플라즈마 방전 특성과 parameter들을 보고할 예정이다.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4102-4110
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• 2022

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m². Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 ℃, much below the permissible value of tungsten material (~1200 ℃). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-active-multijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5° toroidally from the 4.6 GHz LH system and is not magnetically connected.