Hot-Electron–Preheat Mitigation Using Silicon-Doped Layer Shells on OMEGA

The impact of Si-doped CH layer shells on the mitigation of hot-electron preheat has been studied on OMEGA. An implosion experiment with 60-beam symmetric illumination was conducted with the small-spot SG5-650 distributed phase plates and 900-μm-outer-diam targets to increase hot-electron production [W. Theobald et al., Phys Plasmas 29, 012705 (2022)]. This experiment used D₂ gas filled targets with 6% Si-doped CH layer shells with a pure CH inner layer and mass-equivalent pure-CH shells for comparison. Implosions with the Si-doped layer shells produced more neutrons, lower hard x-ray (HXR) signals, and achieved higher areal densities than the pure-CH shell implosions. The hot-electron temperature, T_hot, and total hot-electron energy, E_hot, was inferred from the signal of an absolutely calibrated HXR detector. The Si‑doped layer capsules had lower inferred T_hot and E_hot than the pure-CH shell counterparts by factors of 1.1 and 1.8, respectively, indicating the mitigation of preheat. A follow-up campaign with fully Si-doped CH shells is scheduled to understand the individual contributions to the HXR signal from the corona and payload.