Search

Abstract: A high power target for neutron production has been developed for the upcoming intense neutron source FRANZ at the University of Frankfurt. At this facility neutrons will be produced via the 7Li(p,n)7Be reaction by bombarding layers of a high temperature Li compound with pulsed proton beams of up to 2mA average current and maximum energies of 2.3MeV. Cooling is achieved by water flowing under high pressure through capillaries in a 1.2mm thick copper target. The heat distribution has been calculated with the fluid dynamics code StarCD/3.26, ensuring that the copper surface remains below at the maximum beam power of 5kW. The moderating effect of the cooling water on the neutron spectra was studied by simulations using the GEANT software package. A prototype target was successfully tested at the Karlsruhe Van de Graaff accelerator, confirming stable operation at a thermal load of 5kW/cm2. [Copyright &y& Elsevier]

Two experiments are reported to study slow potentials in the EEG during reactivation of spatial and verbal information. Subjects had to learn associations between drawings and one, two, or three mediators (locations in Experiment 1, nouns in Experiment 2). During recall, subjects had to decide whether or not two drawings were linked to each other by a common mediator. EEG was recorded during learning and recall. Both experiments were completely equivalent. Irrespective of the quality of the mediators, response time proved to be a linear function of the numbers of mediators to be recalled. Negative slow potentials that accompanied the reactivation of information during anticipation learning and cued recall had a material-specific topography: The maximum was found over the parietal cortex for spatial information and over the left frontal cortex for verbal information. Moreover, the amplitude at these scalp locations varied with the amount of the to-be-retrieved information. The results support the claim of topographically distinct cell assemblies specialized for storage and retrieval of distinct kinds of information.