Meirielen Caetano de Sousa

École Polytechnique · LSI Laboratoire des Solides Irradiés

We analyze the behavior of a relativistic particle moving under the influence of a uniform magnetic field and a stationary electrostatic wave. We work with a set of pulsed waves that allows us to obtain an exact map for the system. We also use a method of control for near-integrable Hamiltonians that consists in the addition of a small and simple c...

We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinite number of perturbative terms with the same winding number, which may generate islands in the same region of phase space. As a consequence, the number of isochronous isl...

Intrinsically nonlinear coupled systems present different oscillating components that exchange energy among themselves. We present a new approach to deal with such energy exchanges and to investigate how it depends on the system control parameters. The method consists in writing the total energy of the system, and properly identifying the energy te...

We investigate the interaction of electromagnetic waves and electron beams in a 4 meters long traveling wave tube (TWT). The device is specially designed to simulate beam-plasma experiments without appreciable noise. This TWT presents an upgraded slow wave structure (SWS) that results in more precise measurements and makes new experiments possible....

Intrinsically coupled nonlinear systems typically present different oscillating components that exchange energy among themselves. A paradigmatic example is the spring pendulum, for which we identify spring, pendulum, and coupled oscillations. We propose a new approach that properly accounts for the nonlinear coupling, and allows the analysis of ene...

Recent evidence shows that heteroclinic bifurcations in magnetic islands may be caused by the amplitude variation of resonant magnetic perturbations in tokamaks. To investigate the onset of these bifurcations, we consider a large aspect ratio tokamak with an ergodic limiter composed of two pairs of rings that create external primary perturbations w...

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Recent evidences show that heteroclinic bifurcations in magnetic islands may be caused by the amplitude variation of resonant magnetic perturbations in tokamaks. To investigate the onset of these bifurcations, we consider a large aspect ratio tokamak with an ergodic limiter composed of two pairs of rings that create external primary perturbations w...

Intrinsically coupled nonlinear systems present different oscillating components that exchange energy among themselves. A paradigmatic example is the spring pendulum, which displays spring, pendulum, and coupled oscillations. We analyze the energy exchanges among the oscillations, and obtain that it is enhanced for chaotic orbits. Moreover, the hig...

The resonant interaction between charged particles and electromagnetic waves in plasmas is a very efficient mechanism for particle acceleration. In general, the acceleration process depends on the wave amplitude. For small amplitude waves, the energy transferred to the particles is not enough to produce a considerable amount of acceleration. On the...

We analyze nonlinear aspects of the self-consistent wave–particle interaction using Hamiltonian dynamics in the single wave model, where the wave is modified due to the particle dynamics. This interaction plays an important role in the emergence of plasma instabilities and turbulence. The simplest case, where one particle (N=1) is coupled with one...

We consider a 4 meters long traveling wave tube (TWT) that presents an upgraded slow wave structure. We analyze linear and nonlinear phenomena due to the beam-wave interaction in the device, e.g. beam modulation, and wave growth and saturation.

The study could help upgrade satellite communications equipment. A paper on research conducted by Meirielen Caetano de Sousa, postdoctoral fellow at the University of São Paulo’s Physics Institute (IF-USP) in Brazil, is highlighted as Editor’s Pick in the September issue of Physics of Plasmas, published by the American Institute of Physics with th...

We analyze nonlinear aspects of the self-consistent wave-particle interaction using Hamiltonian dynamics in the single wave model, where the wave is modified due to the particle dynamics. This interaction plays an important role in the emergence of plasma instabilities and turbulence. The simplest case, where one particle (N = 1) is coupled with on...

Studies about electromagnetic waves contribute to the improvement of signal amplifier used in communications satellites

The postdoctoral fellow Meirielen Caetano de Sousa from the Institute of Physics, University of São Paulo, published this week the article “Wave-particle interactions in a long traveling wave tube with upgraded helix” in collaboration with her supervisor (Iberê L. Caldas) and two researchers from the Aix-Marseille University (Fabrice Doveil and Yve...

We investigate the interaction of electromagnetic waves and electron beams in a 4 meters long traveling wave tube (TWT). The device is specially designed to simulate beam-plasma experiments without appreciable noise. This TWT presents an upgraded slow wave structure (SWS) that results in more precise measurements and makes new experiments possible....

Normalized average pendulum energy term as a function of the total energy ET and the parameter f. The hatched area is not allowed because these values of ET and f do not comply with the condition of minimum energy ET >= f^2/2 - f.

Normalized average spring energy term as a function of the total energy ET and the parameter f. The hatched area is not allowed because these values of ET and f do not comply with the condition of minimum energy ET >= f^2/2 - f.

Normalized average energy terms as a function of the parameter f for different values of the total energy ET. The red curves correspond to the normalized average energy of the spring term, the blue curves represent the pendulum energy term, and the green curves represent the coupling energy term.

Greater efficiency in the delivery of particle therapies may soon be available for diagnostic imaging and cancer treatment with the development of a new model for stabilizing particle behavior.

The use of particle accelerators is not confined to basic research in high-energy physics. Large-scale accelerators and gigantic devices, such as the Large Hadron Collider (LHC), are used for this purpose, but relatively small accelerators are used in medicine (diagnostic imaging, cancer treatment), industry (food sterilization, cargo scanning, ele...

Particle accelerators are research equipments producing particle fluxes that follow directions determined by their configurations. Changes in the process can make the particles to behave chaotically, increase the energy cost, or cause damages in the equipments. One method, which implements a transport barrier in the system, prevents the particles f...

Equipments present applications in medicine, industries, and in the inspection of cargos and artworks.

The dynamics of wave-particle interactions in magnetized plasmas restricts the wave amplitude to moderate values for particle beam acceleration from rest energy. We analyze how a perturbing invariant robust barrier modifies the phase space of the system and enlarges the wave amplitude interval for particle acceleration. For low values of the wave a...

The postdoctoral fellow Meirielen Caetano de Sousa from the Institute of Physics, University of São Paulo, gave a talk about the applications of particle accelerators at the last edition of Campus Party Brasil.

When we talk about particle accelerators, the first thing that comes to mind are the huge equipments used to study the particles that constitute the universe. However, large accelerators used for research represent less than 1% of the existing accelerators. The other 99% corresponds to small and medium sized accelerators with applications in medici...

Published as "Improving particle beam acceleration in plasmas", Physics of Plasmas 25, 043110 (2018); doi: 10.1063/1.5017508 - The study of mechanisms for particle acceleration has been a major concern in recent years. We investigate the dynamics of relativistic charged particles interacting with a uniform magnetic field and a stationary electrosta...

We investigate the dynamics of a relativistic low density beam moving in a uniform magnetic field and interacting with a stationary electrostatic wave. In the resonant islands of the system, the wave transfers energy to the particles and they are regularly accelerated. When we increase the wave amplitude, the system becomes chaotic and the islands...

Published as "Energy distribution in intrinsically coupled systems: The spring pendulum paradigm", Physica A 509, 1110-1119 (2018); doi: 10.1016/j.physa.2018.06.089 - Spring pendulums, used to model many systems in physics and engineering, are intrinsically nonlinear coupled systems presenting spring-mass and pendulum like motions that exchange ene...

We investigate how the energy distribution of a spring pendulum varies as a function of its parameters. We split the total energy of the system into three terms: spring, pendulum and coupling. We show numerically that the energy distribution follows a well defined pattern. The maximum values of the spring and coupling energy terms vary regularly wi...

The dynamics of a spring pendulum varies according to its total energy and a parameter, called f , that accounts for its physical characteristics: pendulum mass, spring stiffness constant and spring unstretched length. We build the Poincaré sections of the system and analyze the order-chaos-order transition that it undergoes as we change the contro...

We analyze the isochronous island chains that appear in the Poincaré sections of near integrable twist systems. When the system presents just one resonant perturbation with a winding number, the number of chains is constant and it is completely determined by the perturbation. However, for systems that are perturbed by an infinite number of resonant...

In this thesis, we analyze the dynamics of a relativistic particle moving under the influence of a uniform magnetic field and a stationary electrostatic wave given as a series of periodic pulses. The map that describes the time evolution of the system is explicit, and it can be considered as a magnetized relativistic version of the classical standa...

Widely used as HF wave amplifiers for industrial applications, Traveling Wave Tubes (TWT) are also used to mimic and carefully study wave-particle interaction in a plasma [1-3]. We describe a recently built upgrade of a TWT whose slow wave structure consists of a 4 m long helix, with 3.4 cm diameter and 1 mm pitch, made of a 0.6 mm diameter Be-Cu w...

We analyse the resonant islands that arise in the Poincaré sections of perturbed twist systems. The winding number characterizing the islands defines the number of islands per chain (as stated by the Poincaré-Birkhoff Fixed Point Theorem), but it does not determine the number of isochronous chains. We show that an infinite number of resonances may...

We study the dynamics of a relativistic charged particle in the presence of a uniform magnetic field and a stationary electrostatic wave that propagates at an arbitrary angle. The wave is considered as a series of periodic pulses which allows us to derive an exact map for the system. In particular, we investigate the heating process of an initially...

We analyse the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a stationary electrostatic wave. We show that a pulsed wave produces an infinite number of perturbing terms with the same winding number. The perturbation coupling alters the number of island chains as a function of the parameters of the wave. We...

We analyse the behaviour of a relativistic particle moving under the combined action of a uniform magnetic field and a stationary electrostatic wave given as a series of pulses. We apply to our system a method of chaos control that creates invariant tori in phase space, reducing and confining the chaotic trajectories to small regions. Besides regul...

We investigate the concept of a standard map for the interaction of relativistic particles and electrostatic waves of arbitrary amplitudes, under the action of external magnetic fields. The map is adequate for physical settings where waves and particles interact impulsively, and allows for a series of analytical result to be exactly obtained. Unlik...

This document aims to present a study about the interaction of a relativistic particle with initially low energy and an electromagnetic wave. In order to develop this study, it is presented an introduction to the Dynamical Systems Theory, which includes subjects such as phase space, Poincaré sections and maps, the hamiltonian formulation for dynami...

This document aims to present a study about the interaction of a non relativistic particle and an electromagnetic wave. The hamiltonian of the system is analyzed and a series of analytical estimates is developed from the hamiltonian: the resonant points of the system are calculated and an approximate Poincaré map that describes the time evolution o...