Axial spectrum of Kr(L) emission and corresponding transverse x-ray channel morphology are shown

<p><strong>Figure 11.</strong> Axial spectrum of Kr(L) emission and corresponding transverse x-ray channel morphology are shown. Data correspond to file 520/14 June 2012. (a) Axially recorded Kr(L) spectrum taken with the focal plane of the von Hámos spectrometer positioned at <em>Z</em> = 1.25 mm, the location for the data presented in figures <a href="http://iopscience.iop.org/0953-4075/46/15/155601/article#jpb468344f9" target="_blank">9</a> and <a href="http://iopscience.iop.org/0953-4075/46/15/155601/article#jpb468344f10" target="_blank">10</a>. Spectral narrowing of the Kr<sup>26+</sup> 3s → 2p line at λ 7.504 Å is seen with a width δ<sub>λ,1</sub>  3 eV, a width that matches the axial spectrum shown in figure <a href="http://iopscience.iop.org/0953-4075/46/15/155601/article#jpb468344f7" target="_blank">7</a>(a). (b) The transversely observed Kr(L) x-ray morphology of channel is shown. The centre of the nozzle is located at <em>Z</em> = 0 mm and the focal plane of the axial von Hámos spectrometer positioned at <em>Z</em> = 1.25 mm. The depth-of-field of the spectrometer is indicated by the shaded zone centred on <em>Z</em> = 1.25 mm.</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>