Design of a High-Foot High-Adiabat ICF Capsule for the National Ignition Facility

Abstract

The National Ignition Campaign's [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] point design implosion has achieved DT neutron yields of 7.5×10(14) neutrons, inferred stagnation pressures of 103 Gbar, and inferred areal densities (ρR) of 0.90 g/cm2 (shot N111215), values that are lower than 1D expectations by factors of 10×, 3.3×, and 1.5×, respectively. In this Letter, we present the design basis for an inertial confinement fusion capsule using an alternate indirect-drive pulse shape that is less sensitive to issues that may be responsible for this lower than expected performance. This new implosion features a higher radiation temperature in the "foot" of the pulse, three-shock pulse shape resulting in an implosion that has less sensitivity to the predicted ionization state of carbon, modestly lower convergence ratio, and significantly lower ablation Rayleigh-Taylor instability growth than that of the NIC point design capsule. The trade-off with this new design is a higher fuel adiabat that limits both fuel compression and theoretical capsule yield. The purpose of designing this capsule is to recover a more ideal one-dimensional implosion that is in closer agreement to simulation predictions. Early experimental results support our assertions since as of this Letter, a high-foot implosion has obtained a record DT yield of 2.4×10(15) neutrons (within ∼70% of 1D simulation) with fuel ρR=0.84 g/cm2 and an estimated ∼1/3 of the yield coming from α-particle self-heating.

On the importance of minimizing “coast-time” in x-ray driven inertially confined fusion implosions

“…Implosion data from the high-foot implosion campaign [13][14][15][16][17][18] showed that many ignition relevant parameters (neutron yield, stagnation pressure, etc.) varied strongly with coast-time 19,20 especially as t coast was reduced to a mere hundreds of pico-seconds.…”

Energy Penetration into Arrays of Aligned Nanowires Irradiated with Relativistic Intensities: Scaling to Terabar Pressures

“…However, the creation of matter in this regime in the laboratory has been limited to the central hot spot of the spherically imploded capsule in inertial confinement fusion experiments conducted using the world's highestenergy lasers (8,9). The ability to create UHED matter using smaller facilities is thus of great interest to make this extreme plasma regime more accessible for fundamental studies and applications.…”

Free electron degeneracy effects on collisional excitation, ionization, de-excitation and three-body recombination

“…A double peak in the pressure profile of 10 carbon shell material in the National Ignition Facility (NIF) point design due to carbon Li-like ions may have caused reduced neutron production [5]. ICF seeks to compress material at low temperatures (with pressures below 1.7 times Fermi degenerate [6]]) with high incident radiation flux (e.g.…”