A Study of A Super Muon Beam for New Initiative on Muon Physics

为了进一步推动μ子科学的发展，本项目开发了一种改进μ子束的新技术。由于现有的μ子束在强度和质量上都可能不够，大多数μ子实验在一些实验限制下都存在一些困难。如果我们有一个高强度和单能的μ子束，它将在μ子科学中带来重大突破。我们把这种未来的μ子束称为“超级μ子束”。我们提出了一种新的相位旋转技术，使μ子束的能量扩展变窄，所瞄准的束流强度比PSI的世界最高束流强度高10，000倍以上。大坂大学久野研究组利用这种“超级μ子束”，提出了寻找μ子轻子味破坏过程的新实验，目的是建立一种相位旋转技术，以产生单能束。该项目的两个关键器件是超高场梯度射频系统和大口径固定场交变梯度磁体。物理学（RCNP），大坂大学。利用该环成功地进行了相位旋转的基础实验，确立了实现单能光束相位旋转的关键技术，证明了相位旋转的可行性。该项目的成果将推动未来的μ子科学向前发展。技术的副产品可能会扩展到μ子科学之外。即使是加速器科学，如μ子对撞机和中微子工厂的设计，也获得了巨大的利益。

In this project, a new technology to improve a muon beam has been developed in order to promote muon science further Since the present muon beams might not be sufficient in both their intensity and quality, most of muon experiments have some difficulties with some experimental constraints. If we have a highly intense and monoenergetic muon beam, it would introduce a great breakthrough in muon science. We call such a future muon beam as a “Super Muon Bearm" . We proposed to apply a new technique of phase rotation to make energy spread of a muon beam narrower An aimed beam intensity is more than 10,000 times higher than that of the world highest beam at PSI. New experiments to search for processes of lepton flavor violation of muons are proposed using this “super muon beam" by the Kuno-group, Osaka University.The objective of this research project is to establish a technique of phase rotation to make a monoenergetic beam. The two key devices are an ultra-high field gradient RF system and a large aperture FFAG (Fixed Field Alternating Gradient) magnet, both of which have been developed success fully in this project The FFAG ring, which consists of an RF cavity and 6 FFAG magnets, was constructed at Research Center for Nuclear. Physics (RCNP), Osaka University. Using this ring, basic experiments to demonstrate phase rotation were successfully performed.The project has established the important key-technologies and showed a feasibility of phase rotation for a monoenergetic beam. The achievements of the project will promote future muon science ahead. Technological spin-offs might spread beyond muon science. Even for accelerator science, such as designs of a muon collider and neutrino factories, has received great benefits.