Electron number density measurements in magnesium laser produced plumes

Interferometry has been used to investigate the spatio-temporal evolution of electron number density following 248 nm laser ablation of a magnesium target. Fringe shifts were measured as a function of laser power density for a circular spot obtained using a random phase plate. Line averaged electron number densities were obtained at delay times up to ∼100 ns after the laser pulse. Density profiles normal to the target surface were recorded for power densities on target in the range 125–300 MW cm−2.

Three dimensional number density mapping in the plume of a low temperature laser ablated magnesium plasma

Simultaneous optical absorption and laser-induced fluorescence measurements have been used to map the three-dimensional number densities of ground-state ions and neutrals within a low-temperature KrF laser-produced magnesium plasma expanding into vacuum. Data is reported for the symmetry plane of the plasma, which includes the laser interaction point at a delay of 1 μs after the ∼30 ns KrF laser ablation pulse and for a laser fluence of 2 J cm−2 on target. The number density distributions of ion and neutral species within this plane indicate that two distinct regions exist within the plume; one is a fast component containing ions and neutrals at maximum densities of ∼3×1013 cm−3 and ∼4×1012 cm−3, respectively and the second is a high-density region containing slow neutral species, at densities up to ∼1×1015 cm−3.

Optical Thomson scatter from a laser-ablated magnesium plume

We have carried out an optical Thomson scatter study of a KrF laser-ablated Mg plume. The evolution of the electron temperature and density at distances 2-5 mm from the target surface has been studied. We have observed that the electron density falls more rapidly than the atomic density and believe that this is a result of rapid dielectronic recombination. A comparison of the electron density profile and evolution with simple hydrodynamic modeling indicates that there is a strong absorption of the laser in the plasma vapor above the target, probably due to photoionization. We also conclude that an isothermal model of expansion better fits the data than an isentropic expansion model. Finally, we compared data obtained from Thomson scatter with those obtained by emission spectroscopy under similar conditions. The two sets of data have differences but are broadly consistent.

Le 'bon Allemand' dans le roman français de l'immédiat après-Seconde Guerre mondiale: une erreur de casting?

The end of the Occupation, which was much more violent than its beginning, dramatically affected the overall perception of Germans and Germany for many years in post-WWII France. This vision is of course reflected to a large extent in French literature. Yet, paradoxically, many novels—including the ‘best-sellers’ E ´ ducation europe´enne (1945) by Romain Gary, Mon Village a` l’heure allemande (1945) by Jean-Louis Bory or Les Foreˆts de la nuit (1947) by Jean-Louis Curtis—contain a ‘good German’ character. Firstly, this article will give an overview of the dominant representations of Germans in post-WWII France, before suggesting that the ‘good German’ character follows both a literary tradition and the humanist values of the French Resistance, to which these writers claim to subscribe. Finally, it will show how this character, far from blurring the Manichean ideology of the novel in which he appears, actually reinforces it.