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Doppler Broadening Spectroscopy of the large Ge crystal of an HPGe detector was performed using positrons from pair production of 6.13 MeV γ-rays from the 19F(p,αγ)16O reaction. Two HPGe detectors facing opposite sides of the Ge crystal acting as target provided both coincidence and singles spectra. Changes in the shape of the annihilation peak were observed when the high voltage applied to the target detector was switched on or off, amounting to somewhat less than 20% when the areas of equivalent energy intervals in the corresponding normalized spectra are compared. [ABSTRACT FROM AUTHOR]

The intensities of weak gamma-ray transitions in the 152Sm level scheme from 152Eu decay measured in two gamma-ray coincidence experiments are compared; almost 40 new transitions with intensities around 10-5 gamma-rays per decay and 6 new levels were observed. One of the experiments was reanalysed to confirm some findings and this new data were included in this comparison. Despite some discrepancies, the obtained decay data are in general agreement. The measured energies form a consistent data set but the intensities not, suggesting that the uncertainties are underestimated by a factor of 2. [ABSTRACT FROM AUTHOR]

The Linear Accelerator Laboratory (LAL) of the Instituto de Física da Universidade de São Paulo (IFUSP) is building a two-stage racetrack microtron, which will generate continuous wave electron beams with energies up to 38 MeV. This paper describes the characteristics of the accelerator, and reports on the experimental equipment that will be available in order to pursue the photonuclear physics research program. Operation will begin with the first stage (5 MeV), and concentrate on NRF (Nuclear Resonance Fluorescence) measurements and radiation physics studies. Planned experiments for the second stage explore the cw character of the beam on coincidence experiments. A photon tagger has been already tested with radioactive sources and is ready to be installed. Gamma and neutron detector arrays are being developed for the detailed study of photoneutron reactions. Plans include the study of NRF and pygmy resonances, near the neutron binding energy. [ABSTRACT FROM AUTHOR]

Looking for a possible cosmic-ray chronometer, we have studied the decay modes of [sup 102]Rh[sup m,g]. Its ground state has a half-life of 207 days, and decays to [sup 102]Ru and [sup 102]Pd via β[sup +]+&Vegr; (80%) and β[sup -] (20%) respectively. The meta-stable state has a 2.9-year half-life, and decays to [sup 102]Ru and [sup 102]Rh[sup g] via &Vegr; decay (approx. 100%) and a highly converted isomeric transition (0.23%) respectively, with no indication of β[sup +] or β[sup -] decays. In the absence of the atomic electrons, the isomeric state will only decay either via β[sup +] or an M4 γ decay of 90 keV, both not observed. Measurements of the most probable β[sup +] branch were performed with a germanium multi-detector system, through sum coincidence method, and allow setting an upper limit of 2.5×10[sup -6] per decay, with 95% confidence level. From this upper limit, a partial half-life greater than 1.2×10[sup 6] years is inferred. Investigation of the isomeric transition is under way. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A detailed characterization of a X-ray Si(Li) detector was performed to obtain the energy dependence of efficiency in the photon energy range of 6.4 - 59.5 keV, which was measured and reproduced by Monte Carlo (MC) simulations. Significant discrepancies between MC and experimental values were found when the manufacturer parameters of the detector were used in the simulation. A complete Computerized Tomography (CT) detector scan allowed to find the correct crystal dimensions and position inside the capsule. The computed efficiencies with the resulting detector model differed with the measured values no more than 10% in most of the energy range. [ABSTRACT FROM AUTHOR]