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Recombination of multiply charged ions with electrons at very low relative energies has become a major topic of interest, due to the observation of rates which are enhanced beyond the expectations for radiative recombination. We present results for Ar16+and Ar18+ions from systematic measurements along the argon isonuclear sequence using a high density cold electron beam target (ne= 7 × 109cm-3) at the UNILAC of GSI. The transverse and longitudinal temperatures of the electron beam were determined from DR resonance features observed with metastable Ar16+(23S) ions. The rate at Erel= 0 for radiative recombination of completely stripped Ar18+calculated with electron beam temperatures kT∥ = 0.002 eV, kT⊥= 0.2 eV amounts to α = 10-9cm3s-1. This is exceeded by nearly a factor of 10 by the rate measured in experiments with Ar18+ions.

High intensity Helium beams have been accelerated in the Unilac Wideröe structure. The experimental results, especially the space charge limit and the emittance growth, are reported and compared with computer simulations.