Departamento de Física
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/785
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10 resultados
Resultados da Pesquisa
- Non-Hermitian model for asymmetric tunneling(2014) Santos R.B.B.; Da Silva V.R.© 2014 World Scientific Publishing Company.We present a simple non-Hermitian model to describe the phenomenon of asymmetric tunneling between two energy-degenerate sites coupled by a non-reciprocal interaction without dissipation. The system was described using a biorthogonal family of energy eigenvectors, the dynamics of the system was determined by the Schrödinger equation, and unitarity was effectively restored by proper normalization of the state vectors. The results show that the tunneling rates are indeed asymmetrical in this model, leading to an equilibrium that displays unequal occupation of the degenerate systems even in the absence of external interactions.
- Non-Hermitian model for resonant cavities coupled by a chiral mirror(2012) Santos R.B.B.Inspired by a recently observed asymmetry in the transmission of circularly polarized light through a metamaterial, we present a non-Hermitian PT-symmetric quantum model to describe the interaction of the light fields in two resonant cavities coupled via a 2D-chiral mirror. We compute the time evolution of the light fields in this model, find two sets of operators compatible with the Hamiltonian in a delocalized representation, discover the energies of the system and show that the transmission probability predicted by the model is indeed asymmetric. © EPLA, 2012.
- Plasma-like vacuum in podolsky regularized classical electrodynamics(2011) Santos R.B.B.We analyze wave propagation in the vacuum of Podolsky regularized electrodynamics. Two kinds of waves were found in the theory: the traditional non-dispersive waves of Maxwell electrodynamics, and a dispersive wave reminiscent of wave propagation in a collisionless plasma. Charged particle concentration was determined, and found to be huge in this vacuum. We interpret the results in terms of vacuum polarization effects induced in an otherwise classical theory. © 2011 World Scientific Publishing Company.
- Extracting chaos control parameters from time series analysis(2011) Santos R.B.B.; Graves J.C.We present a simple method to analyze time series, and estimate the parameters needed to control chaos in dynamical systems. Application of the method to a system described by the logistic map is also shown. Analyzing only two 100-point time series, we achieved results within 2% of the analytical ones. With these estimates, we show that OGY control method successfully stabilized a period-1 unstable periodic orbit embedded in the chaotic attractor. © Published under licence by IOP Publishing Ltd.
- The NUMEN project: NUclear Matrix Elements for Neutrinoless double beta decay(2018) Cappuzzello F.; Agodi C.; Cavallaro M.; Carbone D.; Tudisco S.; Lo Presti D.; Oliveira J.R.B.; Finocchiaro P.; Colonna M.; Rifuggiato D.; Calabretta L.; Calvo D.; Pandola L.; Acosta L.; Auerbach N.; Bellone J.; Bijker R.; Bonanno D.; Bongiovanni D.; Borello-Lewin T.; Boztosun I.; Brunasso O.; Burrello S.; Calabrese S.; Calanna A.; Chavez Lomeli E.R.; D'Agostino G.; De Faria P.N.; De Geronimo G.; Delaunay F.; Deshmukh N.; Ferreira J.L.; Fisichella M.; Foti A.; Gallo G.; Garcia-Tecocoatzi H.; Greco V.; Hacisalihoglu A.; Iazzi F.; Introzzi R.; Lanzalone G.; Lay J.A.; La Via F.; Lenske H.; Linares R.; Litrico G.; Longhitano F.; Lubian J.; Medina N.H.; Mendes D.R.; Moralles M.; Muoio A.; Pakou A.; Petrascu H.; Pinna F.; Reito S.; Russo A.D.; Russo G.; Santagati G.; Santopinto E.; Santos R.B.B.; Sgouros O.; da Silveira M.A.G.; Solakci S.O.; Souliotis G.; Soukeras V.; Spatafora A.; Torresi D.; Magana Vsevolodovna R.; Yildirim A.; Zagatto V.A.B.© 2018, SIF, Springer-Verlag GmbH Germany, part of Springer Nature.The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.
- A commercial off-the-shelf pMOS transistor as X-ray and heavy ion detector(2015) Silveira M.A.G.; Melo M.A.A.; Aguiar V.A.P.; Rallo A.; Santos R.B.B.; Medina N.H.; Added N.; Seixas L.E.; Leite F.G.; Cunha F.G.; Cirne K.H.; Giacomini R.; de OLIVEIRA J.A.© Published under licence by IOP Publishing Ltd.Recently, p-channel metal-oxide-semiconductor (pMOS) transistors were suggested as fit for the task of detecting and quantifying ionizing radiation dose. Linearity, small detection volume, fast readout, portability, low power consumption and low radiation attenuation are some of the pMOS advantages over PIN diode and thermoluminiscent dosimeters. A hand-held measurement system using a low power commercial off-the-shelf pMOSas the sensor would have a clear advantage due to the lower cost incurred by a standard technological process. In this research work, we tested the commercial device 3N163 regarding its behaviouras an X-ray sensor, as well as its possible application as a heavy-ion detector. To study the radiation effects of X-rays, a XRD-7000 (Shimadzu) X-ray diffraction setup was used to produce 10-keV effective energy photons. Heavy ions tests involved 12C, 16O, 19F, 28Si, 35Cl, 63Cu and 107Ag beams scattered at 15° by a 275 μg/cm2 gold target, which provide LETs (Linear Energy Transfer) from 4 to 40 MeV/mg/cm2. The signal readout was done using a 1 GHz oscilloscope with a 10-Gsamples/s conversion rate, high enough to permit the recording of transient pulses in the drain current. In this case, an ion can cause a current signal proportional to the ion beam used. Through this study it was found that a simple commercial pMOS device can be reliably used as a detector of X-rays as well as heavy ion detector.
- Experimental setup for Single Event Effects at the São Paulo 8UD Pelletron Accelerator(2014) Aguiar V.A.P.; Added N.; Medina N.H.; Macchione E.L.A.; Tabacniks M.H.; Aguirre F.R.; Silveira M.A.G.; Santos R.B.B.; Seixas Jr. L.E.In this work we present an experimental setup mounted in one of the beam lines at the São Paulo 8UD Pelletron Accelerator in order to study Single Event Effects in electronic devices. The basic idea is to use elastic scattering collisions to achieve a low-flux with a high-uniformity ion beam to irradiate several devices. 12C, 16O, 28Si, 35Cl and 63Cu beams were used to test the experimental setup. In this system it is possible to use efficiently LET values of 17 MeV/mg/cm2 for an external beam arrangement and up to 32 MeV/mg/cm2 for in-vacuum irradiation. © 2014 Elsevier B.V. All rights reserved.
- Comparative study of the proton beam effects between the conventional and Circular-Gate MOSFETs(2012) Cirne K.; Silveira M.A.G.; Santos R.B.B.; Gimenez S.P.; Barbosa M.D.L.; Tabacniks M.H.; Added N.; Medina N.H.; De Melo W.R.; Seixas Jr. L.E.; De Lima J.A.The study of ionizing radiation effects on semiconductor devices is of great relevance for the global technological development and is a necessity in some strategic areas in Brazil. This work presents preliminary results of radiation effects in MOSFETs that were exposed to 3.2 Grad radiation dose produced by a 2.6-MeV proton beam. The focus of this work was to electrically characterize a Rectangular-Gate MOSFET (RGT) and a Circular-Gate MOSFET (CGT), manufactured with the On Semiconductor 0.5 μm standard CMOS fabrication process and to verify a suitable geometry for space applications. During the experiment, I DS × V GS curves were measured. After irradiation, the RGT off-state current (I OFF) increased approximately two orders of magnitude reaching practically the same value of the I OFF in the CGT, which only doubled its value. © 2011 Elsevier B.V. All rights reserved.
- Dynamic distribution of potassium in sugarcane(2013) Medina N.H.; Branco M.L.T.; Silveira M.A.G.D.; Santos R.B.B.In this work the distribution of potassium in sugarcane has been studied during its growth. The soil was prepared with natural fertilizers prepared with sugarcane bagasse. For the measurement of potassium concentration in each part of the plant, gamma-ray spectrometry was used to measure gamma-rays emitted from the radioisotope 40K. The concentrations of potassium in roots, stems and leaves were measured every two to three months beginning about five months after planting the sugarcane. The results show a higher concentration of potassium at the beginning of plant development and over time, there is an oscillatory behavior in this concentration in each part of the plant, reaching a lower concentration in the adult plant. To describe the evolution of potassium distribution in sugarcane we proposed a phenomenological model assuming that the potassium incorporation rate is proportional to the difference between the element concentration in the plant and a very long term equilibrium value and it is coupled to a resource-limited growth model. The proposed model succeeded in interpreting the results for the potassium distribution in stems and leaves during the sugarcane growth. © 2013 Elsevier Ltd.
- Performance of electronic devices submitted to X-rays and high energy proton beams(2012) Silveira M.A.G.; Cirne K.H.; Santos R.B.B.; Gimenez S.P.; Medina N.H.; Added N.; Tabacniks M.H.; Barbosa M.D.L.; Seixas L.E.; Melo W.; De Lima J.A.In this work we have studied the radiation effects on MOSFET electronic devices. The integrated circuits were exposed to 10 keV X-ray radiation and 2.6 MeV energy proton beam. We have irradiated MOSFET devices with two different geometries: rectangular-gate transistor and circular-gate transistor. We have observed the cumulative dose provokes shifts on the threshold voltage and increases or decreases the transistor's off-state and leakage current. The position of the trapped charges in modern CMOS technology devices depends on radiation type, dose rate, total dose, applied bias and is a function of device geometry. We concluded the circular-gate transistor is more tolerant to radiation than the rectangular-gate transistor. © 2011 Elsevier B.V. All rights reserved.