Two lens focusing systems for intense ion beams

We have examined two lens focusing systems for intense ion beams using a thin lens model. With the predictions of the thin lens model we designed and built a two solenoidal lens system to simultaneously correct to first order for chromatic aberration and radial divergence. In an experiment conducted on the CASTOR accelerator, which supplied a 350 kV, 60 kA, 125 ns FWHM proton beam, we confirmed detailed predictions of the thin lens model. In particular, we observed the predicted shape of the focus, the predicted factor of two improvement in intensity on axis as compared to a single lens focus, and the predicted optimum first and second lens currents. We have also applied the thin lens model to geometries appropriate to Inertial Confinement Fusion (ICF). The main goal of the ICF studies was to assess the benefit provided by divergence correction. Experimental and computational results will be presented.