Density perturbations generated by pellet injections in the Tore Supra tokamak
A two step self-consistent model has been developed to describe the ablation of a pellet injected in the Tore Supra tokamak and the parallel expansion of the ablated matter deposited on each magnetic surface the pellet crosses during its penetration in the plasma. Simulations of the line integrated density measurements, made by a five chord laser interferometer sampling data at 50 kHz and toroidally located at -pi/3 to the pellet injector, are used to validate the model. The mass deposition profile in the discharge is described by a neutral gas and plasma shielding model which takes into account explicitly the distribution function of the electrons of the plasma. For 20 radial points along the trajectory, the bulk ionisation degree, the expansion dynamics (radius R and half-length along the magnetic field line Z) and the main parameters (temperatures and density) of the plasmoid (quantity of pellet material released on an individual magnetic surface) are computed using a MHD model. For each chord of the interferometer, the increase of the line integrated density is computed in the exact discharge geometry given by an equilibrium code. To reproduce the experimental signals, it is necessary to take into account a poloidal rotation of the plasmoids in the electronic diamagnetic direction, in addition to the natural motion of particles due to the rotational transform.
Bibliographic Reference: Paper presented: Physiques en Herbe 92, Marseille (FR), July 5-10, 1992
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Record Number: 199310106 / Last updated on: 1994-11-29
Original language: en
Available languages: en