Figure 3

(a) Simulated X-ray energy spectra emitted from the sample and normalized to the incident proton charge. The left spectra are obtained with 2.5 and 5.5 MeV protons; the right spectra result from 2D-PIC laser-driven proton irradiation (200 nm substrate with 0 and 4 μm near-critical thickness case studies). (b) Number of emitted characteristic X-rays per unit time as a function of the average incident proton energy for all the elements. Blue color bands refer to conventional accelerators; purple, red and yellow round dots refer to 2D-PIC laser-driven sources with 0.2, 0.6 and 2.0 μm substrate thicknesses, respectively; the cross markers are obtained with 3D-PIC laser-driven protons