Hot electron and ion spectra on blow-off plasma free target in GXII-LFEX direct fast ignition experiment

Abstract

Polystyrene deuteride shell targets with two holes were imploded by the Gekko XII laser and additionally heated by the LFEX laser in a direct fast ignition experiment. In general, when an ultra-intense laser is injected into a blow-off plasma created by the imploding laser, electrons are generated far from the target core and the energies of electrons increase because the electron acceleration distance has been extended. The blow-off plasma moves not only to the vertical direction but to the lateral direction against the target surface. In a shell target with holes, a lower effective electron temperature can be realized by reducing the inflow of the implosion plasma onto the LFEX path, and high coupling efficiency can be expected. The energies of hot electrons and ions absorbed into the target core were calculated from the energy spectra using three electron energy spectrometers and a neutron time-of-flight measurement system, Mandala. The ions have a large contribution of 74% (electron heating of 4.9 J and ion heating of 14.1 J) to target heating in direct fast ignition.

Diagnosing the fast-heating process of the double-cone ignition scheme with X-ray spectroscopy

“…In the fast ignition scheme, ultra-intense laser pulses are utilized to generate a relativistic electron beam (REB), injecting into the pre-compressed isochoric plasma. The REB then travels forward as a strong current, heating the high-density fuel to generated a hot spot [4][5][6][7][8]. Research conducted over the past few decades has demonstrated that a guiding cone for heating could enhance efficiency by reducing the distance from the source to the core.…”