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1
Taheri, Faissal Bakkali. "Numerical and experimental studies of coherent Smith-Purcell radiation." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d483c501-ba46-4e08-9d38-5af29211aedc.
Повний текст джерелаАнотація:
This thesis investigates the properties of coherent Smith-Purcell radiation (cSPr) at femtosecond-scale in the case of electrons bunches in the ultrarelativistic regimes. Of particular interest is the use of cSPR as a diagnostic tool to determine the longitudinal time profiles of such bunches, the study of azimuthal distribution of the radiated energy, and a contribution to the understanding of polarization properties. The study consists in a first theoretical part carried mostly in the context of the surface-current theory, supported with insights from particle-in-cell simulations. Then, as a step toward a better determination of time profile, the question of phase reconstruction is addressed through the design of a new algorithm proposed in this thesis and tested in known challenging cases. Experimental results are then presented, spanning shifts having taken place at the FACET facility at SLAC, Stanford, between 2013 and 2015.
2
Testa, Mauro. "Charged particle therapy, ion range verification, prompt radiation." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00566188.
Повний текст джерелаАнотація:
This PhD thesis reports on the experimental investigation of the prompt photons created during the fragmentation of the carbon beam used in particle therapy. Two series of experiments have been performed at the GANIL and GSI facilities with 95 MeV/u and 305 MeV/u 12C6+ ion beams stopped in PMMA and water phantoms. In both experiments a clear correlation was obtained between the C-ion range and the prompt photon profile. A major issue of these measurements is the discrimination between the prompt photon signal (which is correlated with the ion path) and a vast neutron background uncorrelated with the Bragg-Peak position. Two techniques are employed to allow for this photon-neutron discrimination: the time-of-flight (TOF) and the pulse-shape-discrimination (PSD). The TOF technique allowed demonstrating the correlation of the prompt photon production and the primary ion path while the PSD technique brought great insights to better understand the photon and neutron contribution in TOF spectra. In this work we demonstrated that a collimated set-up detecting prompt photons by means of TOF measurements, could allow real-time control of the longitudinal position of the Bragg-peak under clinical conditions. In the second part of the PhD thesis a simulation study was performed with Geant4 Monte Carlo code to assess the influence of the main design parameters on the efficiency and spatial resolution achievable with a multidetector and multi-collimated Prompt Gamma Camera. Several geometrical configurations for both collimators and stack of detectors have been systematically studied and the considerations on the main design constraints are reported.
3
Bates, Adrian P. "Small particle characterisation by scattering of polarised radiation." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243345.
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4
Grant, James Paul. "GaN radiation detectors for particle physics and synchrotron applications." Thesis, University of Glasgow, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443418.
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5
Kirby, Daniel James. "Radiation dosimetry of conventional and laser-driven particle beams." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/2816/.
Повний текст джерелаАнотація:
The measurement of radiation dose in radiotherapy is vital in ensuring the accuracy of treatments. As more advanced techniques using protons and ions emerge, they pose challenges to ensure the same level of accuracy of dosimetry is achieved as for conventional X-ray radiotherapy. A relatively new method of particle acceleration using ultra-high intensity lasers and thin metallic targets has sparked a large effort to investigate the possible application of this technology in radiotherapy, which in turn requires accurate methods of dosimetry to be carried out and is the main motivation for this work. Accurate dosimetry was initially performed here using an air ionisation chamber, various models of GafChromic film and a PMMA phantom in 15 and 29 MeV protons and 38 MeV \(\alpha\)-particles from the Birmingham cyclotron. In developing an accurate protocol for absorbed dose-to-water at these relatively low proton energies, new data was generated on the proton energy response of GafChromic films. This enabled accurate dosimetry of a prototype laser-particle source, and provided improvements to a method of spectroscopic measurement in the resultant mixed field of multi-energy protons, electrons and X-rays. Monte Carlo simulations using MCNPX but mainly FLUKA were performed throughout to support and verify experimental measurements.
6
Hegyi, Gyorgy. "Particle size determination for alpha-emitters using CR-39." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0019/MQ55065.pdf.
Повний текст джерела
7
Ulmer, Bernd. "Back scatter imaging with megavoltage radiation." Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246070.
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8
Koziel, Michal. "Development of radiation hardened pixel sensors for charged particle detection." Strasbourg, 2011. http://www.theses.fr/2011STRA6237.
Повний текст джерелаАнотація:
Les capteurs CMOS sont développés depuis une décennie en vue d’équiper les détecteurs de vertex des expériences de physique des particules à venir, avec les avantages d’un faible budget de matière et de bas coûts de production. Les caractéristiques recherchées sont un temps de lecture court, une granularité élevée et une bonne radiorésistance. Cette thèse est principalement consacrée à l’optimisation de ce dernier point. Pour diminuer le temps de cycle vers les 10 microsecondes, la lecture des pixels en parallèle dans chaque colonne a été implémentée, associée à une logique de suppression d’information des pixels sans signal. Les pixels sont devenus plus complexes et plus sensibles aux rayonnements ionisants. L’optimisation de l’architecture des pixels, par des techniques standard de durcissement aux rayonnements, a porté la limite à 300 krad (quelques Mrad attendus) pour le procédé de fabrication à 0,35-um utilisé jusque-là. L’amélioration de la tenue aux rayonnements ionisants passe par l’utilisation de technologies de taille inférieure à 0,35-um, naturellement plus radio-résistantes. Ceci facilitant de plus l’intégration de tous les composants dans un pixel. Un autre aspect abordé dans cette thèse concerne la tolérance aux rayonnements non ionisants. Différentes technologies CMOS améliorant la collecte de charges ont été testées. L’utilisation d’une couche de détection de haute résistivité a porté la tenue à ces rayonnements à 3•1013 neq/cm2, conforme à l’objectif fixé. Ce résultat marque une étape importante pour les capteurs CMOS qui devraient rapidement satisfaire le cahier des charges d’expériences particulièrement contraignantes telles que CBM par exempleCMOS Pixel Sensors are being developed since a few years to equip vertex detectors for future high-energy physics experiments with the crucial advantages of a low material budget and low production costs. The features simultaneously required are a short readout time, high granularity and high tolerance to radiation. This thesis mainly focuses on the radiation tolerance studies. To achieve the targeted readout time (tens of microseconds), the sensor pixel readout was organized in parallel columns restricting in addition the readout to pixels that had collected the signal charge. The pixels became then more complex, and consequently more sensitive to radiation. Different in-pixel architectures were studied and it was concluded that the tolerance to ionizing radiation was limited to 300 krad with the 0. 35-um fabrication process currently used, while the targeted value was several Mrad. Improving this situation calls for implementation of the sensors in processes with a smaller feature size which naturally improve the radiation tolerance while simultaneously accommodate all the in-pixel microcircuitry in small pixels. Another aspect addressed in this thesis was the tolerance to non ionizing radiation, with a targeted value of >1013 neq/cm2. Different CMOS technologies featuring an enhanced signal collection were therefore investigated. It was demonstrated that this tolerance could be improved to 3•1013 neq/cm2 by the means of a high-resistivity epitaxial layer. This achievement triggered a new age of the CMOS pixel sensors and showed that their development is on a good track to meet the requirements of the particularly demanding CBM experiment
9
Mitchell, Edward Frank. "Development of a miniaturised particle radiation monitor for Earth orbit." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11679.
Повний текст джерелаАнотація:
Geometry and algorithm design for a novel highly miniaturised radiation monitor (HMRM) for spacecraft in medium Earth orbit are presented. The HMRM device comprises a telescopic configuration of application-specific active pixel sensors enclosed in a titanium shield, with an estimated total mass of 52 g and volume of 15 cm3. The monitor is intended to provide real-time dosimetry and identification of energetic charged particles in fluxes of up to 108 cm-2 s-1 (omnidirectional). Achieving this capability with such a small instrument could open new prospects for radiation detection in space. The methodology followed for the design and optimisation of the particle detector geometry is explained and analysis algorithms - for real-time use within the monitor and for post-processing reconstruction of spectra - are presented. Simulations with the Geant4 toolkit are used to predict operational results in various Earth orbits. Early test results of a prototype monitor, including calibration of the pixel sensors, are also reported.
10
Thornton, D. A. "Calculating the responses of self-powered radiation detectors." Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237741.
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11
Fulcher, Jonathan Richard. "Radiation effects in electronics for the CMS tracking detector." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250692.
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12
Hossain, Md Anwar. "Fabrication and optimisation of room-temperature CdZnTe radiation detectors." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844281/.
Повний текст джерелаАнотація:
The ternary compound Cadmium Zinc Telluride (CdZnTe) is one of the most promising room-temperature semiconductor detectors. It possesses the necessary material properties that are required to exhibit optimal detection performance. But unfortunately it does not display that expected level of performance because it has some shortcomings at various stages from crystal growth to contact fabrication. Investigations in each area have been pursued individually over the last decades and it is a goal in the field to integrate the optimal properties from each area into a fully optimised detector. In this work, the metal contacts to CdZnTe detectors have been investigated since these are believed to be one of the most vital areas among the possible detrimental aspects. In order to evaluate the contact features, different configurations of contact were fabricated on the supplied CdZnTe detector crystals using the available laboratory facilities. A great deal of effort was put into contact design and fabrication as well as the characterisation of the fabricated devices. Endeavour was made to correlate the characterisation results of different configurations with their physical structure as well as drawing comparison with commercial devices. Work was concluded by focussing on optimum detector designs including the factors that limit their performance.
13
Stejskal, Pavel. "Radiation effects in optical link components for future particle physics detectors." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/12870.
Повний текст джерелаАнотація:
Optical link components used in future particle physics experiments will typically be exposed to intense radiation fields during the lifetime of the experiment and the qualification of these components in terms of radiation tolerance is thus required. Data on semiconductor lasers and photodiodes for use in 10 Gb/s datalinks tested during high-fluence (in excess of 10[to the power of 15] particles/cm2) neutron and pion irradiation in 2009 and 2010 are presented with annealing data. In order to predict the behaviour of a laser irradiated with the different particle fluxes at different locations inside a particle physics experiment, radiation damage in lasers has been modelled. The model describes the degradation of the L-I characteristic of a semiconductor laser undergoing irradiation with the annealing processes taken into account. The robustness of the model has been checked against the experimental data. Additionally, the author’s method to estimate Single Event Upsets in photodetectors using GEANT4 is presented. Use of optoelectronic devices in digital data transmission systems in HEP detectors is also discussed.
14
Lewis, Benjamin Tomos. "Using smoothed particle radiation magnetohydrodynamics to explore how protostars are formed." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/28934.
Повний текст джерелаАнотація:
The properties which define a molecular cloud core — the evolutionary phase bridging between a molecular cloud and a protostar — are extensive. These properties include the initial density profile; velocity field; and magnetic field strength and geometry (and the alignment of this with other fields). These properties have a major effect on the nature of the protostar or protostars ultimately produced when the core collapses. We present a series of calculations using smoothed particle radiation magnetohydrodynamics of the collapse of a molecular cloud core to the first hydrostatic core phase. Before this, we describe and analyse our numerical method, including exploring historical difficulties and the limits of the stability. We explore the role of the geometry of the magnetic field, and showing that the nature of any outflows produced from a first hydrostatic core is closely related to the inclination angle of the field. We continue this analysis into the role of the field strength and geometry. We find that highly misaligned fields do not form bipolar outflows and discuss the cause of this, and additionally find that the angular momentum transport in weak field calculations is insufficient to prevent fragmentation and the formation of binary systems. When an outflow is formed, even in the most idealised initial conditions, the velocity is never |v_z| > 10 km · s^{−1}. We consider next the role of turbulent and rotational kinetic energy, and find that transonic turbulence can prevent the formation of an outflow unless a critical ratio of rotation to turbulent energy is exceeded. Even so, we observe that outflows produced in non–laminar calculations are slower (|v_z| ∼ 1 km · s^{−1}) than those from laminar configurations. We then show that a Bonnor–Ebert density profile can produce a stable binary system with a helical outflow without the prolific fragmentation seen in fast rotating uniform density distributions.
15
Campbell, Steven Conner. "DETERMINATION OF ACOUSTIC RADIATION EFFICIENCY VIA PARTICLE VELOCITY SENSOR WITH APPLICATIONS." UKnowledge, 2019. https://uknowledge.uky.edu/me_etds/133.
Повний текст джерелаАнотація:
Acoustic radiation efficiency is defined as the ratio of sound power radiated to the surface vibration power of a piston with equivalent surface area. It has been shown that the radiation efficiency is maximized and may exceed unity when the structural and acoustic wavelengths are approximately equal. The frequency at which this occurs is called the critical frequency and can be shifted with structural modifications. This has proven to be an effective way to reduce noise. The standard radiation efficiency measurement is comprised of an intensity scan for sound power measurement and accelerometer array for spatially averaged vibration determination. This method is difficult to apply to lightweight structures, complicated geometries, and when acoustic sources are in close proximity to one another. Recently, robust particle velocity sensors have been developed. Combined with a small microphone in the same instrument, particle velocity and sound pressure can be measured simultaneously and at the same location. This permits radiation efficiency to be measured using a non-contact approach with a single sensor. A suggested practice for measuring radiation efficiency has been developed and validated with several examples including two flat plates of different thickness, an oil pan, and components on a running small engine.
16
Nixon, Gilbert. "Data acquisition and control in particle physics and astronomy." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340538.
Повний текст джерела
17
Angus, Stephen Andrew. "Phenomenology of dark radiation and string compactifications." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:739ffcb2-bf9d-4fd3-8d6c-911d2d599f5e.
Повний текст джерелаАнотація:
In this Thesis I explore aspects of dark radiation and its role in String Phenomenology. Dark radiation is any additional hidden type of relativistic matter present in the Universe today, conventionally labelled as an "excess effective number of neutrino species", Δ Neff. It provides a powerful test of hitherto untested theoretical models based on fundamental theories such as String Theory. I begin by considering dark radiation in the LARGE Volume Scenario, a phenomenologically viable class of string compactifications. First I review how the minimal setup slightly overproduces axionic dark radiation via modulus decay. I then demonstrate that loop corrections to the main competing visible-sector decay process have a negligible effect and are unable to alleviate the tension with observations. In the following chapter I explore fibred extensions of the LARGE Volume Scenario. The predictions for Δ Neff are qualitatively different: in particular, models with a sequestered visible sector on D3 branes at a singularity are swamped by massless axions and decisively ruled out. I then consider TeV-scale supersymmetry in a model with anisotropic modulus stabilisation. If the Standard Model is realised on D7 branes wrapping the small volume cycle a hierarchy of soft terms is generated, which may have applications to natural supersymmetry. The final chapter takes a different approach and investigates the proposition that dark radiation, in the form of a Cosmic Axion Background, could explain the long-standing soft X-ray excess from galaxy clusters. I show for the Coma cluster that the morphology of the excess can be reproduced by axion-photon conversion in the intracluster magnetic field, provided the field is allowed to have more structure on smaller scales than typically assumed based on Faraday rotation data. This explanation requires an inverse axion-photon coupling M ∼ 1011 - 1012 GeV and a mean axion energy (ECAB) ∼ 50 - 250 eV.
18
Isoyama, Soichiro. "Radiation reaction to the motion of a point particle in Kerr spcetime." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188475.
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19
Situ, Peter D. "Voxel based beta particle dosimetry methods in mice." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5897.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 14, 2007) Vita. Includes bibliographical references.
20
Pechhacker, Roman. "Particle acceleration with associated generation and absorption of electromagnetic radiation in solar plasmas." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8843.
Повний текст джерелаАнотація:
The heating of solar chromospheric internetwork regions is investigated by means of the absorption of electromagnetic (EM) waves that originate from the photospheric black body radiation. It is studied in the framework of a plasma slab model. The absorption is provided by the electron-neutral collisions in which electrons oscillate in the EM wave field and electron-neutral collisions damp the EM wave. It is shown that for plausible physical parameters, the absorbed heating flux is between 20% and 45% of the chromospheric radiative loss flux requirement. Further, 1.5D particle-in-cell simulations of a hot, low density electron beam injected into magnetized, Maxwellian plasma were used to further explore the alternative non-gyrotropic beam driven EM emission mechanism, which was first studied in Ref.[83]. Variation of beam injection angle and background density gradient showed that the emission is caused by the perpendicular component of the beam injection current, whereas the parallel component only produces Langmuir waves, which play no role in the generation of EM waves in our mechanism. When the beam is injected perpendicularly to the background magnetic field, any electrostatic wave generation is turned off and a purely EM signal is left. Finally, a possible solution to the unexplained high intensity hard x-ray emission observable during solar flares was investigated via 3D particle-in-cell simulations. A beam of accelerated electrons was injected into a magnetised, Maxwellian, homogeneous and inhomogeneous background plasma. The electron distribution function was unstable to the beam-plasma instability and was shown to generate Langmuir waves, while relaxing to plateau formation. Three different background plasma density gradients were investigated. The strong gradient case produced the largest fraction of electrons beyond 15vth. Further, Langmuir wave power is shown to drift to smaller wavenumbers, as found in previous quasi-linear simulations.
21
Longstaff, Wilmer Gregg. "Three-dimensional analysis of optical transition radiation." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23428.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedA three dimensional analysis of the intensity distribution of backward optical transition radiation has been performed. The effects of variations in electron energy and beam divergence and on material properties such as dielectric permittivities and the resultant coherence length upon the angular distribution and polarization of optical transition radiation has been investigated. A surprising observation important to the use of optical transition radiation as a diagnostic tool for high energy electron beams is the behavior of the perpendicular component of the intensity. In contrast to low energies where the parallel component dominates, at electron energies above 200 MeV, the perpendicular component dominates. This requires the use of a polarization filter to diagnose particle beam properties at high energies.
http://archive.org/details/threedimensional00long
Lieutenant, United States Navy
22
Jung, Yun Su. "Effects of charge distribution within a particle beam on the sub-Cerenkov radiation." Thesis, Monterey, California: U.S. Naval Postgraduate School, 1987. http://hdl.handle.net/10945/22767.
Повний текст джерелаАнотація:
The charge distribution of periodic electron beam pulses generates patterns of sub-Cerenkov radiation distinctive of the distribution of charge with in a bunch. Mapping the radiation pattern from different charge shapes may provide insight into whether charge pulse shapes can be determined from observed radiation patterns. The radiation patterns of Gaussian, Level, and Trapezoidal function were mapped by computer simulation. Near 90 degree to the beam, the radiation patterns of all three charge distributions developed an envelope proportional to the fourier transform of the charge bunch distribution when the wavelength of the emitted radiation was comparable to the size of the bunch. For the Gaussian function, the envelope is Gaussian, for the level function it is a sinc function. Since the envelope for the trapezoidal function in the product of two sinc functions it is more difficult to analyze. This work may provide a basis for determining the charge shape of electron beam pulses from the sub-Cerenkov radiation based on the radiation intensity pattern
23
Kubota, Yuko. "Study on Variation of Radiation Belt Electron Fluxes Through Nonlinear Wave-Particle Interactions." Kyoto University, 2018. http://hdl.handle.net/2433/232003.
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24
Mossuz, Laurence. "Etude de la production et de la désintégration semi-électronique de particules charmées dans les diffusions inélastiques de neutrinos." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10087.
Повний текст джерелаАнотація:
Cette these presente une etude de la production et de la desintegration semi-electronique des particules charmees dans la diffusion profondement inelastique de neutrinos mu. L'analyse est basee sur l'ensemble des evenements mu- e+, selectionnes a partir des donnees enregistrees par l'experience nomad dans le faisceau de neutrinos du cern au cours de l'annee 1995. Afin de reduire drastiquement le bruit de fond des evenements mu- e+, nous avons elabore une premiere selection sur les donnees. Puis, une etude d'evenements neutrinos simules dans nomad nous a permis de controler la qualite de la simulation, et d'affiner la selection sur les donnees. Nous avons mesure un signal charme mu- e+. Le nombre total de candidats mu- e+, ainsi que ses distributions cinematiques sont sensibles a la structure interne du nucleon. Par comparaison des distributions cinematiques du signal extrait sur les donnees et des evenements charmes simules, nous avons mesure le contenu en quarks etranges du nucleon. La these comporte une partie instrumentale principalement sur le detecteur a rayonnement de transition (drt), qui contribue a l'identification des electrons dans l'experience. Cependant, pour utiliser au mieux ses capacites de discrimination l'uniformite de la reponse de l'ensemble de ses elements est necessaire. Ce travail a permis d'une part de mesurer et d'ajuster l'uniformite du drt sur l'ensemble de la surface de ses 9 plans, et d'autre part d'etre a meme de controler en permanence cette uniformite au cours de la prise de donnees.
25
Vickers, Colin Edward. "K-shell absorption spectroscopy of radiation and shockwave propagation through low density foams." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271304.
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26
Reeve, John Anthony. "A study of hard radiation in the decay of the Z to dimuons." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267066.
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27
Cullen, Ashley James. "Strip detector for high spatial resolution dosimetry in radiation therapy." Centre for Medical Radiation Physics - Faculty of Engineering, 2009. http://ro.uow.edu.au/theses/848.
Повний текст джерелаАнотація:
Radiation therapy is an established modality in the treatment of tumours. With treatments ever evolving and increasing in terms of their complexities, the need arises to ensure the best quality treatment is delivered; the survival of the patient relies upon it. A modern treatment such as Intensity Modulated Radiation Therapy employs steep dose gradients varying dynamically to deliver complex dose profiles, whilst the experimental Microbeam Radiation Therapy (MRT) involves the delivery of an array of intense beams tens-of-microns wide separated by several hundred microns. In both cases, conventional dosimetry is inadequate in providing both spatial and temporal information about complex dose profiles.The silicon strip detector was created to fill this void in current dosimetry techniques. Designed to withstand the intense beam of a synchrotron wriggler x-rays whilst not significantly perturbing the beam, the detector provides linear sensitive volume elements two hundred microns in pitch. This enables the ability to perform high spatial resolution dosimetry in real time.This thesis investigates the use of the silicon strip detector as an on-line dosimetry system for MRT with applications to clinical radiotherapy. Of particular interest is the distribution and magnitude of energy deposition within the detector and the perturbative effect the strip detector has on a synchrotron wriggler x-ray beam.Monte Carlo simulations are performed to investigate the properties of radiation incident upon the detector. These seek to understand how a beam traversing the detector interacts with it, as well as the effects the detector has on the transmitted beam and its properties.The energy deposition spectrum within the detector was found to be predominant at low energies of below 100 keV. The deposition of dose through the detector was found to be largely constant with depth through the central axis of a beam, dropping to ~10-3 of the central value at 50 µm off the central beam axis for an infinitesimally thin pencil beam and ~10-4 at 100 µm off-axis. Energy deposition laterally through water was determined as dominated by secondary electrons from the beam-edge to 150 µm, and Compton photons thereafter.The depth dose of a MRT pencil beam was found to have an average decrease in dose of (1.44 ± 0.15) % (95% C.I.) when the strip detector was introduced into the beam. The probability of interaction of incident photons with the detector for the MRT spectrum was determined with GEANT4 and theoretically with a comparison made. The overall interaction probability of an MRT photon is (1.97 ± 4.43×10-4) % (95% C.I.).A simulation to determine the PVDR (peak-to-valley dose ratio) in a MRT field was created, however only the peak dose could be determined due to an inadequate primary photon count. The peak dose was found to decrease by 1.41 ± 0.03 % (95% C.I.). Qualitative film measurements (deliberate overexposure of peak regions) displayed an increase of valley dose to film at 10 mm in water with the strip detector in the beam, but no such phenomenon at a depth of 1 mm. A simplified GEANT4 simulation was created to replicate such results with only five beamlets. Peak-to-valley dose ratio calculations from the simulation show no discernible effect at 1 mm depth, but a discernible increase in the PVDR at 10 mm depth; replicating experimental results.Since charge collection across a semiconductor device is often complex and dynamically varies with the bias conditions. Ion beam induced charge collection (IBICC) studies seek to investigate the charge collection properties of the detector in various voltage-biasing conditions. It was found that the application of reverse bias to strips adjacent to that being read out reduced the effective sensitive volume of the read-out strip. This provides evidence for a proposal to incorporate biased guard-ring structures to prevent charge sharing, and improve the confinement of the sensitive volume.Finally, clinical irradiations are performed with a highly collimated orthovoltage x-ray beam down to beam sizes of hundreds of microns. The spatial resolution of the detector in this configuration was found to be 500 µm. The efficacy of the detector in contemporary radiotherapy is also investigated through the use of a 6 MV linear accelerator’s photon beam. Excellent agreement was found between strip detector read-outs and reference data for the linear accelerator. A quadratic relation was found between dose rate and charge per strip.
28
Petkova, Maya Atanasova. "Cloudy with a chance of starlight : coupling of smoothed particle hydrodynamics and Monte Carlo radiative transfer for the study of ionising stellar feedback." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16557.
Повний текст джерелаАнотація:
Ionising radiation is present in a variety of astrophysical problems, and it is particularly important for shaping the process of star formation in molecular clouds, containing hot, high-mass stars. In order to account for the effects of ionising radiation within numerical models of star formation, we need to combine a hydrodynamics method with a radiative transfer method and obtain a radiation hydrodynamics scheme (RHD). In this thesis I achieve live radiation hydrodynamics by coupling the Smoothed Particle Hydrodynamics (SPH) code Phantom with the Monte Carlo Radiative Transfer (MCRT) code CMacIonize. Since SPH is particle-based and MCRT is grid-based, I construct an unstructured, Voronoi grid in order to establish a link between the two codes. In areas with large density gradients, a Voronoi grid based purely on the SPH particle positions achieves insufficient resolution, and therefore I propose a novel algorithm for inserting a small number of additional grid cells to improve the local resolution. Furthermore, the MCRT calculations require the knowledge of an average density for each Voronoi cell. To address this, I develop an analytic density mapping from SPH to a Voronoi grid, by deriving an expression for the integrals of a series of kernel functions over the volume of a random polyhedron. Finally, I demonstrate the validity of the live RHD through the benchmark test of D-type expansion of an H II region, where good agreement is shown with the existing literature. The RHD implementation is then used to perform a proof-of-concept simulation of a collapsing cloud, which produces high-mass stars and is subsequently partially ionised by them. The presented code is a valuable tool for future star formation studies, and it can be used for modelling a broad range of additional astronomical problems involving ionising radiation and hydrodynamics.
29
Tobiasson, John Robert. "Determining H2O Vapor Temperature and Concentration in Particle-Free and Particle-Laden Combustion Flows Using Spectral Line Emission Measurements." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6497.
Повний текст джерелаАнотація:
There is a growing need for the clean generation of electricity in the world, and increased efficiency is one way to achieve cleaner generation. Increased efficiency may be achieved through an improved understanding of the heat flux of participating media in combustion environments. Real-time in-situ optical measurements of gas temperature and concentrations in combustion environments is needed. Optical methods do not disturb the flow characteristics and are not subject to the temperature limitation of current methods. Simpler, less-costly optical measurements than current methods would increase the ability to apply them in more circumstances. This work explores the ability to simultaneously measure gas temperature and H2O concentration via integrated spectral intensity ratios in regions where H2O is the dominant participating gas. This work considered combustion flows with and without fuel and soot particles, and is an extension of work previously performed by Ellis et al. [1]. Five different combustion regimes were used to investigate the robustness of the infrared intensity integral method first presented by Ellis et al. [1]. These included Post-Flame Natural Gas (PFNG), Post-Flame Medium Wood (PFMW), Post-Flame Fine Wood (PFFW), In-Flame Natural Gas (IFNG), and In-Flame Fine Wood (IFFW). Optical spectra were collected as a function of path length for each regime. Methods for processing the spectra to obtain gas temperature, gas concentration, broadband temperature, and broadband emissivity were developed. A one-dimensional spectral intensity model that allowed for specular reflection, and investigated differences between measured and modeled spectral intensities was created. It was concluded that excellent agreement (within 2.5%) was achieved between optical and suction pyrometer gas temperatures as long as 1) the optical probe and cold target used were well-aligned 2) the path length was greater than 0.3 m and 3) the intensity from broadband emitters within the path was smaller than the gas intensity. Shorter path lengths between 0.15 – 0.3 m produced reasonable temperatures with 7 % error while path lengths of 0.05 m or less were as much as 15% in error or the signal would not effectively process. Water vapor concentration was less accurate being at best within 20% (relative) of expected values. The accurate determination of concentration requires first an accurate temperature concentration as well low broadband participation. Some optical concentrations were in error as much as 85%. The 1-D model was compared to the measurement and it was found that the model peaks were sharper and shifted 0.167 cm-1 compared to the measured data. The reason for the shift can be attributed to the uncertainty of the reference laser frequency used in the FTIR. No conclusion was found for the cause of the sharper peaks in the model. The integrated area of bands used to find temperature and concentration matched well between the model and measured spectrum being typically within 3%.
30
Wei, Xiaomin. "Study and improvement of radiation hard monolithic active pixel sensors of charged particle tracking." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00953382.
Повний текст джерелаАнотація:
Monolithic Active Pixel Sensors (MAPS) are good candidates to be used in High Energy Physics (HEP) experiments for charged particle detection. In the HEP applications, MAPS chips are placed very close to the interaction point and are directly exposed to harsh environmental radiation. This thesis focuses on the study and improvement of the MAPS radiation hardness. The main radiation effects and the research progress of MAPS are studied firstly. During the study, the SRAM IP cores built in MAPS are found limiting the radiation hardness of the whole MAPS chips. Consequently, in order to improve the radiation hardness of MAPS, three radiation hard memories are designed and evaluated for the HEP experiments. In order to replace the SRAM IP cores, a radiation hard SRAM is developed on a very limited area. For smaller feature size processes, in which the single event upset (SEU) effects get significant, a radiation hard SRAM with enhanced SEU tolerance is implemented by an error detection and correction algorithm and a bit-interleaving storage. In order to obtain higher radiation tolerance and higher circuitry density, a dual-port memory with an original 2-transistor cell is developed and evaluated for future MAPS chips. Finally, the radiation hardness of the MAPS chips using new available processes is studied, and the future works are prospected.
31
Kraishan, Amani. "MEASUREMENT OF LONGITUDINAL SINGLE-SPIN ASYMMETRY FOR W± BOSON PRODUCTION IN POLARIZED PROTON-PROTON COLLISIONS AT STAR AT FORWARD RAPIDITY." Diss., Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/521379.
Повний текст джерелаАнотація:
PhysicsPh.D.
Spin plays a key role in the determination of the properties of fundamental particles and their interactions. The spin structure of the proton is one of the most challenging open puzzles in Quantum Chromodynamics (QCD). It was believed that the proton spin was carried by the spin of its three valence quarks. However, The results of the EMC (European Muon Collaboration) experiments in 1987 suggested that the quark intrinsic spin contributes, ∆Σ = 0.12 ± 0.09 ± 0.14 of the proton spin setting off the proton spin crisis. ”Where is the rest of the proton spin is coming from?” remains a major challenge to our understanding of the structure of the proton. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) delivers the highest energy polarized proton-proton collisions at a center of mass energy up to 510 GeV and provides a unique opportunity to study quark and gluon spin structure of the proton and the QCD dynamics at high energy scale. The production of W −(+) bosons in polarized proton-proton collisions provides an ideal tool to study the spin-flavor structure of the proton sea quark distributions profiting from the parity-violating nature of the weak interactions. W −(+) bosons are produced in u ̄ + d (d ̄ + u) annihilation and can be detected through their leptonic decay mode. The STAR experiment can detect charged leptons e−(+) at mid and forward rapidity regions. In this analysis, the measurement of the longitudinal single-spin asymmetries at forward rapidity for W boson production will be presented based on the data sample collected in 2013 (RUN-13) corresponding to an integrated luminosity 220 pb−1 with an average beam polarization ∼ 56%.
Temple University--Theses
32
McGarry, Stephen. "Irradiated silicon particle detectors." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369468.
Повний текст джерела
33
Howland, Matthew. "Transcriptomic and Secretomic Profiling of Isolated Leukocytes Exposed to Alpha-Particle and Photon Radiation - Applications in Biodosimetry." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26081.
Повний текст джерелаАнотація:
The general public is at risk of ionising-radiation exposure. The development of high-throughput methods to triage exposures is warranted. Current biodosimetry techniques are low-throughput and encumbered by time and technical expertise. Although there has been an emergence of gene-profiling tools for the purpose of photon biodosimetry, similar capacities do not exist for alpha-particle radiation. Herein is the first genomic study useful for alpha-particle radiation biodosimetric triage. This work has identified robust alpha-particle induced gene-based biomarkers in isolated, ex-vivo irradiated leukocytes from multiple donors. It was found that alpha-particle and photon radiation elicited similar transcriptional responses, which could potentially be distinguished by aggregate-signature analysis. Although no distinct genes were sole indicators of exposure type, clustering algorithms and principal component analysis were able to demarcate radiation type with some success. By comparing the biological effects elicited by photon and alpha-particle radiation, significant contributions have been made to the field of radiation biodosimetry.
34
Perks, Jonathan Michael. "Phosphorus segregation and diffusion in nickel and Fe-Cr-Ni alloys under fast particle irradiation." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329993.
Повний текст джерела
35
Čeponis, Tomas. "Radiation technologies for optimization of Si device parameters and techniques for control of radiation defects." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121001_093158-64168.
Повний текст джерелаАнотація:
In high energy physics experiments the semiconductor particle detectors of pin structure are commonly employed for tracking of the ionising particles. However, ionising radiation creates defects and consequently affects the parameters of particle detectors. Therefore, it is necessary to characterize irradiated detectors and search for the new approaches on how to suppress or control the degradation process. Measurements of current-voltage, capacitance-voltage characteristics as well as deep level transient spectroscopy, thermally stimulated currents spectroscopy are employed for the characterization of irradiated particle detectors. At high irradiation fluences when defects concentration exceeds that of dopants, a generation current increases and, thus, the above mentioned techniques can not be applied for the correct evaluation of defect parameters. In this work, models describing displacement currents in detectors due to redistribution of electric field determined by variations of external voltage or a moving charge in electric field are discussed. These models were applied for creation of the advanced techniques which allow evaluating of charge transport, trapping and recombination/generation parameters in heavily irradiated detectors after irradiation. These techniques were applied for the spectroscopy of deep levels associated with defects, for cross-sectional scans within layered junction structures as well as for examination of defects evolution during irradiation. In... [to full text]Aukštųjų energijų fizikos eksperimentuose plačiai taikomi puslaidininkiniai pin struktūros dalelių detektoriai jonizuojančiosioms dalelėms registruoti. Radiacinė spinduliuotė sukuria defektus medžiagoje ir neigiamai įtakoja detektorių parametrus, todėl būtina charakterizuoti apšvitintus detektorius ieškant būdų, kaip juos patobulinti. Apšvitintų detektorių charakterizavimui taikomi volt-amperinių, volt-faradinių būdingųjų dydžių matavimai ir analizė, giliųjų lygmenų talpinė bei šiluma skatinamų srovių spektroskopija. Tačiau stipriai apšvitintuose detektoriuose, kai defektų koncentracija viršija legirantų koncentraciją bei išauga nuotėkio srovė, šie metodai negali būti taikomi siekiant korektiškai įvertinti radiacinių defektų parametrus. Šiame darbe buvo sukurti modeliai, apibūdinantys slinkties sroves, tekančias detektoriuje dėl elektrinio lauko persiskirstymo keičiantis išorinei įtampai arba elektriniame lauke judant injektuotam krūviui. Šie modeliai buvo pritaikyti naujų metodikų sukūrimui, kurios įgalina įvertinti krūvio pernašos, pagavimo, rekombinacijos/generacijos parametrus stipriai apšvitintuose detektoriuose po apšvitos. Sukurti metodai buvo pritaikyti defektų spektroskopijai ir skersinei žvalgai sluoksninėse struktūrose bei defektų evoliucijos tyrimams apšvitos metu. Disertacijoje pateikti ir aptarti apšvitintų detektorių ir apšvitos metu pasireiškiančios parametrų kaitos rezultatai. Elektronikos grandynuose plačiai naudojami galios pin struktūros diodai, kurie... [toliau žr. visą tekstą]
36
Ede, Anthony. "Studies of crystalline CdZnTe radiation detectors and polycrystalline thin film CdTe for X-ray imaging applications." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/843974/.
Повний текст джерелаАнотація:
The development of a replacement to the conventional film based X-ray imaging technique is required for many reasons. One possible route for this is the use of a large area film of a suitable semiconductor overlaid on an amorphous silicon readout array. A suitable semiconductor exists in cadmium telluride and its tertiary alloy cadmium zinc telluride. In this thesis the spectroscopic characteristics of commercially available CZT X- and gamma-radiation detectors are established. The electronic, optical, electro-optic, structural and compositional properties of these detectors are then investigated. The attained data is used to infer a greater understanding for the carrier transport in a CZT radiation detector following the interaction of a high energy photon. Following this a method used to fabricate large area films of CdTe on a commercial scale is described. This is cathodic electrodeposition from an aqueous electrolyte. The theory and experimental arrangement for this technique are described in detail with preliminary results from the fabricated films presented. Attention is then turned to the CdS/CdTe films that are produced commercially for the photovoltaic industry. In this case the crystalline nature, surface topography and optical properties are investigated. A conclusion examines the progress that has been made towards the development of a large area flat panel digital imaging technique.
37
Pettersson, Nora. "Study of systematic effects from the level of Final State Radiation in tt-background to SUSY dilepton channels." Thesis, KTH, Partikel- och astropartikelfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93450.
Повний текст джерелаАнотація:
Uncertainties in radiative effects of the quarks in -background in the form of final state radiation (FSR) are significant when it comes to reducing all forms of systematics that can arise from measuring the jets energy. Analysis on FSR is in general conducted on different simulated samples where one has included the radiative effect using algorithms such as PYTHIA[29]. The hypothesis is that through the re-weighting of the -background nominal sample one could add a better representation of the FSR effect. Finding a simple way to include a better description of FSR would not only save time in the simulation process but it would also be a way to reduce the systematic errors originating from limited MC statistics. Due to statistical effects coming from the simulations one cannot use the basic approach to define the effect of FSR as simply the difference between nominal and FSR. Two methods are tested to estimate the FSR effects; the first method uses a set of efficiency factors to represent the signal regions, the second method is to add a weight to the events of the nominal sample. The first method show positive results, especially in SR2, compared to a basic analysis, with an uncertainty of the FSR effect of: SR1:±29% SR2: ±51% SR3: ±37%. While a basic analysis gave an uncertainty of ±42%, ±122% and 36%. The second method shows positive signs where the re-weighted sample moves closer to the behaviour of the FSR sample. However, both methods are based on insufficient amount of statistics to draw any absolute conclusions.
38
Gepford, Heather Jean. "Development and implementation of a system for reading nuclear etched tracks in PADC (CR-39) using coherent light scattering." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17134.
Повний текст джерела
39
Martin, Ian Peter Stephen. "Short pulse x-ray generation in synchrotron radiation sources." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:9ac0bcc2-bedb-46d0-b95c-22f4741f45a0.
Повний текст джерелаАнотація:
This thesis describes an investigation into the performance of different schemes for generating short x-rays pulses via synchrotron radiation emission. A review is given of the methods that have been previously proposed for this task. From this review, three leading schemes are selected for in-depth investigations, each of which explores the boundary of what is presently achievable in accelerator-based light sources. The first scheme generates short x-ray pulses by operating an electron storage ring in a quasi-isochronous state using a ‘low-alpha’ lattice. High and low emittance lattices are developed, studied through simulation and then implemented on the Diamond storage ring. Beam dynamics and bunch length measurements are presented for a variety of machine conditions, and an assessment is made of the minimum practically achievable bunch length for stable user operation. Radiation pulses of 1 ps r.m.s. are demonstrated using this scheme. The second and third schemes investigate performance limits for a linac-based light source through numerical simulations. The first of these generates ultra-short pulses by passing a highly compressed electron bunch through a long undulator to radiate in the ‘single-spike’ regime. A comparison is made with theoretical predictions for the required electron bunch length to operate in this way, which highlights the need for accurate start-to-end simulations. The final scheme generates ultra-short x-ray pulses through laser manipulation of the electron bunches. The modulated electrons pass through a long undulator with tapered gap, such that only the centre of the modulated portion experiences high free-electron laser (FEL) gain. A method to enhance the FEL output from this scheme using a wavelength filter and grating-compressor is investigated. The sensitivity of the two schemes to jitter sources is determined, and it is demonstrated both schemes are capable of generating GW-level, fully coherent sub-fs soft x-ray pulses. Such pulses would open up the development of time-resolved science to new regimes.
40
Kersten, Tobias. "Electron acceleration and loss caused by wave-particle interactions in the Van Allen radiation belts." Thesis, Open University, 2016. http://oro.open.ac.uk/47208/.
Повний текст джерелаАнотація:
Modern society relies substantially on satellite technology as it is involved in vital services like telecommunication services, Earth observation, navigation, and many more. There are more than 1000 operational satellites in Earth orbit and most of these spend at least some of their time in the harsh environment of the Van Allen radiation belts. The radiation belts are usually split into two regions, the inner and the outer radiation belt. While the inner belt is considered stable, the flux of electrons in the outer belt can vary over several orders of magnitude, reaching levels that may disrupt satellite operations. It is therefore important to understand the variability of the outer belt and ultimately to predict its behaviour. In this thesis, the radiation belts are described by the BAS Radiation Belt Model (BAS-RBM) which solves a 3D diffusion equation. The BAS-RBM requires accurate diffusion coefficients that describe the interaction between electrons and plasma waves. The most important plasma waves are chorus, plasmaspheric hiss, and EMIC waves. Here, new statistical models of the diffusion coefficients for these waves are presented, which considerably improve existing models. Among others, they benefit from better global wave models due to improved satellite coverage, and revised wave normal angle and plasma density models. The results show that chorus waves are an important acceleration and loss mechanism at energies up to about 1MeV and for all pitch-angles, while plasmaspheric hiss is found to be an essential loss process in the same energy and pitch-angle range. In contrast, EMIC waves proved to be a relevant loss process for ultrarelativistic electrons, but only at lower pitch-angles. The work presented here has led to a better understanding of the variability of the outer radiation belt and has considerably improved the accuracy and reliability of the modelling and forecasting capabilities.
41
Infantino, Angelo <1985>. "Advanced aspects of radiation protection in the use of particle accelerators in the medical field." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6807/1/INFANTINO_PHD.pdf.
Повний текст джерелаАнотація:
In this work, the well-known MC code FLUKA was used to simulate the GE PETrace cyclotron (16.5 MeV) installed at “S. Orsola-Malpighi” University Hospital (Bologna, IT) and routinely used in the production of positron emitting radionuclides. Simulations yielded estimates of various quantities of interest, including: the effective dose distribution around the equipment; the effective number of neutron produced per incident proton and their spectral distribution; the activation of the structure of the cyclotron and the vault walls; the activation of the ambient air, in particular the production of 41Ar, the assessment of the saturation yield of radionuclides used in nuclear medicine. The simulations were validated against experimental measurements in terms of physical and transport parameters to be used at the energy range of interest in the medical field.
The validated model was also extensively used in several practical applications uncluding the direct cyclotron production of non-standard radionuclides such as 99mTc, the production of medical radionuclides at TRIUMF (Vancouver, CA) TR13 cyclotron (13 MeV), the complete design of the new PET facility of “Sacro Cuore – Don Calabria” Hospital (Negrar, IT), including the ACSI TR19 (19 MeV) cyclotron, the dose field around the energy selection system (degrader) of a proton therapy cyclotron, the design of plug-doors for a new cyclotron facility, in which a 70 MeV cyclotron will be installed, and the partial decommissioning of a PET facility, including the replacement of a Scanditronix MC17 cyclotron with a new TR19 cyclotron.In questo lavoro, il codice Monte Carlo (MC) FLUKA è stato utilizzato per simulare il ciclotrone GE PETtrace (16.5 MeV) installato presso l’azienda ospedaliera “S. Orsola-Malpighi” (Bologna, IT), quotidianamente utilizzato per la produzione di radiofarmaci PET. Le simulazioni sono state effettuate per valutare diversi fenomeni e quantità d’interesse radiologico tra cui l’equivalente di dose ambientale nell’intorno dell’acceleratore, il numero di neutroni emessi per protone incidente e la loro distribuzione spettrale, l’attivazione dei componenti del ciclotrone e delle pareti del bunker, l’attivazione dell’aria interna al bunker ed in particolare la produzione di 41Ar, la resa a saturazione di radionuclidi d’interesse in medicina nucleare. Le simulazioni sono state validate, in termini di parametri fisici e di trasporto da utilizzare nel range energetico caratteristico delle applicazioni mediche, con una serie di misure sperimentali. Il modello MC validato è stato quindi applicato ad altri casi pratici quali lo studio di fattibilità della produzione diretta in ciclotrone di 99mTc, la produzione di radionuclidi ad uso medico con il ciclotrone TR13 (13 MeV) installato presso il centro di ricerca TRIUMF (Vancouver, CA), la progettazione completa del nuovo centro PET dell’ospedale “Sacro Cuore-Don Calabria” di Negrar (Verona, IT), incluso il ciclotrone ACSI TR19 (19 MeV), lo studio del campo di dose nell’intorno di un sistema di selezione dell’energia (degrader) di un ciclotrone per terapia, la progettazione di specifiche “porte a tappo” per un sito di produzione di radionuclidi ad uso medico, in cui verrà installato un ciclotrone da 70 MeV e sei diverse beam line, e per il parziale decommissioning di un centro PET e la sostituzione di un ciclotrone Scanditronix MC17 (17 MeV), attualmente installato, con una nuova unità TR19.
42
Infantino, Angelo <1985>. "Advanced aspects of radiation protection in the use of particle accelerators in the medical field." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6807/.
Повний текст джерелаАнотація:
In this work, the well-known MC code FLUKA was used to simulate the GE PETrace cyclotron (16.5 MeV) installed at “S. Orsola-Malpighi” University Hospital (Bologna, IT) and routinely used in the production of positron emitting radionuclides. Simulations yielded estimates of various quantities of interest, including: the effective dose distribution around the equipment; the effective number of neutron produced per incident proton and their spectral distribution; the activation of the structure of the cyclotron and the vault walls; the activation of the ambient air, in particular the production of 41Ar, the assessment of the saturation yield of radionuclides used in nuclear medicine. The simulations were validated against experimental measurements in terms of physical and transport parameters to be used at the energy range of interest in the medical field.
The validated model was also extensively used in several practical applications uncluding the direct cyclotron production of non-standard radionuclides such as 99mTc, the production of medical radionuclides at TRIUMF (Vancouver, CA) TR13 cyclotron (13 MeV), the complete design of the new PET facility of “Sacro Cuore – Don Calabria” Hospital (Negrar, IT), including the ACSI TR19 (19 MeV) cyclotron, the dose field around the energy selection system (degrader) of a proton therapy cyclotron, the design of plug-doors for a new cyclotron facility, in which a 70 MeV cyclotron will be installed, and the partial decommissioning of a PET facility, including the replacement of a Scanditronix MC17 cyclotron with a new TR19 cyclotron.In questo lavoro, il codice Monte Carlo (MC) FLUKA è stato utilizzato per simulare il ciclotrone GE PETtrace (16.5 MeV) installato presso l’azienda ospedaliera “S. Orsola-Malpighi” (Bologna, IT), quotidianamente utilizzato per la produzione di radiofarmaci PET. Le simulazioni sono state effettuate per valutare diversi fenomeni e quantità d’interesse radiologico tra cui l’equivalente di dose ambientale nell’intorno dell’acceleratore, il numero di neutroni emessi per protone incidente e la loro distribuzione spettrale, l’attivazione dei componenti del ciclotrone e delle pareti del bunker, l’attivazione dell’aria interna al bunker ed in particolare la produzione di 41Ar, la resa a saturazione di radionuclidi d’interesse in medicina nucleare. Le simulazioni sono state validate, in termini di parametri fisici e di trasporto da utilizzare nel range energetico caratteristico delle applicazioni mediche, con una serie di misure sperimentali. Il modello MC validato è stato quindi applicato ad altri casi pratici quali lo studio di fattibilità della produzione diretta in ciclotrone di 99mTc, la produzione di radionuclidi ad uso medico con il ciclotrone TR13 (13 MeV) installato presso il centro di ricerca TRIUMF (Vancouver, CA), la progettazione completa del nuovo centro PET dell’ospedale “Sacro Cuore-Don Calabria” di Negrar (Verona, IT), incluso il ciclotrone ACSI TR19 (19 MeV), lo studio del campo di dose nell’intorno di un sistema di selezione dell’energia (degrader) di un ciclotrone per terapia, la progettazione di specifiche “porte a tappo” per un sito di produzione di radionuclidi ad uso medico, in cui verrà installato un ciclotrone da 70 MeV e sei diverse beam line, e per il parziale decommissioning di un centro PET e la sostituzione di un ciclotrone Scanditronix MC17 (17 MeV), attualmente installato, con una nuova unità TR19.
43
Fahy, Katherine Erin. "Thermal Burn Injury Induced Microvesicle Particle Release." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright149383031006972.
Повний текст джерела
44
Amutkan, Ozge. "Space Radiation Environment And Radiation Hardness Assurance Tests Of Electronic Components To Be Used In Space Missions." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612238/index.pdf.
Повний текст джерелаАнотація:
Space radiation is significantly harmful to electronic Components. The operating time, duration and orbit of the space mission are affected by the characteristic of the radiation environment. The aging and the performance of the electronic components are modified by radiation. The performance of the space systems such as electronic units, sensors, power and power subsystem units, batteries, payload equipments, communication units, remote sensing instruments, data handling units, externally located units,
and propulsion subsystem units is determined by the properly functioning of various electronic systems. Such systems are highly sensitive against space radiation.
The space radiation can cause damage to electronic components or functional failure on the electronics. A precisely methodology is needed to ensure that space radiation is not a threat on the functionality and performance of the electronics during their operational lives. This methodology is called as &rdquoRadiation Hardness Assurance&rdquo
. In this thesis, the hardening of electronics against space radiation is discussed. This thesis describes the space radiation environments, physical mechanisms, effects of space radiation, models of the space radiation environment, simulation of the Total Ionizing Dose, and &rdquo
Radiation Hardness Assurance&rdquo
which covers Total Ionizing Dose and Single Event Effects testing and analyzing of the electronics.
45
Gillespie, Douglas Michael. "A radial drift chamber combining tracking and transition radiation detection for use in the H1 experiment and HERA." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316907.
Повний текст джерела
46
Bruckmayer, Manfred. "Imaging cryogenic detectors for astro and particle physics." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312189.
Повний текст джерела
47
Thapa, Pariksha. "Kinetics of Microvesicle Particle Release in Keratinocytes." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1566504910360327.
Повний текст джерела
48
Roth, Olivia. "Physical and Chemical Aspects of Radiation Induced Oxidative Dissolution of UO2." Licentiate thesis, KTH, Kemi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-622.
Повний текст джерелаАнотація:
Denna licensiatavhandling behandlar oxidativ upplösning av UO2. Upplösning av UO2 studeras huvudsakligen då UO2-matrisen hos använt kärnbränsle förväntas fungera som en barriär mot frigörande av radionuklider i ett framtida djupförvar. Lösligheten av U(IV) är mycket låg under i djupförvaret rådande förhållanden emedan U(VI) har betydligt högre löslighet. Oxidation av UO2-matrisen kommer därför att påverka dess löslighet och därmed dess funktion som barriär. I denna avhandling studeras den relativa effektiviteten av en- och två-elektronoxidanter för upplösning av UO2. Vid låga oxidantkoncentrationer är utbytet för upplösningen för en-elektronoxidanter signifikant lägre än för två-elektronoxidanter. För en-elektronoxidanter ökar dock utbytet med ökande oxidanthalt, vilket kan förklaras av den ökade sannolikheten för två konsekutiva en-elektronoxidationer av samma reaktionssite och den ökade möjligheten till disproportionering. Radikaler och molekylära radiolysprodukters relativa inverkan på oxidativ upplösning av UO2 studeras också i denna avhandling genom mätning av mängden upplöst U(VI) i γ-bestrålade system som dominerades av olika oxidanter. Dessa studier visade att upplösningshastigheten av UO2 kan uppskattas från oxidantkoncentrationer framtagna genom simuleringar av radiolys i motsvarande homogena system och hastighetskonstanterna för ytreaktionerna. Simuleringarna visar att de molekylära oxidanterna kommer vara de viktigaste oxidanterna i alla system i denna studie vid långa bestrålningstider (>10 timmar). Vid liknande simuleringar av α-bestrålade system fanns att vid förhållanden relevanta för ett djupförvar för använt kärnbränsle, är det endast de molekylära oxidanterna (i huvudsak H2O2) som är av betydelse för upplösningen av bränslematrisen. Då använt kärnbränsle innehåller en mängd radionuklider som utsätter UO2-matrisen för kontinuerlig bestrålning, är det av vikt att undersöka hur bestrålning påverkar reaktiviteten av UO2. Bestrålningseffekten på reaktionen mellan UO2 och MnO4- studerades. Dessa försök visade att bestrålning av UO2 vid doser >40 kGy leder till att reaktiviteten ökar upp till 1.3 gånger reaktiviteten av obestrålad UO2. Den ökade reaktiviteten kvarstår efter bestrålningen och effekten kan därför möjligen tillskrivas permanenta förändringar i materialet. Vid uppskattning av reaktiviteten hos använt kärnbränsle måste hänsyn tas till denna effekt då bränslet redan efter ett par dagar i reaktor blivit utsatt för doser >40 kGy. Det har tidigare föreslagits att hastigheten för en heterogen västka/fast-fas reaktion är beroende av partikelstorleken hos det fasta materialet, vilket har studerats för UO2-partiklar i denna avhandling. Experimentellt bestämda kinetiska parametrar jämförs med de föreslagna ekvationerna för fyra storleksfraktioner av UO2-pulver och en UO2-pellet. Studien visade partikelstorleksberoendet av andra ordningens hastighetskonstant och aktiveringsenergin för oxidation av UO2 med MnO4- beskrivs relativt väl av de föreslagna ekvationerna.The general subject of this thesis is oxidative dissolution of UO2. The dissolution of UO2 is mainly investigated because of the importance of the UO2 matrix of spent nuclear fuel as a barrier against radionuclide release in a future deep repository. U(IV) is extremely insoluble under the reducing conditions prevalent in a deep repository, whereas U(VI) is more soluble. Hence, oxidation of the UO2-matrix will affect its solubility and thereby its function as a barrier. In this thesis the relative efficiency of one- and two electron oxidants in dissolving UO2 is studied. The oxidative dissolution yield of UO2 was found to differ between one- and two-electron oxidants. At low oxidant concentrations the dissolution yields for one-electron oxidants are significantly lower than for two-electron oxidants. However, the dissolution yield for one-electron oxidants increases with increasing oxidant concentration, which could be rationalized by the increased probability for two consecutive one-electron oxidations at the same site and the increased possibility for disproportionation. Furthermore, the relative impact of radical and molecular radiolysis products on oxidative dissolution of UO2 is investigated. Experiments were performed where the amount of dissolved U(VI) was measured in γ-irradiated systems dominated by different oxidants. We have found that the UO2 dissolution rate in systems exposed to γ-irradiation can be estimated from oxidant concentrations derived from simulations of radiolysis in the corresponding homogeneous systems and rate constants for the surface reactions. These simulations show that for all systems studied in this work, the molecular oxidants will be the most important oxidants for long irradiation times (>10 hours). Similar simulations of α-irradiated systems show that in systems relevant for a deep repository for spent nuclear fuel, only the molecular oxidants (mainly H2O2) are of importance for the dissolution of the fuel matrix. The effect on UO2 reactivity by irradiation of the material is of importance when predicting the spent fuel dissolution rate since the fuel, due to its content of radionuclides, is exposed to continuous self-irradiation. The effect of irradiation on the reaction between solid UO2 and MnO4- in aqueous solutions was studied. It was found that irradiation of UO2 at doses >40 kGy increases the reactivity of the material up to ~1.3 times the reactivity of unirradiated UO2. The increased reactivity remains after the irradiation and can possibly be attributed to permanent changes in the material. This issue must be taken into account when predicting the reactivity of spent nuclear fuel since the fuel is exposed to doses >40 kGy after only a few days in the reactor. It has earlier been suggested that the rate of a heterogeneous liquid-solid reaction depends on the size of the solid particles. This was investigated for UO2 particles in this thesis. Experimental kinetic parameters are compared to the previously proposed equations for UO2 powder of four size fractions and a UO2 pellet. We have found that the particle size dependence of the second order rate constant and activation energy for oxidation of UO2 by MnO4- is described quite well by the proposed equations.
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Kundu, Ashoke. "Monte Carlo simulation of gas-filled radiation detectors." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/987/.
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Hofstetter, Markus [Verfasser], and Stefan [Akademischer Betreuer] Thalhammer. "Gallium nitride based thin films for photon and particle radiation dosimetry / Markus Hofstetter. Betreuer: Stefan Thalhammer." Augsburg : Universität Augsburg, 2013. http://d-nb.info/1077701608/34.
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