X-ray transverse image of the channel and axial Kr(L) spectrum recorded with a mica von Hámos spectrograph
Figure 8. X-ray transverse image of the channel and axial Kr(L) spectrum recorded with a mica von Hámos spectrograph. Single-pulse data correspond to file 677/18 May 2012. (a) Transverse x-ray pinhole camera image of plasma channel morphology that gives an upper bound for the source size ΔCh 150 µm. The spatial resolution of the camera is estimated to be ~50 µm. (b) Two-dimensional Kr(L) axial spectrum recorded with a mica von Hámos spectrometer that gives an estimated source size of ΔSp 150 µm, a value that matches the corresponding width of the x-ray image in panel (a). (c) Isometric view of the axial von Hámos recording showing the spectral peak designated by A with a width δλ,1 3 eV for the Kr26+ 3s → 2p transition at λ 7.5 Å that is also represented in figure 7(a). (d) Magnified cross section of the spectral peak A shown in panel (c) that illustrates its spatial width (FWHM) ΔSp 135 µm. This source size is within one pixel of the spatial diameters estimated in panels (a) and (b).
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.