  In the double-cone ignition inertial confinement fusion scheme, high density
DT fuel is rapidly heated with high-flux fast electrons, which are generated by
short and intense laser pulses. Gold cone target is usually used to shorten the
distance between the critical surface and the compressed high density DT core.
The material properties of solid gold may affect the generation and transport
of fast electrons significantly, among which the effects of ionization and
collision are the main concerns. In this work, the effects of ionization,
collision and blow-off plasma on laser energy absorption rate are investigated
using the LAPINS code: A three-stage model is adopted to explain the mechanism
of fast electron generation and the change in laser energy absorption rate.
With the increase of the charge state of Au ions, the laser-plasma interaction
transfers to the later stage, resulting in a decrease in laser energy
absorption rate. Collision has both beneficial and harmful effects. On one
hand, collision provides a thermal pressure that makes it easier for electrons
to escape into the potential well in front of the target and be accelerated in
the second stage. On the other hand, collision increases stopping power and
suppress electron recirculation within the target in the third stage. The
vacuum sheath field behind the target enhances the electron circulation inside
the target and thus improves the laser energy absorption, however this effect
will be suppressed when the blow-off plasma density behind the target increases
or collision is considered.
