Direct drive target designs for inertial fusion energy

For an inertial fusion energy power plant, high gain, repeatable, robust target designs are needed. Focused Energy is pursuing a fusion pilot plant using a direct drive target design driven by a diode-pumped, solid-state laser at 351 nm wavelength. The fusion pilot plant needs to demonstrate engineering gain (more energy out than needed to run the plant) which requires target gain of about 25. Here, we show preliminary target designs for a fusion pilot plant with 1-d gain > 50, to account for 3-d effects. The main physics risks for these designs are from laser-plasma instabilities (LPI), hydrodynamic instabilities, and low mode asymmetry. Because there is uncertainty in the relative contribution of these risks, we present multiple target designs that span the parameter space for LPI risk (characterized by laser intensity and mitigated via broad bandwidth laser and beam zooming) and hydrodynamic stability risk (characterized and mitigated by controlling the inflight aspect ratio (IFAR) and adiabat). Experimental results will be used to determine the optimum design for our fusion pilot plant from within this parameter space.