Simplified models exist for hot spot ignition, where a burn wave propagates into surrounding cold fuel, and for equilibrium ignition, where a high-Z tamp traps radiation and provides confinement, although the latter are less fully developed and significantly more complex. A simplified model for volume ignition is not known to the authors. These simple models cannot be relied on for accurate target design but they can inform the design process at a fundamental level.

The present work develops a simple ODE model for volume ignition, verifying against prior holistic simulation studies with good results. One aspect necessitated the use of an ODE model, and this is modelling the burn fraction. At lower temperatures the power balance may be positive but the heating rate may be slow, such that the confinement time becomes the limiting factor. The simple burn fraction formula cannot be applied and an ODE approach was needed to capture this trade-off. An additional complication is degeneracy, which is important to understanding the maximum attainable gain. At some point disproportionately more energy is required to reach higher density. Further complication arises from modelling the trapping of radiation, which breaks the normal areal density scaling. This means the parameter space to be explored is 3D rather than 2D.


N. A. Hawker, D. A. Chapman and N.-P. L. Niasse




60th Annual Meeting of the APS Division of Plasma Physics