Abstract
AbstractThe transport of impurities supplied by a multi‐species impurity powder dropper (IPD) in the large helical device (LHD) is investigated using a three‐dimensional peripheral plasma fluid code (EMC3‐EIRENE) coupled with a dust transport simulation code (DUSTT). The trajectories of impurity powder particles (Boron, Carbon, Iron, and Tungsten) dropped from the IPD and the impurity transport in the peripheral plasma are studied in a full‐torus geometry. The simulation reveals an appropriate size of the impurity powder particles and an optimum operational range of the dust drop rates for investigating the impurity transport without inducing radiation collapse. The simulation also predicts a favourable plasma discharge condition for wall conditioning (boronization) using the IPD in order to deposit boron to high plasma flux and neutral particle density areas in the divertor region in the inboard side of the torus.
Highlights
Impurity powder injection has been expected to be an attractive optional technique for impurity seeding for investigating impurity ion transport, wall conditioning, and dust dynamics studies in magnetic plasma confinement devices [1, 2]
This paper describes the simulation results of the trajectories of four kinds of impurity dust particles (Boron, Carbon, Iron, and Tungsten) in order to find an appropriate experimental condition for the impurity powder dropper (IPD)
An appropriate operational condition of plasma discharges for a multi-species impurity powder dropper (IPD) was investigated using the EMC3-EIRENE coupled with the dust transport simulation code (DUSTT)
Summary
A three-dimensional model for the simulation for tracking the impurity dust particles is illustrated in Figure 1, which is for the most typical magnetic configuration where the radial position of the magnetic axis Rax locates at. In the DUSTT, it is assumed that the shape of the dust particles is spherical and the dust consists of a single element This code provides the three-dimensional profile of the production rate of the neutral impurity atoms originated from the dust particles evaporated/sublimated by the plasma heat load. The deviation of the trajectories is more striking in the high plasma density case as depicted as colored broken lines in these figures These lighter and smaller dust particles collide with the surface on the helical coil can or the vacuum vessel in the end. Sublimation positions at a toroidal angle being far away from the IPD position.) This simulation proves that the largest sized dust particles (ddust=200 m) for the lower plasma density are favorable for depositing the impurity sources in the peripheral plasma (ergodic layer) in all four impurity dust particle cases
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