• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.149-149
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• 2012

We introduce Helicon discharge plasma source and Laser Thomson scattering system recently finished an installation in KRISS. Laser Thomson scattering method is promising for diagnostics in Helicon plasma because a measurement by electrical probe typically used has significant errors due to the gyromotion of electrons induced by high magnetic field. However, we found that LTS is affected by magnetic field so that we applied the normalization method for processing data and the results show a clear Maxwellian distribution at various conditions of magnetic field and RF power at low energy part without distortion.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.144-144
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• 2011

Diagnostics of plasma density and temperature play an important role for monitoring plasma processing and Laser Thomson scattering is a one of the most accurate diagnostic technique for measuring plasma density and temperature because of none-perturbation to plasma among various diagnostic techniques invented to measure plasma density and temperature. I will briefly review Laser Thomson scattering experiment performed in KRISS and difficulties for measuring the electron velocity distribution such as Gaussian due to low signal-to-noise ratio with showing results that we got until now. This work is an intermediate step in a process that we will get a reliable data which shows physical phenomenon of plasma compared with other diagnostic techniques and results.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.521-521
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• 2013

Collective Thomson scattering (CTS) system is being developed in KAERI based on high power gyrotrons. CTS is a promising diagnostic method to measure fast ion distributions and potentially the fusion product alpha particles in magnetically confined plasmas. By utilizing millimeter-waves from high power gyrotrons as a probing beam, spatially and temporally resolved 1-D ion velocity distributions can be obtained from the scattered radiation with less scattering geometrical constraints. The pulse modulation of gyrotrons enables to separate scattering signal from ECE background noises. The feasibility was assessed with the calculation of spectral density functions under the condition of KSTAR plasmas. Further CTS system requirements are also discussed.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.107-112
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• 2001

Laser Thomson scattering measurements of electrom temperature and density in a neutral loop discharge (NLD) plasma were performed in order to reveal the electron behavior around the neutral loop (NL). The experimental results were examined by using a simulation model that included effects of a three dimensional electromagnetic field with spatial decay of the RF electric field, and the limitation of the spatial extent of the electron motion and collision effect. From the experiments and modeling of the electron behavior, it was found that NLD plasma posses the electron temeprature $T_{e}$ and density ne peaks around the NL is essential for the formation of plasma. Also, the optimum condition of plasma production could be simply estimated by the calculation of $U_{av}$ and $F_{0}$././.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.525-525
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• 2013

Low temperature plasma diagnosis is one of the big issues in laboratory scale or processing industry. One of the most powerful techniques of plasma diagnostics is the use of the scattering of electromagnetic radiation from the plasma. Electron temperature and density are important parameters for understanding the information of plasmas in the plasma processing industry. Laser scattering experiments on plasma can provide a substantial amount of information about plasma parameters such as the electron density ne, the electron temperature Te, and the neutral density nn and temperature Tn. Thomson scattering spectroscopy is used several method, in accordance with detector type. Commonly, Thomson scattering is used several notch filter to separate expanded wavelength. Since using a spectrometer with surface relief grating or notch filter, the system of the measurement will be complicated and bigger. In this study, using VPHG (Volume Phase Holographic Grating) in order to install the simple and cheap system. VPHG has the advantage of the system installation, because it can be Transmission Type. The diffraction efficiency and dispersion angle of VPHG is higher than the surface relief grating relatively. For a wavelength and bandwidth selection, Using a slit or mask to select a rejection wavelength instead of notch filter.

• Journal of The Korean Astronomical Society
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• v.40 no.1
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• pp.1-7
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• 2007

About 10 percent of quasars are known to exhibit deep broad absorption troughs blueward of prominent permitted emission lines, which are usually attributed to the existence of outflows slightly above he accretion disk around the supermassive black hole. Typical widths up to 0.2c of these absorption roughs indicate the velocity scales in which special relativistic effects may not be negligible. Under he assumption of the ubiquity of the broad absorption line region in quasars, the broad emission line flux will exhibit Thomson scattered components from these fast outflows. In this paper, we provide our Monte Carlo calculation of linear polarization of singly Thomson scattered line radiation with the careful considerations of special relativistic effects. The scattering region is approximated by a collection of rings that are moving outward with speeds ${\upsilon}=c{\beta}<0.2c$ near the equatorial plane, and the scattered line photons are collected according to its direction and wavelength in the observer's rest frame. We find that the significantly extended red tail appears in the scattered radiation. We also find that the linear degree of polarization of singly Thomson scattered line radiation is wavelength-dependent and hat there are significant differences in the linear degree of polarization from that computed from classical physics in the far red tail. We propose that the semi-forbidden broad emission line C III]1909 may be significantly contributed from Thomson scattering because this line has small resonance scattering optical depth in the broad absorption line region, which leads to distinct and significant polarized flux in this broad emission line.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.212-213
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.154.1-154.1
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• 2016

ITER 내부 플라즈마 진단에 대한 연구는 활발히 이루어지고 있다. 그 중에서도 광학 시스템을 이용한 진단방법으로 OES, Bolometer, Stark effects, Thomson scattering이 주로 연구되고 있다. 이러한 방법을 구현하기 위해서는 핵융합로 내부에 first mirror 설치가 필수적이다. 그러나 노 내부에서 발생한 플라즈마에 의한 부식과 증착 및 광 소스에 의한 first mirror 표면 손상이 현재 ITER 주요 난제중 하나로 꼽히고 있다. 이는 추후 건설될 DEMO와 핵융합로 건설을 위해서도 필요한 연구이다. 그러나 국내에서는 이러한 연구가 거의 진행되고 있지 않다. 이에 따라 Thomson scattering 진단계와 first mirror 관련 연구동향을 추적하였다. 그리고 이 추적한 결과를 바탕으로 감마선환경에서 first mirror의 특성을 분석했다. 또한 오염 제거 및 방지를 위하여 TE(thermos-electric) 시스템을 제작하고 있다. 그리고 high energy neutral beam에 대한 플라즈마를 이용한 오염방지 실험을 진행하고 있다.

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.297-298
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• 2006

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.175-176
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• 2006