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

Abstract

The elliptical magnetic mirror scheme for guiding fast electrons for Fast Ignition proposed by Schmitz (H.Schmitz et al., Plasma Phys.Control.Fusion,54 085016 (2012)) is studied for conditions on the multi-kJ scale which are much closer to full-scale Fast Ignition. When scaled up, the elliptical mirror scheme is still highly beneficial to FastIgnition. An increase in the coupling effiency by a factor of 3-4 is found over a wide range of fast electron divergence half-angles.

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.…”

The effect of grading the atomic number at resistive guide element interface on magnetic collimation

“…This "interior" magnetic field is due to the inhomogeneous propagation of the fast electrons. 10 The generation of these fields within the guide is undesirable and inhibits radially uniform fast electron heating. Magnetic fields interior to the guide are not observed in simulations B, C, and D where v < 1 although r guide > r spot in simulations C and D. This implies that more uniformity of the fast electron propagation is obtained in these guides.…”

“…These "interior" magnetic fields are due to inhomogeneous propagation of the fast electrons. 10 They produce an annular transport pattern which leads to preferential heating of the outer regions of the guide.…”

Control of wire heating with resistively guided fast electrons through an inverse conical taper

“…Schemes which exploit the enhanced generation of magnetic fields where fast electron flows intersect resistivity gradients have been proposed for the Fast Ignition (FI) 8,9 variant of Inertial Confinement Fusion (ICF). [5][6][7] Fast electron heating has already been used as a tool for studying the fundamental physics of warm 10 and hot dense matter, 11 and such controlled fast electron transport and heating may be useful for laser-driven x-ray production and for rapid heating of solid density materials for radiation hydrodynamics studies. 12 It should also be noted that the role of resistivity gradients has been noted in other studies not specifically related to either specially engineered targets, 13 or controlling resistive guiding.…”

“…[1][2][3] In a number of previous studies, [4][5][6][7] it has been noted that the strong enhancement of magnetic field generation at the wire-substrate interface due to the resistivity gradient leads to highly effective guiding and confinement of the fast electrons in the wire. Schemes which exploit the enhanced generation of magnetic fields where fast electron flows intersect resistivity gradients have been proposed for the Fast Ignition (FI) 8,9 variant of Inertial Confinement Fusion (ICF).…”