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 Δ_Ch  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 Δ_Sp  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 δ_λ,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) Δ_Sp  135 µm. This source size is within one pixel of the spatial diameters estimated in panels (a) and (b).

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.