Impurity density derivation from bandpass soft x-ray tomography: applicability, perspectives and limitations

Vezinet, D.; Mazon, D.; Guirlet, R.; Decker, J.; Peysson, Y.

doi:10.1088/0029-5515/54/8/083011

Cited by 6 publications

(4 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Soft X-rays (SXR) in the range of 0.1 keV -20 keV provide valuable information on tokamak plasmas for studying e.g. magnetohydrodynamic (MHD) activity, magnetic equilibrium or impurity transport [1]. In particular tungsten which is widely used as the main plasma facing material on major tokamaks such as ITER, Joint European Torus (JET) or WEST, is a source of concern due to significant radiation losses in the plasma core and thus must be kept under acceptable concentrations [2].…”

Section: Introductionmentioning

confidence: 99%

Comparison of two regularization methods for soft x-ray tomography at Tore Supra

2016

View full text Add to dashboard Cite

Soft X-Ray (SXR) emission in the range 0.1 keV-20 keV is widely used to obtain valuable information on tokamak plasma physics, such as particle transport, magnetic configuration or magnetohydrodynamic (MHD) activity. In particular, 2D tomography is the usual plasma diagnostic to access the local SXR emissivity. The tomographic inversion is traditionally performed from line-integrated measurements of two or more cameras viewing the plasma in a poloidal cross-section, like at Tore Supra (TS). Unfortunately, due to the limited number of measured projections and presence of noise, the tomographic reconstruction of SXR emissivity is a mathematical ill-posed problem. Thus, obtaining reliable results of the tomographic inversion is a very challenging task. In order to perform the reconstruction, inversion algorithms implemented in present tokamaks use a priori information as additional constraints imposed on the plasma SXR emissivity. Among several potential inversion methods, some of them have been identified as well suited to tokamak plasmas. The purpose of this work is to compare two promising inversion methods, i.e. the Minimum Fisher Information (MFI) method already used at TS and planned for WEST configuration, and the alternative 2 nd order Phillips-Tikhonov Regularization (PTR) with smoothness constraints imposed on the second derivative norm. Respective accuracy of both reconstruction methods as well as overall robustness and computational time are studied, using several synthetic SXR emissivity profiles. Finally, a real case is studied through tomographic reconstruction from TS SXR database. Figure 1. (a) 3D view of SXR detection system on Tore Supra with 2 cameras, 82 Lines of Sight (LoS) in total and (b) 2D poloidal cross-section.

show abstract

Section: Introductionmentioning

confidence: 99%

Comparison of two regularization methods for soft x-ray tomography at Tore Supra

2016

View full text Add to dashboard Cite

show abstract

“…(2.2) that the f S,q depend a priori on particle transport through the divergence term ì ∇ • ì Γ S,q . In order to take radial transport into account, particle flux is usually [26] expressed as the combination of a convective and a diffusive terms: ì Γ S,q = n S,q ì V S − D S ì ∇n S,q . Thus at steady state the ionization equilibrium of S q+ becomes, assuming here toroidal and poloidal symmetry:…”

Section: Effect Of the Impurity Transport On Its Density Reconstructionmentioning

confidence: 99%

On a gas electron multiplier based synthetic diagnostic for soft x-ray tomography on WEST with focus on impurity transport studies

et al. 2017

Self Cite

View full text Add to dashboard Cite

“…Deuterium is fully ionized where the SXR emissivity is significant inside the separatrix. Dielectronic recombinations are not included here as well as transport effect on L η W [15] for simplicity. W line radiation is the dominant contribution overall.…”

Section: Application To the Standard West Scenario 41 A Scenario From...mentioning

confidence: 99%

Tomographic capabilities of the new GEM based SXR diagnostic of WEST

et al. 2016

Self Cite

View full text Add to dashboard Cite

The tokamak WEST (Tungsten Environment in Steady-State Tokamak) will start operating by the end of 2016 as a test bed for the ITER divertor components in long pulse operation. In this context, radiative cooling of heavy impurities like tungsten (W) in the Soft Xray (SXR) range [0.1 keV; 20 keV] is a critical issue for the plasma core performances. Thus reliable tools are required to monitor the local impurity density and avoid W accumulation. The WEST SXR diagnostic will be equipped with two new GEM (Gas Electron Multiplier) based poloidal cameras allowing to perform 2D tomographic reconstructions in tunable energy bands. In this paper tomographic capabilities of the Minimum Fisher Information (MFI) algorithm developed for Tore Supra and upgraded for WEST are investigated, in particular through a set of emissivity phantoms and the standard WEST scenario including reconstruction errors, influence of noise as well as computational time.

show abstract

Impurity density derivation from bandpass soft x-ray tomography: applicability, perspectives and limitations

Cited by 6 publications

References 48 publications

Comparison of two regularization methods for soft x-ray tomography at Tore Supra

Comparison of two regularization methods for soft x-ray tomography at Tore Supra

On a gas electron multiplier based synthetic diagnostic for soft x-ray tomography on WEST with focus on impurity transport studies

Tomographic capabilities of the new GEM based SXR diagnostic of WEST

Contact Info

Product

Resources

About