Advanced Virtual Accelerator Software: A linear accelerator simulation code

The Advanced Virtual Accelerator Software () has been developed to simulate beam transport processes in high-intensity linear accelerators and has been used in the China Initiative Accelerator Driven System (CiADS) project. In the study of beam dynamics for high-intensity linear accelerators, 3D multiparticle simulations are required due to numerous nonlinear effects caused by strong space charge effects. However, the use of multiparticle simulation is often limited by the computational speed of the particle-in-cell (PIC) algorithm. To achieve fast large-scale multiparticle simulation, uses a parallel framework implemented in ++ and improves related algorithms. Specifically, the PIC algorithm has been modified based on symmetry, resulting in the S-PICNIC algorithm. Under the test conditions described in this paper, compared to the standard algorithm, the S-PICNIC algorithm can accelerate the process of solving the space charge field by 4 times while maintaining the simulation accuracy. In addition, uses a combined particle motion mode that switches between two modes (using either time or position as the independent variable) based on the element type. This adaptive switching effectively balances the accuracy and speed of numerical simulation. This method has enabled the fast simulation of over 100 million macroparticles. Furthermore, uses object-oriented programming methods, where objects are designed based on real physical objects. This design allows to preset operating parameters through numerical simulation. In the test, successfully preset the operating parameters of the superconducting section of the Chinese ADS front-end demonstration linear Accelerator, resulting in a negligible beam loss and a deviation between the energy set value and the actual measured value of about 0.5%. This paper introduces the structure of the program and related physical models. Benchmark results are also discussed to verify the reliability of the code.