Ricerc@Sapienza

Shock-ignition (SI) is a direct-drive laser fusion scheme, in which the fuel is imploded at velocity somewhat smaller than in conventional schemes. The hot spot required for ignition is attained thanks to a converging shock-wave generated by an intense final spike of the laser pulse. Earlier studies show potentials of SI for high gain at driver energy of the order of 1 MJ, provided that laser-plasma instabilities do not degrade laser absorption and do not preheat the fuel. However, also hydrodynamic aspects need investigation.

Simultaneously measured DD, DT, and (DHe)-He-3 reaction histories are used to probe the impacts of multi-ion physics during the shock phase of inertial confinement fusion implosions. In these relatively hydrodynamiclike (burn-averaged Knudsen number NK similar to 0.3) shock-driven implosions, average-ion hydrodynamic DUED simulations are able to reasonably match burnwidths, nuclear yields, and ion temperatures. However, kinetic-ion FPION simulations are able to better simulate the timing differences and time-resolved reaction rate ratios between DD, DT, and (DHe)-He-3 reactions.

The impact of fuel-ion diffusion in inertial confinement fusion implosions is assessed using nuclear reaction yield ratios and reaction histories. In T3He-gas-filled (with trace D) shock-driven implosions, the observed TT/T3He yield ratio is ∼23lower than expected from temperature scaling. InD3He-gas-filled (with trace T) shock-driven implosions, the timing of theD3He reaction history is ∼50 ps earlier than those of the DT reaction histories, and average-ion hydrodynamic simulations cannot reconcile this timing difference.

Fuel-ion species dynamics in hydrodynamiclike shock-driven DT3He-filled inertial confinement fusion
implosion is quantitatively assessed for the first time using simultaneously measured D3He and DT reaction
histories. These reaction histories are measured with the particle x-ray temporal diagnostic, which captures
the relative timing between different nuclear burns with unprecedented precision (∼10 ps). The observed
50 +- 10 ps earlier D3He reaction history timing (relative to DT) cannot be explained by average-ion