Cluster size distributions in gas jets for different nozzle geometries

Abstract

Cluster size distributions were investigated in case of different nozzle geometries in argon and xenon using Rayleigh scattering diagnostics. Different nozzle geometries result in different behaviour, therefore both spatial-and temporal cluster size distributions were studied to obtain a wellcharacterized cluster target. It is shown that the generally used Hagena scaling can result in a significant deviation from the observed data and the behaviour cannot be described by a single material condensation parameter. The results along with the nanoplasma model applied to the data of previous high harmonic generation experiments allow the independent measurement of cluster size and cluster density.

High harmonic generation on noble gas clusters

“…The first one can be clearly ruled out, since much larger clusters do not give more signal for higher values of the ellipticity. Our measurements are above the single atom regime, with the smallest cluster size having ∼11 atoms (with a certain approximation for smaller clusters, since the Rayleigh scattering method can safely identify clusters above ∼100 atoms [38,42]). Knowing this, we cannot fully exclude atom-to-neighbour recombination mechanisms, however we also have to consider that our results agree very well with those of Strelkov et al [20] using Ar monomers (atomic targets), as shown in Fig.…”

“…The laser axis was set to be 1 mm from the nozzle exit and the focal spot was 6 ± 0.5 mm before the jet, resulting in an intensity of (1.42 ± 0.22)×10 14 W/cm 2 that was kept constant during the measurements. Thus, the applied intensity was chosen to be near to the optimal conversion rate [25], which is more than a factor 2 higher than the intensity for which the effect of nanoplasma inside the cluster was demonstrated [37,38] This arrangement of the jet and focus selects short trajectories against long ones [39]. Gas clusters were injected into the chamber with a commercial valve (Parker series 9) using a supersonic de Laval nozzle which is designed for laser-plasma experiments [40].…”

“…We used Ar and Xe gas at backing pressures of 1, 10, 20 bars (Ar) and 1, 5, 10, 14 bars (Xe), respectively. The cluster sizes were determined by Rayleigh scattering diagnostics [38]. Assuming spherical clusters, an approximate diameter can be calculated with the van der Waals radii [41]: 1.88 Å for Ar and 2.16 Å for Xe (see Fig.…”

Nonlinear wakefields and electron injection in cluster plasma

“…As a reference, cluster sizes for argon and hydrogen gas jets were studied for different geometries in [5,7] finding cluster radii between 8 nm and 20 nm for backing pressures between 12 bar and 16 bar.…”

“…Cluster plasmas are produced when atomic structures which were formerly held together by van der Waals forces are ionized within a short amount of time. The clusterization process in high pressure gas jets was described and characterized in [1][2][3][4][5][6][7].…”