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Conception and Software Implementation of a Nuclear Data Evaluation Pipeline
Nuclear Data Sheets ( IF 3.7 ) Pub Date : 2021-05-03 , DOI: 10.1016/j.nds.2021.04.007
G. Schnabel , H. Sjöstrand , J. Hansson , D. Rochman , A. Koning , R. Capote

We discuss the design and software implementation of a nuclear data evaluation pipeline applied for a fully reproducible evaluation of neutron-induced cross sections of 56Fe above the resolved resonance region using the nuclear model code TALYS combined with relevant experimental data. The emphasis of this paper is on the mathematical and technical aspects of the pipeline and not on the evaluation of 56Fe, which is tentative. The mathematical building blocks combined and employed in the pipeline are discussed in detail. In particular, an intuitive and unified representation of experimental data, systematic and statistical errors, model parameters and defects enables the application of the Generalized Least Squares (GLS) and its natural extension, the Levenberg-Marquardt (LM) algorithm, on a large collection of experimental data without the need for data reduction techniques as a preparatory step. The LM algorithm tailored to nuclear data evaluation takes into account the exact non-linear physics model to determine best estimates of nuclear quantities. Associated uncertainty information is derived from a second-order Taylor expansion at the maximum of the posterior distribution. We also discuss the pipeline in terms of its IT (=information technology) building blocks, such as those to efficiently manage and retrieve experimental data of the EXFOR library, which facilitates their appropriate correction, and to distribute computations on a scientific cluster. Relying on the mathematical and IT building blocks, we elaborate on the sequence of steps in the pipeline to perform the evaluation, such as the retrieval of experimental data, the correction of experimental uncertainties using marginal likelihood optimization (MLO) and after a screening of thousand TALYS parameters—including Gaussian process priors on energy dependent parameters—the fitting of about 150 parameters using the LM algorithm. The code of the pipeline including a manual and a Dockerfile for a simplified installation is available at www.nucleardata.com.



中文翻译:

核数据评估管道的概念和软件实现

我们讨论了核数据评估管道的设计和软件实现,该管道用于使用核模型代码TALYS结合相关实验数据对分辨的共振区域以上的56 Fe的中子感应截面进行完全可重复的评估。本文的重点是管道的数学和技术方面,而不是对56的评估。铁,这是暂定的。详细讨论了在管道中组合和采用的数学构建块。特别是,通过直观,统一地表示实验数据,系统和统计误差,模型参数和缺陷,可以在大集合上应用广义最小二乘(GLS)及其自然扩展Levenberg-Marquardt(LM)算法实验数据,无需数据缩减技术作为准备步骤。专为核数据评估量身定制的LM算法考虑了精确的非线性物理模型,以确定核数量的最佳估计。相关的不确定性信息是从后验分布最大值处的二阶泰勒展开中得出的。我们还将根据其IT(信息技术)构建模块来讨论管道,例如有效管理和检索EXFOR库的实验数据的模块,这有助于对其进行适当的修正,并在科学集群上分布计算。依靠数学和IT构造块,我们详细说明了执行评估的流程中的步骤顺序,例如检索实验数据,使用边际似然优化(MLO)校正实验不确定性以及筛选了数千个TALYS参数(包括基于能量的参数的高斯过程先验)使用LM算法拟合约150个参数。可以在www.nucleardata.com上获得该管道的代码,包括用于简化安装的手册和Dockerfile。

更新日期:2021-05-03
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