Simulating Heavy Ion Beams Numerically using Minimum Entropy Reconstructions

本项目的目的是开发一种新的工具，用于模拟重离子束在厚靶中减速的过程。我们希望描述目标中所有初级粒子和次级碎片的空间和能量分布。这是相关的，因为离子束用于各种领域：原子物理学（例如原子碰撞，离子捕获），核物理学（例如原子核结构的研究），电子学（例如元素的沉积），材料科学和化学（例如托卡马克壁上损伤的分析），生物学（例如通过离子分析研究细胞组织的毒理学）。此外，几个世界级的设施致力于这些研究（例如德国的FAIR，法国的GANIL）。重离子束的模拟具有挑战性，主要有两个原因。首先，波束难以用基于网格的方法捕获。其次，模拟依赖于阻止本领的测量，因此必须被视为不确定的。因此，我们开发了一种新的基于熵的离散化方案，它允许亚网格分辨率，并在同一时间非常详细的重建，可以捕获光束。此外，我们将使用类似的方法来表征由于不确定的阻止本领而导致的粒子分布的不确定性。该方法在计算上具有挑战性，但高度并行化，因此非常适合现代计算机架构。

The aim of this project is to develop a novel tool for the simulation of heavy ion beams as they are decelerated in thick targets. We want to characterize the spatial and energy distributions of all primary particles and secondary fragments in a target. This is relevant because ion beams are used in various fields: atomic physics (e.g. atomic collisions, ion capture), nuclear physics (e.g. the study of the structure of nuclei), electronics (e.g. deposition of elements), material science and chemistry (e.g. analysis of damage on the walls of a tokamak), biology (e.g. the study of the toxicology of cellular tissues by ion analysis). Additionally, several world-class facilities are dedicated to these studies (e.g. FAIR in Germany, GANIL in France). Simulations of heavy ion beams are challenging for two main reasons. First, beams are difficult to capture with a grid-based method. Second, the simulations rely on measurements of the stopping power, and therefore must be regarded as uncertain. We therefore develop a new entropy-based discretization scheme which allows both a sub-grid resolution and at the same time a very detailed reconstruction that can capture beams. In addition, we will use a similar method to characterize the uncertainties in the particle distribution due to uncertain stopping powers. The method is computationally challenging but highly parallelizable, and therefore ideally suited for modern computer architectures.