With Regard to the Low Mode Target Lifetime: An Analytical Model

Smooth and uniform solid deuterium-tritium (DT) layers inside a spherical shell are needed in order to achieve ignition on the Laser Mégajoule (LMJ) facility. The thermal environment around the capsule is the key to meeting the DT layer requirements. While keeping high mode roughness within the specifications at the shot temperature is now guaranteed by a rapid cooling technique, low mode roughness ("shape" of the layer) is still a complicated and demanding subject. A perfectly uniform temperature field around the capsule is needed. Final results of the constant thermal perturbation effects on the layer can be calculated, but the dynamic of reaction is not known. This paper presents a model that allows calculation of the low mode layer behavior depending on a change in the temperature field. This comes down to calculating a target lifetime for the low modes during a thermal transient state.