Displacement cascade decomposition within the Binary Collision Approximation
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Displacement cascade decomposition within the Binary Collision Approximation Laurence Luneville1 and David Simeone2 and Gianguido Baldinozzi3and Dominique Gosset2 1 CEA/DEN/DANS/DM2S/SERMA/LLPR-MFE, CEA-CNRS-ECP, CE Saclay, Gif sur Yvette, 91191, France 2 CEA/DEN/DANS/DMN/SRMA/LA2M-MFE, CEA-CNRS-ECP, CE Saclay, Gif sur Yvette, 91191, France 3 CNRS/ECP/SPMS-MFE, Equipe Mixte CEA-CNRS-ECP, SPMS, ECP, Chatenay-Malabry, 92292, France ABSTRACT The mechanism of damage production in solids during irradiation is of great practical interest in nuclear technology. The need to increase the life time of current nuclear plants as well as extreme conditions (high temperature and high neutron flux) in new generations of nuclear plants leads to have a deep insight into radiation damage in solids. In fact, the slowing down of particles in solids leads to a non homogeneous distribution of defects in solids, giving rise to complex microstructures with unusual properties. Numerous experiments, Molecular Dynamics (MD) and Monte Carlo (MC) simulations have clearly shown that highly damaged areas called displacement cascades are produced by neutron or impinging ions in solids. It is now clearly established that the number and the distribution of these subcascades dictate the long term evolution of the microstructure under irradiation. In this work, we present a new model to calculate the mean number of displacement cascades produced in a mono-atomic solid by an incident particle within the Binary Collision Approximation framework (BCA) taking into account all information extracted from MD simulations. To reach such a goal, the notion of subcascade threshold energy is introduced and discussed on some examples. Within this formalism, we exhibit a new way to estimate the number of defects created in a displacement cascade integrating results of MD simulations of cascades. INTRODUCTION In this paper, based on a fractal geometry framework, we present some recent results on the decomposition of high energy displacement cascades into subcascades. In the first part of this work, assessed by Monte Carlo simulations within the Binary Collision Approximation framework, we describe the transition between a cascade and subcascades. In the second part of this work, this approach also leads to determine the number of such subcascades produced in a high energy cascade as well as their energetic distribution. In the last part of this paper, we explain how MD simulations can be integrated into the BCA framework to compute a new estimator of the distribution of primary defects. DISPLACEMENT CASCADE DECOMPOSITION WITHIN THE BCA Subcascade formation
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In a displacement cascade, a particle of incident energy E0 loses an energy T during a collision and travels a length l before the next collision. The mean value of l is equal to ˨(E0-T), the mean free path [8] at the energy E0-T. The recoil particle then generates a subcascade of energy T. Recent results on the fractal feature of a displacement cascade [1] showed that the size of a displacement cascade gen
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