High-yield implosions using DT-wetted foam for inertial fusion energy (IFE)

IFE applications require high repetition rates, and capsules utilizing DT wetted foams have an advantage over those using a DT ice layer, as the foam does not require a prolonged duration for cryogenic layering. However, the C and O in foam absorb hard x-rays that leak through the conventional ablator (Be, CH, or HDC), leading to an increase in fuel adiabat that can substantially degrade yield.¹ For instance, a larger Be capsule with an OR of 2340 µm gives a 1D yield of 400 MJ. The degree of yield reduction varies between 20% and 80%, depending on the O content, for dry foam at 25 mg/cc. Using a pure DU hohlraum or a Planckian radiation source can help reduce hard x-ray intensity. However, yield degradation can still be relatively high. Therefore, it is essential to develop methods to mitigate the significant yield degradation. The Pusher-Single Shell (PSS),^2,3 was designed with a high concentration of Mo dopant to effectively block hard x-rays. The PSS features a Be ablator with a 20 at.% of Mo in the inner region. The concentration of Mo decreases toward the outer region to minimize the RTI.² The Mo blocks almost all the hard x-rays, minimizing the undesirable changes in the adiabat. The yield degradation associated with wetted foam is notably reduced,⁴ e.g., 23% degradation at a dry foam density of 50 mg/cc (80% for HDC). Furthermore, as the DT-wetted foam density increases with dry foam density, the fuel adiabat decreases, a beneficial outcome.