Coulomb explosion of hydrogen clusters irradiated by an ultrashort intense laser pulse

Abstract

The explosion dynamics of hydrogen clusters driven by an ultrashort intense laser pulse has been analyzed analytically and numerically by employing a simplified Coulomb explosion model. The dependence of average and maximum proton kinetic energy on cluster size, pulse duration, and laser intensity has been investigated respectively. The existence of an optimum cluster size allows the proton energy to reach the maximum when the cluster size matches with the intensity and the duration of the laser pulse. In order to explain our experimental results such as the measured proton energy spectrum and the saturation effect of proton energy, the effects of cluster size distribution as well as the laser intensity distribution on the focus spot should be considered. A good agreement between them is obtained.

Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser

“…If something induced a breakup of clusters causing a drop in average ion energy at the highest intensities, it certainly did not appreciably affect the Coulomb nature of the expansion at the optimum intensity of 2.8×10 16 W/cm 2 . It has been speculated that once the laser field is intense enough to strip all electrons from a given cluster, the cluster would also experience total outer ionization for electric fields of even greater intensity, resulting in similar ion kinetic energies [12,21]. According to our measurements, this was not the case and much less energetic ions (∼3 keV) were produced at the highest laser intensities near 1×10 18 W/cm 2 .…”

Self-Guided Propagation of Ultrashort Laser Pulses in the Anomalous Dispersion Region of Transparent Solids: A New Regime of Filamentation

“…The situation is more favorable in condensed media such as fused silica (SiO 2 ), where a broad spectral bandwidth of negative GVD extending over more than 2000 nm beyond 1.26 m is available. Several authors have performed numerical simulations of the propagation of IR laser pulses in fused silica [11][12][13]. On the experimental side, measurements in fused silica have shown that the critical threshold for filamentation is reduced [12] and that a broad conical continuum emission is produced [14,15], suggesting efficient pulse self compression.…”

Phase Evolution and THz Emission from a Femtosecond Laser Filament in Air

“…The propagation of intense few-cycle laser fields in a dispersive medium can be described by using a propagation equation in an axial-symmetric coordinates [42], 1) whereẼ(r, z, ω) is the frequency domain laser field, the nonlinear polarizatioñ P NL accounts for the Kerr effect and the polarizationJ ioni is caused by photoelectrons from the tunneling ionization of N 2 and O 2 in air. The collective motion of the tunneling ionized electrons results in a directional nonlinear photocurrent surge described by [11] ∂ t J e (r, z, t) + ν e J e (r, z, t) = e 2 m ρ e (r, z, t)E(r, z, t), (8.2) where ν e , e, m and ρ e denote the electron-ion collision rate, electron charge, mass, and electron density, respectively.…”

“…Interacting with a nonlinear medium, the variation of CEP becomes more complex because of the dispersion of the medium and the plasma effect. Taking the N 2 molecules (with the peak pressure of 100 torr, thickness of 1 mm) ionized by the intense few-cycle laser fields (with the pulse energy of 4 μJ and assuming the diameter of filament is 140 μm), the CEP shift over the interaction length is calculated by solving the propagation equation [42] and plotted in Fig. 8.9b.…”