Correlating hot-electron preheat from the two-plasmon decay instability to $ρR$ degradation for direct-drive implosions on OMEGA

Focused experiments were performed with the goal of isolating the impact of hot-electron preheat on compression in deuterium–tritium (DT) layered, direct-drive implosions on OMEGA. Preheat from the hot-electrons generated by two-plasmon–decay (TPD) activity was varied through the incident laser intensity, with the total preheat energy deposited into unablated DT fuel being inferred using hard x-ray measurements. Results show a clear correlation between the inferred preheat levels and $ρR$ degradation that is consistent with a derived, 1D preheat model. A fit to the results also provides an estimated range of $ρR$ degradation from non-preheat sources for the adiabat ≈5 implosions used in this study. A follow-up study using targets containing Si-doped (5.5%) CH ablators (CHSi) demonstrated results consistent with mid-Z dopants mitigating TPD activity by showing these targets had almost no $ρR$ degradation as the laser intensity was increased up to levels previously considered damaging.. Authors: Cao, D. [University of Rochester, NY (United States)] (ORCID:0000000310852322); Theobald, W. [University of Rochester, NY (United States); Focused Energy Inc., San Francisco, CA (United States)] (ORCID:0000000304149999); Rosenberg, M. J. [University of Rochester, NY (United States)] (ORCID:000000029924304X); Ceurvorst, L. [University of Rochester, NY (United States)] (ORCID:0000000242153326); Patel, D. [University of Rochester, NY (United States)] (ORCID:0000000312044468). DOE Contract: NA0004144. Subjects: Doping; Fusion experiments; Hard X-rays; Laser plasma interactions; Plasma confinement