We report on a precision energy loss measurement and theoretical investigation of 100  keV/u helium ions in a hydrogen-discharge plasma. Collision processes of helium ions with protons, free electrons, and hydrogen atoms are ideally suited for benchmarking plasma stopping-power models. Energy loss results of our experiments are significantly higher than the predictions of traditional effective charge models. We obtained good agreement with our data by solving rate equations, where in addition to the ground state, also excited electronic configurations were considered for the projectile ions. Hence, we demonstrate that excited projectile states, resulting from collisions, leading to capture-, ionization-, and radiative-decay processes, play an important role in the stopping process in plasma.

The energy deposition and the atomic processes, such as the electron-capture, ionization, excitation and radiative-decays for slow heavy ions in plasma remains an unsolved fundamental problem. Here we investigate, both experimentally and theoretically, the stopping of 100 keV=u helium ions in a well-defined hydrogen plasma. Our precise measurements show a much higher energy loss than the predictions of the semi-classical approaches with the commonly used effective charge. By solving the Time Dependent Rate Equation (TDRE) with all the main projectile states and for all relevant atomic processes, our calculations are in remarkable agreement with the experimental data. We also demonstrated that, acting as a bridge for electron-capture and ionization, the projectile excited states and their radiative decays can remarkably influence the equilibrium charge states and consequently lead to a substantial increasing of the stopping of ions in plasma.

Transmission experiments of 7-200 keV H-2(+) ions through conical multicapillaries with inlet or outlet diameters of 4/2 mu m and a length of 30 mu m etched in a PC polymer are reported. The yield of the transmitted particles as a function of the capillary tilt angle was measured. The results show that for 200 keV H-2(+) ions the guiding effect disappears but a focusing effect is obtained with a density enhancement factor of 3.5. For 7-50 keV H-2(+) ions their transmitted particle curves exhibit a pair of shoulder peaks on the left-and right-hand side of the center angle 0 degrees. As the ion energy increases, the shoulder-peak structure is found to vanish leaving one peak at 0 degrees.

Secondary electron emission yields in forward and backward direction from carbon foils (thickness of 74 nm) induced by O2+ ions of energies form 1.9 keV/u to 11.3 keV/u have been measured. We find that the forward and the backward electron emission yields increase with the projectile kinetic energy. Further studies showed that the forward and the backward electron emission yields are approximately proportional to the electronic stopping power at the exit and entrance surfaces, respectively.

The transmission of 200 keV H+2 ions through tapered capillaries with inlet/outlet diameters of 4 μm/2 μm and a length of 30 μm is reported. The results indicate that 200 keV H+2 ions can be guided through foils tilted up to ±12.5°. The areal density of the transmitted ion beam is estimated to be ~3.7 times larger than that of incident beam.

Transmission of H-2(+) ions through tapered capillaries in insulating polycarbonate (PC) foil is reported. Guiding, focusing effects and multi-peaks phenomena on ions through capillaries have been studied.

Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe22+ to Xe30+) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface.

A platform for the study of highly charged ions (HCIs), the surface–foil–gas–plasma interaction at IMP Lanzhou, is introduced. Some potentially useful results obtain over the last few years on x-ray emission, ion sputtering, secondary electron emission and the nano-etching effects during HCIs’ impact on surfaces, as well as the guiding effect of nano-capillaries, are reviewed. Our ongoing work on the HCI interaction with plasma is also reported.