Spectra of the inner-shell transitions of three Si charge states. Thin lines: No electric field; thick lines: F = 0.5 TV/m is assumed. The strong allowed Kα and the weak, induced by the electric field, forbidden L1-K transitions are seen. The line shapes are area-normalized.
Scheme of the von Hámos spectrometer: Source and detector are located on the axis of the cylindrically bent crystal. Each wavelength is reflected with a Bragg angle Θ by a sector on the crystal surface and refocused onto a point on the axis. φ is the aperture angle of the cylindrically bent crystal.
Ray tracing simulations of the image of a monochromatic point source with the detector at variable distances from the crystal focus. Panel (a) shows these images, their sizes are 5 mm in both directions. The horizontal direction is the dispersion direction. Panel (b) shows the maximum photon flux (full symbols) in the images and the spatial extent (open symbols).
Target and spectrometer geometry used in the experiment.
Parts (100 × 100 pixel) of single pulse CCD images for 5 μm (upper row) and 25 μm (lower row) thick targets. Both targets have an ≈1 μm thick silicon monoxide layer on the rear side. The right column shows the parts of the images recording the Kα emission, the left column shows parts recording the emission at lower energies.
(a) Spectra from the 5 μm targets with (full symbols) and without (open symbols) silicon layer. These spectra were accumulated over 208 and 187 laser pulses, respectively. The errors of the photon counting statistics are smaller than the symbols. (b) Spectrum from a 25 μm thick target, accumulated over 135 laser pulses.
Si Kα emission from 1 μm SiO at the rear side of 25 μm Ti. Spectra from laser pulses where protons were detected (full symbols) are compared with spectra from laser pulses, where no protons were detected (open symbols), for both spectra 15 laser pulses were accumulated. The lower panel shows the difference of the two (protons detected—no protons detected), indicating a line broadening.
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