An Innovative GPU-Optimized Multiscale Code for High-Fidelity Simulation of Collective Effects in Electron Beams

该奖项将引导开发用于高保真电子束模拟的创新计算机代码，利用并行计算机体系结构和应用数学的最新进展。当电子束以接近光速的速度在加速器磁铁的推动下穿过弯曲的路径时，它们会发出明亮的紫外线或x射线辐射。这种沿直线行进的辐射会赶上电子束，从而严重降低电子束的实验效用。减轻这些破坏性影响的第一步是开发一种可靠的计算机代码，能够模拟这种光束自相互作用的物理特性。这个项目将使开发这样一个代码成为可能。对于整个社会来说，这项研究是开发超亮光源的一步，超亮光源是物理、生物、能源和医学科学发现和创新的重要工具。例如，它们允许科学家分析化学反应、分子结构，并提供开发新药的方法。通过培养年轻研究人员，该项目将增加国内急需的加速器科学家的数量，并在招募合格的女性和代表性不足的少数民族候选人方面做出相当大的努力。直接模拟二维和三维的相干同步辐射（CSR）在效率和内存要求方面是非常昂贵的。因此，目前的CSR规范采用了各种近似，不足以解决许多现实情况下的基本物理问题。随着下一代光源设计的开始，现有CSR规范失效的情况将变得司空见惯。该项目将设计、测试并向社区传播一种全新的、多尺度的、细胞内粒子的CSR建模代码，优化后可在由图形处理单元（gpu）组成的并行计算平台上运行。该代码将利用在小波基中转换问题的优点：(i)能够保留有关尺度层次上的动态信息；（ii）利用小波系数的阈值去除数值噪声；（iii）数据和运算符的紧凑表示，从而大大减少了计算负荷。使用NVIDIA的CUDA框架，许多新代码的重要数值算法将被设计在并行GPU平台上运行，算法和架构的成功匹配将导致代码的可扩展性。新的代码将免费提供给社区，以便对许多不同的机器进行建模。

This award will lead to development of an innovative computer code for high-fidelity simulation of electron beams, drawing on recent advances in parallel computer architectures and applied mathematics. When electron bunches traveling at nearly the speed of light are forced by accelerator magnets to traverse a curved path, they emit bright ultraviolet or x-ray radiation. This radiation traveling a straight path catches up with the electron beam and can severely degrade its experimental usefulness. The first step in mitigating these damaging effects is to develop a trustworthy computer code capable of simulating the physics of this beam self-interaction. This project will enable the development of such a code. For the society in general, this research is a step in developing ultra-bright light sources which are essential tools for discoveries and innovations in physical, biological, energy and medical sciences. For example, they allow scientists to analyze chemical reactions, molecular structures and provide ways to develop new drugs. By training young researchers, this project will increase the number of much-needed accelerator scientists in the nation and make considerable effort in recruiting qualified female and under-represented minority candidates.Direct simulation of coherent synchrotron radiation (CSR) in two and three dimensions is prohibitively costly in terms of efficiency and memory requirements. Consequently, the present CSR codes employ various approximations that are inadequate for resolving essential physics in many realistic situations. These situations where existing CSR codes fail will become commonplace as the design of next-generation light sources commences. This project will design, benchmark and disseminate to the community a fundamentally new, multiscale, particle-in-cell code for modeling CSR, optimized to run on a parallel computational platform consisting of graphical processing units (GPUs). The code will exploit advantages of casting the problem in wavelet basis: (i) ability to retain information about the dynamics over the hierarchy of scales; (ii) removal of numerical noise by thresholding of the wavelet coefficients; and (iii) compact representation of data and operators, resulting in significant reduction of the computational load. Using NVIDIA's CUDA framework, a number of new code's vital numerical algorithms will be designed to run on a parallel GPU platform, and the successful matching of the algorithms and architecture will lead to code's scalability. The new code will be freely available to the community to enable modeling of a number of different machines.