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Transport of Energetic Ion and Electron Energy Through the Vapor Shield During a Tokamak Plasma Disruption

E. Tucker, J. Gilligan

Fusion Science and Technology

Volume 26 / Number 4 / December 1994 / Pages 1265-1274


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Energetic (> 10-keV) particles incident on divertor plate surfaces may penetrate the vapor shield formed under extremely high heat flux conditions (> 1010 W/m2). In this case, the total energy transmission factor f through the vapor shield can increase drastically, which leads to more surface damage. A one-dimensional time-dependent coupled magnetohydrodynamic-radiation transport code MAGFIRE, originally used in modeling the vapor shield development under a blackbody radiation source, has been modified to include a charged-particle source. The sources used to model a disruption are monoenergetic beams of electrons and/or deuter-ons with any given incident heat flux and energy per particle. An electron source (≤20 keV) will eventually (for times ≤10 µs) be completely absorbed by the vapor resulting in f converging to the same f (for times ≥100 µs) as an equivalent ion heat flux source. Results show that in fact all three sources converge (at ∼100 µs) to the same steady-state value of f for any given heat flux. Results also show that steady-state f decreases for increasing heat fluxes on a carbon surface. Non-steady-state f, however, depends on total incident beam energy fluence and electron energy per particle. The energetic electron spectrum incident on divertor plates during a disruption needs to be measured on large tokamaks so that reliable simulation can be done for International Thermonuclear Experimental Reactor (ITER)-like conditions.

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