A microwave hairpin resonance probe for measuring electron densitydynamics in laser ablation plasmas

摘要

Time evolution of electron density in a laser ablation plume has been investigated using a floatinghairpin resonance probe in conjunction with the ion density measured using a planar Langmuirprobe. The laser plasma plume is produced by ablation of silver using a 248 nm, 26 ns, KrF, YiGlaser. Due to supersonic flow of ions in the plume; measuring the electron density is difficult usinga Langmuir probe, because of energetic ions bombarding the probes surface. Therefore we used afloating hairpin resonance probe for measuring time varying electron density of the plume. Thistechnique depends only on the local electron density and is independent of the ion fluxes receivedby the probe. The ion density on the other hand is simply obtained from the ion flux and ionflight-time measure to a negatively biased probe, at some distance from the target. We observe agood agreement between the electron and ion density measured using two distinct techniques.