基于超强脉冲激光的医用质子辐射束特性研究

Characteristics of medical proton irradiation beams based on ultra-intense pulse laser

目的:探索一种新型的基于超强脉冲激光的医用质子辐射束,为研制基于小型化的超短超强激光质子加速器的激光质子刀进行肿瘤治疗奠定基础。方法:在超强脉冲激光装置SILEX-I上研究医用高能质子辐射束特性。利用CR39核径迹探测器测量质子束的束密度、产额,并采用Thomson离子谱仪和HD810型号辐射变色膜片在固体靶背表面法线方向分别测量能谱及空间分布。结果:质子束空间分布呈现圆盘状、成丝和环状分布。质子束与入射激光方向无关,沿着靶背表面法线方向发射,质子束发射存在较小立体角。对于复合靶,若保持前表面的Al厚度不变,随着后表面C8H8层厚度的增加,质子束流减小。质子束发射在一定能量处出现截止,截止能量与靶厚度和靶材料密切相关。截止能量的大小随靶厚度的增加而减小;在靶厚度相同的情况下,Al薄膜靶的质子截止能量高于Cu薄膜靶。结论:本实验结果为激光质子加速器治疗装置的小型化研制及肿瘤放射治疗提供了一些重要参考依据。

Objective To explore the medical proton irradiation beams based on ultra-intense pulse laser for laying a foundation for the development of a laser-driven proton knife based on miniaturized ultra-short and ultra-intense laser-driven proton accelerator for tumor therapy. Methods The characteristics of medical proton irradiation beams were explored on SILEX-I laser facility. The density and yield of proton beams were measured with nuclear track detector CR39. Moreover, the proton energy spectra and the spatial distributions of proton beams were measured by Thomson magnetic spectrometer and HD810 radiochromic film, separately. Results The spatial profiles of proton beams showed disc-, filament-, and ring-like distributions. The proton beams emitted along the direction of normals to the rear surface of targets within a small cone angle, irrelevant to the direction of incident laser beams. For composite targets, with the same thickness of Al layer, the proton beam flux decreased with the increase of C8H8 layer thickness. The sharp cutoff energy which existed in the proton energy spectra was depended on target thickness and target material. The sharp cutoff energy was decreased with the increase of target thickness. With the same target thickness, the sharp cutoff energy of Al foil target was higher than that of Cu foil target. Conclusion The experiment results provide an important reference for the development of miniaturized laser-driven proton accelerator and tumor radiotherapy.