Description
The National Institutes for Quantum Science and Technology (QST) is currently conducting the Quantum Scalpel project, which aims to enhance the performance and miniaturization of heavy-ion cancer therapy devices. The “quantum scalpel” refers to cancer treatment using a quantum beam without any physical incision, enabling minimally invasive therapy with few side effects. This makes day‑surgery treatments possible, allowing patients to continue working while receiving therapy.
The fifth-generation heavy-ion therapy system, the Quantum Scalpel, consists of a laser ion injector, a superconducting synchrotron, and a superconducting rotating gantry. To realize a compact system, both the ion injector and the synchrotron must be miniaturized. In this project, miniaturization will be achieved by introducing superconducting technology for the synchrotron and by replacing the conventional linear accelerator with a laser ion injector. Laser-driven ion acceleration provides a high acceleration gradient and is expected to enable a compact injector.
The injector requirements for the Quantum Scalpel specify the generation of more than 10⁸ 4 MeV/u C⁶⁺ ions at 10 Hz with a 1% energy bandwidth. At the laser-acceleration stage, however, an energy bandwidth of approximately 10% is acceptable. After laser acceleration, the carbon ions will be compressed from 10% to 1% energy bandwidth by a phase-rotation technique before being transported to the synchrotron.
To examine the conditions for C⁶⁺ generation, we performed quasi-1D and 2D PIC simulations. The simulation results agree with a simple model that predicts the maximum sheath field and achievable ionization degree. We also carried out 3D PIC simulations to quantitatively evaluate the number of generated carbon ions. Finally, we discuss the laser requirements for implementing a laser ion injector in the Quantum Scalpel project.