No description available.

Beryllium-7 is a cosmogenic radionuclide produced in the atmosphere through the spallation of nitrogen and oxygen nuclei by cosmic-ray-produced neutrons and protons. It is carried in the atmosphere attached to aerosols and is deposited on land and ocean surfaces by wet and dry deposition processes. Beryllium-7 decays by electron capture to lithium-7 and has a half-life of approximately 53 days. It is a potentially useful radionuclide for studying different natural processes. This thesis presents a collection of scientific papers on the occurrence of beryllium-7 in the natural environment, particularly in the Southeast Queensland region of Australia. It shows the results of experimental measurements and discusses their implications. Overall, this thesis contributes to advancing our understanding of the distribution and behaviour of beryllium-7 in the natural environment and provides a foundation for the development of nuclear techniques for the evaluation of environmental problems.

Thesis (M.S.); Submitted to Central Missouri State University, Warrensburg, MO (US); 17 Dec 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. Kerr, Kent. NNSA Kansas City Site Office (US) NNSA Kansas City Site Office. 12/17/2004. Report is also available in paper and microfiche from NTIS.

In Medizin und Technik besteht ein Bedarf an flexiblen, miniaturisierten Dosisleistungs-messgeräten mit hoher Ortsauflösung für den Einsatz in Strahlungsfeldern hoher Dosisleistung und Dosisleistungsgradienten. Lichtwellenleiterbasierte Dosisleistungsmess-systeme können diese Anforderungen erfüllen. Sie bestehen aus einem strahlungssensitiven Leuchtstoff, welcher über einen flexiblen Lichtleiter an einen Lichtdetektor gekoppelt ist. Die Eliminierung des dominierenden Störeinflusses, des bei Bestrahlung des Lichtleiters generierten Stem-Effekts, ist eine inhärente Herausforderung aller lichtwellenleiter¬basierten Dosisleistungsmesssysteme. In der vorliegenden Arbeit wird ein solches System unter Verwendung der Lumineszenz der gewebeäquivalenten Detektormaterialien Berylliumoxid und Lithiumtetraborat realisiert. Der Schwerpunkt liegt dabei auf der Untersuchung von Methoden der Stem-Eliminierung unter Nutzung der zeitlichen Charakteristik der Lumineszenzmaterialien sowie der zeitlichen Struktur des Strahlungsfeldes oder einer modulierten optischen Stimulation. Eine performante Ausleseelektronik auf FPGA-Basis ermöglicht Echtzeit-Messungen mit einer Abtastung von 10 ns. Verschiedene Auswertemethoden generieren aus den Rohdaten in Zeitstempelform eine stem-unabhängige, dosisleistungsproportionale Detektorantwort. / In medicine and technology there is a demand for flexible, miniaturized dose rate measurement systems with high spatial resolution for the application in radiation fields of high dose rates and dose rate gradients. Fiber optic coupled dosimeters can meet these requirements. They consist of a radiation sensitive luminescent material which is connected to a light detector with a flexible light guide. The elimination of the dominant perturbation, which is the stem effect generated by irradiation of the light guide, is one inherent challenge of all fiber optic dosimeters. In the present work such a system is realized, using the luminescence of the two tissue equivalent detector materials beryllium oxide and lithium tetraborate. The main focus is on the investigation of methods of stem elimination, exploiting the temporal characteristics of the luminescent materials, as well as the time structure of the irradiation or a modulated optical stimulation. For this purpose, capable FPGA-based read out electronics are employed, which enable real time measurements with 10 ns sampling. Different methods of analysis process the time stamp raw data and generate a stem-free, dose rate proportional detector response.

Este trabalho teve como foco principal a caracterização espectroscópica dos haletos de berílio, BeCl, BeBr e BeI. O conhecimento acerca dessas espécies foi ampliado significativamente através do cálculo de parâmetros de difícil caracterização experimental. Como os poucos trabalhos experimentais realizados para esses haletos apresentam resultados inconclusivos para a transição C 2Σ+ - X 2Σ+, através do cálculo acurado de probabilidades de transição foi possível oferecer uma nova interpretação para os dados existentes, apresentando inclusive resultados para as outras transições eletrônicas até o presente desconhecidas. Cálculos utilizando o método de Interação de Configurações Multirreferencial (MRCI) com um conjunto de funções de base consistentes na correlação de qualidade quintupla-zeta foram utilizados para se obter as curvas de energia potencial associadas ao primeiro e segundo canais de dissociação para os estados dubleto e quarteto dessas espécies. Parâmetros espectroscópicos como as constantes vibracionais we, wexe, a constante rotacional Be e a distância de equilíbrio foram determinados para os estados de mais baixa energia. Além disso, foram calculadas a energia de excitação (Te) e a energia de dissociação (De) com e sem a inclusão de efeitos spin-órbita. Os resultados obtidos expandiram significativamente nosso conhecimento sobre os estados eletrônicos dessa espécies. Para os estados já investigados experimentalmente, houve boa coerência entre os parâmetros calculados e experimentais. As diferenças de energia entre os dois canais no limite de dissociação para as moléculas BeCl, BeBr e BeI obtidas neste trabalho foram, respectivamente: 21835, 21889 e 21998 cm-1, em concordância com o respectivo resultado experimental das três espécies (21980 cm-1). A determinação teórica da energia de dissociação D0 foi bastante satisfatória. Obtivemos 92,24; 72,77 e 51,75 kcal·mol-1, respectivamente, para as moléculas BeCl, BeBr e BeI incluindo os efeitos spin-órbita, comparados a 91,78, 71 e 57 kcal·mol-1. Para uma análise mais completa das curvas de energia potencial, elas também foram obtidas considerando-se os efeitos relativísticos. A constante de acoplamento spin-órbita calculada na região de equilíbrio de cada uma das moléculas BeCl, BeBr e BeI foi, respectivamente: 41, 207 e 324 cm-1, em boa concordância com os resultados experimentais: 52,8, 198 e 361,1 cm-1, respectivamente. A separação spin-órbita no limite de dissociação calculada foi de 823, 3446 e 6975 cm-1 (BeCl, BeBr e BeI), também coerentes com resultados experimentais: 882, 3685,24 e 7603,15 cm-1, respectivamente. Foi ainda realizada uma análise detalhada sobre os canais de dissociação das moléculas HBeP e BePH. A construção de um diagrama de energias relativas permitiu obter um conjunto de dados importantes a respeito de todos os possíveis canais de dissociação. Em particular é mostrado a estabilidade relativa e a energia no limite de dissociação. Para a energia no limite de dissociação obtivemos resultados consistentes com os valores experimentais. Nossos cálculos para os três primeiros canais de dissociação HBeP = H + Be resultaram nos seguintes valores: H (2Sg) + Be (X 4Σ+), 0 cm-1; H (2Sg) + Be (a 2π), 426 cm-1 (exp. 502 cm-1); H (2Sg) + Be (b 2Σ-), 1896 cm-1 (exp. 1976 cm-1). Por fim, pela primeira vez na literatura, o calor de formação e de atomização foram calculados para estas espécies. Para os isômeros HBeP e BePH, a energia de atomização a 298,15 K calculada foi de 119,02 kcal·mol-1 e 107,40 kcal·mol-1, respectivamente; para o calor de formação a 298,15 K, obtivemos 86,14 e 97,76 kcal·mol-1 para as espécies HBeP e BePH, respectivamente. / This work has mainly focused on the spectroscopic characterization of the beryllium halides, BeCl, BeBr and BeI. Knowledge about these species was substantially increased through the calculation of parameters that are difficult to access in an experimental characterization. As the few experimental works carried out for these halides presented inconclusive results for the C 2Σ+ - X2Σ+ transition, we carried out accurate calculations of transition probabilities, thus offering a new interpretation about the existing data, including also results for other electronic transitions as yet unknown. Calculations using the method Multireference Configuration Interaction (MRCI) along with correlation-consistent basis set functions of quintuple-zeta quality were used to obtain the potential energy curves associated with the first and second dissociation channels for the doublet and quartet states of these species. Spectroscopic parameters such as vibrational constants We, WeXe, the rotational constant Be and the equilibrium distance were determined for the low-lying states. Furthermore, we also calculated the excitation energy (Te) and the dissociation energy (De) with and without the inclusion of spin-orbit effects. The obtained results significantly expanded our knowledge about the electronic states of this species. For states already investigated experimentally, there was good consistency between the calculated and the experimental parameters. The energy differences between the two channels in the dissociation limit for BeCI, BeBr and Bel molecules obtained in this work were: 21835, 21889 and 21998 cm-1, in agreement with the corresponding experimental results of the three species (21 980 cm-1). The theoretical determination of the dissociation energy D0 was very satisfactory. We obtained 92.24, 72.77, and 51.75 kcal·mol-1, respectively, for the BeCl, BeBr and BeI molecules including spin-orbit effects, compared to 91.78, 71 and 57 kcal . mol-1. For a more complete analysis of the potential energy curves, they also were obtained considering relativistic effects. The calculated spin-orbit coupling constants in the equilibrium region of BeCl, BeBr and BeI molecules were respectively 41, 207 and 324 cm-1, in good agreement with the experimental results: 52.8, 198, and 361.1 cm-1, respectively. The calculated spin-orbit splitting in the dissociation limit was 823, 3446 and 6975 cm-1 (BeCl, BeBr and BeI) also consistent with the experimental results: 882, 3685.24 and 7603.15 cm-1, respectively. Additionally, a detailed analysis of the dissociation channels of HBeP and BePH molecules was performed. The construction of a relative energies diagram allowed us to derive a set of important data for all the possible dissociation channels. In particular, it is shown the relative stability and the energy in the dissociation limit. For the energy in the dissociation limit, we obtained results consistent with the experimental values. Our calculations for the first three dissociation channels HBeP = H + Be resulted in the following values: H (2Sg) + Be (X 4Σ+), 0 cm-1; H (2Sg) + Be (a 2π), 426 cm-1 (exp. 502 cm-1); H (2Sg) + Be (b 2Σ-), 1896 cm-1 (exp. 1976 cm-1). Finally, for the first time in the literature, the heat of formation and the atomization energy were calculated for these species. For the HBeP and BePH isomers, the atomization energy calculated at 298.15 K was 119.02 and 107.40 kcal . mol-1, respectively; for the heat of formation at 298.15 K, we obtained 86.14 and 97.76 kcal· mol-1 for HBeP and BePH species, respectively.

Viele Festkörperdosimetriesonden haben eine hohe räumliche und zeitliche Auflösung. Jedoch zeigt ihr Messsignal Quench-Effekte beim Einsatz in Protonenstrahlungsfeldern mit hohem linearen Energietransfer (LET). Ohne eine Korrektur dieses verminderten Messeffekts würde dies zu einer Unterschätzung der Dosis führen. In dieser Arbeit wurde ein Messsystem entwickelt, das auf einem an eine Lichtleitfaser gekoppelten sensitiven Volumen aus Berylliumoxid basiert, dessen Lumineszenzlicht während der Messung spektral geteilt wird. Dadurch entsteht eine zusätzliche Information, die eine Aussage über die Restreichweite und somit über den LET von Protonen am Messort ermöglicht. Es konnte gezeigt werden, dass das Signalverhältnis der beiden spektralen Anteile stark mit der Restreichweite von initial monoenergetischen Protonen korreliert. Auf dieser Basis wurde eine Korrekturfunktion implementiert, welche die Dosisunterschätzung für Protonen mit Anfangsenergien kleiner als 145 MeV gut ausgleicht. Eine beobachtete Abhängigkeit der Signalverhältnisbasierten Dosiskorrektur von der initialen Protonenenergie führt jedoch dazu, dass die Korrektur für initial höherenergetische Protonen bei hohem LET weiterhin eine unterschätzte Dosis liefert.:1 Einleitung 2 Physikalische Grundlagen zur Dosimetrie in Photonen- und Protonenfeldern 2.1 Strahlungsfeldgrößen 2.2 Wechselwirkungen von Photonen mit Materie 2.3 Wechselwirkungen geladener Teilchen mit Materie 2.4 Wichtige Größen der Dosimetrie und dosimetrische Konzepte 2.5 BeO-basierte Faser-Dosimetriesonden 3 Material und Methoden 3.1 Verwendetes Messsystem 3.2 Dosis-Kalibrierung des Messsystems im Photonen-Referenzfeld 3.3 Messungen im Protonenfeld an der UPTD 3.4 LET-abhängige Korrektur des Messeffekts 3.5 Verifikation 4 Ergebnisse 4.1 Dosis-Kalibrierung im Photonen-Referenzfeld 4.2 Messungen im Protonenfeld 4.3 LET-abhängige Korrektur des Messeffekts 4.4 Verifikation 5 Diskussion 6 Zusammenfassung / Many solid dosemeters offer high spatial and temporal resolution. However, a common problem is their quenching in regions of high linear energy transfer (LET) during measurements in proton beams. This leads to reduced measurement signal, and thus, to dose underestimation. Hence, a dose correction is necessary. In this work a dosimetric system was developed which is based on a fiber coupled sensitive volume of beryllium oxide. Its radioluminescence signal is split into two spectral parts during measurement. Thereby one can obtain additional information that enables access to the values of residual range and LET of proton beams at the point of measurement. It could be shown that there exists a strong correlation between the signal ratio of both spectral parts of luminescence and the residual range of monoenergetic proton beams. Based on this, a correction function was implemented which allows for the adjustment of dose underestimation for measurements in proton beams of initial energies less than 145 MeV. Nevertheless, the signal ratio based correction function was observed to be dependent on the initial proton beam energy. Hence, the underestimation of the dose remains in the case of higher initial proton energies in regions of high LET.:1 Einleitung 2 Physikalische Grundlagen zur Dosimetrie in Photonen- und Protonenfeldern 2.1 Strahlungsfeldgrößen 2.2 Wechselwirkungen von Photonen mit Materie 2.3 Wechselwirkungen geladener Teilchen mit Materie 2.4 Wichtige Größen der Dosimetrie und dosimetrische Konzepte 2.5 BeO-basierte Faser-Dosimetriesonden 3 Material und Methoden 3.1 Verwendetes Messsystem 3.2 Dosis-Kalibrierung des Messsystems im Photonen-Referenzfeld 3.3 Messungen im Protonenfeld an der UPTD 3.4 LET-abhängige Korrektur des Messeffekts 3.5 Verifikation 4 Ergebnisse 4.1 Dosis-Kalibrierung im Photonen-Referenzfeld 4.2 Messungen im Protonenfeld 4.3 LET-abhängige Korrektur des Messeffekts 4.4 Verifikation 5 Diskussion 6 Zusammenfassung

Beryllium-7 (Be-7) only decays by electron capture into lithium-7 (Li-7) with a half life of 53 days. We study the effect of ionization on this decay rate. We do so by trapping a Be-7 ion plasma in a cylindrical Malmberg-Penning trap and measuring Be-7 and Li-7 concentrations as functions of time by using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). We have simulated these signals in a 2-dimensional electrostatic particle-in-cell (PIC) code. The two spectrum peaks merge at high ion densities whereas at low ion densities they can be resolved. The merged peak shifts linearly according to the relative abundances of these species. We have also simulated singly-ionized beryllium-7 hydride (BeH+) and Li-7 ion plasmas at high densities. These two separate peaks shift according to their relative abundances. We describe an analytical model that explains how these peaks shift.

No description available.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and the Woods Hole Oceanographic Institution), September 2003. / Includes bibliographical references. / The cosmogenic radionuclide ¹⁰Be is a unique tracer of shallow sediment subduction in volcanic arcs. The range in ¹⁰Be enrichment in the Central American Volcanic Arc between Guatemala and Costa Rica is not controlled by variations in ¹⁰Be concentrations in subducting sediment seaward of the Middle America Trench. Sedimentary ¹⁰Be is correlated negatively with ¹⁴³ND/¹⁴⁴Nd, illustrating that ¹⁰Be concentrations varied both between and within cores due to mixing between terrigenous clay and volcanic ash endmember components. This mixing behavior was determined to be a function of grain size controls on ¹⁰Be concentrations. A negative correlation of bulk sedimentary ¹⁰Be concentrations with median grain size and a positive correlation with the proportion of the sediment grains that were <32 [mu]m in diameter demonstrated that high concentrations of ¹⁰Be in fine-grained, terrigenous sediments were diluted by larger grained volcanogenic material. The sharp decrease in ¹⁰Be enrichment in the Central American Volcanic Arc between southeastern Nicaragua and northwestern Costa Rica correlates with changes in fault structure in the subducting Cocos plate. Offshore of Nicaragua, extensional faults associated with plate bending have throw equal to or greater than the overlying subducting sediment thickness. These faults enable efficient subduction of the entire sediment package by preventing relocation of the d6collement within the downgoing sediments. / (cont.) Offshore of Costa Rica, the reduction of fault relief results in basement faults that do not penetrate the overlying sediment. A conceptual model is proposed in which the absence of significant basement roughness allows the d6collement to descend into the subducting sediment column, leading to subsequent underplating and therefore removal of the bulk of the sediment layer that contains ¹⁰Be. Basement fault relief was linearly related to plate curvature and trench depth. The systematic shoaling of the plate from southeastern Nicaragua to northwestern Costa Rica is not explained by changes in plate age for this region. Instead, it is hypothesized that the flexural shape of the plate offshore of southeastern Nicaragua and northwestern Costa Rica represents a lateral response to a buoyant load caused by the thick crust and elevated thermal regime in the Cocos plate offshore of southeastern Costa Rica. / by Robyn K. Kelly. / Ph.D.

The build–up of 6Li and 3He, that is, the strong thermal neutron absorbers or the so called "neutron poisons", in the beryllium reflector changes the physical characteristics of the reactor, such as reactivity, neutron spectra, neutron flux level, power distribution, etc.; furthermore,gaseous isotopes such as 3H and 4He induce swelling and embrittlement of the reflector. The SAFARI–1 research reactor, operated by Necsa at Pelindaba in South Africa, uses a beryllium reflector on three sides of the core, consisting of 19 beryllium reflector elements in total. This MTR went critical in 1965, and the original beryllium reflectors are still used. The individual neutron irradiation history of each beryllium reflector element, as well as the impact of beryllium poisoning on reactor parameters, were never well known nor investigated before. Furthermore, in the OSCAR{3 code system used in predictive neutronic calculations for SAFARI–1, beryllium reflector burn–up is not accounted for; OSCAR models the beryllium reflector as a non–burnable, 100% pure material. As a result, the poisoning phenomenon is not accounted for. Furthermore, the criteria and hence the optimum replacement time of the reflector has never been developed. This study presents detailed calculations, using MCNP, FISPACT and the OSCAR{3 code system, to quantify the influence of impurities that were originally present in the fresh beryllium reflector, the beryllium reflector poisoning phenomenon, and further goes on to propose the reflector's replacement criteria based on the calculated fluence and predicted swelling. Comparisons to experimental low power flux measurements and effects of safety parameters are also established. The study concludes that, to improve the accuracy and reliability of the predictive OSCAR code calculations, beryllium re flector burn–up should undoubtedly be incorporated in the next releases of OSCAR. Based on this study, the inclusion of the beryllium reflector burn–up chains is planned for implementation in the currently tested OSCAR–4 code system. In addition to beryllium reflector poisoning, the replacement criteria of the reflector is developed. It is however crucial that experimental measurements on the contents of 3H and 4He be conducted and thus swelling of the reflector be quantifed. In this way the calculated results could be verified and a sound replacement criteria be developed. In the absence of experimental measurements on the beryllium reflector, the analysis and quantifcation of the calculated results is reserved for future studies. / Thesis (M.Sc. Engineering Sciences (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.