Evaluation of beamline subsystem performance during technical commissioning of an superconducting proton therapy facility

Abstract

ABSTRACT The new superconducting proton therapy facility consists of a dedicated 200 MeV superconducting cyclotron, new beamlines, a 360° gantry and a fixed beam room for eye treatment. A degrader and laminated magnets in the beamline enable rapid energy changes to modulate the range of the scanning pencil beam applied to patients. In the design of the systems, much emphasis was placed on reliability, easy maintenance, and clear separation of responsibilities. To evaluate the performance of the beamline’s subsystems, technical commissioning began as soon as a proton beam of sufficient intensity could be obtained from the cyclotron. According to the new beam’s parameters, the beamline optics were designed. A mathematical model relating magnetic field (B) and current (I) was established to determine the magnet coil currents required for the different types of magnets, whose magnetic field error was totally controlled to within 5 Gs. A 200 MeV proton beam was extracted from the cyclotron and transported to the fixed treatment room via the beam transport system within 10 days. The terminal equipment of the fixed beamline successfully detected proton beam, indicating that the physical design, engineering, manufacturing and integration of the beamline’s subsystems are highly reliable.