Interpretive modeling of simple-as-possible-plasma discharges on DIII-D using the OEDGE code

Stangeby, P.C.; Elder, J.D.; Boedo, J.A.; Bray, B.D.; Brooks, N.H.; Fenstermacher, M.E.; Groth, M.; Isler, R.C.; Lao, L. L.; Lisgo, S.; Porter, G. D.; Reiter, D.; Rudakov, D.L.; Watkins, J.G.; West, W.P.; Whyte, D.G.

doi:10.1016/s0022-3115(02)01470-8

Cited by 70 publications

(53 citation statements)

References 8 publications

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“…Taking into account the radial profile of the C-ions in the main plasma, from CER, the particle confinement time is found to be τ c ~ 5.5 msec (where τ c ≡ (total core content)/(methane puff rate)). This value is fairly close to the values reported by West [13], of ~ 10 ms, also for CH 4 puffing into DIII-D, although using localized wall puffing. The closely related OEDGE modeling of Elder [7] showed that τ c would be ~4X higher if the CH 4 were ionized at the separatrix, rather than at the actual location -~ 3 cm radially outside the separatrix.…”

Section: Experiments and Modelingsupporting

confidence: 90%

“…This injection is unusual in being toroidally-symmetrical -CH 4 injection was through the upper outer pumping plenum ( Fig. 1) -thus justifying the standard, but often not satisfied, code assumption of symmetry.…”

Section: Introductionmentioning

confidence: 96%

“…A methane-break-up module has been added to the OEDGE [4] (DIVIMP) code in order to interpretively model the results of the injection of 13 CH 4 into DIII-D [5].…”

Section: Introductionmentioning

confidence: 99%

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DIVIMP modeling of the toroidally symmetrical injection of 13CH4 into the upper SOL of DIII-D

McLean

Elder

Stangeby

et al. 2005

Journal of Nuclear Materials

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As part of a study to elucidate carbon-tritium co-deposition, an experiment was carried out on DIII-D involving a toroidally symmetric injection of 13 CH 4 at the top of the vessel (LSN divertor). The focus here is on interpretation of the region near the gas injection point using a Monte Carlo code, DIVIMP-HC, which models molecular breakup. The interpretive analysis indicates a parallel flow in the SOL of M || ~ 0.4 directed toward the inner divertor and D ⊥ ~ 0.3 m 2 /s. For such a wall injection location most of the CH 4 gets ionized, becomes C + , and is efficiently transported along the SOL as C-ions to deposit in the inner divertor. The CH 4 is ionized deeply in the SOL and so the 'contamination efficiency' of the confined plasma is not high: the confinement time is only ~ 5 ms, about 4X lower than if the CH 4 were ionized at the separatrix.2

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Section: Experiments and Modelingsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 96%

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DIVIMP modeling of the toroidally symmetrical injection of 13CH4 into the upper SOL of DIII-D

McLean

Elder

Stangeby

et al. 2005

Journal of Nuclear Materials

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“…A low-density L-mode plasma was chosen as the target plasma in the 2003 13 C injection experiment [Stangeby_JNM03]: n e = 2.8 "10 19 m -3 , or n e n GW~0 .28, where n GW is the Greenwald density [Greenwald_NF88]. Plasma heating was predominately ohmic heating with short neutral beam pulses applied to permit charge exchange spectroscopy measurements.…”

Section: A 13 Ch 4 Injection Into L-mode Plasmasmentioning

confidence: 99%

“…To clarify the controlling physics processes of carbon transport in DIII-D, comprehensive modeling using the OEDGE [Stangeby_JNM03] and UEDGE [Rognlien_JNM92] code packages has been carried out. In general, carbon migration involves (1) primary erosion due to plasma impact on plasma-facing components, (2) transport, dissociation, and ionization of hydrocarbon molecules and carbon atoms, (3) initial deposition, and (4) multi-step re-erosion and redeposition [Matthews_JNM05].…”

Section: Introductionmentioning

confidence: 99%

Scrape-off layer transport and deposition studies in DIII-D

Groth

Allen

Boedo³

et al. 2007

Physics of Plasmas

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Trace 13 CH 4 injection experiments into the main scrape-off layer of low density L-mode and high-density H-mode plasmas have been performed in the DIII-D tokamak[Luxon_NF02] to mimic the transport and deposition of carbon arising from a main chamber sputtering source. These experiments indicated entrainment of the injected carbon in plasma flow in the main SOL, and transport toward the inner divertor. Ex-situ surface analysis showed enhanced 13 C surface concentration at the corner formed by the divertor floor and the angled target plate of the inner divertor in L-mode; in H-mode, both at the corner and along the surface bounding the private flux region inboard of the outer strike point. Interpretative modeling was made consistent with these experimental results by imposing a parallel carbon ion flow in the main SOL toward the inner target, and a radial pinch toward the separatrix. Predictive modeling carried out to better understand the underlying plasma transport processes suggests that the deuterium flow in the main SOL is related to the degree of detachment of the inner divertor leg. These simulations show that carbon ions are entrained with the deuteron flow in the main SOL via frictional coupling, but higher charge state carbon ions may be suspended upstream of the inner M. Groth et al.Scrape-off layer transport and deposition studies in DIII-D GA-A25625, DRAFT 3 APS/DPP Invited ms 2 divertor X-point region due to balance of the friction force and the ion temperature gradient.

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Multi‐fluid code simulations including anomalous non‐diffusive transport of plasma and impurities in the tokamak SOL

Pigarov

Krasheninnikov

Rognlien

et al. 2004

Contrib. Plasma Phys.

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Fast intermittent transport has been observed in the scrape-off layer (SOL) of major tokamaks including Alcator C-Mod, DIII-D, and NSTX. This kind of transport is not diffusive but rather convective. It strongly increases plasma flux to the chamber walls and enhances the recycling of neutral particles in the main chamber. We discuss the anomalous cross-field convection (ACFC) model for impurity and main plasma ions and its relation to intermittent transport events, i.e. plasma density blobs and holes in the SOL. Along with plasma diffusivity coefficients, our transport model introduces time-independent anomalous convective velocities across the confining magnetic field. In the discharge modeling, diffusivity coefficients and ACFC velocity profiles are adjusted to match a set of representative experimental data. We use this model in the edge plasma physics code UEDGE to simulate the multi-fluid two-dimensional transport for these three tokamaks. We present simulation results suggesting the dominance of anomalous convection in the far SOL transport. These results are consistent with the hypothesis that the chamber wall is an important source of impurities and that different impurity charge states have different magnitude and sign of their anomalous radial convective velocities.

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Interpretive modeling of simple-as-possible-plasma discharges on DIII-D using the OEDGE code

Cited by 70 publications

References 8 publications

DIVIMP modeling of the toroidally symmetrical injection of 13CH4 into the upper SOL of DIII-D

DIVIMP modeling of the toroidally symmetrical injection of 13CH4 into the upper SOL of DIII-D

Scrape-off layer transport and deposition studies in DIII-D

Multi‐fluid code simulations including anomalous non‐diffusive transport of plasma and impurities in the tokamak SOL

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