No description available.

<p> A study of the inter-multiplet Ml transition probability for states populated by the (n,γ) reaction in a number of odd-odd nuclei has been performed. Using a high resolution delayed coincidence system and specially developed calibration and data analysis techniques, lifetime measurements have been made for low energy transitions in 28Al, 32P, 40K, 46Sc, 52v and 56Mn. A theoretical model which uses the static magnetic dipole moments of the corresponding odd-A nuclei as the base states has been investigated and was shown able to produce a very satisfactory agreement with the experimental inter-multiplet B(Ml) values.</p> / Thesis / Doctor of Philosophy (PhD)

The technique of recording coincidence events has been applied in the study of several nuclei. Two platinum nuclides have been investigated experimentally through the use of two types of coincidence spectrometers. For both these nuclei, Pt^192 and Pt^194, the investigation included beta-gamma experiments which measured the intensities of the beta groups feeding some of the levels in these nuclei and directional correlation experiments which determined the spins of some of their excited states. A study of the gamma-gamma coincidences of Pt^194 confirmed the decay scheme proposed by previous workers. The directional correlation of the one cascade in Co^58 forms the part of the paper present in Chapter IV. Finally, the appendices contain a description of an apparatus for the preparation of beta sources and an explanation of a set of experiments designed to calibrate the gamma-gamma coincidence spectrometer for its tasks. / Thesis / Doctor of Philosophy (PhD)

With the recent change of the equivalent dose limit for the lens of eyes from 150 to 20 mSv/yr., averaged over 5 years, it is of great importance to investigate the beta-ray spectrum in the maintenance areas of the nuclear power plants, where workers are exposed to mixed beta-gamma fields. A beta-ray spectrometer consisting of a thin silicon detector and a plastic scintillator has been developed, which can accept only beta detection events while rejecting gamma events via coincidence. Based on the spectroscopy system that has been built, a comprehensive upgrade of software and hardware has been conducted. The data acquisition software MC2 was replaced with CoMPASS, developed by CAEN to achieve higher stability and functionality. Optimal shaping parameters and coincidence time window were determined by instruction and sample tests. The fast event signal from the plastic scintillator does not provide enough energy information. Therefore, three approaches were executed, including adding a capacitor, adding a preamplifier, and changing the digital pulse processor to solve the problem. The method of changing digitizer was accepted as the final solution to obtain the best spectrum through benchmark tests. The experimental measurements characterized the response of the beta-ray coincidence spectrometer under the mixed beta/gamma radiation field with a various count rate ratio from 0.00625 to 0.8. Experimental result shows excellent and stable performance of the detector system under a higher beta to gamma ratio. Gamma contribution of the coincidence spectrum, especially in low energy region, significantly increased when beta count rate was controlled to a minor level. Monte Carlo simulations are also carried out using the MCNP6 code to validate the measurements. / Thesis / Master of Science (MSc) / With the recent change of the equivalent dose limit for the lens of eyes from 150 to 20 mSv/yr., averaged over 5 years, it is of great importance to investigate the beta-ray spectrum in the maintenance areas of the nuclear power plants, where workers are exposed to mixed beta-gamma fields. A beta-ray spectrometer consisting of a thin silicon detector and a plastic scintillator has been developed, which can accept only beta detection events while rejecting gamma events via coincidence. Based on the spectroscopy system that has been built, a comprehensive upgrade of software and hardware has been conducted to slow down the signal and achieve higher stability. The experimental measurements characterized the response of the beta-ray coincidence spectrometer under the mixed beta/gamma radiation field with a various count rate ratio from 0.00625 to 0.8. Experimental result shows excellent and stable performance of the detector system under a higher beta to gamma ratio. Gamma contribution of the coincidence spectrum, especially in low energy region, significantly increased when beta count rate was controlled to a minor level. Monte Carlo simulations are also carried out using the MCNP6 code to validate the measurements.

An initial study of the delayed coincidence technique and methods of analysis has been made. Three methods of analysis are attempted: the slope, the method of moments and the "unfolding" method. Necessary corrections to minimize errors of calculation are proposed and numerical checks of the methods are performed. Half lives of the levels 829 and 864 keV in ¹¹⁵In were separately measured by means of β-γ delayed coincidence technique. A Ge (Li) detector of 4cc active volume, in conjunction with a constant fraction timing discriminator, was used to detect the γ- branch. The data from this experiment were analysed by the above mentioned methods and the proposed corrections were made. Good correspondence was obtained between the unfolding and the method of moments, while the valµe obtained using the slope method was slightly higher. The numerical test of the analysis methods could not explain this difference completely. It was assumed that the difference was due to fluctuations in the collected data. / Master of Science

Made available in DSpace on 2014-10-09T12:48:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:57Z (GMT). No. of bitstreams: 1 09020.pdf: 3988111 bytes, checksum: 2604028ac5be423a7b85b745a959fb86 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:48:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:57Z (GMT). No. of bitstreams: 1 09020.pdf: 3988111 bytes, checksum: 2604028ac5be423a7b85b745a959fb86 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Abstract Experimental synchrotron radiation induced electron- and ion spectroscopies together with electron-ion and ion-ion coincidence techniques as well as electron energy loss spectroscopy have been used to study the electronic properties of several vapor phase samples. In this thesis studies of the electronic structure and fragmentation of Sb4 clusters, photo- and Auger electron spectroscopy of atomic Si and Pb as well as ultra high resolution VUV absorption of vapor phase KF molecules have been performed. The instrumentation and techniques used in the studies, especially the electron energy loss apparatus and the newly built ultra high resolution FINEST beamline branch, are presented.

Os principais mecanismos da reação supracitada foram examinados: breakup, transferência, fusão completa e incompleta e excitação inelástica. / The mains mechanisms of the mencioned reaction were study, namely: breakup, fusion (complete and incomplete), transfer and inelastic excitation.

Os principais mecanismos da reação supracitada foram examinados: breakup, transferência, fusão completa e incompleta e excitação inelástica. / The mains mechanisms of the mencioned reaction were study, namely: breakup, fusion (complete and incomplete), transfer and inelastic excitation.