Fast-neutron induced background in LaBr3:Ce detectors

The response of a scintillation detector with a cylindrical 1.5-inch LaBr3:Ce crystal to incident neutrons has been measured in the energy range En = 2-12 MeV. Neutrons were produced by proton irradiation of a Li target at Ep = 5-14.6 MeV with pulsed proton beams. Using the time-of-flight information between target and detector, energy spectra of the LaBr3:Ce detector resulting from fast neutron interactions have been obtained at 4 different neutron energies. Neutron-induced gamma rays emitted by the LaBr3:Ce crystal were also measured in a nearby Ge detector at the lowest proton beam energy. In addition, we obtained data for neutron irradiation of a large-volume high-purity Ge detector and of a NE-213 liquid scintillator detector, both serving as monitor detectors in the experiment. Monte-Carlo type simulations for neutron interactions in the liquid scintillator, the Ge and LaBr3:Ce crystals have been performed and compared with measured data. Good agreement being obtained with the data, we present the results of simulations to predict the response of LaBr3:Ce detectors for a range of crystal sizes to neutron irradiation in the energy range En = 0.5-10 MeVComment: 28 pages, 10 figures, 4 Table

Investigation of chirality in the case of 102Rh

Excited states in 102Rh were populated in the fusion-evaporation reaction 94Zr(11B, 3n)102Rh at a beam energy of 36 MeV using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in details. A new chiral candidate sister band was found. Lifetimes of exited states in 102Rh were measured using the Doppler-shift attenuation technique and the derived reduced transition probabilities are compared to the predictions of the Two Quasiparticles Plus Triaxial Rotor model

²²⁶Ra and natural uranium in Bulgarian mineral waters

Abstract A complex investigation on Bulgarian mineral waters from certain frequently used sources have been carried out. Specific activities of 226Ra and concentration levels of natural uranium in mineral waters samples were analyzed using nuclear and analytical methods. 226Ra is a naturally occurring radioisotope with a period of half live 1 600 years, which specific activity in water was determined through analysis of the daughter 222Rn. The measurements were carried out using a low-level liquid scintillation counting in a Packard Tri-Carb 2770 TR/SL liquid scintillation spectrometer. Uranium concentration was measured in water samples using a luminescent method. In addition to 226Ra and natural uranium, determination of gross alpha and beta activities of waters was made by means of the same liquid scintillation spectrometer. The concentrations values obtained were compared with data reported by other authors in different countries and with reference values accepted for drinking water. The expected annual effective doses for ingestion of natural uranium and 226Ra in the analysed waters were calculated.</jats:p

Monte Carlo Simulations for Shielding Analysis of the TR-24 Cyclotron at INRNE-BAS

Abstract The Institute for Nuclear Research and Nuclear Energy at the Bulgarian Academy of Sciences is building an accelerator laboratory to operate a TR-24 cyclotron. Thus, a preliminary radiation shielding analysis of the accelerator bunker is required. For this purpose Monte-Carlo simulations have been performed and dosimetric (Dose equivalent) quantities have been estimated in two model geometries - simplified spherical geometry and full-scale bunker, respectively during operation and after the end of the cyclotron life. Our current efforts are directed to the production of 18F thus in all the conducted simulations a water target enriched with 18O is considered. NiGa3 as a target for production of 68Ge has also been simulated and a comparison of the radiation shielding characteristics of the bunker for the two targets has been made.</jats:p