Enhancing the number of high-energy electrons deposited to a compressed pellet via double cones in fast ignition.
Particle-in-cell simulations aimed at improving the coupling efficiency of input laser energy deposited to a compressed core by using a double cone are described. It is found that the number of high-energy electrons escaping from the sides of the cone is greatly reduced by the vacuum gap inside the wing of the double cone. Two main mechanisms to confine high-energy electrons are found. These mechanisms are the sheath electric field at the rear of the inner cone wing and the quasistatic magnetic field inside the vacuum gap. The generation mechanism for the quasistatic magnetic fields is discussed in detail. It is found that the quasistatic fields continue to confine the high-energy electrons for longer than a few picoseconds. The double cones provide confinement and focusing of about 15% of the input energy for deposition in the compressed core.
Cai
Hong-bo
HB
Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan. hongbo-cai@ile.osaka-u.ac.jp
Mima
Kunioki
K
Zhou
Wei-min
WM
Jozaki
Tomoyuki
T
Nagatomo
Hideo
H
Sunahara
Atsushi
A
Mason
Rodney J
RJ