Demonstration of indirectly driven implosion experiments with cryogenic pure deuterium layered capsules on the Shenguang Laser Facility

Abstract

To achieve ignition in a laboratory via inertial confinement fusion, a spherical capsule containing a frozen layer of deuterium and tritium (DT) fuel will be imploded on an MJ-class laser facility. However, if pure deuterium fuel can be used in place of DT fuel for tuning shots, we may speed up the process of ignition experiments while maintaining the surrogacy by significantly reducing the level of radioactivity. Unfortunately, it has long been assumed that neither the approach of symmetrical infrared irradiation used in the Omega direct-drive experiments nor the method of beta-layering used in the NIF experiments can be used to smooth the D layered capsule in cylindrical hohlraums. The difficulty in smoothing the D ice layer prevents us from taking advantage of cryogenic D-layered capsules in indirect-drive experiments. In this work, we established a procedure to form a uniform D-ice layer for capsules held in cylindrical hohlraums and carried out indirect-drive cryogenic D-layered implosion experiments using a squared laser pulse on the Shenguang Laser Facility in China. The quality of the D ice layer is characterized by phase-contrast imaging. The root-mean-square of the power spectrum in modes 2–100 is about 2.2 μ m. The implosion performance of the D-layered capsules is close to the prediction of one-dimensional simulations. The measured neutron yield and areal fuel density are 1.2 × 10 ^11 and 80 mg cm ^−2 , respectively.

Keywords

• indirectly driven implosion
• Shenguang Laser Facility
• cryogenic deuterium layered target