Angular distribution of Cu ions by Nd:YAG laser using faraday cups

Abstract

The infrared radiation from Nd:YAG laser (1604 nm, 8ns, 125mJ, 15.6MW) is focused by IR lens (20cm) to irradiate Cu (99.99%) target in air. The angular distribution and arrival of ions are collected by Faraday Cups (FC). For anisotropic investigation, the cups are arranged at different positions (5cm and 10cm) from the target at different angles (5°, 30°, 45°, 60° and 90°) with respect to the normal on target surface. Faraday Cups are biased at -100V and the ion current signals are obtained on Tektronix TDS 3054B Digital Storage oscilloscope (500 MHz) through integrated circuit. The debris that deposited on FC is also characterized by SEM and EDX analysis. Metallurgical analysis of exposed FC provides evidences of Cu material on Faraday's cup. Mass removal rate for copper target is also calculated. Maximum arrival rate of ions is observed at angle 5° and minimum ions flux is at angle 90° to normal on the target surface. The results show the plume is peaked strongly in forward direction. The laser matter interaction is good for the laser based ion sources generation, which can produce a collimated beam of ions because of forward peaking.