0000000000261614
AUTHOR
J.c. Soares
Characterization of alpha sources prepared by direct evaporation using Rutherford backscattering spectrometry
Abstract Standardization of solutions containing alpha emitting nuclides by direct evaporation onto metal supports is a widely used technique due to its simplicity in providing good quantitative results. In order to avoid inhomogeneity in the deposition surface, polished stainless steel disks and a spreading agent are generally used. These sources are usually measured by alpha spectrometry using passivated implanted silicon detectors. The resolution of the source is a measure of the thickness and homogeneity of the evaporated layer. Rutherford backscattering of He+ and H+ was here used to measure directly this thickness and homogeneity. The results were in agreement with semiconductor detec…
Neutron capture cross section measurements for nuclear astrophyisics at CERN n_TOF
A series of neutron capture cross section measurements of interest to nuclear astrophysics have been recently performed at n_TOF, the neutron spallation source operating at CERN. The low repetition frequency of the proton beam driver, the extremely high instantaneous neutron flux, and the low background conditions in the experimental area are optimal for capture cross section measurements on low-mass or radioactive samples. An overview of the measurements performed during the two experimental campaigns in 2002 and 2003 is presented with special emphasis on the measurement of the capture cross sections of the Os isotopes relevant for the cosmochronology based on the Re/Os clock. http://www.s…
Semipermeable membrane to retain platinum atoms in the electrodeposition process of alpha spectrometry sources
Abstract In earlier work alpha sources electrodeposited on stainless steel backings were analyzed by X-ray fluorescence (XRF) and Rutherford backscattering spectrometry (RBS) finding that during the electrodeposition process large quantities of platinum from the anode were deposited on the cathode surface jointly with the actinides. In the present work, a method to retain platinum atoms using an electrodeposition cell with a semipermeable membrane located between anode and cathode is proposed and tested. The XRF and RBS of alpha sources electrodeposited using this method show that there is less platinum on the stainless steel backing, thereby improving the quality of sources to be measured …
Characterization of alpha sources by Rutherford backscattering spectrometry
Radioactive sources for alpha spectrometry are usually prepared by electrodeposition onto stainless steel backings (and sometimes heated). In earlier work, using the conventional method with passivated implanted planar silicon detectors for the measurements, several sources had been characterized in terms of various parameters by fitting the data of each spectrum to a certain mathematical function. In the present work, the Rutherford Backscattering Spectrometry (RBS) technique with a 1.6 MeV He+ beam was used to study the influence of those factors on the surface distribution and depth profiles of the thin radionuclide layers. Simulations of the measurements using the RUMP computer code wer…
Ion beam analysis and alpha spectrometry of sources electrodeposited on several backings
Abstract Alpha sources of several activities were prepared by electrodeposition of natural uranium onto four different backings: stainless steel, Ni, Mo and Ti. The influence of the activity, the type of backing, and the process of heating the source on the energy resolution of the spectra were investigated using alpha spectrometry and Rutherford Backscattering Spectrometry (RBS) techniques. Diffusion profiles of the radioactive deposits in the backings were obtained from RBS and related to the results using alpha spectrometry
Selective area vapor-phase epitaxy and structural properties of Hg1 − xCdxTe on sapphire
Selective area (SA) Hg1 − xCdxTesapphire layers have been grown using the recently developed technique of the vapor-phase epitaxy (VPE) of Hg1 − xCdxTe layers on CdTesapphire heteroepitaxial substrates (HS), which we have called “VPE on HS technique” (Sochinskii et al., J. Crystal Growth 149 (1995) 35; 161 (1996) 195). First, planar CdTe (1 1 1) 5–7 μm thick layers were grown on sapphire (0 0 0 1) wafers by metalorganic vapor-phase epitaxy (MOVPE) at 340°C for 1–2.5 h using dimethylcadmium and di-isopropyltellurium as precursors. Second, CdTe/sapphire mesas were formed using standard photolithography in the form of alternating parallel linear arrays consisting of 500 × 70 μm2 elements. Thir…
Measurements of the 90,91,92,94,96 Zr n, gamma cross-sections at n_TOF
Neutron capture cross sections of the 90,91,92,94,96Zr have been measured over the energy range from 1 eV to 1 MeV at the spallation neutron facility n TOF at CERN in 2003. The innovative features of the neutron beam, in particular the high instantaneous flux, the high energy resolution and low background, together with improvements of the neutron sensitivity of the capture detectors make this facility unique for neutron-induced reaction cross section measurements with much improved accuracy. The preliminary results of the Zr measurements show capture resonance strengths generally smaller than in previous measurements. Peer Reviewed