Coupling of high-intensity laser light to fast electrons in cone-guided fast ignition.
Cu wires attached to Al cones are used to investigate the energy coupling efficiency of laser light to fast electrons through a cone into a dense plasma. We present experimental and simulation results demonstrating the effect on the energy coupling of effectively placing the cone in a surrounding high density plasma as well as the effect of a large preformed plasma inside the cone. Thick cone walls, simulating plasma surrounding the cone in fast ignition, reduce the energy coupling by a factor of up to 4. An increase in prepulse inside the cone by a factor of 50 further reduces coupling by a factor of 3. Simulations with the pic code lsp that include the laser plasma interaction and the preformed plasma from the flash code show that electron refluxing in thin cone-wall targets enhances coupling to the wire. The implications for full-scale cone-guided fast ignition are discussed.
The Ohio State University, Columbus, Ohio 43210, USA.
K U
KU
Akli
C
C
Orban
D
D
Schumacher
M
M
Storm
M
M
Fatenejad
D
D
Lamb
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RR
Freeman