Laboratoire d'Optique Appliquée, ENSTA-ParisTech, École Polytechnique, CNRS-UMR7639, Institut Polytechnique de Paris, 828 bd des Maréchaux, 91762 Palaiseau cedex, France.
Laboratoire d'Optique Appliquée, ENSTA-ParisTech, École Polytechnique, CNRS-UMR7639, Institut Polytechnique de Paris, 828 bd des Maréchaux, 91762 Palaiseau cedex, France.
Phys Med. 2019 Nov;67:123-131. doi: 10.1016/j.ejmp.2019.10.027. Epub 2019 Nov 6.
Laser-accelerated protons have a great potential for innovative experiments in radiation biology due to the sub-picosecond pulse duration and high dose rate achievable. However, the broad angular divergence makes them not optimal for applications with stringent requirements on dose homogeneity and total flux at the irradiated target. The strategy otherwise adopted to increase the homogeneity is to increase the distance between the source and the irradiation plane or to spread the beam with flat scattering systems or through the transport system itself. Such methods considerably reduce the proton flux and are not optimal for laser-accelerated protons. In this paper we demonstrate the use of a Genetic Algorithm (GA) to design an optimal non-flat scattering system to shape the beam and efficiently flatten the transversal dose distribution at the irradiated target. The system is placed in the magnetic transport system to take advantage of the presence of chromatic focusing elements to further mix the proton trajectories. The effect of a flat scattering system placed after the transport system is also presented for comparison. The general structure of the GA and its application to the shaping of a laser-accelerated proton beam are presented, as well as its application to the optimisation of dose distribution in a water target in air.
激光加速质子由于可实现亚皮秒脉冲持续时间和高剂量率，因此在辐射生物学的创新实验中具有很大的潜力。然而，由于其宽角发散，对于在辐照靶标处对剂量均匀性和总通量有严格要求的应用来说，它们并不是最佳选择。否则，为了提高均匀性而采用的策略是增加源与辐照平面之间的距离，或者通过平面散射系统或通过传输系统本身来扩展光束。这些方法会大大降低质子通量，对于激光加速质子来说并不是最佳选择。在本文中，我们展示了使用遗传算法 (GA) 来设计最佳的非平面散射系统，以对光束进行整形，并有效地使辐照靶标处的横向剂量分布变平。该系统放置在磁传输系统中，以利用色聚焦元件的存在进一步混合质子轨迹。还介绍了在传输系统之后放置平面散射系统的效果，以进行比较。本文介绍了 GA 的一般结构及其在激光加速质子束整形中的应用，以及在空气中水靶中优化剂量分布的应用。
