Calculation of D/XB Values of Hydrocarbon Molecules in Tokamak Edge Plasmas

Kawazome, H.; Ohya, Kaoru; Inai, K.; Kawata, Jun; Nishimura, Kenji; Tanabe, Tada-aki

doi:10.1585/pfr.5.s2073

Cited by 4 publications

(3 citation statements)

References 15 publications

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“…The D/XB scaling in [42] was derived only for attached plasma conditions. Subsequent measurements [47] and modeling [48] have indicated the D/XB value may be a factor of 2-3 lower than predicted by the empirical scaling at very low values of 𝑇𝑇 𝑒𝑒,𝑑𝑑𝑆𝑆𝑑𝑑 . C chemical erosion yields for 𝑇𝑇 𝑒𝑒,𝑑𝑑𝑆𝑆𝑑𝑑 = 1 eV have been directly measured in DIII-D using the DiMES porous plug injector (PPI) [49] and found to be approximately 5x10 -3 , in line with expectations from the Roth scaling [27].…”

Section: Erosionmentioning

confidence: 99%

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

Abrams¹,

Bringuier²,

Thomas³

et al. 2021

Nucl. Fusion

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Silicon carbide (SiC) represents a promising but largely untested plasma-facing material (PFM) for next-step fusion devices. In this work, an analytic mixed-material erosion model is developed by calculating the physical (via SDTrimSP) and chemical (via empirical scalings) sputtering yield from SiC, Si, and C. The Si content in the near-surface SiC layer is predicted to increase during D plasma bombardment due to more efficient physical and chemical sputtering of C relative to Si. Silicon erosion from SiC thereby occurs primarily from sputtering of the enriched Si layer, rather than directly from the SiC itself. SiC coatings on ATJ graphite, manufactured via chemical vapor deposition, were exposed to repeated H-mode plasma discharges in the DIII-D tokamak to test this model. The qualitative trends from analytic modeling are reproduced by the experimental measurements, obtained via spectroscopic inference using the S/XB method. Quantitatively the model slightly underpredicts measured erosion rates, which is attributed to uncertainties in the ion impact angle distribution, as well as the effect of edge-localized modes. After exposure, minimal changes to the macroscopic or microscopic surface morphology of the SiC coatings were observed. Compositional analysis reveals Si enrichment of about 10%, in line with expectations from the erosion model. Extrapolating to a DEMO-type device, an order-of-magnitude decrease in impurity sourcing, and up to a factor of 2 decrease in impurity radiation, is expected with SiC walls, relative to graphite, if low C plasma impurity content can be achieved. These favorable erosion properties motivate further investigations of SiC as a low-Z, non-metallic PFM.

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Section: Erosionmentioning

confidence: 99%

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

Abrams¹,

Bringuier²,

Thomas³

et al. 2021

Nucl. Fusion

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“…Instead, the loss-events/photon data should be determined in the same device as the chemical sputtering yield is determined, in order to compensate for geometry effects such as the plasma-wall interactions and transport effects as concluded in [27]. In addition to extensive experimental studies on molecular process [28], modelling approaches to effective emission rates, which consider the effects of local transport and chemical reactions near the carbon plate surface [29], are encouraged in future. Comparison of the effective emission rates between the present experiment and the modelling is planned.…”

Section: Effect Of the Formation Of Heavier Hydrocarbons From Chmentioning

confidence: 99%

The emission rates of CH, CD and C₂spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

Nakano

Higashijima²,

Kubo³

et al. 2014

Nucl. Fusion

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The CH photon emission rate, defined as the number of photons over a dissociation and/or ionization event of CH4, has been determined from the ratio of the measured emission intensity of the CH spectral band over the CH4 injection rate into the divertor plasma of JT-60U. Similar photon emission rates of CD for CD4, and CH and C2 for C2H4 and C2H6, have also been determined. Interestingly, the C2 spectral band intensity is found to increase during the CH4 and CD4 injection, suggesting that the injected CH4 reacts with the carbon divertor plates to form heavier hydrocarbons. Previously published chemical sputtering yields (Nakano et al 2002 Nucl. Fusion 42 689) evaluated with the photon efficiencies determined in PISCES-A (Pospieszczyk et al 1989 UCLA Report UCLA-PPG-1251) have been re-evaluated using the measured emission rates. By applying the photon emission data found here and taking into account the C2 emission process originating from CH4, the re-evaluated total chemical sputtering yield becomes lower (∼7%) compared to the original in (Nakano et al 2002 Nucl. Fusion 42 689) (∼8%), and the dependence on the incident ion flux and energy becomes weaker.

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“…In addition, these molecules find their significance in the edge plasmas of magnetically confined high-temperature hydrogen plasma [2]. In the next-generation fusion devices such as ITER, it is crucial to estimate the lifetime of plasma facing carbon materials, since chemical sputtering decreases their lifetime and increases fuel retention by means of redeposition [5]. Propene is not only an important molecule in the field of plasma science but also in astrophysics.…”

Section: Introductionmentioning

confidence: 99%

Plasma-relevant electron scattering cross sections of propene

Singh

Gupta²,

Antony

2018

Plasma Sources Sci. Technol.

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Propene (C 3 H 6 ) is considered to be an important molecule in the field of plasma science due to it being recognized as a by-product of plasma irradiation at the diverter regions and plasma facing walls in modern fusion devices. This article reports electron scattering elastic, momentum transfer, differential and excitation cross sections of propene. The rate coefficients for the elastic and momentum transfer cross sections are also reported. The data reported in this article are considered to be important in the field of plasma physics due to their direct influence on plasma modeling applications. Two theoretical methods were used for the present study; the R-matrix method for low energy and spherical complex optical potential formalism for high energy. The R-matrix calculation was performed using the correlation-consistent polarized valence-only triple-zeta basis set and a reasonable agreement with the target properties was obtained. The scattering calculations were then performed using these parameters to compute various cross sections. The present cross sections compare reasonably well with the only available data in the literature. More experimental studies of a similar nature are encouraged for the validation of the present results.

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Calculation of D/XB Values of Hydrocarbon Molecules in Tokamak Edge Plasmas

Cited by 4 publications

References 15 publications

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

The emission rates of CH, CD and C₂spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

Plasma-relevant electron scattering cross sections of propene

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Calculation of D/XB Values of Hydrocarbon Molecules in Tokamak Edge Plasmas

Cited by 4 publications

References 15 publications

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

Evaluation of silicon carbide as a divertor armor material in DIII-D H-mode discharges

The emission rates of CH, CD and C2spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

Plasma-relevant electron scattering cross sections of propene

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The emission rates of CH, CD and C₂spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates