An improved Boris algorithm for charge particle orbit in tokamak plasmas

An improved Boris algorithm for simulating the motion of charged parti cles in electromagnetic fields has been developed. This enhancement addresses the issue of inaccurate fast-scale cyclotron phase calculations present in the original Boris algorithm, while preserving its advantage in simulating slow scale guiding center motion. As a result, it strikes a balance between low and high-frequency dynamics, overcoming the limitations of traditional second-order volume-preserving algorithms (VPAs) which are constrained to a single charac teristic frequency. Test particle simulations indicate that, in most cases, the improved Boris algorithm achieves significantly higher accuracy than conven tional VPAs when simulating cases involving various frequencies of electric field within a typical tokamak magnetic field, highlighting its superior efficacy in handling problems across a wide range of characteristic frequencies.