The global total- $f$ gyrokinetic particle-in-cell code XGC, used to study transport in magnetic fusion plasmas or to couple with a core gyrokinetic code while functioning as an edge gyrokinetic code, implements a five-dimensional continuum grid to perform the dissipative operations, such as plasma collisions, or to exchange the particle distribution function information with a core code. To transfer the distribution function between marker particles and a rectangular two-dimensional velocity-space grid, XGC employs a bilinear mapping. The conservation of particle density and momentum is accurate enough in this bilinear operation, but the error in the particle energy conservation can become undesirably large and cause non-negligible numerical heating in a steep edge pedestal. In the present work we update XGC to use a novel mapping technique, based on the calculation of a pseudo-inverse, to exactly preserve moments up to the order of the discretization space. We describe the details of the implementation and we demonstrate the reduced interpolation error for a tokamak test plasma using first- and second-order elements with the pseudo-inverse method and comparing with the bilinear mapping.

中文翻译：

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粒子单元代码XGC中标记粒子与网格之间高阶速度映射的实现

全球总量—— $f$ 旋动粒子细胞代码新高地，用于研究磁聚变等离子体中的传输或与核心旋动代码耦合，同时用作边缘旋动代码，实现五维连续网格来执行耗散操作，例如等离子体碰撞，或交换粒子分布函数带有核心代码的信息。为了在标记粒子和矩形二维速度空间网格之间传递分布函数，新高地采用双线性映射。在这种双线性运算中，粒子密度和动量的守恒足够准确，但粒子能量守恒的误差可能会变得非常大，并在陡峭的边缘基座中导致不可忽略的数值加热。在目前的工作中，我们更新新高地使用一种新的映射技术，基于伪逆的计算，将矩精确地保留到离散空间的数量级。我们描述了实现的细节，并展示了使用伪逆方法的一阶和二阶元素减少托卡马克测试等离子体的插值误差，并与双线性映射进行比较。