Дисертації з теми "Neutron emissions"
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Khrbish, Yabia Saleh. "Application of neutron and proton induced prompt emissions for elemental analysis." Thesis, University of Surrey, 1987. http://epubs.surrey.ac.uk/844238/.
Повний текст джерелаSteer, Steven John. "Isomer decay spectroscopy of N<126 neutron-rich nuclei." Thesis, University of Surrey, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493243.
Повний текст джерелаThomson, Brent Wayne. "Determining the origin and possible mechanisms of QPOS in x-ray emissions of neutron stars and black holes." Thesis, The University of North Dakota, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3681134.
Повний текст джерелаQPOs (Quasi-Periodic Oscillations) are time oscillations that appear in the light curve of observational data in x-ray bands. They are of mysterious origin although they are believed to be a result of the intense gravity around neutron stars and black holes and emit x-rays from accretion disks. I investigate a derived ratio between two periods has been found in the QPO data. The two periods, which appear as peaks in the power density spectrum have been found to be in a 3:2 ratio and can possibly distinguish theoretical models. In the work presented here, two physical approaches are developed that can explain the integer resonance ratio. One is a cusp layer model, which is based on a boundary layer model that uses the physical conditions at opposite sides of said layer to explore the magnitude of the vertical versus radial epicyclic frequencies and confirm the anticipated scales of the observed frequencies. It also happens to recreate a 3:2 resonance ratio for the Keplerian angular frequencies at the ISCO, taken as the preferred radius for the boundary layer model.
A toy model was recreated and utilized to emulate the Alfven radius due to the accretion disk's innate magnetic field and explore how it serves as a disruption radius and impacts the accretion of mass and the effective inner edge of the disk. The simulations show that there is no significance deviation from the ISCO as an effective inner edge for the accretion disk due to the magnetospheric influence of the disk alone.
I also invoke a parameter to handle the coupling between the vertical and radial epicyclical frequencies and relate it to the pressure within the disk. I show the coupling is strongest at the equatorial plane where pressure is at its maximum value.
A model I utilize is a relativistic resonance model, combined with a helioseismological approach to explore the pulsation of the inner edge of the accretion disk that imparts the resonance of the accreting matter moving along the Kerr space-time orbits. The helioseismological model gives a characteristic frequency for small perturbations in the stellar matter within the atmosphere of a star. The diskoseismological model extends that principle to material within an accretion disk. I take it to the same extent that the QPO frequencies are due to small perturbations along the marginally stable circular orbit, in the vertical and radial directions and use it as a probe into the inner disk and what information it yields. The inner disk edge, per the model, is treated as a vibrating surface that yields the radial and vertical epicyclic frequencies as characteristic features of the vibration. The epicyclical frequencies found using the physical parameters of the model within the cusp layer inside the disk could explain the physical context of the phenomenon responsible for the creation of the QPOs. An approach within the diskoseismological model uses the cylindrical reference frame of a disk in terms of the distribution of mass in combination with the strong gravity of the central object and the Keplerian velocity and sonic speed to yield a natural resonance ratio of 3/2 as well.
The model can be used as a diagnostic tool to explore the physical phenomena of the material orbits and the disk itself. Most importantly, the model can be used to determine and constrain the ratio of spin to mass of the compact object itself. It yields new information as previously undetermined by any earlier model; the adiabatic index at a specific radius within the accretion disk, which serves to lend insight into the innate phenomena of accretion disks at large. It establishes what were previously unknown information, such as the mass density distribution at a specific radius and outward, the radius of influence in terms of the sonic radius, the accretion rate, and the temperature distribution at the same radius for the accretion disk, as all are dependent on the adiabatic index. In all previous literature, the adiabatic index is taken as an assumptive estimate, and the models build on that assumed value of the adiabatic index. This model allows us to obtain an actual value of the adiabatic index at the ISCO and use it as an establishing feature to refine models on for more physically realistic observations.
Ryan, James. "Measuring the energies and multiplicities of prompt gamma-ray emissions from neutron-induced fission of 235 U using the STEFF spectrometer." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/measuring-the-energies-and-multiplicities-of-prompt-gammaray-emissions-from-neutroninduced-fission-of-235-u-using-the-steff-spectrometer(5fca332e-58ef-463f-96ba-99d87f0ecf44).html.
Повний текст джерелаSnowden, Mareena Robinson. "Nuclear warhead monitoring : a study of photon emissions from fission neutron interactions with high explosives as a tool in arms control verification." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113723.
Повний текст джерелаThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Since the signing of the Nuclear Nonproliferation Treaty, the technical community has been working to develop verification options that provide confidence in the reduction or elimination of nuclear warheads, while respecting countries' requirement of limited access to national secrets. This dissertation used a simplified open-source warhead model as a vehicle to investigate the use of secondary gammas, generated passively by neutron interactions inside high explosive (HE), as a signature for the presence of a warhead-like object. Analytical calculations were done to estimate the detectability of radiative capture and inelastic scatter emissions generated within the warhead model. Results showed the emission of gammas from nitrogen, between 5-7 MeV, to be detectable above background with dwell-times exceeding 90 minutes. These calculations motivated the systematic study of the signal experimentally using surrogate materials to represent the warhead's weapons-grade plutonium and HE. The experiment did not show the expected signals. This motivated a simulation of the mock-up experiment using the radiation transport code MCNP6 to help understand the observed results. The experimental and simulation data suggest that correlated backgrounds from neutron interactions with environmental materials dominate the signal. This finding helped provide a basis for understanding the feasibility and challenges to detecting this neutron-induced gamma signal. Three sets of pulse-height spectra have been analyzed: experimental spectra that looked at the effect of the HE surrogate on the overall detected counts; simulated spectra that helped to understand the underlying contributors to the observed experimental result; and a data-MCNP6 comparison that assessed the accuracy of the simulated results. Each set contributed to the quantification of detectability for the emissions of interest. The findings suggest the passive detection of the expected high-energy gamma signal is not feasible, unless backgrounds can be better controlled. The difficulty is attributed to low solid-angle coverage of the neutron source by the melamine explosive surrogate, and competing backgrounds produced by neutron-source interactions with surrounding materials. This thesis also examined the benefits and tradeoffs of this particular verification approach by investigating the non-technical context of the verification, such as the preferences of negotiators. The tradeoffs between confidence and intrusiveness highlight the need for technical verification solutions that span the diversity of options. Factors limiting the development of warhead verification systems, from the bias of researchers to issues of classification and sensitive geometries, were discussed.
by Mareena Robinson Snowden.
Ph. D.
Kundu, Anu. "Contribution of multipolar electromagnetic fields to the radio and high energy emission of pulsars." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE014/document.
Повний текст джерелаStudying the electromagnetic field around neutron stars is one of the vital methods to understand the physics of the pulsars. While major literature uses assumption of a standard centred dipolar electromagnetic field, recent studies have focused on including higher multipolar field components and have presented a more generalized picture for pulsars in which the magnetic dipole moment is shifted off from the centre of the star. This work discusses the consequences of an off centred rotating magnetic dipole in vacuum by showing various characteristic features of magnetic field lines and pulsar emission. A broadband spectrum study of pulsar radiation is also laid out by creating maps of different emission regions of pulsars distinguished on the basis of their frequency with the main aim of looking for the evolution of the pulse profile with frequency. The thesis presents all the above results accompanied by the necessary discussions to understand the theoretical models used and the details of the numerical methods applied
Klimek, Iwona. "Modelling and Measurements of MAST Neutron Emission." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-282122.
Повний текст джерелаTaverna, Roberto. "Polarized emission from highly-magnetized neutron stars." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424483.
Повний текст джерелаLo studio delle magnetars, anomalous X-ray pulsars (AXPs) e soft gamma repeaters (SGRs), e delle X-ray Dim Isolated Neutron Stars (XDINSs) è di particolare rilevanza, dal momento che questi oggetti mostrano i più forti campi magnetici mai osservati nell'universo (10^13-10^15 G) e rappresentano i soli laboratori dove la fisica in presenza di campi magnetici così forti può essere testata. Fino ad ora, queste particolari stelle di neutroni sono state studiate attraverso misure spettroscopiche e di timing, che hanno portato a corroborare i modelli teorici formulati per spiegare la loro fenomenologia, come nel caso del "twisted magnetosphere'' model per le magnetars o dei diversi modelli di emissione superficiale per le XDINSs. Cionondimeno, questa analisi da sola non riesce a fornire informazioni complete. A questo riguardo, la polarimetria X può svelare un approccio completamente nuovo nello studio delle stelle di neutroni altamente magnetizzate. La radiazione emessa in presenza di forti campi magnetici, infatti, è attesa essere altamente polarizzata; le misure di polarizzazione forniscono due osservabili aggiuntivi, la frazione di polarizzazione lineare e l'angolo di polarizzazione, che possono determinare senza ambiguità i parametri dei modelli anche quando la sola analisi spettrale si dimostra insufficiente. Il segnale di polarizzazione che un osservatore riceve all'infinito, tuttavia, non coincide necessariamente con ciò che i modelli predicono per la polarizzazione alla superficie, a causa degli effetti dell'elettrodinamica quantistica nel vuoto fortemente magnetizzato attorno alla stella, accoppiato con la rotazione dei parametri di Stokes nel piano perpendicolare alla linea di vista, indotta dal campo magnetico non uniforme. In questa tesi presento i risultati dei codici numerici che ho sviluppato per simulare il pattern di polarizzazione, sia alla superficie che all'infinito, della radiazione emessa da stelle di neutroni isolate altamente magnetizzate, usando come modelli la luminosa AXP 1RXS 170849.0-400910 e la XDINS RX J1856.5-3754. Dimostrerò che le misure di polarizzazione possono effettivamente fornire informazioni cruciali sulle proprietà fisiche e geometriche di queste sorgenti, permettendo di testare direttamente i modelli teorici. Questo lavoro è inoltre rilevante in vista del lancio di polarimetri X di nuova generazione, attualmente in fase di sviluppo, come l'X-ray Imaging Polarimetry Explorer (XIPE). Per questa ragione, confronterò i modelli teorici con osservazioni simulate di XIPE, allo scopo di mostrare come le misure di polarizzazione possono essere utilizzate per estrarre i valori dei parametri relativi alla magnetosfera e gli angoli di vista.
Chietera, Andreina. "Angular correlations between fragments and neutrons in the spontaneous fissions of 252 Cf." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE048/document.
Повний текст джерелаThe subject of this thesis is to explore the neutron emission mechanisms in the fission process. In particular a long standing open question, the existence of a dynamical anisotropy in the centre of mass of the fission fragments and/or a possible scission neutron emission is explored. The thesis starts with an overview of the theoretical concepts on the fission process and on the neutron emission mechanisms. Also the necessity to conceive an appropriate analysis method is stressed when a very subtle mechanism is studied as various approximations and/or experimental biases not completely handled can hide the physical phenomena. In the presented work a huge effort was required to write a Monte Carlo procedure based on a coherent model for the spontaneous fission of 252Cf and to couple it with the devices exploited in the CORA3 experiment
GILIBERTI, ELIA. "ON NEUTRON STARS'CRUST BREAKING AND GRAVITATIONAL WAVES EMISSION." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/704603.
Повний текст джерелаAgerhäll, Isabella, Malin Kindmark, and Cecilia Stern. "Towards Climate Neutral Facility Management : Improved Greenhouse Gas Emission Calculations for Ihus." Thesis, Uppsala universitet, Institutionen för samhällsbyggnad och industriell teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-413768.
Повний текст джерелаBalogun, Fatai Akintunde. "Compton scattering and neutron induced gamma-ray emission tomography." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/842882/.
Повний текст джерелаField, G. M. "Pre-equilibrium processes in nuclear reactions." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233509.
Повний текст джерелаToner, Mark P. "High energy neutral emissions from solar flares." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412948.
Повний текст джерелаChen, Yong. "Delayed neutron emission measurements for U-235 and Pu-239." Thesis, [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1134.
Повний текст джерелаHellesen, Carl. "Diagnosing Fuel Ions in Fusion Plasmas using Neutron Emission Spectroscopy." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-114449.
Повний текст джерелаNadel-Turonski, Pawel. "Experimental Studies of Neutron Emission Induced by Heavy-Ion Scattering." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3570.
Повний текст джерелаHiggins, Mark. "Gamma-ray emission from neutron stars and the Deutsch field pulsar." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20564.pdf.
Повний текст джерелаDaniels, Graham Clinton. "Observing flow using fast neutron radiography and positron emission particle tracking." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33606.
Повний текст джерелаHasper, Jens. "Systematic study of photoneutron reactions just above the neutron emission threshold /." Phd thesis, München : Verl. Dr. Hut, 2008. http://tuprints.ulb.tu-darmstadt.de/1011/1/Hasper_Systematic_study_of_photoneutron_reactions.pdf.
Повний текст джерелаValenzano, Michael Peter. "Neutron measurements in the vicinity of a self-shielded PET cyclotron." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17574.
Повний текст джерелаEriksson, Jacob. "Neutron Emission Spectrometry for Fusion Reactor Diagnosis : Method Development and Data Analysis." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-247994.
Повний текст джерелаOlsson, Fredrik. "Estimating the fuel ion dilution in fusion plasmas using neutron emission spectrometry." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-227653.
Повний текст джерелаTardocchi, Marco. "Neutron emission spectroscopy studies of fusion plasmas of Deuterium-Tritium in Tokamaks /." Uppsala : Suède : Acta Universitatis Upsaliensis, 2000. http://catalogue.bnf.fr/ark:/12148/cb40206623k.
Повний текст джерелаBinda, Federico. "Neutron emission spectroscopy of fusion plasmas with a NE213 liquid scintillator at JET." Licentiate thesis, Uppsala universitet, Tillämpad kärnfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-291506.
Повний текст джерелаDavies, Glyn. "Emission tomography in the determination of the spatial distribution of neutron induced radionuclides." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/847355/.
Повний текст джерелаNOCENTE, MASSIMO. "Neutron and gamma-ray emission spectroscopy as fast ion diagnostics in fusion plasmas." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28397.
Повний текст джерелаHime, Andrew. "Heavy neutrino emission in nuclear beta decay spectra." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293432.
Повний текст джерелаTavares, Leonardo Estêvão Schendes. "Tomography of the Earth by Geo-Neutrino Emission." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-02102014-121344/.
Повний текст джерелаGeo-neutrinos são neutrinos provindos do decaimento beta de alguns poucos elementos nas cadeias de $^$Th e $^$U presentes no interior da Terra. Recentes medidas experimentais dessas partículas têm proporcionado grandes expectativas como uma nova maneira de se investigar o interior do planeta diretamente. Trata-se de uma área multidisciplinar nova, que poderá no futuro próximo nos trazer grandes esclarecimentos sobre a dinâmica térmica e o processo de formação da Terra. Neste trabalho, construímos um modelo de inferência baseado no método de multigrid de priors para tratar, de modo genérico, o problema da reconstrução das fontes de geo-neutrinos no interior da Terra. Trata-se de um problema inverso; dada uma região do espaço V e um número finito e pequeno de medidas do potencial gerado na superfície de V por uma distribuição de carga $ho$, tentamos inferir $ho$. Apresentamos exemplos de aplicações e análises do método em modelos bidimensionais e tridimensionais e também comentamos como outras informações a priori podem ser incorporadas. Além disso, indicamos os passos para se inferir onde detectores futuros devem ser posicionados. O objetivo é maximizar a informação passível de ser obtida das medidas experimentais. Utilizamos um método baseado em inferência entrópica e que pode ser aplicado diretamente depois que os resultados do método de multigrid são obtidos.
TARDELLI, TIAGO C. "Avaliação de dados nucleares para dosimetria de nêutrons." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10587.
Повний текст джерелаMade available in DSpace on 2014-10-09T14:05:21Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
Lin, Yawei. "Spectroscopy of High Energy Ion-neutral Collisions." Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19720.
Повний текст джерелаRIGOSELLI, MICHELA. "X-ray emission from the magnetic polar caps of old rotation-powered pulsars." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/277373.
Повний текст джерелаNeutron stars are the remnants of massive stars whose cores collapse during the supernova explosions. The project of this PhD Thesis consisted in the study of the X-ray emission from isolated neutron stars older than about 100000 years. The work was based mainly on data obtained with the XMM-Newton satellite (ESA). To extract the best possible information from the data, I implemented a maximum likelihood (ML) technique and used it to derive the X-ray spectra and pulse profiles of several old pulsars, that were then studied with state-of-the-art models of X-ray emission. The Thesis is structured as follows: in the first three chapters I outline the main properties of neutron stars, with a major focus on the thermal and nonthermal processes that produce X-rays. The nonthermal X-rays are produced by relativistic particles accelerated by rotation-induced electric fields and moving along the magnetic field lines. A fraction of these particles is accelerated backward and returns on the stellar surface, heating the magnetic polar caps. The thermal component, that can be produced by the whole stellar surface or by small hot spots, can be described, in a first approximation, by a blackbody. However, the presence of intense surface magnetic fields strongly affects the properties of matter, and the emergent radiation is widely anisotropic. In Chapter 4, I describe how I generated synthetic spectra and pulse profiles using thermal emission models that consider polar caps covered by a magnetized hydrogen atmosphere or with a condensed iron surface. I relied on an existing software that, given a set of stellar parameters, evaluates the emerging intensity of the radiation. A second software, which I adapted on the sources I analyzed in the Thesis, collects the contribution of surface elements which are in view at different rotation phases from a stationary observer. Then, in Chapter 5, I describe how I implemented an analysis software that relies on the ML method. It estimates the most probable number of source and background counts by comparing the spatial distribution of the observed counts with the expected distribution for a point source plus an uniform background. I demonstrated that the ML method is particularly effective for dim sources, as most old pulsars are. Subsequently, I applied the methods described above to some old pulsars. In Chapter 6, I report the analysis of PSR J0726-2612, a radio pulsars that shares some properties with the radio-silent XDINSs, as the long period, the high magnetic field, and the thermal X-ray emission from the cooling surface. Thanks to an in-depth analysis of the combined spectrum and pulse profile, I showed that the presence of radio pulses from PSR J0726-2612, as well as the absence from the XDINSs, might simply be due to different viewing geometries. In Chapter 7, I present the case of PSR B0943+10, a pulsar with a nonthermal and thermal X-ray spectrum but that, despite being an aligned rotator, has a large pulsed fraction. I could reconcile the two opposite properties analyzing with the ML the spectrum and the pulse profile, and considering the magnetic beaming of a magnetized atmosphere model, that well fits the thermal component. In Chapter 8, I applied the ML method to seven old and dim pulsars, of which four had controversial published results, and three were so far undetected. I found convincing evidence of thermal emission only in the phase-averaged spectrum of two of them, plus a hint for a thermal pulsed spectrum in a third object. Finally, I considered all the old thermal emitters and I compared their observed temperatures, radii and luminosities to the expectations of the current theoretical models for these objects. In particular, I found that the emitting area are generally in agreement with the polar cap regions evaluated in a dipole approximation, if the combined effects of geometry projections plus realistic thermal models (as the magnetic atmosphere) are taken into account.
Diniz, Gabriel Sousa. "High energy emissions from thunderstorms: HEETs, from photons to neutrons toward the ground." Instituto Nacional de Pesquisas Espaciais (INPE), 2016. http://urlib.net/sid.inpe.br/mtc-m21b/2016/02.04.22.21.
Повний текст джерелаNuvens de tempestade são o início de vários fenômenos intensos como os raios gama e raios X, bem como de emissões de nêutrons, pósitrons e elétrons. As emissões de raios X e raios gama possuem energias que alcançam 100 MeV. As emissões de nêutrons podem ser criadas por interações entre raios gamma com o ar através da Ressonância Gigante de Dipolo, uma reação foto-nuclear, relacionadas com as nuvens de tempestade e com raios de um modo ainda não totalmente compreendido. Neste trabalho supõe-se que os nêutrons são criados por fótons de raios gamma com energia entre 10-30 MeV emitidos durante a propagação do líder negativo. A produção e a propagação pelo ar destes nêutrons foram investigadas utilizando simulações computacionais. Bancos de dados de seções de choque foram analisados para estimar a probabilidade por colisão de uma reação foto-nuclear acontecer. A análise revelou que essa probabilidade varia entre 0\% e 3.2\% para fótons com energia entre 10 e 30 MeV. O livre caminho médio dos fótons no intervalo de energia de 10-30 MeV foi analisado junto com o perfil de densidade atmosférica. A análise mostrou que para fótons com altitude inicial acima de 1 km, eles passam por livres caminhos médios o suficiente para a probabilidade de ocorrência de ao menos uma colisão ser garantida. O software livre EGS5 baseado no método Monte Carlo foi usado para tratar o movimento dos fótons e elétrons pela atmosfera no intuito de estudar a difusão de feixes monodirecionais dessas partículas. Foi observado que o feixe de fótons possui uma abertura entre 2-6$^{o}$ $\pm$ 2$^{o}$ enquanto o feixe de elétrons possui uma abertura de 11-13$^{o}$ $\pm$ 3$^{o}$ . A análise de nêutrons foi feita com o software FLUKA simulando um feixe de fótons em diferentes altitudes iniciais e estimando a detecção de fótons e nêutrons no solo. As simulações do FLUKA mostraram que os nêutrons se distribuem no solo em uma distância radial da fonte de 2 km, chegando ao solo numa razão entre 10$^{-4}$ até 10$^{-2}$ nêutrons/fótons, o que concorda com a análise das seções de choque. A diminuição dos nêutrons detectados em solo permitiu a estimativa de uma altura limite de 5 km para uma fonte pontual de fótons capaz de produzir nêutrons detectáveis em solo.
Skiba, Mateusz. "Making TOFu : Fusion Plasma Neutron Emission Spectrometry with a Fully Digital Data Acquisition System." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304383.
Повний текст джерелаOlivo, Martino. "Neutrino emission from high-energy component gamma-ray bursts." Licentiate thesis, Uppsala universitet, Högenergifysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132961.
Повний текст джерелаRaab, Christoph. "Searches for Neutrino Emission from Blazar Flares with IceCube." Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/325215/3/toc.pdf.
Повний текст джерелаLes rayons cosmiques proviennent d'au-delà de la Voie lactée et atteignent la Terre avec des énergies pouvant aller jusqu'à 10^20 eV. Les objets qui accélèrent ces rayons cosmiques n'ont toujours pas été découverts. Toutefois, l'astronomie multimessager peut apporter un élément de réponse à cette question, en supposant que les protons et les noyaux accélérés dans des environnements denses et énergétiques pourraient également produire des rayons gamma et des neutrinos. Les "blazars" sont de possibles candidats pour les accélérateurs de rayons cosmiques. Une augmentation de leurs émissions de rayons gamma, parfois de plusieurs ordres de grandeur, a été observée lors de phénomènes qu'on appelle "éruption", comme le montrent les courbes de lumière prises par le télescope spatial Fermi-LAT. Lorsque ce dernier a été lancé en 2008, l'observatoire de neutrinos IceCube avait également commencé à prendre des données, détectant la lumière Tcherenkov provenant d'interactions de neutrinos à haute énergie dans la glace qui se trouve sous le Pôle Sud géographique. Ces deux expériences ont permis de mener à bien des recherches multi-messagers de neutrinos en corrélation temporelle avec l'émission de rayons gamma des blazars. Ce principe est le point de départ de cette thèse, qui va plus loin en employant la méthode du "stacking", qui consiste à combiner les signaux provenant de plusieurs éruptions de blazars. Ainsi, leurs émissions individuelles de neutrinos, habituellement indétectables, pourraient être découvertes après combinaison. Une première analyse s'est concentrée sur le blazar TXS 0506+056, dont l'éruption en 2017 a coïncidée avec l'arrivée de l'évènement IceCube-170922A. En considérant une gamme d'énergie inférieure à celle de l'alerte 170922-A, pas d’autres neutrino excédentaire n’a été associé à l'éruption. Une deuxième analyse est basée sur 179 blazars lumineux et variables. Ces blazars ont été répartis en deux classes spécifiques, et chacun d'entre eux a reçu un poids relatif. Trois schémas de pondération ont été considérés :les deux premiers étant motivés par des observations, le troisième étant plus générique. Aucun excès significatif de neutrinos n'a été observé après avoir effectué des ajustements par maximum de vraisemblance sur les données non masquées, pour les différents catalogues de sources et schémas de pondération. Leur valeur-p combinée est de p=(79.1 +/- 0.3)%. Les limites dérivées de cette analyse sont discutées ainsi que leur rapport avec les résultats d'autres recherches. Puisqu'il s'agit du premier stacking d'éruptions de blazars, nous suggérons également des améliorations à apporter à l'analyse afin de permettre la poursuivre de la recherche d'accélérateurs de rayons cosmiques.
Kosmische straling afkomstig van buiten de Melkweg bereikt de Aarde met energieën tot wel 10^20 eV. De astrofysische bronnen waarin deze deeltjes worden versneld zijn tot op heden nog niet ontdekt. De multi-boodschapperastronomie kan een nieuw licht werpen op de oorsprong van kosmische straling, aangezien protonen en atoomkernen die worden versneld in een dichte en energetische omgeving ook gammastralen en neutrino’s produceren. „Blazars” zijn mogelijke kandidaat-versnellers. Observaties van blazars, gemaakt met de ruimtetelescoop Fermi-LAT ,tonen aan dat hun gammastraling tijdens zogenaamde „flakkers” toeneemt. Rond de tijd dat deze werd gelanceerd, begon het IceCube Neutrino Observatorium ook gegevens te verzamelen. Deze laatste detecteert hoog-energetische neutrino’s aan de hand van het Cherenkovlicht dat geproduceerd wordt tijdens hun interacties met de ijskap bij de geografische zuidpool. Deze twee experimenten hebben het mogelijk gemaakt om een multibooschapperzoektocht te verrichten naar neutrino’s van blazars die een tijdscorrelatie hebben met diens flakkers van gammastraling. Dit is het uitgangspunt van dit proefschrift, waarbij er ook een zogenaamde „stapelmethode” wordt toegepast. Op deze manier kan de neutrino-emissie van indivuele blazarflakkers, die afzonderlijk te zwak is om te detecteren, gecombineerd worden en mogelijks toch worden ontdekt. Een eerste analyse legt de focus op de blazar TXS 0506+056, waarvan een flakker in 2017 samenviel met de aankomst van het neutrino IceCube 170922-A. In een relatief lager energiebereik wordt er geen surplus aan neutrino’s gevonden gecorreleerd met de flakker. In een tweede analyse maken we gebruik van de stapelmethode om neutrino’s te zoeken afkomstig van 179 heldere en variabale blazars. Deze worden onderverdeeld in twee specifieke klassen en krijgen elks een zeker gewicht in de stapelanalyse. Hiervoor worden twee wegingsschema’s gebruikt die gemotiveerd zijn door de geobserveerde gammastraling, alsook een derde generieke weging. Ook hierwordt er geen significant neutrinosignaal geobserveerd. De gecombineerde p waarde is p=(79.1 +/- 0.3)%. Hieruit worden limieten afgeleid, en worden de verbanden met andere zoekacties besproken. Aangezien dit werk de eerste analyse omvat naar neutrino’s afkomstig van blazarflakkers gebruik makende van een stapelmethode, worden er in dit werk ook verdere verbeteringen van de analyse voorgesteld. Deze zullen als een startpunt dienen voor toekomstige zoektochten naar de nog onbekende bronnen van kosmische straling.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
O'Rourke, Brogan Roisín. "AGN Candidates for High Energy Neutrino Emission in IceCube." Thesis, Uppsala universitet, Högenergifysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-409739.
Повний текст джерелаCAVALIERI, TASSIO A. "Emprego do NCNP no estudo dos TLDs 600 e 700 visando a implementação da caracterização do feixe de irradiação na instalação de BNCT do IEA-R1." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10565.
Повний текст джерелаMade available in DSpace on 2014-10-09T14:04:33Z (GMT). No. of bitstreams: 1 19174.pdf: 31751 bytes, checksum: 7f1e1ac2bd5fcea7b8edbb1e6ba7a12b (MD5)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
Trinh, Ngoc Duy. "Emission de neutrons par les réactions d'ions lourds (4,6-95 MeV/nucléon)." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC234/document.
Повний текст джерелаHeavy-ion accelerators are an essential tool for nuclear physics research. They are also adopted in several applications. It is necessary to characterize the secondary neutrons production in order to guarantee a safe operation in every circumstance in accelerators. However, experimental data are very rare or even non-existent. For some data, we notice disagreements between different publications. Disagreements are also observed between measurements data and simulations. For all these reasons, we established the program Thick Target Neutron Yields (TTNY). This program aims to measure the double differential neutron spectra (energy, angle) generated by the interactions of heavy-ions (12≤Abeam≤208 and 4.6 MeV/nucleon≤Ebeam≤95 MeV/nucleon) on thick targets (natC, natCu and natNb). Two measurements methods were adopted: Activation and Time of Flight. This choice allows having a better confidence on the measurements, studying experimental limits and consolidating the conclusions that could be drawn from the experimental results. The measurements are compared to the simulations performed with some Monte-Carlo widely used in nuclear simulation: PHITS (Japanese), FLUKA (European (CERN/INFN)) and MCNP (American). These comparisons allowed evaluating the modeling quality of heavy-ion reactions for the energies and masses explored in this work. We also conclude on the systematic uncertainties and on the potential improvements to be introduced to physics models of these codes
Reed, Alan Thomas. "Decay studies of neutron-rich nuclei." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367175.
Повний текст джерелаEriksson, Jacob. "Fuel ion densities and distributions in fusion plasmas : Modeling and analysis for neutron emission spectrometry." Licentiate thesis, Uppsala universitet, Tillämpad kärnfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-192530.
Повний текст джерелаGiacomelli, Luca. "Development of Neutron Emission Spectroscopy Instrumentation for Deuterium and Deuterium-Tritium Fusion Plasmas at JET." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8199.
Повний текст джерелаHenriksson, Hans. "Neutron Spectroscopy Studies of Heating Effects in Fusion Plasmas." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3492.
Повний текст джерелаNchodu, M. R. "Alpha emission from the interactions of 14-200 MeV neutrons on carbon-12." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/17513.
Повний текст джерелаBibliography: pages 89-93.
Cross-sections for the production of alpha particles from the ¹²C(n,α)⁹Begs and ¹²C(n,n')3α reactions were measured for incident neutrons in the energy range 25 to 52 MeV. The measurements were reduced to absolute cross-sections by simultaneously observing deuteron recoils from n-d elastic scattering in the scintillator using D(n,n)D elastic scattering cross-section as a reference standard. Neutron energy was determined by time-of-flight and pulse shape discrimination (PSD) was used to identify and separate alphas and deuterons from other reaction products. The feasibility of distinguishing different mechanisms for the ¹²C(n,n')3α reaction by means of PSD was also investigated.
Testov, Dmitry. "Effect of shell closure N = 50 and N = 82 on the structure of very neutron-rich nuclei produced at ALTO : measurements of neutron emission probabilities and half lives of nuclei at astrophysical r-processes path." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01059803.
Повний текст джерелаCaballero, Folch Roger. "First measurement of beta-decay half-lives and neutron emission probabilities in several isotopes beyond N = 126." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/299373.
Повний текст джерелаEn aquest treball s'han determinat, experimentalment i per primera vegada, vides mitjanes i valors de probabilitat d'emissió de neutrons de diversos nuclis amb més de 126 neutrons. Per tal d'obtenir les dades es va realitzar un experiment a les instal·lacions del centre d’investigació d'ions pesats GSI a (Alemanya), combinat amb el separador de fragments FRS. El sistema de detecció d'ions i desintegracions beta va consistir d'un detector de partícules carregades anomenat SIMBA, que estava envoltat per una matriu de comptadors proporcionals d’'He-3 que conformen el detector de neutrons BELEN. En total s'han determinat valors de vida mitjana de divuit isòtops d'or, mercuri, tal·li, plom i bismut, així com també la probabilitat d'emissió de neutrons (o llindars superiors) de set d'ells. Comparant els resultats amb les mesures de vides mitjanes anteriors en aquesta regió de nuclis s'observa un bon acord, reflectint la validesa de la sistemàtica de les dades existents. D’'altra banda, fent la comparació amb els models teòrics, els resultats mostren un acord raonable per la meitat dels isòtops analitzats, i grans discrepàncies, de fins a un factor 10, per l'altra meitat. Pel que fa a les probabilitats d'emissió de neutrons mesurades, essent la primera mesura experimental a la regió per a diversos nuclis, no és possible comparar amb altres els valors obtinguts. La única comparació que es pot avaluar és amb les prediccions teòriques. En resum, els resultats són compatibles amb el model FRDM + QRPA, no obstant s'observen discrepàncies considerables en alguns isòtops de fins a un factor 5, com és el cas del valor obtingut per Tl-215, que correspon al nucli més exòtic del qual s'’ha determinat la probabilitat d’'emissió de neutrons.
Liland, Lukas. "Neutrino Emission From Supernovae : At what distance will it kill you?" Thesis, Uppsala universitet, Högenergifysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414990.
Повний текст джерелаGiraud, Quentin. "Corrections général-relativistes à l’émission radio et haute énergie des pulsars." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE024.
Повний текст джерелаNeutron stars are very dense objects, denser than an atomic nucleus, formed during a supernova. A typical neutron star concentrates a mass superior to the one of the Sun in its diameter of around twenty kilometers. According to general relativity, which describes gravity as a space-time distorsion, the gravitational field of those stars should have a non-negligible impact on electromagnetic radiations close to them. During my thesis, I have simulated radio and high-energy emission originating from particules accelerated along the magnetic field lines of the neutron star inside the Schwarzschild metric to have an insight of how this kind of radiations would be affected by space-time distorsions in the vicinity of the neutron star
Wickman, Erik. "Simulation of neutron generator assisted gamma emission tomography for inspection of fissile content in spent nuclear fuel." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-335161.
Повний текст джерелаSaion, Elias bin. "On microdosimetry of neutrons of selectable energy in mixed (n,y) fields." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/2640.
Повний текст джерела