Study of Laser Plasmas Dynamics Through Real and Virtual Langmuir Probes

A novel technique for laser produced plasmas (LPPs) investigation is proposed. It combines high time resolved measurements using a compact Langmuir probe (LP) with simulated data obtained with a numerical model designated as hybrid laser ablation simulations (HYBLAS). The code simulates charged particle collection with what we will refer to as a virtual LP. With the use of an appropriate experimental setup and with a MATLAB software, which analyzes the experimental I-V curves, LPPs can be investigated properly even if the probe is placed very close to the target surface. The method permits to study the plume expansion with a high temporal resolution and to correctly estimate the self-generated Coulomb electric field inside the plume. It permits to detect the inner structure of the first upcoming expanding plasma. HYBLAS is able to describe the plume expansion at relatively low power densities if the initial conditions are set properly. A direct comparison of the theoretical data with the experimental ones realized on different metal targets shows that this method is able to predict properly the overall plasma expansion in the nanosecond laser pulse duration regime. The virtual probe method was moreover tested by comparing the numerical results with the numerical code called MULTI.