强流RFQ加速器瞬态束流负载效应研究

射频四极（RFQ）加速器由于其结构紧凑，在对束流加速的同时还能产生足够强的横纵向聚焦，已被广泛用作质子和重离子加速器的注入器。对于一些特殊应用，如散裂中子源、加速器驱动的次临界系统、高通量离子束材料辐照装置和重离子惯性约束聚变装置的加速器，需使用RFQ对长脉冲或连续波强流束进行加速。由于经典束流负载效应解析理论产生和发展的历史背景，以及这类RFQ目前的数量仍相对较少，导致经典束流负载效应解析理论并不能解释强流RFQ上观察到的部分束流负载现象。本研究项目拟基于束流等效阻抗模型，对经典束流负载效应理论进行扩展，使其能够用于分析RFQ这类多主导电磁模式腔的束流负载效应，构建RFQ瞬态束流负载效应物理模型，并对RFQ各加速单元的局域束流负载效应的一致性进行判定。利用该物理模型，可更好的实现这类RFQ的电磁场设计和低电平控制，从而提升其束流品质和运行可靠性。

Radio frequency quadrupole (RFQ) Linacs have been widely used as injectors for proton and heavy-ion accelerators, due to they can accelerate and strongly focus the beam at the same time with their compact structures. For some specific applications, such as RFQs in accelerators for spallation neutron source, accelerator-driven subcritical system, high-flux ion beam material irradiation and heavy-ion inertial confinement fusion, where long macro-pulse or continuous-wave high intensity beam is required to be accelerated. Due to the historical background of the development of the classical analytical theory of beam loading effects and the relatively small amount of such type of high intensity beam RFQ, the classical analytical theory of beam loading effects cannot explain some of the beam loading phenomenon observed on a high intensity continuous-wave beam RFQ. This research project is proposed to extend the classical theory of beam loading effects to account for the multiple dominant electromagnetic mode cavity such as RFQ, from the viewpoint of equivalent impedance model of the beam. With the extended beam loading theory, the physical model of the transient beam loading effects of a RFQ can be built and the consistency of the local beam loading effects in each accelerating cell of a RFQ can be verified. With this physical model, the RF design and low-level RF control of such a high intensity beam RFQ can be improved to increase its beam quality and availability.