TRANSPORT OF ENERGETIC ION AND ELECTRON-ENERGY THROUGH THE VAPOR SHIELD DURING A TOKAMAK PLASMA DISRUPTION

Energetic (> 10-keV) particles incident on divertor plate surfaces may penetrate the vapor shield formed under extremely high heat flux cond itions (> 10(10) W/m2). In this case, the total energy transmission fa ctor f through the vapor shield can increase drastically, which leads to more surface damage. A one-dimensional time-dependent coupled magne tohydrodynamic-radiation transport code MAGFIRE, originally used in mo deling the vapor shield development under a blackbody radiation source , has been modified to include a charged-particles source. The sources used to model a disruption are monoenergetic beams of electrons and/o r deuterons with any given incident heat flux and energy per particle. An electron source (less-than-or-equal-to20 keV) will eventually (for times less-than-or-equal-to10 mus) be completely absorbed by the vapo r resulting in f converging to the same f (for times greater-than-or-e qual-to100 mus) as an equivalent ion heat flux source. Results show th at in fact all three sources converge (at approximately 100 mus) to th e same steady-state value of f for any given heat flux. Results also s how that steady-state f decreases for increasing heat fluxes on a carb on surface. Non-steady-state f, however, depends on total incident bea m energy fluence and electron energy per particle. The energetic elect ron 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 condi tions.