P. Pavlopoulos

Neutron cross-section measurements in the Th–U cycle by the activation method

The 232 Th(n,2n) 231 Th reaction cross-section was measured relative to the 56 Fe(n,p) 56 Mn and 27 Al(n,a) 24 Na reaction cross-sections with the activation method for neutron energies up to 11 MeV. Neutrons were produced by the 2 H(d,n) reaction in the 5.5 MV Tandem accelerator of the NCSR ‘‘Demokritos’’. The characteristic g lines of the product nuclei 231 Th (25.646 keV) and 56 Mn (846.771 keV) or 24 Na (1368 keV) were measured with an 80 mm 2 Si(Li) and a 20% reverseelectrode coaxial germanium detector, respectively. The results indicate that our values are in agreement with the JEF2 and BROND2 database values up to 9 MeV and slightly higher than those from all the libraries for higher energies. r 2003 Elsevier Science B.V. All rights reserved.

Hardware realization of a fast neural network algorithm for real-time tracking in HEP experiments

Abstract A fast pattern recognition system for HEP experiments, based on artificial neural network algorithms (ANN), has been realized with standard electronics. The multiplicity and location of tracks in an event are determined in less than 75 ns. Hardware modules of this first level trigger were extensively tested for performance and reliability with data from the CPLEAR experiment.

Measurements of neutron capture cross-sections for ADS-related studies

Capture cross-sections on several isotopes relevant to accelerator driven systems for energy production and nuclear waste transmutation, and to stellar nucleosynthesis can be studied at the innovative neutron time of flight facility (n_TOF) at CERN. The experimental apparatus is based on a low-mass Si-based flux monitor and a set of C6D6 liquid scintillator detectors. The accurate reconstruction of the cross-sections relies on the pulse height weighting function technique. The set-up used in the measurements is here described. The first results on reference isotopes, Au, Ag and Fe, used to verify the accuracy of the method are presented. � 2003 Elsevier B.V. All rights reserved.

Capture Cross Section Measurements of 186,187,188Os at n_TOF: The Resolved Resonance Region

The neutron capture cross sections of 186,187,188Os have been measured at the CERN neutron time-of-flight facility, n TOF, in the neutron energy range from 1 eV up to 1MeV. In this contribution, we report the results of the analysis of the resolved resonance region (RRR). Resonance parameters have been extracted from a full R-matrix fit of the capture yields with the SAMMY code. A statistical analysis has been performed and the related average resonance parameters are derived. This information is crucial for a complete understanding and modeling in terms of the Hauser-Feshbach statistical model of the capture and inelastic reaction channels, required for the evaluation of the stellar reaction rates of these isotopes. Maxwellian average cross sections for the range of temperatures relevant for s-process nucleosynthesis have been derived from the combined information of the experimental data in the resolved and unresolved resonance regions. A brief account of the implications of this analysis in the estimation of the s-process component of the 187Os abundance and the related impact on the estimates of the time-duration of the galactic nucleosynthesis through the Re/Os clock is given.

Identification of pp → K±π±K0(K0) events using artificial neural networks

Abstract An artificial neural network classifier has been developed in order to separate on-line events containing a decaying neutral kaon. The proposed system performs better than classical selection methods in real-time applications. The biases due to the on-line selection are smaller than few per cent and are known. The system is robust against calibration variations and missing information. A hardware implementation of the algorithm allows an event selection in less than 40 μs and provides a considerable on-line rate reduction in tagged neutral kaon experiments. This classifier has been developed within the framework of the CPLEAR experiment.