Enhanced surface acceleration of fast electrons by using subwavelength grating targets

Abstract

Surface acceleration of fast electrons in intense laser-plasma interaction is improved by using sub-wavelength grating targets. The fast electron beam emitted along the target surface was enhanced by more than three times relative to that by using planar target. The total number of the fast electrons ejected from the front side of target was also increased by about one time. The method to enhance the surface acceleration of fast electron is effective for various targets with sub-wavelength structured surface, and can be applied widely in the cone-guided fast ignition, energetic ion acceleration, plasma device, and other high energy density physics experiments.

Effects of front-surface target structures on properties of relativistic laser-plasma electrons

“…There is a substantial body of experimental work on the effect of surface roughness of targets on laser-plasma coupling, including the laser absorption and the production efficiency and energy spectrum of the generated xrays or ions [14][15][16][17][18][19][20][21]. Various simulation works attribute the observed improvement to a surface area increase and the local field enhancement introduced by the roughness [22][23][24][25].…”

Efficient laser-overdense plasma coupling via surface plasma waves and steady magnetic field generation

“…This point is a drastic limitation in all applications related to particle acceleration and for the fast ignitor scheme in the framework of the inertial confinement fusion. 9,10 To overcome these difficulties, new mechanisms have been investigated in order to improve laser absorption and electron acceleration by considering structured targets [11][12][13][14][15][16] which, in particular, allow the excitation of surface plasma waves (SPWs). 17 These waves are supported by a stepwise profile, overdense (x pe > x 0 , with x 0 the laser frequency) plasma when the condition for resonant excitation are satisfied.…”

Steady magnetic-field generation via surface-plasma-wave excitation

“…Recently the idea of improving the laser absorption in an overdense plasma created by laser-solid interactions has been investigated considering structured targets [8][9][10][11][12] in order to enhance electrons acceleration to values in the range of keV to MeV. Of particular interest is the possibility of laser excitation of surface plasma waves (SPWs) [13] in structured systems in a large range of laser intensities, from low ∼ 10 15 to high 10 20 Wcm −2 μm 2 .…”

“…Typically in these studies a sharp-edged overdense plasma is created by an ultrashort (τ < 100 fs) intense (I λ 2 < 10 15 Wcm −2 μm 2 ) IR laser pulse. Electromagnetic energy is then partially absorbed (< 30%), and electrons are heated through collisionless mechanisms such as sheath inverse bremsstrahlung [4], J × B heating [5], vacuum heating [6], and anomalous skin-layer heating [7].Recently the idea of improving the laser absorption in an overdense plasma created by laser-solid interactions has been investigated considering structured targets [8][9][10][11][12] in order to enhance electrons acceleration to values in the range of keV to MeV. Of particular interest is the possibility of laser excitation of surface plasma waves (SPWs) [13] in structured systems in a large range of laser intensities, from low ∼ 10 15 to high 10 20 Wcm −2 μm 2 .…”