Characterization of 1064 nm Nd:YAG laser-produced cu plasma

Abstract

The plasma was produced by focusing Nd:YAG laser pulses of 1064 nm wavelength on to a copper target at laser fluences of 5.35, 6.95, and 9.33 J/cm2. An ion collector placed along the target surface normal was used to record the time-of-flight (TOF) ion signal during plasma expansion in vacuum. The TOF ion pulses were deconvoluted using the Coulomb-Boltzmann-shifted function to estimate the available Cu ion charge states, equivalent plasma ion temperature, and accelerating potential in the nonequilibrium plasma. The maximum available ion charge state, equivalent plasma ion temperature, and accelerating potential are found to increase with laser fluence. In the local thermal equilibrium conditions, the accelerating potential can be supposed to apply across a distance of the order of the Debye length. The Debye length and, hence, the electric field in the laser produced plasma at three laser fluences values were estimated. The electric field was in the range of 1 MV/cm and increased with laser fluence. In the laser fluence range used in this work, the sum of thermal and adiabatic energy of the ion was slightly higher than its Coulomb energy.