[en] In (ns-np)-excitation of alkali atoms by polarized electrons some of the spin orientation of the primary electron beam is transferred to the excited atoms because of exchange collisions. In the present work the polarization transfer to Na, K, Rb, and Cs respectively is studied by looking for the circular light polarization transfer of (np-ns)-decay radiation emitted in forward direction following impact excitation by a beam of longitudinally polarized electrons. Maximum polarization transfers are observed at collision energies with values about 1.5 times that of np-thresholds. The transfer increases with increasing atomic number. In case of (6s-6p)-excitation of cesium 45% of primary electron spin polarization is transferred to the atoms at maximum. The agreement with available close coupling data is statisfactory. (orig.)

[en] The present work investigates the 4 ²P impact excitation of potassium by longitudinally polarized electrons. Exchange scattering causes a polarization transfer from the primary electron beam to the ensemble of excited atoms which results in a non zero circular polarization of the fluorescence light emitted in foreward direction. The experimental values of light polarization agree well with values calculated using close coupling data of Moores. (orig.)

[en] Scintillating fibers are of growing interest in high energy physics for applications in calorimetry and in tracking detectors. At present plastic scintillating fibers are mainly used in these applications because of their high light yield and their fast decay rates; however, in thin fibers, required for high spatial resolution, these suffer from low attenuation lengths. Moreover, cross-talk is still a severe problem. As alternatives the authors will discuss the following two concepts: (1) using Ce- and Tb-doped multicomponent glasses as active core material of glass fibers and (2) using liquid scintillator filled glass capillary arrays. The optical properties of the rare earth doped glasses are described and the scintillation efficiency of the fibers and fiber bundles utilizing these glasses as core material are presented. Broad applications appear to be possible with liquid scintillator filled capillary arrays. Suitable liquid scintillators with high refractive index solvents and locally emitting solutes with high yields, short decay times and large Stokes-shifts are available. Arrays can be produced with and without extra mural absorber in various sizes and shapes. Theoretical estimates show that reflection losses at the liquid/glass interface do not effect the overall transmission up to length/diameter ratios of 10⁵. In addition recent results have shown that the system resists radiation doses in the 100 kGy range. Further experimental results obtained at CERN with these arrays will be discussed

[en] Glass capillaries filled with liquid scintillators of high refractive index are shown to be efficient optical light guides with surface reflection losses at the core/cladding interface of less than one part in 10⁵. In addition new binary liquid scintillator compositions are presented, which are suitable as capillary core medium. Coherent arrays of 20 μm diameter capillaries filled with liquid scintillators are technically feasible and could find interesting applications in particle tracking and vertex detection. In particular a massive vertex detector for τ-lepton detection in ν_τ charged current interactions is under investigation. (orig.)