Ion Debris and X-ray Energy Deposition and Response of Fusion Reactor First Walls*

The energy deposition of the thermonuclear target explosion products in Inertial Confinement Fusion (ICF) reactors, i.e., ion debris and X-rays and the resulting thermal response of first wall materials, is calculated using the computer code ATEN. Models to accurately simulate the ion and X-ray energy deposition and the consequent response of the wall are implemented in the code. Simultaneous multiple ions and X-rays with different yields and spectra incident on various wall materials are easily handled by the code. In a laser driven ICF reactor, in addition to X-rays, ions, and neutrons, the first wall will be exposed to the portion of the laser light reflected from the target. This could have an important effect on the overall performance of the wall. The thermal response and the resulting melting and erosion due to vaporization of wall materials are found to be critically dependent on target design configuration. Depending on the details of target design, its constituents and the driver beam, a wide range of X-ray and ion debris yields and spectra can be generated as a result of the thermonuclear reaction. A parametric study of first wall temperature excursion, resulting melt thickness and material loss for different candidate wall materials is presented. It is found that controlling the partition between X-ray energy yield and ion energy yield and their spectra can substantially result in a longer first wall lifetime for the same total target yield.