HARD PHOTON PRODUCTION IN NUCLEUS-NUCLEUS COLLISIONS AT 30 MeV/u AND 44 MeV/u

Doubly differential cross-sections for Bremsstrahlung production have been measured in the reactions 40Ar + 197Au at 30 MeV/u and 86Kr +12C, AgNat and 197Au at 44 MeV/u. A qualitative analysis of the characteristics of the γ-ray emission suggests strongly that the initial proton-neutron collisions are the main source of nuclear Bremsstrahlung

Suppression of soft nuclear bremsstrahlung in proton-nucleus collisions

Photon energy spectra up to the kinematic limit have been measured in 190 MeV proton reactions with light and heavy nuclei to investigate the influence of the multiple-scattering process on the photon production. Relative to the predictions of models based on a quasi-free production mechanism a strong suppression of bremsstrahlung is observed in the low-energy region of the photon spectrum. We attribute this effect to the interference of photon amplitudes due to multiple scattering of nucleons in the nuclear medium.Comment: 12 pages, 3 figures, submitted to Phys. Rev. Let

Use of Dirac-Coulomb Sturmians of the first order for relativistic calculations of two-photon bound-bound transition amplitudes in hydrogen-like ions

A fully relativistic treatment of the S-matrix elements describing two-photon bound - bound transition amplitudes in hydrogen-like ions is undertaken in the present work. Several selected transitions from the ground state vertical bar 1(2)S > towards the L and M shells (vertical bar 2(2)S >, vertical bar 3(2)S >, vertical bar 3(2)D(3/2)> and vertical bar 3(2)D(5/2)>) are described. For that purpose, we use the complete set of relativistic Sturmian functions derived by Szmytkowski ( 1997 J. Phys. B: At. Mol. Opt. Phys. 30 825) from the first-order Sturm-Liouville problems for the Dirac equation. The method followed consists of writing the matrix elements in terms of Green functions expanded over the first-order Dirac - Coulomb Sturmians. Previous approaches used a Sturmian basis associated with the Gell-Mann-Feynman equation. On the other hand, a distinctive feature of our tensor treatment is that the expressions derived are quite general and could be applied to any multipole of the two-photon bound - bound transitions. In the case of dipole transitions, considered also by Szymanowski et al ( 1997 Phys. Rev. A 56 700) in their calculations, the selection rules derived from our method lead to two additional terms related to l(1p) = 2 and l(2p) = 2. The numerical results obtained for the transition from the ground state vertical bar 1(2)S > towards the L and M shells enable us to draw inferences as to the improvements of our method

Natural radiation exposure to the public in the oil-bearing Bakassi Peninsula, Cameroon

The objective of the present study was to carry out natural radioactivity measurements and corresponding dose assessment in the Bakassi Peninsula, an oil-bearing area located in the Gulf of Guinea. This pilot study required E-perm Electret Ionization Chamber (EIC) exposure in homes and the sampling of soils and foodstuffs representative of the food consumption patterns of the population of Bakassi. The results show high exposure of members of the public to natural radiation. Elevated indoor radon concentrations due to building construction were observed, and high exposure to 210Po attributable to the dietary habits of the local population, mainly consisting of seafood. Finally, a total dose of 34.6 mSv.y-1 was found, much higher than the world average value. In the case of confirmation of the results of this study, countermeasures must be taken into consideration to avoid such a high level of exposure, to reduce the radiation dose to the population. Taking into account the limited number of samples, the present work should be considered as a preliminary study

Radioactivity level and soil radon measurement of a volcanic area in Cameroon

The radioactivity level of soils in a volcanic area in Cameroon was determined and discussed. Thirty soils samples were collected from Buea and Limbé cities located in the south-western Cameroon. These two regions are known for theirs volcanic grounds due to the presence of Mount Cameroon Mountain. The activity concentrations of natural radionuclides as well as that of the fission product were evaluated by gamma-ray spectrometry using a hyper-purity germanium detector (HPGe). The ranges of concentrations in the surveyed soils were 11–17 Bq kg−1, 22–36 Bq kg−1 and 43–201 Bq kg−1 for 226Ra, 232Th and 40K, respectively. The radioisotope 137Cs was also found but in a very small amount. The outdoor absorbed dose rate 1 m above ground with the corresponding annual effective dose rate, assuming a 20% occupancy factor was estimated. The radium equivalent and the external hazard index were also evaluated and results are compared with available data from other studies and with the world average value [United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), 1988. Sources, Effects and Risks of Ionizing Radiation. Report to the General Assembly on the Effects of Atomic Radiation. United Nations, New York; UNSCEAR, 2000. Sources and Effects of Ionizing Radiations. Report to the General Assembly with Scientific Annexes. United Nations, New York]. A solid state nuclear track detector (SSNTD), LR-115 was used for soil radon measurements at a depth of 50 cm. The ranges of soil radon concentrations were 6.7–10.8 kBq m−3 and 5.5–8.7 kBq m−3 in Buea and Limbé, respectively. A positive correlation was found between concentrations of radium measured with γ-spectrometry and the soil radon concentrations measured with the nitrate cellulose detectors. The results of this study provide the radioactivity level in soil of a volcanic area, which has been found to be within the safety limits. The south-western Cameroon can be considered as having normal natural background radiatio