Time of flight in electrostatic ion analyser for laser produced plasma ion resolving

Abstract

This work addresses the use of an electrostatic analyser as a method of resolving ion species and charge state in the plasma ablation plume. Passing charged particles between a pair of electrodes at a known voltage and correlating with charge to mass ratio Z/M and arrival time, allows one to perform ion spectroscopy. The time of flight showed a decrease in its value with the increase of the potential across the analyser plates. Higher plate voltage requires higher energy particles to pass through, thus higher speed and lower arrival time. LORENTZ 3D numerical software was used to model the trajectory of test ion beams and charged particles showed good agreement with simple modelling of the particles trajectory in an analytical description. The analysis of the experimental data was cross checked with the modelling of the analyser and the simulated LORENTZ 3D results and revealed the same general trends. Small differences were observed between the measured and simulated time of flight (< 1μs) which can be attributed to either the electronics used which has to respond on the order of nanoseconds or the simulated data are imperfect models for physical reality and can be reliable only if they demonstrate agreement with experimental results. This work presents also evidence on successfully resolving 15 of the distinct charged particle species (proton and ions released from the VHS tape used as the primary target in this work) emitted from the laser plasma.