人类与癌症的抗争，促进了癌症治疗技术的不断革新。近几十年来，随着强流质子和碳离子加速器技术的迅猛发展，越来越多的质子治疗、碳离子治疗和硼中子俘获治疗装置在国内外医疗机构落地使用。国内外近 1/4 的质子治疗装置采用同步加速器设计，全部的碳离子治疗装置采用同步加速器的设计，约 1/3 的硼中子俘获治疗采用射频直线加速器的方案。 Alvarez型DTL在加速?范围为 0.03~0.5的中、低能带电粒子时，具有横向聚集强、束流品质高、加速效率高等优点，可满足医用直线加速器的需求，因此常应用于这三类治疗装置中。Alvarez型DTL腔体的场稳定性对医用治疗束的平稳运行具有重要意义。论文针对医用直线加速器中Alvarez型DTL腔体稳定性的内容，借助等效电路模型和传输线模型研究了腔体稳定性原理；后续从三个方面开展研究，包括杆耦合器数目对场稳定性影响，多杆耦合器下腔体的快速调谐方法以及无杆耦合器下腔体的快速调谐方法。 论文首先系统地研究了杆耦合器数目和纵向位置对腔体场稳定性的影响。利用等效电路模型和连续传输线模型分析了Alvarez型DTL中，电场分布曲线和倾斜敏感度曲线变化的幅度与腔体参数的关系，通过模拟和实验验证了腔体的稳定性和腔体?值随着杆耦合器数目变化的趋势。为简化腔体杆耦合器的设计、减少加速器成本、简化调谐流程、增加腔体无载品质因数提供了有效依据。 针对多杆耦合器的Alvarez型DTL腔体，论文提出了频移曲线判别法用于快速确定杆耦合器最优均匀深度。通过测量TM010、TM011 和杆耦合器模式PC1随不同插入深度变化的频移曲线，寻找TM011和PC1关于TM010的对称区间，锁定最优均匀深度区间。该法能避免每个插入深度下测场分布和倾斜敏感度的繁琐操作，保证了实验的连贯性，节省时间至少一个数量级。模拟和实验结果一致，验证了该方法能够实现多杆耦合器下Alvarez型DTL场稳定性的快速调谐。 针对无杆耦合器Alvarez型DTL腔体，论文提出了扩维的伪逆矩阵法来实现频率和场分布同时调谐的目标，同时优化了矩阵求解过程和实验流程以加速迭代。利用该方法在包含23个单元、5个调谐器的斜梯度DTL中进行模拟和实验，在仅使用调谐器下，一般一轮迭代共设置7次深度值分布、测量7次场分布即可将频率调至325±0.007MHz 附近，将轴向峰值电场分布的相对误差调到3%以内。

The fight against cancer has promoted the continuous innovation of cancer treatment methods. With the rapid development of proton and carbon ion accelerator technology over the past few decades, more and more proton beam therapy, carbon ion beam therapy and boron neutron capture therapy facilities have been used in medical institutions at home and abroad. Almost a quarter of proton therapy devices and all carbon ion therapy devices use synchronous accelerator design all over the world, and about one-third of boron neutron capture therapy facilities use RF linac. The Alvarez-type drift tube linac (DTL) has strong transverse focusing, high beam quality, and high acceleration efficiency when accelerating low-energy charged particles in the ? range of 0.03 to 0.5, making it suitable for use in medical linear accelerators. The field stability of the Alvarez-type DTL cavity is of great significance for the smooth operation of medical treatment beams. This paper focuses on the stability of Alvarez- type DTL cavity in medical linacs, and studies the stability principle of the cavity using equivalent circuit model and transmission line model. The paper then conducts research in three aspects: the influence of the number of post couplers on field stability, the fast tuning method of the cavity under multiple post couplers, and the fast tuning method of the cavity without post couplers. The paper studies the relationship between the number of post couplers and cavity stability systematically.By equivalent circuit and transmission line model, the relationship between the amplitude of the electric field distribution and the tilt sensitivity curve in the Alvarez-type DTL and the cavity parameters is analyzed. The field stability and the trend of ? value in the cavity variation with the number of post couplers are verified by the simulation and experiment. These provide an effective advice for simplifying the design of post couplers, reducing accelerator costs, simplifying tuning processes, and increasing cavity ? values. The paper proposes a discrimination method of frequency shift curve to quickly determine the optimal insertion depth of post couplers in the Alvarez-type DTL cavity with multiple post couplers. This method determines the range of optimal depth by measuring the frequency shift curves of TM010, TM011 and the highest mode of post couplers (PC1) as the insertion depth changes and looking for the symmetric interval of TM011 and PC1 about TM010. This method can avoid the tedious operation of measuring field distribution and calculating tilt sensitivity at each depth, ensuring the continuity of the experiment and saving at least an order of magnitude in manpower and time. Simulated and experimental results confirm that this method can achieve fast tuning of the Alvarez-type DTL field stability under multiple post couplers. For Alvarez-type DTL cavities without post couplers, the paper proposes an expanded pseudoinverse matrix method to achieve the tuning goal of frequency and field distribution simultaneously, and optimizing the matrix solution process and experimental process to iteration more quickly. By this method, simulation and experiment were carried out in a ramped-gradient DTL with 23 cells and 5 tuners. By adjusting the insertion depths of the tuners, the tuning was achieved in merely one round of iteration. After tuning, the relative error of the peak field distribution and resonant frequency of the cavity reached to within ±3% and 325±0.007 MHz (25℃, vacuum), respectively. It was verified that the field stability meets the requirement from the physical design both before andafter tuning.