Photon Beam
Mostrando 1-12 de 31 artigos, teses e dissertações.
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1. LABORATORY INVESTIGATION OF X-RAY PHOTOLYSIS OF METHANOL ICE AND ITS IMPLICATION ON ASTROPHYSICAL ENVIRONMENTS
Methanol (CH3OH) is one of the most abundant organic molecules in astrophysical environments. It has been found in cold regions such as surfaces of comets, ices near young stellar objects and protoplanetary disks, as well as in the gas phase in different regions in space. In this work, we experimentally simulate the methanol ice and its behavior when irradia
Quím. Nova. Publicado em: 2020-05
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2. Bremsstrahlung de elétrons no microtron do IFUSP: medidas, simulação e proposta de aplicação ao estudo da ressonância fluorescente nuclear / Electron Bremssthahlung in the IFUSP microton: measurements, simulation and proposal for a nuclear resonance fluorescence observation setup
The results of the first experiments carried out in the new electron accelerator of the Linear Accelerator Laboratory (LAL) of the Physics Institute of Universidade de São Paulo are reported here. A 1.9 MeV beam line, which allows the use of the injector beam for experimental physics, was added to the original accelerator design. Electron bremsstrahlung spe
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 20/06/2011
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3. Trapping state stabilization in a micromaser with a mixed atomic beam
A scheme which stabilizes the trapping states in micromasers is proposed and studied. It uses an atomic beam composed of a mixture of two types of atoms. Numerical simulations based on the Monte Carlo wavefunction method show that, despite collective events, it is possible to obtain a steady-state photon number distribution limited (‘‘trapped’’) to a
Publicado em: 2011
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4. 6 MV wedge photon beam profiles with the fricke xylenol gel dosimeter
Wedged beam are often used in clinical radiotherapy to compensate missing tissues and dose gradients. In this work, the Fricke Xylenol Gel (FXG) dosimeter was used for 6 MV photons radiation wedge field profiles measurements, allowing to infer the wedge filter physical attenuation coefficient. This dosimeter is a chemical system of a Fe3+-Xylenol complex con
Brazilian Journal of Physics. Publicado em: 2009-12
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5. Development and application of the pulse train hyper-Rayleigh scattering technique. / Desenvolvimento e aplicação da técnica de hiper Rayleigh com trem de pulsos
This thesis reports an extension of the Hyper-Rayleigh scattering technique (HRS) and its application to study the mechanisms that contribute to the molecular first hyperpolarizabilities (). We use a Nd:YAG laser, Q-switched and mode-locked, as pumping beam to excite the samples. The laser delivers 100 ps pulses modulated by a Q-switch envelope, and the outp
Publicado em: 2008
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6. Acoplamento de dois feixes com lasers de femtossegundos em vapor de Rb
Femtosecond lasers operating in the mode-locked regime have a repetition rate determined by the round trip time of the pulse inside the laser cavity (TR = 2L/c). For Ti:sapphire lasers the repetition rate is typically of the order of 100 MHz, with TR 10 ns. Under this condition TR may be smaller then the population relaxation time (T1) and the coher
Publicado em: 2007
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7. Assessment of radiotherapic treatments with thermoluminescent dosimetry / Verificação de tratamentos radioterápicos diversos com dosimetria termoluminescente
The last decades noticed a massive improvement in radiotherapy techniques and the use of segmented beams produced by multileaf collimators. However, the dose radiation therapy planning systems (TPS) in use are characterized by the restriction of access to the calculation algorithms. The aim of this work was to compare dose values measured in an anthropomorph
Publicado em: 2007
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8. Métodos para implementação da dosimetria in vivo (dose de entrada) com dosímetros termoluminescentes na radioterapia externa com feixe de fóton / Methods for implementation of in vivo dosimetry (entrance dose) using thermoluminescent dosimeters during radiotherapy treatment with photon beam
Neste trabalho, estão descritos os métodos de seleção, calibração e de determinação dos fatores de correção, as características físicas dos dosímetros termoluminescentes, o procedimento de cálculo para converter a leitura do dosímetro em dose absorvida e a metodologia para se determinar a dose de entrada. Foram investigadas a praticidade e a u
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 23/11/2006
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9. Ionic desorption in valence- and core- excited polymers: poly(vinyl chloride) and poly(vinylidene chloride)
Photon stimulated ion desorption (PSID) studies have been performed in poly(vinyl chloride) (PVC) and poly(vinylidene chloride) (PVDC) using synchrotron radiation, covering from valence to core electron (Cl 2p and C 1s) energy ranges. Data acquisition was performed at the TGM beam line from the Brazilian Synchrotron Light Source (LNLS), operating in a multi-
Brazilian Journal of Physics. Publicado em: 2006-06
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10. SEMI-EMPIRICAL SIMULATION OF THERMOLUMINESCENT RESPONSE UNDER DIFFERENT FILTER GEOMETRIES / "Simulação semi-empírica da resposta termoluminescente sob diferentes geometrias de filtro"
Many thermoluminescent materials has been developed and used for photon personal dosimetry but no one has all desired characteristics alone. These characteristics include robustness, high sensitivity, energy photon independence, large range of photon energy detection, good reproductibility, small fading and simple glow curve with peaks above 150oC. Calcium S
Publicado em: 2006
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11. Dependence of transition probabilities for non-linear photo-ionization of He atoms on the structure of the exciting radiation pulses
We discuss the expected dependence of the probability transitions for 2-photon and 3-photon absorption in Helium gas on the spatial and temporal structure of the exciting radiation pulses. Regarding spatial structure, we assumed a Gaussian radial intensity distribution; we find, as expected, that the 2-photon and 3-photon processes become negligible at dista
Brazilian Journal of Physics. Publicado em: 2005-09
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12. "Espalhamento Compton e medida absoluta da energia de fótons marcados - Uma simulação Monte Carlo" / Compton scattering and absolute measurement of tagged photon energies.
A simulation based on Monte Carlo methods was created in order to evaluate the potentiality of using Compton scattering at high energies to obtain high precision absolute measurements of tagged photon energies. This method is based on angular measurements of the scattering products to reconstruct the incident photon energy using the kinematics of Compton sca
Publicado em: 2005