Realistic simulations of a cyclotron spiral inflector within a particle-in-cell framework

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. * winklehn@mit.edu; Massachusetts Institute of Technology,

What is the potential impact of the IsoDAR cyclotron on radioisotope production: a review

“…from 10% to 20%. Winklehner et al (2017). This figure illustrates two-fold symmetry of the RF system.…”

“…Septum extraction requires clean turn separation, with the highest possible RF voltage, and a strategy for mitigating space-charge forces. Well-benchmarked simulation codes including space charge (Adelmann et al 2008;Winklehner et al 2017; Spiral Inflector design routines n.d.) have been used to plot the orbits and particle dynamics throughout the injection and acceleration process, and verify that very little beam loss occurs between capture and the extraction radius. The objective is clean turn separation at the location of the extraction septum.…”

Order-of-magnitude beam current improvement in compact cyclotrons

“…This does not hold for the spiral inflector itself, where including space charge will lead to slightly lower transmission. Future work will combine the results presented in section 4 with the design work performed in the AIMA study, by importing the 3D magnetic and electric fields of the CAD model into OPAL and tracking with space charge, using the cyclotron injection mode described in reference [39]. (c) AIMA Right: demonstrated turn separation of 1 cm (edge-to-edge) after placing a single collimator in the first turn.…”

“…One of the available flavors is OPAL-CYCL, which is specifically created to simulate cyclotrons, and which we used for this study. The following is a brief summary of the description in [39]. OPAL uses the particle-in-cell (PIC) method to solve the collisionless Vlasov equation df dt…”

On Nonintrusive Uncertainty Quantification and Surrogate Model Construction in Particle Accelerator Modeling

“…A large turn separation between the extracted turn n and the turn n−1 allows the insertion of a septum to change the sign of curvature of the nth orbit, hence facilitate clean (lossless) extraction of the beam. Detailed initial conditions for the cyclotron simulation are obtained from a 3D spiral inflector model, as shown schematically in Figure 15 [56]. From the exit of the spiral inflector, we need to find optimal initial conditions for the full cyclotron favorable.…”