Achieving Global Thermal Uniformity of a Compact Cylindrical Deuterium-Tritium Target

The roughness of the fuel ice layer at low modes significantly impacts the hydrodynamic instability in inertial confinement fusion experiments with indirect-drive cryogenic targets. It is primarily determined by the thermal uniformity of the capsule. Due to the beta-decay heat of tritium, the temperature profiles of targets filled with deuterium-tritium differ from those filled with deuterium-deuterium in a cylindrical hohlraum. The cylindrical shape causes the equator of the capsule to be cooler than the two poles in the steady state without any intervention. Tuning the vertical temperature distribution is essential and requires a high thermal resistance in the target thermal mechanical package. It is very difficult for a compact target which is just half of the National Ignition Facility (NIF) target scale, and is contrary to the previous design of deuterium- deuterium target, which used a high-conductive jacket made from Oxygen-Free Copper (OFC), to provide a relatively uniform thermal field around the capsule. To realize the vertical tuning capability and achieving global thermal uniformity of the capsule, we propose in this paper a novel design featuring a grooved aluminum-alloy jacket, as well as the methods to improve thermal contact reliability and conductivity, including decreasing the width of arm-jacket interface, enhancing the adhesive conductivity by doping silver, and replacing the aluminum diagnosis band with conductive OFC. We further verified this design through experiments. It has reduced the global temperature difference of the capsule by about 70 % and significantly improved the quality of the deuterium-tritium ice layer.