Modeling of velocity distributions of dust in tokamak edge plasmas and dust–wall collisions

Smirnov, R.D.; Krasheninnikov, S. I.; Pigarov, A. Yu.; Rosenberg, M.; Mendis, D. A.

doi:10.1016/j.jnucmat.2009.01.090

Cited by 30 publications

(28 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An inverse dependence with a slope close to R −1/2 d (dashed line shown for comparison in figure 7) has been found. This is consistent with modelling by the DustT code [32], which predicts that smaller particles experience faster acceleration by the ion drag force. The R −1/2 d scaling of the dust velocity is also predicted by a simplified one-dimensional uniform plasma model [32].…”

Section: Correlation Of the Dust Velocity And Sizesupporting

confidence: 90%

Dust studies in DIII-D and TEXTOR

et al. 2009

Self Cite

View full text Add to dashboard Cite

Studies of naturally occurring and artificially introduced carbon dust are conducted in DIII-D and TEXTOR. In DIII-D, dust does not present operational concerns except immediately after entry vents. Submicrometre sized dust is routinely observed using Mie scattering from a Nd : Yag laser. The source is strongly correlated with the presence of type I edge localized modes (ELMs). Larger size (0.005–1 mm diameter) dust is observed by optical imaging, showing elevated dust levels after entry vents. Inverse dependence of the dust velocity on the inferred dust size is found from the imaging data. Heating of the dust particles by the neutral beam injection (NBI) and acceleration of dust particles by the plasma flows are observed. Energetic plasma disruptions produce significant amounts of dust; on the other hand, large flakes or debris falling into the plasma may induce a disruption. Migration of pre-characterized carbon dust is studied in DIII-D and TEXTOR by introducing micrometre-size particles into plasma discharges. In DIII-D, a sample holder filled with 30–40 mg of dust is inserted in the lower divertor and exposed, via sweeping of the strike points, to the diverted plasma flux of high-power ELMing H-mode discharges. After a brief dwell (∼0.1 s) of the outer strike point on the sample holder, part of the dust penetrates into the core plasma, raising the core carbon density by a factor of 2–3 and resulting in a twofold increase in the radiated power. In TEXTOR, instrumented dust holders with 1–45 mg of dust are exposed in the scrape-off-layer 0–2 cm radially outside of the last closed flux surface in discharges heated with 1.4 MW of NBI. Launched in this configuration, the dust perturbed the edge plasma, as evidenced by a moderate increase in the edge carbon content, but did not penetrate into the core plasma.

show abstract

Section: Correlation Of the Dust Velocity And Sizesupporting

confidence: 90%

Dust studies in DIII-D and TEXTOR

et al. 2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…For particles that survive multiple ELMs, a discrete velocity increase up to a factor of 3 is observed following the sudden ablation caused by an ELM. The 2D velocity data roughly agree with the R d À1/2 scaling predicted by a simple 1D analytic model of spherical dust particles accelerated due to ion drag in a uniform plasma, for a fixed distance between the dust origin and the measurement region [18]. DUSTT modeling shows that dust acceleration takes place mainly in the region near the divertor where parallel flow is largest, and that particles can reach $1 km/s after rapid reduction in mass due to ablation [17].…”

Section: Dust Velocitysupporting

confidence: 75%

Fast camera imaging of dust in the DIII-D tokamak

Rudakov

Pigarov

et al. 2009

Journal of Nuclear Materials

Self Cite

View full text Add to dashboard Cite

“…At estimated equilibrium temperatures of dust particles in the divertor plasma from 2000 K to 4000 K [33], their hydrogen and beryllium content would probably be released before arriving in the inner louvre. Dust particles of sub-micrometer size can gain velocities up to ~1000 m/s and be destroyed upon collision with the wall [34]. The background flux of neutral deuterium can then lead to the saturation of the carbon layer with deuterium corresponding to the layer temperature, in agreement with the hydrogen-rich characteristic of the carbon layers observed on the cooled structure of the inner louvre [4].…”

Section: Surface Layers and Elm-induced Enhanced Erosionsupporting

confidence: 54%

Dynamics of erosion and deposition in tokamaks

Kreter

Brezinsek

Coad

et al. 2009

Journal of Nuclear Materials

View full text Add to dashboard Cite

In recent years, a general qualitative understanding has been reached about the major pathways of material migration in divertor tokamaks. Main chamber wall components have been identified as the major source of material erosion. The eroded material is transported by scrape-off layer flows, in the case of the ion B×∇B drift pointing towards the X-point, predominately towards the inner divertor leg, where it is deposited in the form of amorphous layers. On JET, where carbon is the main plasma-facing material, it has been found that the presence of deposited carbon rich layers determines the dynamic characteristics of further redistribution of carbon, in particular towards remote areas. The transport from the strike point to the deposition location is mainly line-of-sight. The amount of eroded carbon depends on the surface type, with lower rates for the bare CFC and higher rates for deposited layers. The erosion rates in the inner divertor increase non-linearly with increasing ELM energies.

show abstract

Modeling of velocity distributions of dust in tokamak edge plasmas and dust–wall collisions

Cited by 30 publications

References 12 publications

Dust studies in DIII-D and TEXTOR

Dust studies in DIII-D and TEXTOR

Fast camera imaging of dust in the DIII-D tokamak

Dynamics of erosion and deposition in tokamaks

Contact Info

Product

Resources

About