Investigation of Plasma Formation with ns Laser by Using Focused Sub-ns Laser Probe

Shunsuke Ikeda,Masahiro Okamura,Takeshi Kanesue,L Torrisi,M Cutroneo

doi:10.1051/epjconf/201816702005

Abstract

A laser ablation plasma formation process was investigated by shooting another laser beam. The initial plasma was created by a mildly focused nanosecond laser beam and the probe laser, which has about ten times shorter pulse length with tightly focussed condition, was irradiated on it. By analysing high temperature plasma created by the probe laser, we could detect an interaction between the initial low temperature plasma and the probe laser. The interaction caused that the velocity of high temperature plasma generated by the sub-ns laser became smaller and the amount of the highly charged ions decreased. We found that the interaction does not occur during the irradiation of the first half of the ns laser. This fact indicates that the plasma is not produced during the first half of the ns laser.

Highlights

Laser ablation plasma is suitable for providing intense ion flux with various charge states ranging from singly charged to fully stripped
For production of low charge state ions, laser intensity on a target surface is close to the laser ablation threshold
If one irradiates a laser target with a focused subnanosecond laser during the irradiation of a mildly focused ns laser pulse, the interaction of the sub-ns laser and the ns-laser plasma depends on the property of the ns-laser plasma

Summary

Introduction

Laser ablation plasma is suitable for providing intense ion flux with various charge states ranging from singly charged to fully stripped. For production of low charge state ions, laser intensity on a target surface is close to the laser ablation threshold. Most of the ions are singly charged for the laser intensity [5, 6]. If one irradiates a laser target with a focused subnanosecond laser during the irradiation of a mildly focused ns laser pulse, the interaction of the sub-ns laser and the ns-laser plasma depends on the property of the ns-laser plasma. The interaction makes the difference of the plasma property after the expansion. One can investigate the property of the ns-laser plasma with temporal and spatial resolutions by analysing the plasma after the expansion with different spot positions and timings of the sub-ns laser

Methods

Results

Conclusion