Modeling of Electron and Ion Interaction with the Vapor Shield during a Tokamak Disruption

During a tokamak disruption, material surfaces are exposed to extremely high heat fluxes from ions and electrons transporting energy from the device. Ablated material from the surface forms a 'vapor shield' and absorbs some of the incident energy flux. It is important to model energy transport through ablated material in order to predict the erosion depth of the material. This vapor shield will absorb most of the incident disrupting plasma energy, and re-radiate part of the incident energy to the divertor channel (used for diverting most of the plasma from the wall via open ended magnetic field lines), and therefore shield the divertor plate from much of the heat flux. The end result will be a great reduction in predicted erosion damage to the divertor plate. It is important to model the effects of a tokamak fusion reactor disruption on reactor materials such as the divertor plate. This will allow us to know how many disruptions will occur before a particular material compound will fail. Knowing the material disruption lifetime would ultimately determine whether the material is of practical use for this application; i.e., will it be cost effective when maintenance and replacement are considered. Computer models can offer a cost effective method of determining erosion depths. Computer modeling of this event can also give us a better understanding of the mechanisms by which this is accomplished and perhaps aid us in choosing the "best" divertor plate material. The code MAGFIRE is a self-consistent one-dimensional time dependent MHD-radiation energy coupled model, formerly used to predict radiation transport into and through ablated material, which has been upgraded to give a more realistic simulation of a disruption plasma incident on a divertor plate than the former blackbody radiation source heat flux. The upgrades accomplished for MAGFIRE include an analysis of ion and electron energy deposition, momentum transfer and particle mass sources in the vapor shield.