A plastic scintillator array of 3.4m2 total area for the detection of neutrons in medium-energy nucleon–nucleon reactions was constructed and built. Calibration procedures for the detector were developed which allow the monitoring of gain shifts by means of muons from the cosmic radiation. Experiments were performed in order to calibrate the efficiency simulations and study the performance of the detector using the d+t→α+n reaction at 14.7MeV neutron energy and proton-induced deuteron breakup at 300MeV.

A novel scintillating fiber hodoscope in helically cylindric geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles in the internal target experiment EDDA at the Cooler Synchrotron COSY. The hodoscope consists of 640 scintillating fibers (2.5mm diameter), arranged in four layers surrounding the COSY beam pipe. The fibers are helically wound in opposing directions and read out individually using 16-channel photomultipliers connected to a modified commercial encoding system. The detector covers an angular range of 9°⩽Θ⩽72° and 0°⩽ϕ⩽360° in the lab frame. The detector length is 590mm, the inner diameter 161mm. Geometry and granularity of the hodoscope afford a position resolution of about 1.3mm. The detector design took into consideration a maximum of reliability and a minimum of maintenance. An LED array may be used for monitoring purposes.

We study the simultaneous influence of s and d electrons on the local densities of states at transition metal surfaces by using a model Hamiltonian which consists of the Moriya Hamiltonian for the d electrons, an effective one-particle Hamiltonian for the s electrons, and the Coulomb interaction between s and d electrons. The s electron density is calculated by the density functional method. The lifting of the degeneracy of the d states at the surface is explicitly taken into account. As a result, there is a strong reduction of the total charge transfer to the surface by the response of the s electrons. Moreover, there is only a weak dependence of the d and s occupation numbers on the choice of the d-d Coulomb integral Ud-d. The existence of magnetic solutions at the surface is briefly discussed.

In the presence of a surface the L-level width of the Al due to Auger processes is calculated using the simple theory of Inkson for the screened Coulomb interaction near an interface. It is demonstrated that near the surface the L-core level width shows an additional broadening due to surface excitations (surface plasmons). This broadening is especially large for those transitions which result from the L-core orbitals with their dipole parallel to the surface. The result is consistent with the level widths observed experimentally.

For a nondegenerate narrow energy band spanned by a semiinfinite chain of three-dimensional atoms, the electronic potential and the electron density of states are calculated selfconsistently in the vicinity of the chain end. The electron-electron interaction is treated in the Hartree-Fock approximation, using the Green function method. The results for the potential and the density of states are discussed in terms of the parameters which determine the bulk electronic structure, such as the Fermi energy E F and the intra- and interatomic Coulomb repulsion k 0 and K 1 . Futhermore, the self consistent method is extended to an impurity atom at the chain end. The existence of bonding and antibonding surface states is found to depend on both the bulk and impurity parameters, such as the intraatomic Coulomb repulsion U α and the nearest neighbour hopping element T .