Realistic Injection Simulations of a Cyclotron Spiral Inflector using OPAL

TL;DR

This paper enhances the OPAL simulation code to accurately model the complex boundary conditions of a cyclotron's spiral inflector, enabling realistic injection simulations validated against analytical and experimental data.

Contribution

The paper introduces new geometry and field solver features in OPAL for realistic spiral inflector simulations in cyclotrons, handling complex boundaries and self-fields.

Findings

OPAL can now simulate arbitrary boundary geometries effectively.

Simulated injection efficiencies match measured values.

Beam shape and distribution are accurately reproduced in simulations.

Abstract

We present an upgrade to the particle-in-cell ion beam simulation code OPAL that enables us to run highly realistic simulations of the spiral inflector system of a compact cyclotron. This upgrade includes a new geometry class and field solver that can handle the complicated boundary conditions posed by the electrode system in the central region of the cyclotron both in terms of particle termination, and calculation of self-fields. Results are benchmarked against the analytical solution of a coasting beam. As a practical example, the spiral inflector and the first revolution in a 1 MeV/amu test cyclotron, located at Best Cyclotron Systems, Inc., are modeled and compared to the simulation results. We find that OPAL can now handle arbitrary boundary geometries with relative ease. Comparison of simulated injection efficiencies, and beam shape compare well with measured efficiencies and a preliminary measurement of the beam distribution after injection.