We have developed a delay-line readout technique for microchannel plate detectors with an increased acceptance for multiple hit events compared to standard two-layer delay-line anodes. This technique allows unambiguous determination of arrival time and position of at least two simultaneously detected particles, and/or to detect an even larger number of particles in a shower, as long as any two particles do not arrive both at the same time and at the same position within certain limits. We demonstrate and discuss the abilities and limitations of this technique and the relevance for certain experimental tasks.

For radiative electron capture into the $K$ shell of bare uranium ions, a study of the polarization properties has been performed. For this purpose a position sensitive germanium detector has been used as an efficient Compton polarimeter. This enabled us to measure the degree of linear polarization by analyzing Compton scattering inside the detector and to determine the orientation of the polarization plane. Depending on the observation angle and the beam energy used, the radiation is found to be linearly polarized by up to 80%. In all cases studied, the plane of polarization coincides with the collision plane. The results will be discussed in the context of rigorous relativistic calculations, showing that relativistic effects tend to lead to a depolarization of the radiation emitted.

Isotope shifts in dielectronic recombination spectra were studied for Li-like ${}^A\mathrm{Nd}^{57+}$ ions with $A=142$ and $A=150$. From the displacement of resonance positions energy shifts $\delta E^{142\hspace{0.17em}150}(2s-2p_{1/2})=40.2(3)(6)\mathrm{meV}$ [(stat)(sys)] and $\delta E^{142\hspace{0.17em}150}(2s-2p_{3/2})=42.3(12)(20)\mathrm{meV}$ of $2s-2p_j$ transitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of ${}^{142\hspace{0.17em}150}\delta ⟨r^2⟩=-1.36(1)(3){\mathrm{fm}}^2$. The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.