Design and Magnetic Field Measurement of the Superconducting Magnets for the Next-Generation Rotating Gantry

This paper describes the design and reports the test results of the world's most compact rotating gantry for a heavy-ion therapy system mounted with superconducting bending and focusing magnets. A rotating gantry is cylindrical irradiation equipment with magnets for beam transport and beam scanning that delivers energetic carbon ions at up to 430 MeV/u precisely to a tumor from any direction without changing the posture of the patient. However, because of the high magnetic rigidity of therapeutic carbon ions, the rotating gantry was too big to be installed at general hospitals. Therefore, the superconducting rotating gantry had been developed in collaboration with Yamagata University. In the project, to achieve further downsizing of the rotating gantry, the length of the scanning irradiation system is reduced and the magnetic field of the superconducting magnet is increased to 3.5 T from the 2.88 T of the first superconducting gantry installed in the National Institutes for Quantum and Radiological Science and Technology (QST). As a result, the gantry is downsized to 2/3 of the first superconducting rotating gantry. This next-generation small superconducting rotating gantry has already been installed and is undergoing preclinical commissioning at Yamagata University.