Transversely observed Kr(L) spectrum and corresponding x-ray image of plasma channel morphology
Figure 5. Transversely observed Kr(L) spectrum and corresponding x-ray image of plasma channel morphology. These data represent file 677/18 May 2012. (a) Kr(L) transverse spectrum recorded at longitudinal coordinate Z = −0.9 mm as indicated in panel (b). The Kr26+ 3s → 2p line at λ 7.504 Å exhibits a width δλ,l,t 4.5 eV. The Doppler width expected from a coulomb explosion of the Kr clusters is estimated to be ~4.4 eV; see text for discussion. The limiting spectral resolution of the instrument is estimated to be ~3 eV. (b) X-ray image of Kr(L) emission from the plasma channel recorded transversely with the x-ray pinhole camera. The (y, z) spatial resolution is estimated to be ~50 µm in both coordinates. The centre of the 2.65 mm diameter nozzle is located at Z 0.6 mm. The 248 nm pulse energy was 182 mJ, the plenum pressure was 141 psi, and the nozzle temperature was 262 K.
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.