Simulation Study of Ignition and Burn Characteristics of Fast Ignition DT Targets

Abstract

The ignition and burn properties of fast ignition DT targets are evaluated for various-sized core (ignition experiment ∼ high gain) on the basis of two-dimensional (2D) burn simulations. A core size of ρR 2.0 g/cm2 is required to achieve explosive burning and then high gain. When the core size is smaller, the target gain drops sharply as core size decreases. Assuming the energy coupling efficiencies from laser to core of 5 % for implosion and 30 % for heating, a target gain of ∼170 is obtained with a 1 MJ implosion laser and a 70 kJ heating laser, under optimum heating conditions (10 ps duration, 15 μm spot radius, and 1.0 g/cm2 heating depth). This requires a very high intensity heating laser (∼ 1 × 1021 W/cm2). In accordance with a scaling for temperature of fast electrons generated by long-duration intense lasers, such a intense laser will generate fast electrons having suitable stopping range for efficient core heating. The sensitivities of ignition condition and gain performance to heating conditions, and the influence of high-Z ions contained in a foam layer on ignition and gain performance are also discussed.