Classical Radiation Reaction in Particle-In-Cell Simulations

Under the presence of ultra high intensity lasers or other intense electromagnetic fields the motion of particles in the ultrarelativistic regime can be severely affected by radiation reaction. The standard particle-in-cell (PIC) algorithms do not include radiation reaction effects. Even though this is a well known mechanism, there is not yet a definite algorithm nor a standard technique to include radiation reaction in PIC codes. We have compared several models for the calculation of the radiation reaction force, with the goal of implementing an algorithm for classical radiation reaction in the Osiris framework, a state-of-the-art PIC code. The results of the different models are compared with standard analytical results, and the relevance/advantages of each model are discussed. Numerical issues relevant to PIC codes such as resolution requirements, application of radiation reaction to macro particles and computational cost are also addressed. The Landau and Lifshitz reduced model is chosen for implementation.Comment: 12 pages, 8 figure

Pullback attractors for a singularly nonautonomous plate equation

We consider the family of singularly nonautonomous plate equation with structural damping $$u_{tt} + a(t,x)u_{t} + (- \Delta) u_{t} + (-\Delta)^{2} u + \lambda u = f(u),$$ in a bounded domain $\Omega \subset \R^n$, with Navier boundary conditions. When the nonlinearity $f$ is dissipative we show that this problem is globally well posed in $H^2_0(\Omega) \times L^2(\Omega)$ and has a family of pullback attractors which is upper-semicontinuous under small perturbations of the damping $a$

Full-scale ab initio 3D PIC simulations of an all-optical radiation reaction configuration at 1021W/cm210^{21}\mathrm{W/cm^2}

Using full-scale 3D particle-in-cell simulations we show that the radiation reaction dominated regime can be reached in an all optical configuration through the collision of a $\sim$1 GeV laser wakefield accelerated (LWFA) electron bunch with a counter propagating laser pulse. In this configuration radiation reaction significantly reduces the energy of the particle bunch, thus providing clear experimental signatures for the process with currently available lasers. We also show that the transition between classical and quantum radiation reaction could be investigated in the same configuration with laser intensities of $10^{24}\mathrm{W/cm^2}$

Particle Merging Algorithm for PIC Codes

Particle-in-cell merging algorithms aim to resample dynamically the six-dimensional phase space occupied by particles without distorting substantially the physical description of the system. Whereas various approaches have been proposed in previous works, none of them seemed to be able to conserve fully charge, momentum, energy and their associated distributions. We describe here an alternative algorithm based on the coalescence of N massive or massless particles, considered to be close enough in phase space, into two new macro-particles. The local conservation of charge, momentum and energy are ensured by the resolution of a system of scalar equations. Various simulation comparisons have been carried out with and without the merging algorithm, from classical plasma physics problems to extreme scenarios where quantum electrodynamics is taken into account, showing in addition to the conservation of local quantities, the good reproducibility of the particle distributions. In case where the number of particles ought to increase exponentially in the simulation box, the dynamical merging permits a considerable speedup, and significant memory savings that otherwise would make the simulations impossible to perform

An analysis of the potentialities of portuguese vernacular architecture to improve energy efficiency

Vernacular architecture is characterised by a type of formal expression that has been developed in response to a number of factors â climatic, lithologic, cultural and economic â characterising the local area or region. In its various forms, a range of techniques has been employed in different regions to mitigate the effects of climate. Despite the fact that Portugal is a small country, it has a territory full of contrasts, which gave origin to many different architectural manifestations. The approaches adopted in the design and construction of vernacular buildings have the potential for further development and could be adapted in response to contemporary needs. In the future, a blend of tradition and modernity should be aimed at in order to develop a new form of aesthetics and functional construction. Portuguese vernacular architecture is associated with a fund of valuable knowledge that should be studied and aligned with the principles of sustainability. In this paper, is presented the climatic contrast between the northern and southern parts of Portugal and the relation with the purpose of different passive solar techniques used in vernacular architecture to provide comfort. The focus is on the effectiveness of passive cooling techniques (e.g. high thermal inertia, the use of light colours and patios), and the findings of a case study in which the thermal performance during the summer of a vernacular residential building located in the south of Portugal are presented. In the context of the current global drive for clean energy and sustainable buildings, much can be learned from a review of past experience in order to provide an understanding of such forms of construction, which are an intrinsic feature of specific places and have evolved over time in the face of a lack of resources

As metodologias BIM como auxiliar no projeto de reabilitação energética de edifícios

Atualmente o edificado europeu é responsável por 40% do total da energia consumida e por 36% da emissão de gases que contribuem para o efeito de estufa. A reabilitação energética do edificado existente, especialmente daquele construído antes da entrada em vigor da primeira regulamentação térmica, aliada a práticas sustentáveis, é um passo essencial e uma prioridade da UE para que os seus Estados-Membro reduzam a sua dependência energética e as suas emissões de gases de efeito de estufa, tornando os seus edifícios mais sustentáveis.Neste contexto, o presente estudo mostra a reabilitação energética de um edifício residencial português, construído no final da década de 60, utilizando uma abordagem baseada no Building Information Modelling (BIM) durante as fases iniciais de projeto. A metodologia BIM foi utilizada com o objetivo de realizar análises de desempenho energético do caso de estudo, de maneira a analisar as vantagens desta abordagem na identificação dos melhores cenários de reabilitação energética. Após a referida análise, foi possível constatar que a utilização de metodologias BIM, permite aos projetistas a rápida realização de comparações entre as possíveis soluções a adotar, auxiliando assim a tomada de decisão. Ao mesmo tempo, possibilita ainda a redução de tempo e custos durante as fases iniciais de um projeto e, consequentemente, promove a eficiência e a sustentabilidade do edificado.info:eu-repo/semantics/publishedVersio

Acoustic evaluation of beam and pot slabs with lightweight regularization layers: a case study

The objective of this work is to evaluate the acoustic performance of beam and pot slabs with regularization layers made of lightweight concrete. The study consists on the analysis of the acoustic behaviour of three types of solutions, through the execution of "in situ" measurements for the determination of the airborne sound insulation index and of the impact sound insulation index. The studied elements have the same support element (concrete slab), but regularization layers made of different materials. The regularization layers studied were: concrete with granulated expanded polystyrene, concrete with expanded clay aggregates and cellular concrete. The acoustic performance of the three slabs is evaluated and compared with the performance of conventional solutions in way of evaluating their potentialities