A study of charge dependence of particle transport using impurity pellet injection and high-spatial resolution bremsstrahlung measurement on the Large Helical Device

Nozato, Hideaki; Morita, S.; Goto, M.; Takase, Y.; Ejiri, A.; Amano, Tsuneo; Tanaka, K.; Inagaki, S.

doi:10.1063/1.1695355

Cited by 41 publications

(41 citation statements)

References 20 publications

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“…The experimental result can be approximately explained by the diffusion coefficient of 0.1 m 2 /s. The coefficient estimated here is very close to the values obtained from our previous experimental results in LHD [10,11]. The radial profile of the total K α emissivity is also discussed as well as the energy shift for the determination of the iron density in order to check calculation parameters.…”

Section: Results Of Data Analysis and Discussionsupporting

confidence: 67%

Determination of Iron Density at the Plasma Center Using Radial Profile of FeKα Lines in LHD

Muto

Morita

2008

Plasma and Fusion Research

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Radial profiles of K α X-ray spectra of metallic impurities have been measured using an assembly of soft X-ray pulse-height analyzers in Large Helical Device. The assembly is quipped with a radial scanning system, which gives us detailed profile information, especially in long pulse discharges. The local emissivity profiles of the Fe-K α X-ray spectra have been quantitatively obtained by an Abel inversion technique. The density profile of the iron impurity in each charge state is analyzed using the energy shift profiles of the Fe-K α spectra with the help of an impurity code analysis. As an example of the present method, the iron density of 1.2 × 10 9 cm −3 in the plasma center is obtained at the line-averaged electron density of 2.6 × 10 13 cm −3 .

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Section: Results Of Data Analysis and Discussionsupporting

confidence: 67%

Determination of Iron Density at the Plasma Center Using Radial Profile of FeKα Lines in LHD

Muto

Morita

2008

Plasma and Fusion Research

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“…parameter of 0=0.05, 0.2 and 1.0m2/s. Here, V(a)= -lm/s is used, which is already evaluated in the former impurity transport study [16]. It is clear that the Fe23+ density profile can not be reconstructed by changing D values.…”

Section: Resultsmentioning

confidence: 99%

Behavior of metallic impurity in divertor configuration of Large Helical Device

Dong

Morita

Kobayashi

et al. 2011

2011 IEEE/NPSS 24th Symposium on Fusion Engineering

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Numerical transport study predicts that the edge surface layer in ergodic layer of Large Helical Device (LHD) has a favorable capability of impurity screening for materials of not only divertor plates but also vacuum vessel. In order to demonstrate the theoretical prediction, the density of iron originating in the LHD vacuum vessel made of stainless steel, which is not covered by carbon plates like tokamaks, is accurately determined with its radial profile using a space resolved extreme ultraviolet (EUV) spectrometer, of which absolute intensity calibration is done with bremsstrahlung continuum. For the purpose effective intensity coefficients are precisely calculated for iron ions based on a collisional-radiative model. The iron ion density profiles of Fe14+, Fe15+, Fe22+ and Fe23+ are then evaluated with the radial emissivity profile reconstructed from chord-integrated profile and the effective intensity coefficient. The ratio of iron density to electron density integrated over the whole plasma volume can be finally calculated by fitting the iron density profile using one dimensional impurity transport code. Thus, the analysis on the ratio gives a typical value of 8 X 10-7 in experimental campaign at last year. The entirely small value of the iron density demonstrates the theoretical prediction. The radial structure of transport coefficients are also obtained from the impurity transport code, showing a large inward convection velocity.

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“…The inward velocity is usually seen in the edge region of the core plasma as a function of charge state of impurity ions. 32,33 However, the C 3þ ions exist in the edge boundary with short connection lengths of 5 L c 30 m which correspond to roughly one toroidal turn. The density gradient, which can introduce the inward velocity, at the edge boundary of the ergodic layer is not so large compared to that of the plasma core.…”

Section: Simulation Of CIV Profilesmentioning

confidence: 99%

A study on plasma edge boundary in ergodic layer of LHD based on radial profile measurement of impurity line emissions

et al. 2011

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Vertical profiles of edge impurity emissions have been measured in upper half region of elliptical plasmas at horizontally elongated plasma cross section in large helical device (LHD). The vertical profiles near upper O-point located just below helical coil are analyzed to study the plasma edge boundary of the ergodic layer consisting of stochastic magnetic field lines with connection lengths of 30 L c 2000 m. As a result, C 3þ ion emitting CIV spectrum is identified as the ion existing in the farthest edge of the ergodic layer. The peak position of CIV (312.4 Å : 1s 2 3p 2 P 1=2,3=2 -1s 2 2s 2 S 1=2 ) vertical profile does not change at all in a wide temperature range of 150 T e (q ¼ 1) 400 eV, whereas it moves inside the ergodic layer when T e (q ¼ 1) is reduced below a threshold temperature, e.g., 130 eV at R ax ¼ 3.75 m configuration. It is found that the C 3þ ion exists at the boundary between ergodic layer and open magnetic filed layer at which the L c distributes in lengths of 5 to 30 m. The result indicates that the edge boundary near the O-point in LHD is determined by a starting point of the open filed layer, where a tokamak-like steeper edge temperature gradient is formed, although the edge boundary is quite obscure at the X-point region. Any plasma does not exist between the edge boundary and the vacuum vessel. The CIV profile at the O-point is simulated using a three-dimensional edge transport code of EMC3-EIRENE in which the magnetic field structure in vacuum is used for the ergodic layer. A clear discrepancy of 8 mm is found in the peak positions of CIV between measurement and simulation for magnetic configurations with thick ergodic layer, i.e., R ax ¼3.90 m, while only a small discrepancy of 3 mm is observed for those with relatively thin ergodic layer, i.e., R ax ¼ 3.75 m. It suggests that the discrepancy is caused by a modification of the magnetic filed due to the presence of plasma pressure.

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A study of charge dependence of particle transport using impurity pellet injection and high-spatial resolution bremsstrahlung measurement on the Large Helical Device

Cited by 41 publications

References 20 publications

Determination of Iron Density at the Plasma Center Using Radial Profile of FeKα Lines in LHD

Determination of Iron Density at the Plasma Center Using Radial Profile of FeKα Lines in LHD

Behavior of metallic impurity in divertor configuration of Large Helical Device

A study on plasma edge boundary in ergodic layer of LHD based on radial profile measurement of impurity line emissions

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