NOVA UPGRADE PROGRAM - IGNITION AND BEYOND

The Lawrence Livermore National Laboratory (LLNL) Inertial Confinement Fusion (ICF) Program is addressing the critical physics and technolog y issues directed toward demonstrating and exploiting ignition and pro pagating burn to high gain with ICF targets for both defense and civil ian applications. Nova is the primary U.S. facility employed in the st udy of the X-ray-driven (indirect drive) approach to ICF. Nova's princ ipal objective is to demonstrate that laser-driven hohlraums can achie ve the conditions of driver-target coupling efficiency, driver irradia tion symmetry, driver pulseshaping, target preheat, and hydrodynamic s tability required by hot-spot ignition and fuel compression to realize a fusion gain. The LLNL ICF Program believes that the next major step in the national ICF Program is the demonstration of ignition and mode rate gain (G less-than-or-equal-to 10). Recent theoretical and experim ental results show that the ignition drive energy threshold can be red uced significantly by operating indirectly driven targets at radiation temperatures approximately 1.3-1.6 times higher (thereby achieving hi gher implosion velocity) than originally proposed for the Laboratory M icrofusion Facility (LMF). (Temperatures of approximately 1.3 times hi gher have already been demonstrated on Nova.) Specifically, it should be possible to demonstrate ignition and propagating with burn about 1- 2 MJ of laser energy as against the 5-10 MJ necessary for the high-yie ld LMF. LLNL proposes to upgrade the existing Nova facility to 1-2 MJ (2- to 4-ns pulses) and demonstrate ignition and propagating burn to m oderate gain with appropriately scaled hydrodynamic equivalents of hig h-yield targets. Once moderate gain has been demonstrated at 1-2.0 MJ on the Nova Upgrade, investigations into improving, by about 50%, the coupling efficiency between the driver and the capsule could provide g ains >20 at about 1 MJ or less. A database for gain below 1-MJ driver energies could lead to a low-capital-cost Engineering Test Facility (E TF) for a first inertial fusion energy engineering reactor. Because th e capital cost for both the target chamber and the driver scale with s ize, there is the opportunity to realize large savings by lowering the required driver energy necessary to demonstrate the technology for a first demonstration power plant. A target gain, G approximately 25, at a driver energy, E(D) approximately 0.75 MJ, would be self-sustaining for a driver efficiency of approximately 10% and a thermal-to-electri c conversion efficiency of approximately 33% and at 12 Hz would genera te approximately 10 MW of gross electric power. Although the cost of e lectricity would be high, the combination of low capital cost and earl y demonstration of reactor technology would be an attractive step in t he development of inertial fusion energy.