scholarly journals Spectroscopic measurement of impurity transport coefficients and penetration efficiencies in Alcator C‐Mod plasmas

1995 ◽  
Vol 66 (1) ◽  
pp. 636-638 ◽  
Author(s):  
M. A. Graf ◽  
J. E. Rice ◽  
J. L. Terry ◽  
E. S. Marmar ◽  
J. A. Goetz ◽  
...  
Keyword(s):  
Transport Coefficients ◽  
Spectroscopic Measurement ◽  
Impurity Transport

Experimental and simulation study of impurity transport response to RMPs in RF-heated H-mode plasmas at EAST

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Germán Vogel ◽  
Hongming Zhang ◽  
Yongcai Shen ◽  
Shuyu Dai ◽  
Youwen Sun ◽  
...  
Keyword(s):  
Inner Core ◽  
Extreme Ultraviolet ◽  
Transport Coefficients ◽  
Three Dimensional ◽  
Line Emission ◽  
Core Region ◽  
Emission Mitigation ◽  
One Dimensional ◽  
Impurity Transport ◽  
Transport Code

Spatial profiles of impurity emission measurements in the extreme ultraviolet (EUV) spectroscopic range in radiofrequency (RF)-heated discharges are combined with one-dimensional and three-dimensional transport simulations to study the effects of resonant magnetic perturbations (RMPs) on core impurity accumulation at EAST. The amount of impurity line emission mitigation by RMPs appears to be correlated with the ion Z for lithium, carbon, iron and tungsten monitored, i.e. stronger suppression of accumulation for heavier ions. The targeted effect on the most detrimental high-Z impurities suggests a possible advantage using RMPs for impurity control. Profiles of transport coefficients are calculated with the STRAHL one-dimensional impurity transport code, keeping $\nu /D$ fixed and using the measured spatial profiles of $\textrm{F}{\textrm{e}^{20 + }}$ , $\textrm{F}{\textrm{e}^{21 + }}$ and $\textrm{F}{\textrm{e}^{22 + }}$ to disentangle the transport coefficients. The iron diffusion coefficient ${D_{\textrm{Fe}}}$ increases from $1.0- 2.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ to $1.5- 3.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ from the core region to the edge region $(\rho \gt 0.5)$ after the onset of RMPs. Meanwhile, an inward pinch of iron convective velocity ${\nu _{\textrm{Fe}}}$ decreases in magnitude in the inner core region and increases significantly in the outer confined region, simultaneously contributing to preserving centrally peaked $\textrm{Fe}$ profiles and exhausting the impurities. The ${D_{\textrm{Fe}}}$ and ${\nu _{\textrm{Fe}}}$ variations lead to reduced impurity contents in the plasma. The three-dimensional edge impurity transport code EMC3-EIRENE was also applied for a case of RMP-mitigated high-Z accumulation at EAST and compared to that of low-Z carbon. The exhaust of ${\textrm{C}^{6 + }}$ toward the scrape-off layer accompanying an overall suppression of heavier ${\textrm{W}^{30 + }}$ is observed when using RMPs.

scholarly journals Evaluation of an Oxygen Transport Coefficient in the Aditya Tokamak Using the Radial Profile of O4+ Emissivity and the Importance of Atomic Data Used Therein

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 90 ◽  
Author(s):  
Chowdhuri ◽  
Ghosh ◽  
Dey ◽  
Patel ◽  
Yadava ◽  
...  
Keyword(s):  
Spectral Line ◽  
Oxygen Transport ◽  
Diffusion Coefficients ◽  
Transport Coefficients ◽  
Radial Profile ◽  
Atomic Data ◽  
Oxygen Impurity ◽  
Impurity Transport ◽  
Field Edge ◽  
The Difference

Oxygen impurity transport in the typical discharges of the Aditya tokamak was investigated using emissivity radial profile of emissivity of the spectral line (2p3p 3D3–2p3d 3F4) at 650.024 nm from the Be-like oxygen ion. This O4+ spectral line was recorded using a 1.0 m multi-track spectrometer capable of simultaneous measurements from eight lines of sight passing through the plasma. The oxygen transport coefficients were determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional impurity transport code, STRAHL, and photon emissivity coefficient (PEC) belonging to that transition. The PEC values were obtained from both ADAS and NIFS atomic databases. Using both the databases, much higher values of diffusion coefficients compared to the neo-classical values were observed in both high and low magnetic field edge regions of typical Aditya tokamak Ohmic plasma. Although, almost similar profiles of diffusion coefficients were obtained using PEC values from both databases, the magnitude differs considerably. The maximum values of diffusion coefficients in the plasma edge at low field side of tokamak were ~45 and ~25 m2·s−1 when modeling was done using the ADAS and NIFS databases, respectively. Further analysis on the atomic data used in the calculation indicates that the difference in diffusion coefficients is mainly related to the variation in the values of atomic data of the two databases.

Determination of impurity transport coefficients by harmonic analysis

1990 ◽  
Vol 30 (11) ◽  
pp. 2392-2396 ◽  
Author(s):  
K. Krieger ◽  
G. Fussmann ◽  
Keyword(s):  
Harmonic Analysis ◽  
Transport Coefficients ◽  
Impurity Transport

A dependence of carbon impurity transport coefficients on fuel ions in hydrogen and helium plasmas of Large Helical Device

2006 ◽  
Vol 13 (9) ◽  
pp. 092502 ◽  
Author(s):  
H. Nozato ◽  
S. Morita ◽  
M. Goto ◽  
Y. Takase ◽  
A. Ejiri ◽  
...  
Keyword(s):  
Transport Coefficients ◽  
Carbon Impurity ◽  
Impurity Transport

scholarly journals The importance of the classical channel in the impurity transport of optimized stellarators

2019 ◽  
Vol 85 (4) ◽  
Author(s):  
S. Buller ◽  
A. Mollén ◽  
S. L. Newton ◽  
H. M. Smith ◽  
I. Pusztai
Keyword(s):  
Electrostatic Potential ◽  
Transport Coefficients ◽  
Magnetic Confinement ◽  
Flux Surface ◽  
Classical Counterpart ◽  
Impurity Transport ◽  
Neoclassical Transport ◽  
Order Of Magnitude ◽  
Classical Transport

In toroidal magnetic confinement devices, such as tokamaks and stellarators, neoclassical transport is usually an order of magnitude larger than its classical counterpart. However, when a high-collisionality species is present in a stellarator optimized for low Pfirsch–Schlüter current, its classical transport can be comparable to the neoclassical transport. In this letter, we compare neoclassical and classical fluxes and transport coefficients calculated for Wendelstein 7-X (W7-X) and Large Helical Device (LHD) cases. In W7-X, we find that the classical transport of a collisional impurity is comparable to the neoclassical transport for all radii, while it is negligible in the LHD cases, except in the vicinity of radii where the neoclassical transport changes sign. In the LHD case, electrostatic potential variations on the flux surface significantly enhance the neoclassical impurity transport, while the classical transport is largely insensitive to this effect in the cases studied.

scholarly journals Validation of low-Z impurity transport theory using boron perturbation experiments at ASDEX Upgrade

2021 ◽  
Author(s):  
Rachael M McDermott ◽  
Clemente Angioni ◽  
Marco Cavedon ◽  
Athina Kappatou ◽  
Ralph Dux ◽  
...  
Keyword(s):  
Particle Flux ◽  
Transport Theory ◽  
Electron Cyclotron Resonance ◽  
Transport Coefficients ◽  
Electron Cyclotron Resonance Heating ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Density Profiles ◽  
Boron Particle ◽  
Impurity Transport

Abstract An experimental technique has been developed at ASDEX Upgrade (AUG) to separately identify the diffusive and convective components of the boron particle flux. Using this technique a database of B transport coefficients has been assembled that shows that the normalized ion temperature gradient (R/LTi) is the strongest organizing parameter for both the B diffusion and convection and large R/LTi is a necessary ingredient to obtain hollow B density profiles in AUG. This database also shows that large changes in the applied neutral beam injection (NBI) have a relatively small impact on impurity transport compared to similar changes in electron cyclotron resonance heating (ECRH). Even low levels of ECRH power dramatically increase both the diffusive and convective fluxes and lead to peaking of the impurity density profile. Comparisons to a combination of neoclassical and quasi-linear gyrokinetic simulations show good agreement in the measured and predicted diffusion coefficients. The outward convection measured in NBI dominated plasmas, however, is not well captured by the simulations, despite the inclusion of fast ions. In contrast, the convection is reasonably well reproduced for plasmas with flat or peaked boron density profiles. This dataset provides an excellent experimental validation of the non-monotonic, predicted, convective-particle-flux created by the combination of pure-pinch, thermo-diffusion, and roto-diffusion. In addition, this dataset demonstrates a non-monotonic dependence of the experimental particle diffusivity to ion heat conductivity (D/χi) in qualitative agreement with theoretical predictions.

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