Laser acceleration of protons for radiation therapy

描述（由申请人提供）：我们提出的研究目标是使用高强度、短脉冲激光将质子加速到230兆电子伏特的治疗能量。这一关键目标的成功完成将为激光加速器的发展打开大门，它将取代质子加速的标准模式。这可能会使质子治疗的剂量学优势以一种经济有效的方式用于癌症的一般治疗。虽然理论结果表明治疗能量是可以实现的，但关键问题是在实验上向薄目标提供足够的强度，而不会产生过多的预等离子体或损害后目标表面的物理完整性。这需要非常高的激光对比度，定义为主脉冲强度和较弱的预脉冲强度之比，这是这些激光器的一个特点。本课题的具体目标是：1)将质子加速到治疗能量；2)进行理论模拟以指导实验程序，完善理论模型，并确认我们对基于激光的质子加速机制的理解。这将是第一个使用激光强度的研究，预计会产生具有治疗能量的质子。在我们提出的方法中，我们将使用“倍频”来提高对比度以消除等离子体前效应，并系统地研究一系列二维参数空间，以确定激光强度和目标厚度对几个不同目标的质子能量的影响。所产生的最大质子能量将被测量，使用飞行时间和光谱仪，并与几个不同目标的这两个变量相关联。我们将更详细地研究产生更大质子能量的参数空间区域。理论模拟将指导实验工作，同时在实验结果的基础上对其进行完善。在过去的50年里，质子治疗已经被证明比x射线治疗对癌症的局部控制相似或更好。然而，由于它的价格是它的十倍以上，所以它并没有被广泛使用。这项研究将在确定是否可以通过使用新的加速技术大幅降低成本方面迈出关键的第一步。

DESCRIPTION (provided by applicant): The goal of our proposed research is to use high-intensity, short-pulse lasers to accelerate protons to a therapeutic energy of 230 MeV. The successful completion of this critical goal would open the door to the development of a laser-accelerator that would replace standard modes of proton acceleration. This would potentially allow the dosimetric advantages of proton therapy to become available in a cost-effective manner for general use in the management of cancer. While theoretical results indicate that therapeutic energies are attainable, the critical issue is to experimentally deliver a sufficient intensity to a thin target without creating an excessive preplasma or compromising the physical integrity of the rear target surface. This requires a very high laser contrast, which is defined as the ratio of the intensities of the main pulse and a weaker prepulse, which is a feature of these lasers. The specific aims of this proposal are 1) to accelerate protons to therapeutic energies, and 2) conduct theoretical simulations to guide experimental procedure, refine theoretical models, and confirm our understanding of laser-based proton acceleration mechanisms. This will be the first study using laser intensities which are predicted to yield protons of therapeutic energies. In our proposed method, we will use "frequency-doubling" to improve the contrast to eliminate preplasma effects and systematically study a series of 2D parameter spaces to determine the effect of laser intensity and target thickness on proton energy using several different targets. The maximum resulting proton energy would be measured, using time-of-flight and a spectrometer, and correlated to these two variables for several different targets. Regions of parameter space resulting in greater proton energies will be studied in greater detail. Theoretical simulations will guide experimental work, while themselves being refined based on experimental results. Over the past 50 years, proton therapy has been shown to give similar or better local control of cancer than X-ray therapy. However, because it costs more than ten times as much, it is not widely available. This research will conduct the first critical step in determining if the cost can be dramatically reduced through the use of new acceleration technology.