Equivalent ion temperature in Ta plasma produced by high energy laser ablation

Abstract

High energy laser, 400ps pulse duration, irradiating heavy targets in vacuum produce intense plasma and generate emission of various energetic ion groups. The ion intensity is high along the normal to the irradiated target surface and high charge state and high velocity ions are produced. The characteristics of the ion streams were investigated by using an electrostatic ion energy analyzer and different ion collectors were placed at various angles with respect to the target normal. The ion energy distribution as a function of the ion charge state was measured and the comparison of the properties of different ion groups generated by laser beams at two different energies was carried out. Measurements point out that five ion groups or more can be generated by the laser interaction with the preformed plasma, with different “equivalent ion temperatures.” Slow, thermal, fast, and very fast ions follow a Boltzmann-like distribution; the equivalent temperatures of different ion groups were estimated to reach values up to about 80keV.

Tantalum ion acceleration in laser‐generated plasma and dependence on the pulse duration

“…This result confirms that protons and carbon ions are accelerated by the same value of the electric field conferring about 2 MeV/z. The obtained results confirm those previously obtained at PALS laboratory in 2006 …”

Ge and Ti post-ion acceleration from laser ion source

“…Moreover, the Ge 2+ /Ge 1+ ion yield ratio is about 0.75 while the Ge 3+ /Ge 1+ is about 0.35. These values are in good agreement with the Ge electron ionization cross-section ratios calculable from literature by using the Lotz approach [10].…”

“…The Ge Boltzmann distributions are in agreement with an equivalent plasma temperature of about 40 eV and a plasma intrinsic ion acceleration of about 400 V, which is responsible of the energy shift towards high energy increasing the charge state. At this temperature, obtained by the experimental data fit, as presented in previous articles [10], the mean electron energy should be:…”

Coulomb-Boltzmann-Shifted distribution in laser-generated plasmas from 1010up to 1019 W/cm2intensities

“…Experimental measurements of ion energy distributions demonstrated that the energy distributions are regularly shifted in energy, exhibit a width depending on the plasma temperature and have an intensity distribution correlated to the multiple ionization cross section of the ion species (3). Assuming the main accelerations due to thermal and Coulomb interactions, the ion emission occurring along the normal to the target surface follows the Coulomb-Boltzmann-Shifted (CBS) function (3):…”