Beta energy driven uniform deuterium–tritium ice layer in reactor‐size cryogenic inertial fusion targets

We have studied the effectiveness of beta heating on driving a deuterium–tritium (DT) ice layer toward uniformity within spherical inertial fusion targets. Beta heating results from the deposition of energy from the beta particles from the tritium decay in these targets. These targets are enclosed in a constant temperature environment. This study first considered a one‐dimensional heat transfer model of an idealized target, geometry, and environment. We concluded that beta energy deposition can drive a nonuniform DT ice layer towards uniformity. The maximum rate at which this redistribution can occur is given by dδ/dt=δ̇=−δ/θ_TC, where δ=DT ice thickness in excess of that for a uniform layer and θ_TC=a time constant ≊1500 s. This translates to a factor of 10 reduction in nonuniformity every hour. We also evaluated, and continue to do so, the consequences of deviations from the idealized case assumptions and the selection of certain experimental parameters, on the actual behavior of DT ice in such cryogenic targets. The status of this work is such that we have confidence in the use of beta heating to drive the DT ice toward uniformity for reactor‐size targets (∼1 mm and larger in diameter).