The accurate particle tracer code

Abstract

The Accurate Particle Tracer (APT) code is designed for large-scale particle simulations on dynamical systems. Based on a large variety of advanced geometric algorithms, APT possesses long-term numerical accuracy and stability, which are critical for solving multi-scale and nonlinear problems. Under the well-designed integrated and modularized framework, APT serves as a universal platform for researchers from different fields, such as plasma physics, accelerator physics, space science, fusion energy research, computational mathematics, software engineering, and high-performance computation. The APT code consists of seven main modules, including the I/O module, the initialization module, the particle pusher module, the parallelization module, the field configuration module, the external force-field module, and the extendible module. The I/O module, supported by Lua and Hdf5 projects, provides a user-friendly interface for both numerical simulation and data analysis. A series of new geometric numerical methods and key physical problems, such as runaway electrons in tokamaks and energetic particles in Van Allen belt, have been studied using APT. As an important realization, the APT-SW version has been successfully distributed on the world's fastest computer, the Sunway TaihuLight supercomputer, by supporting master-slave architecture of Sunway many-core processors.

Degenerate variational integrators for magnetic field line flow and guiding center trajectories

“…Over sufficiently long times, the conservative algorithm will eventually out-perform the non-conservative algorithm, but the timescale for this may be longer than the timescale of interest for particular studies especially under equal computational expense comparisons; the implicit DVI advance is several times more expensive than the explicit RK4 advance on a per-step basis 27 , and the error of the RK4 scheme, being fourth-order accurate, decreases rapidly as the step size is reduced. Still, energetic particle processes often require long time integrations, and there is great interest in conservative algorithms for modeling these processes 10,11,22,23,49,54,55 . The conservative character of the DVI does not preclude the incorporation of dissipative dynamics, including collisional drag.…”

Modeling of beam ions loss and slowing down with Coulomb collisions in EAST

“…In addition, for large variations in magnetic field gradients within a gyro-orbit, such as complex perturbation fields, the results of full-orbit-following calculations are more accurate. As a full-orbit following program, the Monte Carlo parallel program ISSDE uses the splitting method to construct the volume-preserving algorithms (VPAs) [28][29][30] for the collisionless part like the SOFT program. Based on this, ISSDE treats the collision part as a subsystem divided by the splitting method and uses an implicit midpoint format to enhance the long-term stability of the collision part.…”

Beijing Union Medical College Hospital and China’s Modern Medical Development

“…We calculate a guiding center trajectory in a magnetic mirror field, which is widely used to confine charged particles or plasmas for a variety of purposes [30,31]. The setup of the mirror field and other details of numerical calculations are introduced in the Supplemental Material [32]. When properly choosing its initial condition, the guiding center is bounced back by the magnetic mirror, with its reflection point denoted by a black solid circle.…”