The Beam Commissioning of SC Cyclotron-Based Proton Therapy System With Fast Energy Selection and Precise Gantry

Since 2016, a superconducting cyclotron (SC)-based proton therapy (PT) system has been designed, constructed, installed, and commissioned at the China Institute of Atomic Energy (CIAE). It includes a SC CYCIAE-230, a beamline with a fast energy selection system (ESS), a 360° gantry, and a pencil beam scanning nozzle. Also, there is another beamline for proton irradiation, for example, used for space science research. This article will briefly introduce the overall design of the PT system. The results of the beam commissioning, from the cyclotron to the nozzle, will be emphasized. As early as September 2020, the proton beam’s energy accelerated by the SC reached 231 MeV; the 360° gantry had been tested by experts and found an isocenter better than 0.3 mm at any angle. After obtaining comprehensive commissioning permission in late November last year, we finished the test of the PT system with the following results: the energy of the cyclotron is 242 MeV, the energy range of the degrader is 71–242 MeV, the maximum average beam intensity extracted is 462 nA, and the measured efficiency of the beam from the central region to outside the cyclotron is 74%; it is 45 ms the time interval varying one energy step of the degrader and 51 units of the magnets. The results will be presented in detail in this article.