Focusing of Relativistic Electrons in Dense Plasma Using a Resistivity-Gradient-Generated Magnetic Switchyard

Abstract

A method for producing a self-generated magnetic focussing structure for a beam of laser-generated relativistic electrons using a complex array of resistivity gradients is proposed and demonstrated using numerical simulations. The array of resistivity gradients is created by using a target consisting of alternating layers of different Z material. This new scheme is capable of effectively focussing the fast electrons even when the source is highly divergent. The application of this technique to cone-guided fast ignition inertial confinement fusion is considered, and it is shown that it may be possible to deposit over 25% of the fast electron energy into a hot spot even when the fast electron divergence angle is very large (e.g., 70° half-angle).

Control of an electron beam using strong magnetic field for efficient core heating in fast ignition

“…As for the beam divergence, however, it is difficult to control the angular spread of fast electrons since laserplasma interactions are the strongly-non-linear phenomena. Instead of reducing the angular spread, some ideas of the guiding of the fast electron beam with large angular spread have been proposed, e.g., the double cone [4][5][6] and the resistive guiding [7][8][9][10][11][12][13]. Those are based on using of self-generated magnetic fields.…”

Integrated simulation of magnetic-field-assist fast ignition laser fusion

“…By improving the contrast ratio of heating laser pulse, we have eliminated the plasma formation inside the guiding cone before the main part of the heating pulse comes, and successfully reduced the energy (or temperature) of fast electrons with keeping the energy convergence from laser to relativistic electron beam (REB) as constant [4]. As for the beam divergence, instead of the control of laser-plasma interactions to supress the angular spread of the fast electron distribution function, some guiding ideas for fast-electron beam with large beam divergence have been proposed, e.g., guiding schemes using self-generated magnetic fields (resistive guiding [5][6][7][8][9][10][11] and vacuum gap guiding [2,12,13]) and using the externally-applied magnetic fields [14][15][16][17][18]. In the present paper, the latter scheme is discussed.…”

Elliptical magnetic mirror generated via resistivity gradients for fast ignition inertial confinement fusion

“…25,26,28 This is based on the hybrid method developed by Davies in a series of publications. 27 A 250 Â 200 Â 200 grid was used with a 1 lm cell size in each direction.…”