Ti post-ion acceleration from a laser ion source

Abstract

Laser ion sources are employed with success to generate, in vacuum, any ion species with high current, ion energy, charge states and directivity. Nanosecond infrared laser pulses, with intensities of the order of 10¹⁰ W/cm², induce ablation in metals. Ions are produced in vacuum with energy distribution following the Coulomb–Boltzmann-shifted distribution and are ejected mainly along the normal to the target surface. The free ion expansion process occurs in a constant potential chamber placed at high positive voltage variable between 0 and 30 kV, by means of nose along the normal to the target surface. The electric field reaches 5 kV/cm and is used to accelerate Ti ions emitted from the plasma at the INFN–LNS laser facility. The time-of-flight technique is employed to measure the mean ion energies of the post-accelerated particles. Ion charge states and energy distributions were measured through an ion energy spectrometer. Ion energies, charges per pulse, ion currents and beam directivity of Ti beams were measured, and the results were compared with those coming from simulation programs.

Keywords:

• laser-generated plasma
• post-acceleration
• Coulomb–Boltzmann-shifted distributions
• time-of-flight technique
• laser ion source

Acknowledgements

The authors thank the 5th Net Scientific Committee of INFN for the financial support given to the PLEIADI project in which frame this research has been developed.