The high current plasma lens: investigations of fine focusing of high energy heavy ion beams

Fine focusing and transport of heavy ion beams in plasma lenses and z-discharge channels is a significant issue for inertial confinement fusion. Therefore, some of the corresponding questions are addressed in an experimental programme at GSI, using a wall-stabilized discharge as an active plasma lens for fine focusing experiments of heavy ion beams. Very accurate and reproducible focusing of ion beams (Ne, C, Ar, Au) at energies between 10 and 300 MeV a.m.u.−1 is now achieved. Emittance measurements and the determination of the emittance growth that results from scattering in thin foils of the heavy ion beam have been possible with the plasma lens. The minimum achieved spot diameter was 390 μm in the vertical plane at a target distance of 53 mm and 150 kA plasma current, with a plasma column of length 100 mm and diameter 14 mm. The corresponding beam emittance was 40 π mm mrad (r.m.s.).