Perturbation of the ECR plasma ion energy distribution function during the interaction with a laser-generated plasma

The electron cyclotron resonance coupled to a laser ion source for charge state enhancement method, based on the coupling of a laser ion source with an electron cyclotron resonance (ECR) ion source in order to produce highly charged ions of metallic elements, demonstrated its validity some years ago, although some aspects remained unclear, in particular the optimization of the ion capture probability through ion-ion scattering. Another crucial item that determines the efficiency of the coupling is the variation of the energy content of the electron cyclotron resonance ion source (ECRIS) plasma: when the ions produced by means of the laser ablation are captured, they deposit a great amount of energy into the magnetically confined plasma. The released energy perturbs the ECR plasma, thus increasing the losses onto the chamber walls and the emittance of the extracted beam. Only a rough estimation of the energy content perturbations has been available up to now, so Monte Carlo simulations have been used to improve the description of the ion capture mechanism and the energy perturbation. The real magnetic field structure of ECRIS and a realistic plasma density distribution have been taken into account, as the code considers the ECR plasma properties emerging from particle in cell (PIC) simulations and from experimental measurements that permit one to determine locally the energy perturbation. The effects of electric fields on the ion stream coming from the laser-ablated target have been also considered, resulting in better coupling after the ion energy decrease.