Spectral details of Kr(L) amplification are presented

<p><strong>Figure 7.</strong> Spectral details of Kr(L) amplification are presented. These data correspond to file 677/18 May 2012. (a) Composite spectra are shown illustrating the axial (red) and transverse (brown) spectra. The transverse Kr(L) spectrum corresponding to <em>Z</em> = 0.3 mm is practically null; the axial von Hámos spectrometer, with the focal plane located at <em>Z</em> = 0.3 mm, as shown in panel (b), reveals sharp spectral structure with a width δ<sub>λ,l</sub>  3 eV that is particularly obvious on the dominant Kr<sup>26+</sup> 3s → 2p transition at λ 7.5 Å. The depth-of-field of the axial von Hámos spectrometer is estimated to be ≤ 300 µm, as indicated by the shaded zone centred at <em>Z</em> = 0.3 mm in panel (b). Compare these spectra to those presented in figure <a href="http://iopscience.iop.org/0953-4075/46/15/155601/article#jpb468344f6" target="_blank">6</a>(a). (b) Transverse x-ray camera image of Kr(L) emission profile with a spatial resolution estimated to be ~50 µm. The axial position <em>Z</em> = 0.3 mm corresponds to the location of the focal plane of the axial von Hámos spectrometer.</p> <p><strong>Abstract</strong></p> <p>Experimental evidence demonstrating amplification on the Kr<sup>26+</sup> 3s→2p transition at λ 7.5 Å (~1652 eV) generated from a (Kr)<em><sub>n</sub></em> 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.</p>