Scaling of Vaporization and Condensation in Heavy Ion Fusion Reactors

Abstract

The vaporization and condensation of material in ICF reaction chambers has been modeled through computer simulation, and scaling laws have been determined. The vaporization and recondensation of material in the target chamber of a heavy-ion-beam-driven ICF reactor can be broken down into two distinct phenomena. Vaporization can occur through the very rapid adiabatic process due to the absorption of target-generated x rays in the first-wall material, or through a much slower mechanism caused by radiant and conducted heat from the vapor and gases in the reaction chamber that is absorbed on the surface of the material. Condensation also occurs in two separate phases; an early period when the vapor density is high and condensation is controlled by the speed at which the vapor atoms can reach the surface where condensation takes place, and later, when the vapor density is lower and heat conduction through the material on which the condensation occurs is the phenomenon that governs the condensation rate. The CONRAD computer code simulates these processes by modeling the vapor as a one-dimensional Lagrangian mesh through which heat is transferred via conduction and multigroup radiative heat transfer, by calculating the heat transfer through the wall material with a standard finite more » difference method, and by considering the energy, momentum, and mass exchanged between the wall material and the vapor. This code has been used parametrically to aid in the development of scaling laws that show how the vaporization and condensation depend on various reaction chamber parameters. « less