Speaker
Description
Many experimental and theoretical research studies have been conducted in recent years at the Paul Scherrer Institute (PSI, Switzerland) on the treatment of cancer with proton therapy. The PSI approach is based on fast volumetric rescanning, a technique in which the energy of the beam changes quickly. The development of a suited electromagnetic model to study superconducting magnets for proton therapy in fast ramping regime would allow simulating their transient behavior and compare different configurations, such as the curved Canted Cosine Theta (CCT) and conventional accelerator dipoles. The availability of validated numerical tools would also make it possible to carry out studies to select the most suitable technical superconductor for fast ramping applications.
In this work, we present a comparison between three numerical approaches to simulate insulated high-temperature superconducting (HTS) pancakes in AC mode. Two of them are based on well-known and approved in many papers FEM models implemented in COMSOL Multiphysics and Quanscient (cloud computations with domain decomposition). In particular, the A-H formulation is used in the COMSOL model, while the H-phi formulation is applied in the Quantscient model.
The third approach is based on a lumped parameter non-linear circuit model, called CALYPSO, developed at the University of Bologna to investigate the electrodynamic behavior of HTS cables and magnets. The main advantage of the circuit model is to avoid the use of the fine meshes usually required by FEM models, it results then in quicker computations, extremely important for large magnets. A difference between the CALYPSO code and other circuit models presented in the literature is the use of a sparse matrix of the mutual inductances instead of a full one. This is achieved by neglecting the contribution to the magnetic vector potential and the magnetic flux density at a node in a given location due to the currents flowing at a sufficient distance from the considered node.
The goal of this study is to benchmark the three aforementioned numerical methods in operating conditions relevant for the operation in the PSI proton therapy machines and to assess the most adequate approach for the analysis of more complex magnet designs.
