标题： 不同散射几何结构的比较研究，用于使用Geant4的印度X射线偏振测量实验 显示英文标题

标题： Comparative study of different scattering geometries for the proposed Indian X-ray polarization measurement experiment using Geant4

摘要： X射线的偏振测量可以提供独特的机会，研究物质和辐射在极端磁场和极端引力场下的行为。 不幸的是，在过去的二十年里，尽管X射线天文学在时间、空间和光谱灵敏度方面有了多个数量级的提升，但在天体物理X射线偏振测量领域几乎没有（或非常少）进展。 最近，已经向印度空间研究组织（ISRO）提交了一个专门的小卫星实验提案，用于进行X射线偏振测量，该实验旨在自1976年以来首次进行X射线偏振测量。 该实验将基于著名的汤姆逊散射偏振测量原理，并采用中心低Z散射体被X射线探测器包围的基本设计，以测量散射X射线的角度强度分布。 此类实验的灵敏度由收集面积、散射和探测效率、X射线探测器背景以及调制因子决定。 因此，有必要仔细选择能够提供最高调制因子并从而在指定实验约束条件下实现最高灵敏度的散射几何结构。 通过蒙特卡罗模拟研究各种可能的散射几何结构是确定最佳散射几何结构的有效方法。 在这里，我们展示了基于Geant4模拟的五种不同散射几何结构的详细比较研究结果，这些几何结构可以在所提议的小卫星X射线偏振测量实验的重量和尺寸限制范围内考虑。 显示英文摘要

摘要： Polarization measurements in X-rays can provide unique opportunity to study the behavior of matter and radiation under extreme magnetic fields and extreme gravitational fields. Unfortunately, over past two decades, when X-ray astronomy witnessed multiple order of magnitude improvement in temporal, spatial and spectral sensitivities, there is no (or very little) progress in the field of polarization measurements of astrophysical X-rays. Recently, a proposal has been submitted to ISRO for a dedicated small satellite based experiment to carry out X-ray polarization measurement, which aims to provide the first X-ray polarization measurements since 1976. This experiment will be based on the well known principle of polarization measurement by Thomson scattering and employs the baseline design of a central low Z scatterer surrounded by X-ray detectors to measure the angular intensity distribution of the scattered X-rays. The sensitivity of such experiment is determined by the collecting area, scattering and detection efficiency, X-ray detector background, and the modulation factor. Therefore, it is necessary to carefully select the scattering geometry which can provide the highest modulation factor and thus highest sensitivity within the specified experimental constraints. The effective way to determine optimum scattering geometry is by studying various possible scattering geometries by means of Monte Carlo simulations. Here we present results of our detailed comparative study based on Geant4 simulations of five different scattering geometries which can be considered within the weight and size constraints of the proposed small satellite based X-ray polarization measurement experiment.