Ion beams from laser-generated plasmas

Abstract

Space‐charge‐limited heavy ion beams have been produced by utilizing the plasma blowoffs generated by 20‐MW bursts of 1.06‐μ radiation from an active Q‐switched Nd:Yag laser. Laser power densities near a moment 1011 W/cm2 on solid targets generate thermalized plasma plumes which drift to a 15‐kV gridded extraction gap where the ions are extracted, accelerated, and subsequently electrostatically focused. The spatially defined ion beams are then magnetically analyzed to determine the charge‐state content in the beams. Results are presented for the more significant amounts of charge states Z?5 contained in the beams formed from carbon,aluminum,copper, and lead targets. The extraction and acceleration technique preserves time‐of‐flight (TOF) information in the plasma drift region, which allows plasma ion temperatures and mass flow velocities to be determined from the Maxwellian ion curve TOF shapes for the individual charge species.