Low emittance ion beams by laser interaction

Laser ion sources offer the possibility to get ion beam utilizable to improve particle accelerators. Pulsed lasers at intensities of the order of 108 W/cm2 and of ns pulse duration interact with solid matter in vacuum to produce plasma of high temperature and density. The charge state distribution of the plasma generates high electric fields which accelerate ions along the normal to the target surface. The energy of emitted ions has a Maxwell Boltzmann distribution, which depends on the ion charge state. To increase the ion energy, a post-acceleration system can be employed by means of high voltage power supplies of about 100 kV. The post-acceleration system results in a good method to obtain high ion currents by an inexpensive system and the final ion beams find interesting applications in the field of the ion implantations, scientific applications and industrial use. In this work we compare the electromagnetic and geometric properties, like the emittance, of the beams delivered by a Cu and Y target. The characterization of the plasma was performed by a Faraday cup for the electromagnetic characteristics and a pepper pot system for the geometric ones. At 60 kV accelerating voltage and 5.5 mA output current the normalized beam emittance resulted in 0.22 π mm mrad for the Cu target, while under the same accelerating voltage but with 7.4 mA output current, a lower normalized beam emittance value was reached for the Y target. It resulted in 0.14 π mm mrad. The brightness of the beams was of 114 and 378 mA (π mm mrad)−2 for the Cu and Y targets, respectively.