Abstract This paper presents the first application of model calibration to neutron multiplicity counting (NMC) experiments for cross-section optimization that is informed by adjoint-based sensitivity analysis (SA) and first-order uncertainty quantification (UQ). We summarize previous work on SA applied to NMC and describe notable modifications and additions. We give the procedure for first-order UQ and Bayesian-inference-based parameter estimation (PE). We then discuss model calibration applied to NMC of a 4.5-kg sphere of weapons-grade, alpha-phase plutonium metal (the BeRP ball) with the nPod neutron multiplicity counter. For the BeRP ball in bare and polyethylene-reflected configurations, we discuss the sensitivity of the first- and second-moment detector responses (i.e., first and second moments of the NMC distribution, respectively) to the cross sections. We describe the sources of uncertainty in the measured and simulated responses. Specifically, uncertainty in the measured responses is due to both random and systematic sources. Uncertainty in the simulated responses is due to the cross-section covariances. We describe in detail the adjustment to the cross sections and cross-section covariances due to the optimization. Due to the contribution of systematic uncertainties to the measured response uncertainties, the adjustment to the cross sections is similar in trend but larger in magnitude compared to that recommended by previous work. We compare the measured responses to responses simulated with nominal and optimized cross sections, demonstrating that the best-estimate cross sections produce simulations of NMC experiments that are more accurate with reduced uncertainty.

中文翻译：

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中子多重计数实验在最佳截面调整中的应用

摘要 本文首次将模型校准应用于中子多重性计数 (NMC) 实验，以通过基于伴随的灵敏度分析 (SA) 和一阶不确定性量化 (UQ) 获得横截面优化。我们总结了以前应用于 NMC 的 SA 的工作，并描述了显着的修改和添加。我们给出了一阶 UQ 和基于贝叶斯推理的参数估计（PE）的过程。然后，我们讨论了使用 nPod 中子多重性计数器对 4.5 千克武器级、α 相钚金属球（BeRP 球）进行 NMC 的模型校准。对于裸露和聚乙烯反射配置的 BeRP 球，我们讨论了第一和第二时刻检测器响应的灵敏度（即 NMC 分布的第一和第二时刻，分别）到横截面。我们描述了测量和模拟响应中的不确定性来源。具体而言，测量响应的不确定性是由随机和系统来源造成的。模拟响应的不确定性是由横截面协方差造成的。我们详细描述了由于优化对横截面和横截面协方差的调整。由于系统不确定性对测量响应不确定性的贡献，与以前工作推荐的相比，对横截面的调整趋势相似，但幅度更大。我们将测量的响应与使用标称和优化横截面模拟的响应进行比较，