[en] The design and performance of a cluster ionizer of the Bayard--Alpert type which is intended to be used in cluster accelerators is described. Positive cluster ions are formed from neutral hydrogen clusters with an efficiency of up to 80%. The mean size of clusters can be reduced by an order of magnitude by multiple ionization followed by splitting into charged fragments due to the repulsion between the individual charges. The fraction of the electrical current carried by cluster ions exceeds 90% of the total ion current. At low particle density two modes of operation are found. The ''normal'' mode A with high efficiency is characterized by space charge compensation of the primary electrons. In mode B this compensation is missing and the efficiency drops to less than 20% of that of mode A

[en] The energy dependence of neutralization of slow highly charged Ar^q+ (q=7,9,13) ions scattered at large angle (Ψ=37.5 deg., θ=75 deg.) from a clean Au(1 1 1) single crystal surface was studied for incidence energies E₀=2, 4 and 8 keV. For Ar⁷⁺ the neutralization yield is almost constant for all incoming ion energies, while with L-shell vacancies (q=9,13), the neutralization yield increases with increasing energy. The experimental results are compared with model calculations that contain side-feeding process of the Ar inner shells, the electron recapture to the surface and the Auger transitions during the ion-surface interaction

[en] We investigated the influence of the scattering geometry and incident energy on the neutralization degree of highly charged Ar^q+ (q=7-13) ions scattered from single Au crystal. It is found that at large scattering angle the probability of detecting multiple charged ions after interaction is high. We point out that besides the interaction time, additional ionization in hard collisions is also important. The results are supported by model calculations which consider electron exchange processes along the ion trajectory. (orig.)

[en] Within the field of particle-induced ionization, particular attention has been devoted to the molecular target H₂. Cross sections were measured for electron emission in 60.5 MeV/u Kr³⁴⁺ + H₂ collisions for electron energies ranging from 2-300 eV at the GANIL accelerator facility in Caen, France. To guide the search for interference, model calculations were performed showing that the ratio of cross sections for the H₂ molecule and the two independent H atoms exhibits an oscillatory pattern. (R.P.)

[en] The interaction of slow, highly charged ions (HCIs) with surface drawn considerable interest in last years. One of the aspects of investigation is the neutralization i.e. final charge state distribution and energy loss of HCIs, which provide integral information about the whole interaction process. Recently, strong shell effects in the neutralization seen in large angle scattering of 4 keV Ar ions from Au surface are reported. When the L-shell of incident ions is opened, the yield of multiply charged scattered ions drastically increased. Further, an influence of energy and scattering geometry on the neutralization process is reported too. The results are compared with a parameterized side-feeding model, which includes electron exchange processes along the ion trajectory. The spectrum obtained for 31.5 keV Ar⁹⁺ incident ions and the scaled energy spectra of single charged scattered ions for 8 keV energy of incident ions are shown for comparison. The main difference arising from the plot is the low energy tail, which originates from multiple collisions inside the solid