QST demonstrates high-speed ion control technology — Path to miniaturization of heavy-ion cancer therapy devices

Senior Principal Researcher Hironao Sakaki (Visiting Professor, Kyushu University), Principal Researcher Sadaoki Kojima, and their colleagues at the Department of Quantum Applied Photonics, Kansai Institute for Photon Science, the National Institutes for Quantum Science and Technology (QST), along with Senior Fellow Tsuyoshi Suwada of the High Energy Accelerator Research Organization (KEK), Sumitomo Heavy Industries, Ltd., Kyushu University, and Yamagata University, demonstrated technology for controlling high-speed ions generated by laser for use in cancer therapy devices through joint research. Their work was published in Review of Scientific Instruments.

Heavy-ion cancer therapy places less burden on the body and has fewer side effects, but because it requires large-scale accelerators, it can only be performed at seven facilities in Japan. Since only about 4,000 patients per year (approximately 0.4% of new cancer patients in Japan) can receive treatment, miniaturization of the accelerator section is needed.

In 2023, QST completed the world's first prototype laser-accelerated ion injection device. However, because ions accelerated by laser are non-uniform, unlike those from accelerators, they cannot be introduced into heavy-ion cancer therapy devices. For them to be introduced, a certain number of ions must be temporally aligned.

In this study, the research group suppressed the divergence angle of ions dispersed by laser acceleration using a magnetic field lens, then introduced a phase rotation cavity to increase the number of ions within an ion group by up to approximately tenfold. The phase rotation cavity accelerates or decelerates ion groups before and after those passing through in 100 picoseconds by applying negative or positive electric fields, thereby forming a peak. This established the prospect of achieving the number of ions required for cancer therapy devices (10⁹ ions).

Sakaki said: "The ion acceleration section we are currently using was inherited when SPring-8 was renovated, so we want to proceed with designing an optimized device and build a dedicated device from the fiscal year after next onward. Currently, construction of a fourth-generation heavy-ion cancer therapy device miniaturized using superconducting accelerators is underway, aiming for clinical use to begin in fiscal year 2028. While accumulating clinical experience with this, we will proceed with the development of an even more miniaturized fifth generation using laser acceleration devices."

Journal Information
Publication: Review of Scientific Instruments
Title: Demonstration and real-time non-destructive diagnosis of a high-flux laser-driven proton bunch
DOI: 10.1063/5.0274838