Details of Thomson images shown in panels (a) and (b) of figure 9

Figure 10. Details of Thomson images shown in panels (a) and (b) of figure 9. These data correspond to file 520/14 June 2012. (a) Isometric view of Thomson image showing extension into the dark x-ray zone Z ≥ 0.5 mm illustrated in figure 9(c). The arrow at Z = Z1  1.8 mm specifies the location of the endpoint of the visible Thomson signal that indicates the presence of ionized material. (b) Axial line-out of the Thomson data pictured in panel (a). A discernable extension of the ionization is visible out to Z = Z1  1.8 mm, a distance that represents a penetration of ~1.3 mm into the x-ray dark region shown in figure 9(c) and is estimated to be comparable to the linear absorption length of the Kr cluster medium. This observation agrees with an earlier estimate [13] of the ability to reach saturation of the absorption in Kr by Kr(L) emission; the clear conclusion was that, with a saturation parameter ħω/σ 400 J cm−2, linear absorption would necessarily govern.

Abstract

Experimental evidence demonstrating amplification on the Kr26+ 3s→2p transition at λ 7.5 Å (~1652 eV) generated from a (Kr)n cluster medium in a self-trapped plasma channel produced with 248 nm femtosecond pulses is presented. The x-ray beam produced had a spectral width of ~3 eV and a corresponding beam diameter of ~150 µm, properties that were simultaneously determined by a two-dimensional x-ray spectral image formed with an axially placed von Hámos spectrometer and a matching Thomson image of the spatial electron density generated by the x-ray propagation.