Top view scheme of the interaction chamber. For all detectors, the position is represented by two angles ( ): ψ varying in the equatorial plane, and φ varying with respect to the equatorial plane. p( ) corresponds to the normal to the target front surface. The inset on the top left shows the three different target designs.
Typical images obtained during the experimental campaign varying laser energy, target material, and thickness. The images are chosen so to show the effects of changing: the laser energy (c e), the target material (b e and a c), and the target thickness (c d).
Image of 25 μm thick Cu target, 250 ps after the laser (E = 130 mJ) was focused on it, as obtained by using shadowgraphy technique. Shadowgraphy results shown that (1) the target surface remains intact until the arrival of the laser (from the left), and (2) the target is not completely destroyed by the laser pulse (this may not be the case for thinner targets).
Energy distribution as a function of the energy Cartesian coordinates (top) and time-angular integrated energy spectrum (bottom) of the fast electron beam, as predicted by the PIC code.
Evolution of the electron angular distributions for different energy groups (left) and , (center) and , (right) and , as predicted by the PIC code.
Simple scheme for electron divergence: The faster electrons (red continuous cone) have lower divergence than the slower ones (blue dashed cone) which are characterized by higher divergence . All the electrons contribute to the spot for thin targets z 1, while only faster ones contribute for thicker ones.
signal radius (left) and yield (right) for different type of target as a function of the areal density at .
Theoretical estimation of the total electron penetration range for three different target materials: plastic (top), aluminium (center) and copper (bottom), compared with experimental results (shadowed regions). Theoretical values are calculated at target temperature of 6 eV and three different values of conversion efficiency: 5% (dashed gray), 10% (dotted-dashed red), and 15% (dotted blue). The continuous line is the electron range calculated varying conversion efficiency as a function of laser intensity or electron beam temperature (we use the scaling law proposed by Solodov et al. 34 ). The red line in the left side picture is the electron beam range in plastic for Tc = 2 eV.
Typical results obtained with target [Al(1 μm)-Cu(3 μm)-Al(1 μm)], laser energy EL = 2.9 J and intensity I = 1.8 × W/cm2. (a) spot, (b) pinhole camera image, and (c) HOPG spectrometer showing the line (integrated signal from 4 successive shots). The line is also visible. The imaging system magnification is X4.6 while the pinhole camera magnification is X4. A 13 μm thick foil was placed in front of the pinhole camera to stop photons below 4 keV.
spot radius (left) and yield (right) for different type of targets as a function of the crossed areal density at W/cm2
Theoretical estimations of the total electron penetration range for two different target materials: aluminium (left), and titanium (right) compared with experimental results. Theoretical values are calculated at target temperature of 60 eV (aluminium), 120 eV (titanium), and three different values of efficiencies of conversion: 10% (dashed gray), 20% (dotted-dashed red), and 30% (dotted blue). The continuous line is the electron range calculated varying conversion efficiency as a function of laser intensity according to the scaling law proposed by Solodov et al. 34 ).
Ionization degree and conductivity of plastic, aluminium and copper for I = 1017 W/cm2.
Ionization degree and conductivity of aluminium and titanium for I = 1019 W/cm2.
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