Oxford Centre for High Energy Density Science (OxCHEDS)

Abstract:

Experimental results showing hot electron penetration into Cu wires using Kα fluorescence imaging are presented. A 500 J, 1 ps laser was focused at f/3 into hollow aluminum cones joined at their tip to Cu wires of diameters from 10 to 40 μm. Comparison of the axially diminishing absolute intensity of Cu Kα with modeling shows that the penetration of the electrons is consistent with one dimensional Ohmic potential limited transport. The laser coupling efficiency to electron energy within the wire is shown to be proportional to the cross sectional area of the wire, reaching 15% for 40 μm wires. Further, we find the hot electron temperature within the wire to be about 750 keV. The relevance of these data to cone coupled fast ignition is discussed. © 2009 American Institute of Physics.

Abstract:

Guided transport of a relativistic electron beam in solid is achieved experimentally by exploiting the strong magnetic fields created at the interface of two metals of different electrical resistivities. This is of substantial relevance to the Fast Ignitor approach to fusion energy production, since it allows the electron deposition to be spatially tailored-thus adding substantial design flexibility and preventing inefficiencies due to electron beam spreading. In the experiment, optical transition radiation and thermal emission from the target rear surface provide a clear signature of the electron confinement within a high resistivity tin layer sandwiched transversely between two low resistivity aluminum slabs. The experimental data are found to agree well with numerical simulations. © 2009 The American Physical Society.