Generation of B5+ ions from a nanosecond laser plasma

Fully-stripped boron ions are generated by a nanosecond Nd:YAG laser (wavelength λ = 1064 nm, pulse width τ = 7 ns, and maximum laser pulse energy E = 175 mJ) ablation of a B target in vacuum. Time-of-flight and three-grid electrostatic retarding field ion energy-to-charge analyzers are used to detect charge and kinetic energy distribution of the ions. Higher charge states, along with the increase in the number of ions detected, are observed with the increase in the laser fluence. An external electric field between the end of the expansion chamber and a grounded grid is used to extract the ions and accelerate them according to their charge state. For 5 kV accelerating voltage applied to the B target and using a laser fluence of 115 J/cm2, ∼1.5 nC of total charge is delivered to the detector which is located ∼150 cm away from the B target. Ion deflection by an electrostatic field separates the ions from the neutrals and makes this geometry suitable for ion implantation.