Experimental scheme for proton imaging (left) and for chirped shadowgraphy (right).
Proton images taken ≈210 ps after firing the laser beam. gas at 15 bars (left), 30 bars (center), and 100 bars (right). In all cases, the size of the radiochromic films is , the proton target Au, the electron target Al, the distance proton target—gas jet 5 mm, the distance gas jet—films 38 mm, and the energy on the proton target ≈22 and 1.1 J on the electron target. In all images, the thick line shows the approximate position of the electron target and the arrow shows the approximate position to which the laser beam was focused on target front side.
Proton profile obtained from optical densities (in arbitrary units) of radiochromic films obtained with the gas, without and in presence of the metal target (with the main laser beam fired). In the second case, we also show the proton profile corrected for the source profile. Note that all protons are expelled from the inner region, where we get the same value of optical density of regions at the edges of the proton beam.
Chirped shadowgraphy images for a Al target and an Ar jet at 20 bars (bottom) and 100 bars (top).
Reconstruction, for typical shots, of the spatial expansion of the electronic cloud vs time for different gas pressures and gas type. Also shown the typical error bar arising from considering different laser shots.
(a) Simulation of a proton radiography image obtained with 4 MeV proton energy and the parameters: , , , , and (internal and external fall-off distances); (b) scheme for the calculation of electric field needed to remove all the protons from the origin to the distance .
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