Beam dynamics and characterization of a new high-intensity compact air-core high temperature superconducting skeleton cyclotron (HTS-SC)

A new air-core high-temperature superconducting skeleton cyclotron (HTS-SC) is proposed to produce a 50 MeV H+ beam of up to 0.5 mA for the accelerator-based multi-port BNCT system (AB-mBNCT). The HTS-SC is a unique air-core K-50 cyclotron, characterized by a combination of air-core high-temperature superconducting coils to avoid any non-linear effects arising from saturation of an iron core and yoke, while ensuring a linear magnetic field adjustment. This study discusses the basic design of the HTS-SC, including a specific configuration of the air-core coils and central region, as well as the corresponding beam dynamics calculations from injection to extraction for a high-intensity beam. In order to achieve a beam intensity of about 0.5 mA at an ambitiously small radius of 40 cm, particular attention is given at the vicinity of extraction, where the beam condition is volatile and beam loss is severe. Besides, combinations of techniques such as beam collimation in the central region, flat-top acceleration and precessional extraction have been applied to improve the extraction efficiency by almost 50%. Finally, this work concludes with the feasibility of the compactness of the HTS-SC to inject, accelerate and extract up to 0.5 mA H+ for the realization of AB-mBNCT and RI production.