应用于质子治疗的紧凑型直线加速器物理设计和研究

Proton therapy is a new frontier in cancer radiation therapy which is nowadays undergoing rapid development in China and around the world. In the past, because a cyclotron or a synchrotron cost much less than a linac, those two types of accelerators are widely used in proton therapy. However, as the linac technology is by far mature for the development of compact proton linacs operating in S-band, the construction cost of a linac reduced sharply and is now similar to the expense of a circular accelerator. Other than circular accelerators, linacs have some specifically characters. The high repetition rate together with the possibility of very rapid energy variations offers an optimal solution to the present challenge of hadrontherapy: "paint" a moving tumor target in three dimensions with a pencil beam. This project is planning to design a high accelerating gradient, low power consumption, compact linear accelerator applied in proton therapy. It may be consisted of several types of linac. For the first time, an S band Pi mode structure will be designed and used for the medium energy part. Besides physics designs, a beam experiment will be carried out. We hope to realize continuous beam energy variations by adjusting the cavity voltage and phase. This method will make the therapy facility more flexible and useful.

质子治疗技术在全世界范围内迅速发展，我国也在积极发展该技术。过去由于直线加速器造价昂贵，从经济的角度出发，质子治疗加速器一般都采用环形加速器。随着S波段(3~11GHz)质子直线加速器技术的发展，直线加速器的建造成本已经低于或接近环形加速器的造价。与环形加速器相比，直线加速器有着突出的优点：出口束流能量快捷可调，束流品质优良，可用于动态扫描，是质子治疗加速器下一步的发展趋势。本课题将设计一台高加速效率，低功耗，紧凑型直线加速器应用于质子治疗，为我国质子治疗设备的国产化提供技术路线。在中能段，本课题将首次设计工作频率在S波段的Pi模式直线加速器（PIMS）并研究其性能。通过计算机模拟和实际束流实验，掌握通过调节腔压和相位来选择直线加速器出口能量的方法，使得在一定范围内，直线加速器出口能量连续可调，提高质子治疗用加速器的灵活性。

质子直线加速器技术的发展，为医用加速器提供了更多的选择，提高医用加速器的性能。PIMS是一种新型的质子直线加速器，结构简单，维护方便，非常适合应用于质子治疗领域。本项目设计了一台加速能量范围80~300MeV的PIMS加速器，包括动力学设计，耦合孔和调谐器设计等。本课题依托于中国散裂中子源直线加速器的调束条件，应用了相位扫描法来精确确定加速腔场幅和相位，使得加速腔出口处束流达到设计能量；应用了飞行时间法精确测定加速腔出口能量，并研究了强流时，利用测量的束流参数做横向匹配，减少束流损失。