Target Thermal Response to Gas Interactions

Detailed analysis of convection heat transfer and gas condensation on direct drive targets has been performed in order to provide a more accurate estimate of the temperature rise. Transient analysis of the target thermal response was performed near the triple point using DT properties corresponding to each phase. The calculations provide better insight into the knee in the maximum temperature curve. As compared with previous estimates, lower allowable heat flux is predicted as the triple point is reached. Careful examination of gas transport near the target surface indicates that shielding of the incident particle flux by uncondensed gas is important for pressures greater than 1 mtorr. Therefore, more accurate treatment of particle sticking must be used. High sticking coefficients will lower the allowable gas temperature and pressure in the chamber.