Ion motion in the wake driven by long particle bunches in plasmas

We explore the role of the background plasma ion motion in self-modulated plasma wakefield accelerators. We employ J. Dawson's plasma sheet model to derive expressions for the transverse plasma electric field and ponderomotive force in the narrow bunch limit. We use these results to determine the on-set of the ion dynamics, and demonstrate that the ion motion could occur in self-modulated plasma wakefield accelerators. Simulations show the motion of the plasma ions can lead to the early suppression of the self-modulation instability and of the accelerating fields. The background plasma ion motion can nevertheless be fully mitigated by using plasmas with heavier plasmas.Comment: 23 pages, 6 figure

Magnetically assisted self-injection and radiation generation for plasma based acceleration

It is shown through analytical modeling and numerical simulations that external magnetic fields can relax the self-trapping thresholds in plasma based accelerators. In addition, the transverse location where self-trapping occurs can be selected by adequate choice of the spatial profile of the external magnetic field. We also find that magnetic-field assisted self-injection can lead to the emission of betatron radiation at well defined frequencies. This controlled injection technique could be explored using state-of-the-art magnetic fields in current/next generation plasma/laser wakefield accelerator experiments.Comment: 7 pages, 4 figures, accepted for publication in Plasma Physics and Controlled Fusio

Transverse self-modulation of ultra-relativistic lepton beams in the plasma wakefield accelerator

The transverse self-modulation of ultra-relativistic, long lepton bunches in high-density plasmas is explored through full-scale particle-in-cell simulations. We demonstrate that long SLAC-type electron and positron bunches can become strongly self-modulated over centimeter distances, leading to wake excitation in the blowout regime with accelerating fields in excess of 20 GV/m. We show that particles energy variations exceeding 10 GeV can occur in meter-long plasmas. We find that the self-modulation of positively and negatively charged bunches differ when the blowout is reached. Seeding the self-modulation instability suppresses the competing hosing instability. This work reveals that a proof-of-principle experiment to test the physics of bunch self-modulation can be performed with available lepton bunches and with existing experimental apparatus and diagnostics.Comment: 8 pages, 8 figures, accepted for publication in Physics of Plasma

Magnetic control of particle-injection in plasma based accelerators

The use of an external transverse magnetic field to trigger and to control electron self-injection in laser- and particle-beam driven wakefield accelerators is examined analytically and through full-scale particle-in-cell simulations. A magnetic field can relax the injection threshold and can be used to control main output beam features such as charge, energy, and transverse dynamics in the ion channel associated with the plasma blowout. It is shown that this mechanism could be studied using state-of-the-art magnetic fields in next generation plasma accelerator experiments.Comment: 10 pages, 3 figure

The ion motion in self-modulated plasma wakefield accelerators

The effects of plasma ion motion in self-modulated plasma based accelerators is examined. An analytical model describing ion motion in the narrow beam limit is developed, and confirmed through multi-dimensional particle-in-cell simulations. It is shown that the ion motion can lead to the early saturation of the self-modulation instability, and to the suppression of the accelerating gradients. This can reduce the total energy that can be transformed into kinetic energy of accelerated particles. For the parameters of future proton-driven plasma accelerator experiments, the ion dynamics can have a strong impact. Possible methods to mitigate the effects of the ion motion in future experiments are demonstrated.Comment: 11 pages, 3 figures, accepted for publication in Phys. Rev. Let

Jalo MG-65 - Common bean cultivar.

Jalo MG-65 is a large-seeded common bean cultivar with indeterminate growth habit (type III) released for planting in Minas Gerais State. It belongs to the Jalo class (yellow seeds) and has a high yield potential. Usually, it is ready for harvesting within 70-80 days. It is resistant to fusarium with and moderately resistant to rust, angular leaf spot, alternaria leaf spot, and powdery mildew

Redução da viabilidade de esporângios de Plasmopara viticola por bactérias nativas do filoplano da videira.

Resumo: O míldio é uma das principais doenças da videira, capaz de causar danos significativos à cultura e aumentar os custos de produção. Seu controle demanda o uso intensivo de agrotóxicos, cujos resíduos são indesejáveis. Este trabalho teve como objetivo investigar o potencial uso de bactérias do filoplano em reduzir a viabilidade de esporângios de Plasmopara viticola. Foram testados trinta e cinco isolados bacterianos obtidos do filoplano de videira. Os testes de antagonismo foram feitos em lâminas de microscopia e em discos de folha, adicionando-se 50 microL de uma suspensão bacteriana e 50 microL de uma suspensão de esporângios. Nos testes em lâmina de microscopia, vinte e nove isolados inibiram a germinação dos esporângios de Plasmopara viticola. Destes, os isolados 1, 37 e 12 se destacaram, por serem capazes de inibir também a liberação de zoósporos. Em discos de folha, o isolado 1 foi o único capaz de inibir a liberação dos zoósporos, significativamente em relação à testemunha. Nesta condição, não houve a germinação dos esporângios, apenas a liberação de zoósporos. Abstract: The downy mildew is one of the main grapevine diseases, able to cause significant damage to the crop and increase production costs. It?s control demand intensive use of pesticides, which residues are undesirable. This study aimed to investigate the potential of phylloplane bacteria in reducing the viability of sporangia of Plasmopara viticola. Thirty-five bacterial isolates from phylloplane of grapevine were tested. The antagonism tests were conducted on microscopy glass blades and on leaf discs, adding microL of a bacterial suspension and 50 microL of a suspension of sporangia. Twenty-nine isolates inhibited the germination of the sporangia of Plasmopara viticola in tests conducted on glass blades. Of these, isolates 1, 37 and 12 were able to inhibit the release of zoospores. In the leaf discs test, the isolate 1 was the single able to inhibit the release of zoospores, significant compared to the control. In this condition, there wasn?t germination of sporangia, only zoospores release

Utilização da bandarra (Schizolobiuim amazonicum) em sistemas agroflorestais

Renovação de lavouras cafeeiras e cacaueiras. Plantio novos: bandarra e café ou bandarra e cacau. Bandarra e cupuaçu e pimenta-do-reino e banana. SAF´s a partir de regeneração natural de bandarra. Uso de outras leguminosas em sistemas agroflorestais com bandarra. Bandarra e culturas anuais. Manutenção de sistemas agroflorestais.bitstream/item/67601/1/CPAF-RO-DOCUMENTOS-42-UTILIZACAO-DE-BANDARRA-SCHIZOLOBIUM-AMAZONICUM-EM-SISTEMAS-AGROFLORESTAIS-F.pd

Produção e avaliação da qualidade do leite na microrregião de Castanhal.

bitstream/item/63529/1/Oriental-Doc95.PD

Dynamics of magnetic moments coupled to electrons and lattice oscillations

Inspired by the models of A. Rebei and G. J. Parker and A. Rebei et. al., we study a physical model which describes the behaviour of magnetic moments in a ferromagnet. The magnetic moments are associated to 3d electrons which interact with conduction band electrons and with phonons. We study each interaction separately and then collect the results assuming that the electron-phonon interaction can be neglected. For the case of the spin-phonon interaction, we study the derivation of the equations of motion for the classical spin vector and find that the correct behaviour, as given by the Brown equation for the spin vector and the Bloch equation, using the results obtained by D. A. Garanin for the average over fluctuations of the spin vector, can be obtained in the high temperature limit. At finite temperatures we show that the Markovian approximation for the fluctuations is not correct for time scales below some thermal correlation time $\tau_{Th}$. For the case of electrons we workout a perturbative expansion of the Feynman-Vernon functional. We find the expression for the random field correlation function. The composite model (as well as the individual models) is shown to satisfy a fluctuation-dissipation theorem for all temperature regimes if the behaviour of the coupling constants of the phonon-spin interaction remains unchanged with the temperature. The equations of motion are derived