Activation method combined with characteristic X-ray counting : A possibility to measure (alpha, gamma) cross sections on heavy p-nuclei

For an improved modeling of the astrophysical nucleosynthesis of p-nuclei, low energy cross section data of alpha-induced reactions on heavy isotopes are needed. Technical difficulties hamper the experimental determination of these cross sections, therefore the relevant experimental data are almost completely missing. Here we present a new method for the cross section measurements, the activation technique based on the detection of characteristic X-ray radiation. The feasibility of the method is illustrated through the measurement of the Tm-169(alpha, gamma)Lu-173 and Tm-169(alpha, n)Lu-172 reaction cross sections. Despite the relatively long half-life of the reaction products (T-1/2 = 500 and 6.7 days, respectively) it was possible to measure the cross section of the Tm-169(alpha, gamma)Lu-173 reaction between E-c.m. = 13.16 and 17.08 MeV. The Tm-169(alpha, n)Lu-172 reaction cross section was derived from close above the threshold up to E-c.m.. = 17.08 MeV. Details of the new method and the experimental results are presented. (C) 2011 Elsevier B.V. All rights reserved.Peer reviewe

Entwicklung von Verfahren und Werkzeugsystemen zur Hydroumformung hoeherfester Stahlbleche

Available from TIB Hannover: RR 7808(274) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEStifterverband fuer die Deutsche Wissenschaft e.V., Essen (Germany). Stiftung StahlanwendungsforschungDEGerman

Alpha-induced reaction cross section measurements on Eu-151 for the astrophysical gamma-process

In order to extend the experimental database relevant for the astrophysical gamma-process towards the unexplored heavier mass region, the cross sections of the Eu-151(alpha, gamma)Tb-155 and Eu-151 (alpha, n)Tb-154 reactions have been measured at low energies between 12 and 17 MeV using the activation technique. The results are compared with the predictions of statistical model calculations and it is found that the calculations overestimate the cross sections by about a factor of 2. A sensitivity analysis shows that this discrepancy is caused by the inadequate description of the alpha+nucleus channel. A factor of 2 reduction of the reaction rate of Eu-151(alpha, gamma)Tb-155 in gamma-process network calculations with respect to theoretical rates using the optical potential by McFadden and Satchler (1966 Nucl. Phys. 84 177) is recommended

Investigation of alpha-induced reactions on the p nucleus Yb-168

Cross sections for the Yb-168(alpha,beta)Hf171- reactions were measured by means of the activation method using alpha particles with energies between 12.9 MeV and 15.1 MeV. The spectroscopy of the gamma rays emitted by the reaction products was performed using three different HPGe detector types, namely clover-type high-purity germanium detectors, a low-energy photon spectrometer detector, and a coaxial high-purity germanium detector. The results were compared to Hauser-Feshbach statistical model calculations. Within certain assumptions, astrophysical conclusions could be drawn concerning the production of the p nucleus Yb-168. The data in this work can serve as alpha contribution to the current very fragmentary experimental data base for charged-particle induced reactions. In addition, the absolute intensity for nine gamma-ray transitions following the electron capture decay of Hf-171 could be derived. (C) 2013 Elsevier B.V. All rights reserved

Cross section and neutron angular distribution measurements of neutron scattering on natural iron

New measurements of the neutron scattering double differential cross section of iron were carried out at the neutron time-of-flight facilities GELINA and nELBE. A neutron spectrometer consisting of an array of up to 32 liquid organic scintillators was employed, which was designed to measure the scattering differential cross section at eight scattering angles and to simultaneously determine the integral cross section via numerical quadrature. The separation of elastic from inelastic scattering was achieved by analysing the time-of flight dependent light-output distributions to determine the scattered neutron energy. The method was validated by studying elastic scattering on carbon and it was proved to work well for the determination of the elastic cross section. Here, the possibility to extend it to inelastic scattering was investigated too. For these experiments a sample of natural iron was used and the results cover the incident neutron energy range from 2 to 6 MeV. Both the differential and the integral elastic cross sections were produced for natFe, while for inelastic scattering, partial angular distributions for scattering from the first excited level of 56Fe could be determined.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard