Implosion and core heating requirements in subignition experiments FIREX-I

In the fast ignition realization experiment project phase-I (FIREX-I) [H. Azechi and the FIREX Project, Plasma Phys. Control. Fusion 48, B267 (2006)], core heating up to an ion temperature of 5 keV is expected for subignition-class carbon-deuterium (CD) and deuterium-tritium (DT) fuels. The dependence of the achieved ion temperature on heating pulse parameters, and core density is investigated using two-dimensional simulations. Since the core size in FIREX-I is insufficient for self-ignition, and the confinement time is comparable to the heating duration (∼10 ps), the temperature relaxation between the bulk electrons and ions is important for efficient ion heating. High compression (a core density of ρ>200 g/cm³) is required for pure DT fuel to shorten the relaxation time. In this case, a heating energy of E_h>2 kJ and a duration of τ_h<10 ps are required to achieve an ion temperature of 5 keV. For CD and DT+foam fuels, the requirement for implosion is relaxed since the relaxation is fast, due to a large effective charge; 5 keV ion heating is achieved at ρ≥50 g/cm³ with E_h>2 kJ and τ_h∼10 ps