980 resultados para . neutron radiation field
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Detailed knowledge of the characteristics of the radiation field shaped by a multileaf collimator (MLC) is essential in intensity modulated radiotherapy (IMRT). A previously developed multiple source model (MSM) for a 6 MV beam was extended to a 15 MV beam and supplemented with an accurate model of an 80-leaf dynamic MLC. Using the supplemented MSM and the MC code GEANT, lateral dose distributions were calculated in a water phantom and a portal water phantom. A field which is normally used for the validation of the step and shoot technique and a field from a realistic IMRT treatment plan delivered with dynamic MLC are investigated. To assess possible spectral changes caused by the modulation of beam intensity by an MLC, the energy spectra in five portal planes were calculated for moving slits of different widths. The extension of the MSM to 15 MV was validated by analysing energy fluences, depth doses and dose profiles. In addition, the MC-calculated primary energy spectrum was verified with an energy spectrum which was reconstructed from transmission measurements. MC-calculated dose profiles using the MSM for the step and shoot case and for the dynamic MLC case are in very good agreement with the measured data from film dosimetry. The investigation of a 13 cm wide field shows an increase in mean photon energy of up to 16% for the 0.25 cm slit compared to the open beam for 6 MV and of up to 6% for 15 MV, respectively. In conclusion, the MSM supplemented with the dynamic MLC has proven to be a powerful tool for investigational and benchmarking purposes or even for dose calculations in IMRT.
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In this phase III, multinational, randomized trial, the International Breast Cancer Study Group, Breast International Group, and the National Surgical Adjuvant Breast and Bowel Project will attempt to define the effectiveness of cytotoxic therapy for patients with locoregional recurrence of breast cancer. We will evaluate whether chemotherapy prolongs disease-free survival and, secondarily, whether its use improves overall survival and systemic disease-free survival. Quality of life measurements will be monitored during the first 12 months of the study. Women who have had a previous diagnosis of invasive breast cancer treated by mastectomy or breast-conserving surgery and who have undergone complete surgical excision of all macroscopic disease but who subsequently develop isolated local and/or regional ipsilateral invasive recurrence are eligible. Patients are randomized to observation/no adjuvant chemotherapy or to adjuvant chemotherapy; all suitable patients receive radiation, hormonal, and trastuzumab therapy. Radiation therapy is recommended for patients who have not received previous adjuvant radiation therapy but is required for those with microscopically positive margins. The radiation field must encompass the tumor bed plus a surrounding margin to a dose of >or= 40 Gy. Radiation therapy will be administered before, during, or after chemotherapy. All women with estrogen receptor-positive and/or progesterone receptor-positive recurrence must receive hormonal therapy, with the agent and duration to be determined by the patient's investigator. Adjuvant trastuzumab therapy is permitted for those with HER2- positive tumors, provided that intent to treat is declared before randomization. Although multidrug regimens are preferred, the agents, doses, and use of supportive therapy are at the discretion of the investigator.
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The usage of intensity modulated radiotherapy (IMRT) treatments necessitates a significant amount of patient-specific quality assurance (QA). This research has investigated the precision and accuracy of Kodak EDR2 film measurements for IMRT verifications, the use of comparisons between 2D dose calculations and measurements to improve treatment plan beam models, and the dosimetric impact of delivery errors. New measurement techniques and software were developed and used clinically at M. D. Anderson Cancer Center. The software implemented two new dose comparison parameters, the 2D normalized agreement test (NAT) and the scalar NAT index. A single-film calibration technique using multileaf collimator (MLC) delivery was developed. EDR2 film's optical density response was found to be sensitive to several factors: radiation time, length of time between exposure and processing, and phantom material. Precision of EDR2 film measurements was found to be better than 1%. For IMRT verification, EDR2 film measurements agreed with ion chamber results to 2%/2mm accuracy for single-beam fluence map verifications and to 5%/2mm for transverse plane measurements of complete plan dose distributions. The same system was used to quantitatively optimize the radiation field offset and MLC transmission beam modeling parameters for Varian MLCs. While scalar dose comparison metrics can work well for optimization purposes, the influence of external parameters on the dose discrepancies must be minimized. The ability of 2D verifications to detect delivery errors was tested with simulated data. The dosimetric characteristics of delivery errors were compared to patient-specific clinical IMRT verifications. For the clinical verifications, the NAT index and percent of pixels failing the gamma index were exponentially distributed and dependent upon the measurement phantom but not the treatment site. Delivery errors affecting all beams in the treatment plan were flagged by the NAT index, although delivery errors impacting only one beam could not be differentiated from routine clinical verification discrepancies. Clinical use of this system will flag outliers, allow physicists to examine their causes, and perhaps improve the level of agreement between radiation dose distribution measurements and calculations. The principles used to design and evaluate this system are extensible to future multidimensional dose measurements and comparisons. ^
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The Baseline Surface Radiation Network (BSRN) and its central archive - the World Radiation Monitoring Center (WRMC) - was created in 1992. It is a project of the Data Assimilation Panel from the Global Energy and Water Cycle Experiment (GEWEX) under the umbrella of the World Climate Research Programme (WCRP) and as such is aimed at detecting important changes in the Earth's radiation field at the Earth's surface which may be related to climate changes. The data are of primary importance in supporting the validation and confirmation of satellite and computer model estimates of these quantities. At a small number of stations in contrasting climatic zones, covering a latitude range from 80N to 90S, solar and atmospheric radiation is measured with instruments of the highest available accuracy and with high time resolution (1 to 3 minutes). Since 2008 the WRMC is hosted by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Bremerhaven, Germany (http://www.bsrn.awi.de/).
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This work discusses an iterative procedure of shaping offset dual-reflector antennas based on geometrical optics considering both far-field and near-field measurements of amplitude and phase from the feed horn. The surfaces synthesized will transform a known radiation field of a feed to a desired aperture distribution. This technique is applied for both circular and elliptical apertures and has the advantage to simplify the problem compared with existing techniques based on solving nonlinear differential equations. A MATLAB tool has been developed to implement the shaping algorithms. This procedure is applied for the design of a 1.1 m high-gain antenna for the ESAs Solar Orbiter spacecraft. This antenna operating at X-band will manage high data rate and high efficiency communications with Earth stations.
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La fusin nuclear es, hoy en da, una alternativa energtica a la que la comunidad internacional dedica mucho esfuerzo. El objetivo es el de generar entre diez y cincuenta veces ms energa que la que consume mediante reacciones de fusin que se producirn en una mezcla de deuterio (D) y tritio (T) en forma de plasma a doscientos millones de grados centgrados. En los futuros reactores nucleares de fusin ser necesario producir el tritio utilizado como combustible en el propio reactor termonuclear. Este hecho supone dar un paso ms que las actuales mquinas experimentales dedicadas fundamentalmente al estudio de la fsica del plasma. As pues, el tritio, en un reactor de fusin, se produce en sus envolturas regeneradoras cuya misin fundamental es la de blindaje neutrnico, producir y recuperar tritio (fuel para la reaccin DT del plasma) y por ltimo convertir la energa de los neutrones en calor. Existen diferentes conceptos de envolturas que pueden ser slidas o lquidas. Las primeras se basan en cermicas de litio (Li2O, Li4SiO4, Li2TiO3, Li2ZrO3) y multiplicadores neutrnicos de Be, necesarios para conseguir la cantidad adecuada de tritio. Los segundos se basan en el uso de metales lquidos o sales fundidas (Li, LiPb, FLIBE, FLINABE) con multiplicadores neutrnicos de Be o el propio Pb en el caso de LiPb. Los materiales estructurales pasan por aceros ferrtico-martensticos de baja activacin, aleaciones de vanadio o incluso SiCf/SiC. Cada uno de los diferentes conceptos de envoltura tendr una problemtica asociada que se estudiar en el reactor experimental ITER (del ingls, International Thermonuclear Experimental Reactor). Sin embargo, ITER no puede responder las cuestiones asociadas al dao de materiales y el efecto de la radiacin neutrnica en las diferentes funciones de las envolturas regeneradoras. Como referencia, la primera pared de un reactor de fusin de 4000MW recibira 30 dpa/ao (valores para Fe-56) mientras que en ITER se conseguiran <10 dpa en toda su vida til. Esta tesis se encuadra en el acuerdo bilateral entre Europa y Japn denominado Broader Approach Agreement (BA) (2007-2017) en el cual Espaa juega un papel destacable. Estos proyectos, complementarios con ITER, son el acelerador para pruebas de materiales IFMIF (del ingls, International Fusion Materials Irradiation Facility) y el dispositivo de fusin JT-60SA. As, los efectos de la irradiacin de materiales en materiales candidatos para reactores de fusin se estudiarn en IFMIF. El objetivo de esta tesis es el diseo de un mdulo de IFMIF para irradiacin de envolturas regeneradoras basadas en metales lquidos para reactores de fusin. El mdulo se llamar LBVM (del ingls, Liquid Breeder Validation Module). La propuesta surge de la necesidad de irradiar materiales funcionales para envolturas regeneradoras lquidas para reactores de fusin debido a que el diseo conceptual de IFMIF no contaba con esta utilidad. Con objeto de analizar la viabilidad de la presente propuesta, se han realizado clculos neutrnicos para evaluar la idoneidad de llevar a cabo experimentos relacionados con envolturas lquidas en IFMIF. As, se han considerado diferentes candidatos a materiales funcionales de envolturas regeneradoras: Fe (base de los materiales estructurales), SiC (material candidato para los FCIs (del ingls, Flow Channel Inserts) en una envoltura regeneradora lquida, SiO2 (candidato para recubrimientos antipermeacin), CaO (candidato para recubrimientos aislantes), Al2O3 (candidato para recubrimientos antipermeacin y aislantes) y AlN (material candidato para recubrimientos aislantes). En cada uno de estos materiales se han calculado los parmetros de irradiacin ms significativos (dpa, H/dpa y He/dpa) en diferentes posiciones de IFMIF. Estos valores se han comparado con los esperados en la primera pared y en la zona regeneradora de tritio de un reactor de fusin. Para ello se ha elegido un reactor tipo HCLL (del ingls, Helium Cooled Lithium Lead) por tratarse de uno de los ms prometedores. Adems, los valores tambin se han comparado con los que se obtendran en un reactor rpido de fisin puesto que la mayora de las irradiaciones actuales se hacen en reactores de este tipo. Como conclusin al anlisis de viabilidad, se puede decir que los materiales funcionales para mantos regeneradores lquidos podran probarse en la zona de medio flujo de IFMIF donde se obtendran ratios de H/dpa y He/dpa muy parecidos a los esperados en las zonas ms irradiadas de un reactor de fusin. Adems, con el objetivo de ajustar todava ms los valores, se propone el uso de un moderador de W (a considerar en algunas campaas de irradiacin solamente debido a que su uso hace que los valores de dpa totales disminuyan). Los valores obtenidos para un reactor de fisin refuerzan la idea de la necesidad del LBVM, ya que los valores obtenidos de H/dpa y He/dpa son muy inferiores a los esperados en fusin y, por lo tanto, no representativos. Una vez demostrada la idoneidad de IFMIF para irradiar envolturas regeneradoras lquidas, y del estudio de la problemtica asociada a las envolturas lquidas, tambin incluida en esta tesis, se proponen tres tipos de experimentos diferentes como base de diseo del LBVM. stos se orientan en las necesidades de un reactor tipo HCLL aunque a lo largo de la tesis se discute la aplicabilidad para otros reactores e incluso se proponen experimentos adicionales. As, la capacidad experimental del mdulo estara centrada en el estudio del comportamiento de litio plomo, permeacin de tritio, corrosin y compatibilidad de materiales. Para cada uno de los experimentos se propone un esquema experimental, se definen las condiciones necesarias en el mdulo y la instrumentacin requerida para controlar y diagnosticar las cpsulas experimentales. Para llevar a cabo los experimentos propuestos se propone el LBVM, ubicado en la zona de medio flujo de IFMIF, en su celda caliente, y con capacidad para 16 cpsulas experimentales. Cada cpsula (24-22 mm de dimetro y 80 mm de altura) contendr la aleacin eutctica LiPb (hasta 50 mm de la altura de la cpsula) en contacto con diferentes muestras de materiales. sta ir soportada en el interior de tubos de acero por los que circular un gas de purga (He), necesario para arrastrar el tritio generado en el eutctico y permeado a travs de las paredes de las cpsulas (continuamente, durante irradiacin). Estos tubos, a su vez, se instalarn en una carcasa tambin de acero que proporcionar soporte y refrigeracin tanto a los tubos como a sus cpsulas experimentales interiores. El mdulo, en su conjunto, permitir la extraccin de las seales experimentales y el gas de purga. As, a travs de la estacin de medida de tritio y el sistema de control, se obtendrn los datos experimentales para su anlisis y extraccin de conclusiones experimentales. Adems del anlisis de datos experimentales, algunas de estas seales tendrn una funcin de seguridad y por tanto jugarn un papel primordial en la operacin del mdulo. Para el correcto funcionamiento de las cpsulas y poder controlar su temperatura, cada cpsula se equipar con un calentador elctrico y por tanto el mdulo requerir tambin ser conectado a la alimentacin elctrica. El diseo del mdulo y su lgica de operacin se describe en detalle en esta tesis. La justificacin tcnica de cada una de las partes que componen el mdulo se ha realizado con soporte de clculos de transporte de tritio, termohidrulicos y mecnicos. Una de las principales conclusiones de los clculos de transporte de tritio es que es perfectamente viable medir el tritio permeado en las cpsulas mediante cmaras de ionizacin y contadores proporcionales comerciales, con sensibilidades en el orden de 10-9 Bq/m3. Los resultados son aplicables a todos los experimentos, incluso si son cpsulas a bajas temperaturas o si llevan recubrimientos antipermeacin. Desde un punto de vista de seguridad, el conocimiento de la cantidad de tritio que est siendo transportada con el gas de purga puede ser usado para detectar de ciertos problemas que puedan estar sucediendo en el mdulo como por ejemplo, la rotura de una cpsula. Adems, es necesario conocer el balance de tritio de la instalacin. Las prdidas esperadas el refrigerante y la celda caliente de IFMIF se pueden considerar despreciables para condiciones normales de funcionamiento. Los clculos termohidrulicos se han realizado con el objetivo de optimizar el diseo de las cpsulas experimentales y el LBVM de manera que se pueda cumplir el principal requisito del mdulo que es llevar a cabo los experimentos a temperaturas comprendidas entre 300-550C. Para ello, se ha dimensionado la refrigeracin necesaria del mdulo y evaluado la geometra de las cpsulas, tubos experimentales y la zona experimental del contenedor. Como consecuencia de los anlisis realizados, se han elegido cpsulas y tubos cilndricos instalados en compartimentos cilndricos debido a su buen comportamiento mecnico (las tensiones debidas a la presin de los fluidos se ven reducidas significativamente con una geometra cilndrica en lugar de prismtica) y trmico (uniformidad de temperatura en las paredes de los tubos y cpsulas). Se han obtenido campos de presin, temperatura y velocidad en diferentes zonas crticas del mdulo concluyendo que la presente propuesta es factible. Cabe destacar que el uso de cdigos fluidodinmicos (e.g. ANSYS-CFX, utilizado en esta tesis) para el diseo de cpsulas experimentales de IFMIF no es directo. La razn de ello es que los modelos de turbulencia tienden a subestimar la temperatura de pared en mini canales de helio sometidos a altos flujos de calor debido al cambio de las propiedades del fluido cerca de la pared. Los diferentes modelos de turbulencia presentes en dicho cdigo han tenido que ser estudiados con detalle y validados con resultados experimentales. El modelo SST (del ingls, Shear Stress Transport Model) para turbulencia en transicin ha sido identificado como adecuado para simular el comportamiento del helio de refrigeracin y la temperatura en las paredes de las cpsulas experimentales. Con la geometra propuesta y los valores principales de refrigeracin y purga definidos, se ha analizado el comportamiento mecnico de cada uno de los tubos experimentales que contendr el mdulo. Los resultados de tensiones obtenidos, han sido comparados con los valores mximos recomendados en cdigos de diseo estructural como el SDC-IC (del ingls, Structural Design Criteria for ITER Components) para as evaluar el grado de proteccin contra el colapso plstico. La conclusin del estudio muestra que la propuesta es mecnicamente robusta. El LBVM implica el uso de metales lquidos y la generacin de tritio adems del riesgo asociado a la activacin neutrnica. Por ello, se han estudiado los riesgos asociados al uso de metales lquidos y el tritio. Adems, se ha incluido una evaluacin preliminar de los riesgos radiolgicos asociados a la activacin de materiales y el calor residual en el mdulo despus de la irradiacin as como un escenario de prdida de refrigerante. Los riesgos asociados al mdulo de naturaleza convencional estn asociados al manejo de metales lquidos cuyas reacciones con aire o agua se asocian con emisin de aerosoles y probabilidad de fuego. De entre los riesgos nucleares destacan la generacin de gases radiactivos como el tritio u otros radioistopos voltiles como el Po-210. No se espera que el mdulo suponga un impacto medioambiental asociado a posibles escapes. Sin embargo, es necesario un manejo adecuado tanto de las cpsulas experimentales como del mdulo contenedor as como de las lneas de purga durante operacin. Despus de un da de despus de la parada, tras un ao de irradiacin, tendremos una dosis de contacto de 7000 Sv/h en la zona experimental del contenedor, 2300 Sv/h en la cpsula y 25 Sv/h en el LiPb. El uso por lo tanto de manipulacin remota est previsto para el manejo del mdulo irradiado. Por ltimo, en esta tesis se ha estudiado tambin las posibilidades existentes para la fabricacin del mdulo. De entre las tcnicas propuestas, destacan la electroerosin, soldaduras por haz de electrones o por soldadura lser. Las bases para el diseo final del LBVM han sido pues establecidas en el marco de este trabajo y han sido incluidas en el diseo intermedio de IFMIF, que ser desarrollado en el futuro, como parte del diseo final de la instalacin IFMIF. ABSTRACT Nuclear fusion is, today, an alternative energy source to which the international community devotes a great effort. The goal is to generate 10 to 50 times more energy than the input power by means of fusion reactions that occur in deuterium (D) and tritium (T) plasma at two hundred million degrees Celsius. In the future commercial reactors it will be necessary to breed the tritium used as fuel in situ, by the reactor itself. This constitutes a step further from current experimental machines dedicated mainly to the study of the plasma physics. Therefore, tritium, in fusion reactors, will be produced in the so-called breeder blankets whose primary mission is to provide neutron shielding, produce and recover tritium and convert the neutron energy into heat. There are different concepts of breeding blankets that can be separated into two main categories: solids or liquids. The former are based on ceramics containing lithium as Li2O , Li4SiO4 , Li2TiO3 , Li2ZrO3 and Be, used as a neutron multiplier, required to achieve the required amount of tritium. The liquid concepts are based on molten salts or liquid metals as pure Li, LiPb, FLIBE or FLINABE. These blankets use, as neutron multipliers, Be or Pb (in the case of the concepts based on LiPb). Proposed structural materials comprise various options, always with low activation characteristics, as low activation ferritic-martensitic steels, vanadium alloys or even SiCf/SiC. Each concept of breeding blanket has specific challenges that will be studied in the experimental reactor ITER (International Thermonuclear Experimental Reactor). However, ITER cannot answer questions associated to material damage and the effect of neutron radiation in the different breeding blankets functions and performance. As a reference, the first wall of a fusion reactor of 4000 MW will receive about 30 dpa / year (values for Fe-56) , while values expected in ITER would be <10 dpa in its entire lifetime. Consequently, the irradiation effects on candidate materials for fusion reactors will be studied in IFMIF (International Fusion Material Irradiation Facility). This thesis fits in the framework of the bilateral agreement among Europe and Japan which is called Broader Approach Agreement (BA) (2007-2017) where Spain plays a key role. These projects, complementary to ITER, are mainly IFMIF and the fusion facility JT-60SA. The purpose of this thesis is the design of an irradiation module to test candidate materials for breeding blankets in IFMIF, the so-called Liquid Breeder Validation Module (LBVM). This proposal is born from the fact that this option was not considered in the conceptual design of the facility. As a first step, in order to study the feasibility of this proposal, neutronic calculations have been performed to estimate irradiation parameters in different materials foreseen for liquid breeding blankets. Various functional materials were considered: Fe (base of structural materials), SiC (candidate material for flow channel inserts, SiO2 (candidate for antipermeation coatings), CaO (candidate for insulating coatings), Al2O3 (candidate for antipermeation and insulating coatings) and AlN (candidate for insulation coating material). For each material, the most significant irradiation parameters have been calculated (dpa, H/dpa and He/dpa) in different positions of IFMIF. These values were compared to those expected in the first wall and breeding zone of a fusion reactor. For this exercise, a HCLL (Helium Cooled Lithium Lead) type was selected as it is one of the most promising options. In addition, estimated values were also compared with those obtained in a fast fission reactor since most of existing irradiations have been made in these installations. The main conclusion of this study is that the medium flux area of IFMIF offers a good irradiation environment to irradiate functional materials for liquid breeding blankets. The obtained ratios of H/dpa and He/dpa are very similar to those expected in the most irradiated areas of a fusion reactor. Moreover, with the aim of bringing the values further close, the use of a W moderator is proposed to be used only in some experimental campaigns (as obviously, the total amount of dpa decreases). The values of ratios obtained for a fission reactor, much lower than in a fusion reactor, reinforce the need of LBVM for IFMIF. Having demonstrated the suitability of IFMIF to irradiate functional materials for liquid breeding blankets, and an analysis of the main problems associated to each type of liquid breeding blanket, also presented in this thesis, three different experiments are proposed as basis for the design of the LBVM. These experiments are dedicated to the needs of a blanket HCLL type although the applicability of the module for other blankets is also discussed. Therefore, the experimental capability of the module is focused on the study of the behavior of the eutectic alloy LiPb, tritium permeation, corrosion and material compatibility. For each of the experiments proposed an experimental scheme is given explaining the different module conditions and defining the required instrumentation to control and monitor the experimental capsules. In order to carry out the proposed experiments, the LBVM is proposed, located in the medium flux area of the IFMIF hot cell, with capability of up to 16 experimental capsules. Each capsule (24-22 mm of diameter, 80 mm high) will contain the eutectic allow LiPb (up to 50 mm of capsule high) in contact with different material specimens. They will be supported inside rigs or steel pipes. Helium will be used as purge gas, to sweep the tritium generated in the eutectic and permeated through the capsule walls (continuously, during irradiation). These tubes, will be installed in a steel container providing support and cooling for the tubes and hence the inner experimental capsules. The experimental data will consist of on line monitoring signals and the analysis of purge gas by the tritium measurement station. In addition to the experimental signals, the module will produce signals having a safety function and therefore playing a major role in the operation of the module. For an adequate operation of the capsules and to control its temperature, each capsule will be equipped with an electrical heater so the module will to be connected to an electrical power supply. The technical justification behind the dimensioning of each of these parts forming the module is presented supported by tritium transport calculations, thermalhydraulic and structural analysis. One of the main conclusions of the tritium transport calculations is that the measure of the permeated tritium is perfectly achievable by commercial ionization chambers and proportional counters with sensitivity of 10-9 Bq/m3. The results are applicable to all experiments, even to low temperature capsules or to the ones using antipermeation coatings. From a safety point of view, the knowledge of the amount of tritium being swept by the purge gas is a clear indicator of certain problems that may be occurring in the module such a capsule rupture. In addition, the tritium balance in the installation should be known. Losses of purge gas permeated into the refrigerant and the hot cell itself through the container have been assessed concluding that they are negligible for normal operation. Thermal hydraulic calculations were performed in order to optimize the design of experimental capsules and LBVM to fulfill one of the main requirements of the module: to perform experiments at uniform temperatures between 300-550C. The necessary cooling of the module and the geometry of the capsules, rigs and testing area of the container were dimensioned. As a result of the analyses, cylindrical capsules and rigs in cylindrical compartments were selected because of their good mechanical behavior (stresses due to fluid pressure are reduced significantly with a cylindrical shape rather than prismatic) and thermal (temperature uniformity in the walls of the tubes and capsules). Fields of pressure, temperature and velocity in different critical areas of the module were obtained concluding that the proposal is feasible. It is important to mention that the use of fluid dynamic codes as ANSYS-CFX (used in this thesis) for designing experimental capsules for IFMIF is not direct. The reason for this is that, under strongly heated helium mini channels, turbulence models tend to underestimate the wall temperature because of the change of helium properties near the wall. Therefore, the different code turbulence models had to be studied in detail and validated against experimental results. ANSYS-CFX SST (Shear Stress Transport Model) for transitional turbulence model has been identified among many others as the suitable one for modeling the cooling helium and the temperature on the walls of experimental capsules. Once the geometry and the main purge and cooling parameters have been defined, the mechanical behavior of each experimental tube or rig including capsules is analyzed. Resulting stresses are compared with the maximum values recommended by applicable structural design codes such as the SDC- IC (Structural Design Criteria for ITER Components) in order to assess the degree of protection against plastic collapse. The conclusion shows that the proposal is mechanically robust. The LBVM involves the use of liquid metals, tritium and the risk associated with neutron activation. The risks related with the handling of liquid metals and tritium are studied in this thesis. In addition, the radiological risks associated with the activation of materials in the module and the residual heat after irradiation are evaluated, including a scenario of loss of coolant. Among the identified conventional risks associated with the module highlights the handling of liquid metals which reactions with water or air are accompanied by the emission of aerosols and fire probability. Regarding the nuclear risks, the generation of radioactive gases such as tritium or volatile radioisotopes such as Po-210 is the main hazard to be considered. An environmental impact associated to possible releases is not expected. Nevertheless, an appropriate handling of capsules, experimental tubes, and container including purge lines is required. After one day after shutdown and one year of irradiation, the experimental area of the module will present a contact dose rate of about 7000 Sv/h, 2300 Sv/h in the experimental capsules and 25 Sv/h in the LiPb. Therefore, the use of remote handling is envisaged for the irradiated module. Finally, the different possibilities for the module manufacturing have been studied. Among the proposed techniques highlights the electro discharge machining, brazing, electron beam welding or laser welding. The bases for the final design of the LBVM have been included in the framework of the this work and included in the intermediate design report of IFMIF which will be developed in future, as part of the IFMIF facility final design.
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The Atomic Bomb Casualty Commission was established in Hiroshima in 1947 and in Nagasaki in 1948 under the auspices of the U.S. National Academy of Sciences to initiate a long-term and comprehensive epidemiological and genetic study of the atomic bomb survivors. It was replaced in 1975 by the Radiation Effects Research Foundation which is a nonprofit Japanese foundation binationally managed and supported with equal funding by the governments of Japan and the United States. Thanks to the cooperation of the survivors and the contributions of a multitude of scientists, these studies flourish to this day in what must be the most successful long-term research collaboration between the two countries. Although these studies are necessarily limited to the effects of acute, whole-body, mixed gamma-neutron radiation from the atom bombs, their comprehensiveness and duration make them the most definitive descriptions of the late effects of radiation in humans. For this reason, the entire world relies heavily on these data to set radiation standards. As vital as the study results are, they still represent primarily the effects of radiation on older survivors. Another decade or two should correct this deficiency and allow us to measure definitively the human risk of heritable mutation from radiation. We look to the worldwide radiation and risk community as well as to the survivors who have contributed so much to what has been done already to accomplish this goal.
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Context. Galaxies, which often contain ionised gas, sometimes also exhibit a so-called low-ionisation nuclear emission line region (LINER). For 30 years, this was attributed to a central mass-accreting supermassive black hole (more commonly known as active galactic nucleus, AGN) of low luminosity, making LINER galaxies the largest AGN sub-population, which dominate in numbers over higher luminosity Seyfert galaxies and quasars. This, however, poses a serious problem. While the inferred energy balance is plausible, many LINERs clearly do not contain any other independent signatures of an AGN. Aims. Using integral field spectroscopic data from the CALIFA survey, we compare the observed radial surface brightness profiles with what is expected from illumination by an AGN. Methods. Essential for this analysis is a proper extraction of emission lines, especially weak lines, such as Balmer H beta lines, which are superposed on an absorption trough. To accomplish this, we use the GANDALF code, which simultaneously fits the underlying stellar continuum and emission lines. Results. For 48 galaxies with LINER-like emission, we show that the radial emission-line surface brightness profiles are inconsistent with ionisation by a central point-source and hence cannot be due to an AGN alone. Conclusions. The most probable explanation for the excess LINER-like emission is ionisation by evolved stars during the short but very hot and energetic phase known as post-AGB. This leads us to an entirely new interpretation. Post-AGB stars are ubiquitous and their ionising effect should be potentially observable in every galaxy with the gas present and with stars older than ~1 Gyr unless a stronger radiation field from young hot stars or an AGN outshines them. This means that galaxies with LINER-like emission are not a class defined by a property but rather by the absence of a property. It also explains why LINER emission is observed mostly in massive galaxies with old stars and little star formation.
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We present Submillimeter Array [C II] 158 m and Karl G. Jansky Very Large Array 12^CO(1-0) line emission maps for the bright, lensed, submillimeter source at z = 5.2430 behind A 773: HLSJ091828.6+514223 (HLS0918). We combine these measurements with previously reported line profiles, including multiple 12^CO rotational transitions, [C I], water, and [N II], providing some of the best constraints on the properties of the interstellar medium in a galaxy at z > 5. HLS0918 has a total far-infrared (FIR) luminosity L_FIR(81000 m) = (1.6 0.1) 10^14 L_ ^1, where the total magnification _total = 8.9 1.9, via a new lens model from the [C II] and continuum maps. Despite a HyLIRG luminosity, the FIR continuum shape resembles that of a local LIRG. We simultaneously fit all of the observed spectral line profiles, finding four components that correspond cleanly to discrete spatial structures identified in the maps. The two most redshifted spectral components occupy the nucleus of a massive galaxy, with a source-plane separation <1 kpc. The reddest dominates the continuum map (demagnified L_FIR, component = (1.1 0.2) 10^13 L_) and excites strong water emission in both nuclear components via a powerful FIR radiation field from the intense star formation. A third star-forming component is most likely a region of a merging companion (V ~ 500 km s^1) exhibiting generally similar gas properties. The bluest component originates from a spatially distinct region and photodissociation region analysis suggests that it is lower density, cooler, and forming stars less vigorously than the other components. Strikingly, it has very strong [N II] emission, which may suggest an ionized, molecular outflow. This comprehensive view of gas properties and morphology in HLS0918 previews the science possible for a large sample of high-redshift galaxies once ALMA attains full sensitivity.
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Tese de mestrado em Fsica, apresentada Universidade de Lisboa, atravs da Faculdade de Cincias, 2016
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We introduce a Gaussian quantum operator representation, using the most general possible multimode Gaussian operator basis. The representation unifies and substantially extends existing phase-space representations of density matrices for Bose systems and also includes generalized squeezed-state and thermal bases. It enables first-principles dynamical or equilibrium calculations in quantum many-body systems, with quantum uncertainties appearing as dynamical objects. Any quadratic Liouville equation for the density operator results in a purely deterministic time evolution. Any cubic or quartic master equation can be treated using stochastic methods.
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Multipole expansion of an incident radiation field-that is, representation of the fields as sums of vector spherical wavefunctions-is essential for theoretical light scattering methods such as the T-matrix method and generalised Lorenz-Mie theory (GLMT). In general, it is theoretically straightforward to find a vector spherical wavefunction representation of an arbitrary radiation field. For example, a simple formula results in the useful case of an incident plane wave. Laser beams present some difficulties. These problems are not a result of any deficiency in the basic process of spherical wavefunction expansion, but are due to the fact that laser beams, in their standard representations, are not radiation fields, but only approximations of radiation fields. This results from the standard laser beam representations being solutions to the paraxial scalar wave equation. We present an efficient method for determining the multipole representation of an arbitrary focussed beam. (C) 2003 Elsevier Science Ltd. All rights reserved.
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We review the field of quantum optical information from elementary considerations to quantum computation schemes. We illustrate our discussion with descriptions of experimental demonstrations of key communication and processing tasks from the last decade and also look forward to the key results likely in the next decade. We examine both discrete (single photon) type processing as well as those which employ continuous variable manipulations. The mathematical formalism is kept to the minimum needed to understand the key theoretical and experimental results.
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Absolute calibration relates the measured (arbitrary) intensity to the differential scattering cross section of the sample, which contains all of the quantitative information specific to the material. The importance of absolute calibration in small-angle scattering experiments has long been recognized. This work details the absolute calibration procedure of a small-angle X-ray scattering instrument from Bruker AXS. The absolute calibration presented here was achieved by using a number of different types of primary and secondary standards. The samples were: a glassy carbon specimen, which had been independently calibrated from neutron radiation; a range of pure liquids, which can be used as primary standards as their differential scattering cross section is directly related to their isothermal compressibility; and a suspension of monodisperse silica particles for which the differential scattering cross section is obtained from Porod's law. Good agreement was obtained between the different standard samples, provided that care was taken to obtain significant signal averaging and all sources of background scattering were accounted for. The specimen best suited for routine calibration was the glassy carbon sample, due to its relatively intense scattering and stability over time; however, initial calibration from a primary source is necessary. Pure liquids can be used as primary calibration standards, but the measurements take significantly longer and are, therefore, less suited for frequent use.
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The astrophysical context in which this thesis project lies concerns the comprehension of the mutual interaction between the accretion onto a Super Massive Black Hole (SMBH) and the Star Formation (SF), that take place in the host galaxy. This is one of the key topic of the modern extragalactic astrophysical research. Indeed, it is widely accepted that to understand the physics of a galaxy, the contribution of a possible central AGN must be taken into account. The aim of this thesis is the study of the physical processes of the nearby Seyfert galaxy NGC 34. This source was selected because of the wide collection of multiwavelength data available in the literature. In addition, recently, it has been observed with the Atacama Large Submillimeter/Millimeter Array (ALMA) in Band 9. This project is divided in two main parts: first of all, we reduced and analyzed the ALMA data, obtaining the continuum and CO(6-5) maps; then, we looked for a coherent explaination of NGC 34 physical characteristics. In particular, we focused on the ISM physics, in order to understand its properties in terms of density, chemical composition and dominant radiation field (SF or accretion). This work has been done through the analysis of the spectral distribution of several CO transitions as a function of the transition number (CO SLED), obtained joining the CO(6-5) line with other transitions available in the literature. More precisely, the observed CO SLED has been compared with ISM models, including Photo-Dissociation Regions (PDRs) and X-ray-Dominated Regions (XDRs). These models have been obtained through the state-of-the-art photoionization code CLOUDY. Along with the observed CO SLED, we have taken into account other physical properties of NGC 34, such as the Star Formation Rate (SFR), the gas mass and the X-ray luminosity.
