Measurement of hot-electron-driven fast ions in polar-direct drive exploding pusher implosions at the NIF*

When hot electrons, generated through laser-plasma interactions (LPI) such as two-plasmon decay (TPD) or stimulated raman scattering (SRS), are accelerated away from a directly driven inertial confinement fusion implosion, the resulting charge gap can lead to acceleration of ions on the capsule surface to MeV energies. In this talk, we will show the first measurements of such MeV protons from polar direct drive exploding pusher (PDXP) implosions on the NIF. Correcting for blowby due to the large NIF laser spots to calculate an effective intensity on capsule, the maximum proton energies generated through this mechanism at NIF are higher than previously observed at OMEGA, but lower than predicted from TPD common wave theory. We explore if this observation is consistent with SRS being the dominant hot-electron generating mechanism on NIF and TPD on OMEGA. In addition, strong energy modulations have been observed in broad spectra of ions born in the NIF PDXP implosions, and we discuss if this could also be related to LPI effects.