抄録
The Fast Ignition (FI) Concept for Inertial Confinement Fusion (ICF) has the potential to provide a
signifi cant advance in the technical attractiveness of Inertial Fusion Energy (IFE) reactors. FI is different
from conventional “central hot spot” (CHS) target ignition due to separate compression and ignition
phases. In this concept, laser (or heavy ion or Z pinch) drive pulses (10’s of ns) are used to assemble a
dense fuel mass and a much shorter (~10 ps) high intensity pulse is used to ignite a small region of it. FI
could signifi cantly reduce the driver energy (and cost) required for an IFE power plant. FI targets can
burn with ~3X lower fuel density than CHS targets, resulting in (all other things being equal) lower
required compression energy and relaxed drive symmetry/target smoothness requirements at a higher
gain. Experiments in this area provide some of the most extreme High Energy Density (HED) conditions
accessible. Here, we report results from experiments carried out using the OMEGA EP laser with ~ 1 kJ
and 10 picosecond pulses. We used a gold cone attached to a copper wire to characterize the electrons
generated by the laser by observing copper Kα and proton emission from the wire. Results show that the
copper Kα yield increases with the laser energy, and proton emission is mainly due to three factors: i) the
divergence of the fast electrons’ beam entering into the wire ii) the collisional scattering of fast electrons
and iii) formation of a cloud of electrons around the wire due to the refl uxing of electrons from the far
end of the wire.
