核共振荧光的高精度Geant4模拟和半解析建模
High-accuracy Geant4 simulation and semi-analytical modeling of nuclear resonance fluorescence
摘要：
核共振荧光（NRF）是一种光核相互作用，能够在纯物理和应用物理场景中进行高度同位素特异性的测量。光子物理学和输运的蒙特卡罗模拟有助于复杂几何结构中NRF测量的高精度设计和分析，这促使Jordan和Warren（2007）在Geant 4中开发用于NRF模拟的G4 NRF代码库。在这项工作中，我们提高了G4NRF代码的物理精度，并进行了改进的基准测试模拟。G4 NRF中的NRF截面计算，以前是高斯近似，已被完全数值积分取代，以提高厚目标场景中的精度。一个高精度的半解析模型，在一个典型的NRF测量的预期NRF计数率，然后构建和G4NRF模拟简单的同质和更复杂的异质几何形状进行比较。在简单测试用例中的${\sim}1\%$水平和更现实场景中的${\sim}3\%$水平上，发现半分析模型和G4NRF模拟预测的速率之间的一致性，改进了初始基准研究的${\sim}20\%$水平，并为Geant 4建立了高度准确的NRF框架。
英文摘要：
Nuclear resonance fluorescence (NRF) is a photonuclear interaction that enables highly isotope-specific measurements in both pure and applied physics scenarios. High-accuracy design and analysis of NRF measurements in complex geometries is aided by Monte Carlo simulations of photon physics and transport, motivating Jordan and Warren (2007) to develop the G4NRF codebase for NRF simulation in Geant4. In this work, we enhance the physics accuracy of the G4NRF code and perform improved benchmarking simulations. The NRF cross section calculation in G4NRF, previously a Gaussian approximation, has been replaced with a full numerical integration for improved accuracy in thick-target scenarios. A high-accuracy semi-analytical model of expected NRF count rates in a typical NRF measurement is then constructed and compared against G4NRF simulations for both simple homogeneous and more complex heterogeneous geometries. Agreement between rates predicted by the semi-analytical model and G4NRF simulation is found at a level of ${\sim}1\%$ in simple test cases and ${\sim}3\%$ in more realistic scenarios, improving upon the ${\sim}20\%$ level of the initial benchmarking study and establishing a highly-accurate NRF framework for Geant4.
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