Global simulation for laser-driven MeV electrons in fast ignition.
A comprehensive examination of the interaction of a picosecond-long ignition pulse on high-density (40 times critical density) pellets using a two-dimensional particle-in-cell model is described. The global geometry consists of a 50 mum diameter pellet surrounded by a corona which is isolated by a vacuum region from the boundary. For cone-attached targets, as much as 67% of the incident laser energy is absorbed with 12% sent forward as fast electrons in a 23 degrees cone. The current filaments are driven by the Weibel instability of the forward-going fast electron flux and its return current with the ions playing an important role of neutralizing the space charge. No global current filament coalescence has been observed. The electron distribution function obeys a power law, which begins at E approximately 0.2 MeV and falls off as E-(2-3).
Ren
C
C
Department of Physics & Astronomy, University of California-Los Angeles, Los Angeles, CA 90095, USA.
Tzoufras
M
M
Tsung
F S
FS
Mori
W B
WB
Amorini
S
S
Fonseca
R A
RA
Silva
L O
LO
Adam
J C
JC
Heron
A
A