OPALX: A performance-portable framework for particle accelerator simulations
Accurate charged-particle beam simulations require self-consistent collective fields and realistic accelerator models, while their computational cost motivates efficient use of heterogeneous computing systems. We present OPALX, a performance-portable accelerator simulation framework that builds on the beam-dynamics capabilities of OPAL. Its modular architecture uses the Independent Parallel Particle Layer (IPPL) and Kokkos to support distributed-memory execution on multicore CPUs and GPUs from a common codebase. The framework combines relativistic particle tracking with prescribed accelerator fields, particle-in-cell space charge calculations, and spin tracking. We describe the physical and numerical models and their integration into the simulation workflow. The implementation is assessed using disorder-induced heating and frozen-spin test cases, together with comparisons of spin evolution with G4Beamline and beam transport with TraceWin. A three-dimensional space charge benchmark evaluates throughput on CPU and GPU systems, reaching approximately $10^9$ macroparticles per second on a single NVIDIA A100 GPU for this benchmark. These results provide initial verification of the implemented models and demonstrate CPU and GPU execution of self-consistent space charge calculations. OPALX provides a common foundation for extending accelerator models and numerical methods across heterogeneous computing platforms.