Shock-Augmented Ignition

This work describes a new pulse-shaping methodology which, according to radiation hydrodynamic simulations, enables the benefits of Shock Ignition but without the requirement for high peak laser intensity and/or power. If this can be realized, this work indicates that Laser Direct Drive implosions could be fielded on existing facilities which would achieve gains of ~85 with a peak implosion velocity of <330km/s. Shock Ignition appears an attractive route to achieving ignition and high gain via laser fusion. The strong shock enables ignition at implosion velocities below the self-ignition threshold, limiting growth of the ablative Rayleigh-Taylor instability. However, it does have potential disadvantages, caused by the need for high peak intensity to drive the strong shock. This work details a novel pulse shape which enables the creation of a very strong shock (>1 Gbar), thereby enabling the benefits of Shock Ignition, but with a peak intensity of ~1.3x10¹⁵W/cm². The reduced intensity may reduce deleterious parametric instabilities, while the reduced peak power requirements, would enable a large capsule (radius 1720µm) to be fielded on NIF while remaining within the current 1.8MJ, 500TW limitations.

This work is funded by EPSRC Grants EP/P023460/1, EP/P026486/1, EP/P026796/1 and EP/L01663X/1.