He Xiaozhong, Yang Liu, Liao Shuqing, Tang Ruo, Peng Yufei, Wang Yi, Yang Guojun, Wei Tao, Yang Xinglin, Jiang Xiaoguo, Long Jidong, Zhang Huang, Xie Weiping
Institute of Fluid Physics, China Academy of Engineering Physics, P.O. Box 919-106, Mianyang, 621900, China.
Institute of Fluid Physics, China Academy of Engineering Physics, P.O. Box 919-106, Mianyang, 621900, China.
Appl Radiat Isot. 2022 Nov;189:110446. doi: 10.1016/j.apradiso.2022.110446. Epub 2022 Sep 7.
High energy over MeV bremsstrahlung sources that employ normal conducting radio frequency linear accelerators have expanding applications in industrial computerized tomography (CT) for non-destructive inspection and evaluation. The X-ray spot size that mainly affects the imaging quality is yet limited by the electron beam width in the high resolution CT systems. In a short exposure time, high beam power is required to generate sufficient photons to improve the signal to noise ratio of imaging. However, with ∼kW level of average beam power these linear accelerators usually have a beam spot size over 1 mm since the temperature rising due to the beam energy deposition in the target should be far below its melting point. We propose a concept of using a Rhodotron-based accelerator to provide high power electron beams in a long duration pulse and a rotating target to mitigate the overheating issue, such that the gap between micro-spot and high dose rate can be bridged in the high energy bremsstrahlung sources. This article presents an in-depth simulation work to discuss and evaluate this scheme of X-ray source. The simulations of beam dynamics in the accelerator and bremsstrahlung process in the target predict the generated X-rays with a spot size as small as 68 μm at full-width half-maximum and a dose rate as high as 4700 cGy/min from a 9 MeV electron beam interacting with a 1 mm thickness tantalum target. Further thermal analysis in the rotating target indicates a significant improvement of beam power handling in comparison with the conventional stationary one.
采用常规导电射频直线加速器的兆电子伏特以上高能轫致辐射源在工业计算机断层扫描（CT）的无损检测和评估中有着越来越广泛的应用。在高分辨率CT系统中，主要影响成像质量的X射线光斑尺寸受电子束宽度的限制。在短曝光时间内，需要高束流功率来产生足够的光子以提高成像的信噪比。然而，对于平均束流功率在千瓦级别的这些直线加速器，由于靶中束流能量沉积导致的温度升高应远低于其熔点，其束斑尺寸通常超过1毫米。我们提出了一种概念，即使用基于回旋加速器的加速器在长脉冲持续时间内提供高功率电子束，并使用旋转靶来缓解过热问题，从而在高能轫致辐射源中弥合微光斑和高剂量率之间的差距。本文进行了深入的模拟工作，以讨论和评估这种X射线源方案。加速器中的束流动力学模拟和靶中的轫致辐射过程模拟预测，9兆电子伏特的电子束与1毫米厚的钽靶相互作用时，产生的X射线半高宽光斑尺寸小至68微米，剂量率高达4700厘戈瑞/分钟。旋转靶的进一步热分析表明，与传统的固定靶相比，束流功率处理能力有显著提高。
