Improvement in the heating efficiency of fast ignition inertial confinement fusion through suppression of the preformed plasma

[摘要] The study of fast electron spectrum optimization by suppression of preformed plasma in fast ignition targets is presented in this work. Integrated fast-electron spectra for electron energies below 3 MeV—the energy range responsible for core heating—are compared for different preformed plasma conditions. The pulse contrast (the ratio of peak-to-pedestal laser intensities) is compared for 10⁸, 10⁹ and 10¹¹ conditions at constant laser energy (~500 J), pulse duration (2 ps), spot size (30% encircled energy on 50µ m diameter) and laser intensity (around 1   ×   10¹⁹ W cm⁻²). The best electron spectrum optimization, consisting of maximized electron number for energies below 3 MeV was obtained with 14µ m thick cone targets. The energy coupling efficiency from heating laser to core plasma, assuming typical core plasma parameters, was estimated to be 2%, although 0.37% was obtained with previous conditions with poor pulse contrast and a 7µ m thick cone target.

[关键词] fast ignition inertial confinement fusion;electron acceleration by ultra intenselaser;laser–plasma interaction