CM on International Nuclear Data Evaluation Network for Light Elements (INDEN-LE)

18 Nov 2025, 09:00 → 21 Nov 2025, 17:00 Europe/Zurich

C0221 (IAEA, Vienna, Austria)

Paraskevi DIMITRIOU (International Atomic Energy Agency)

The annual meeting of the INDEN-LE working group will be held from 18 to 21 November 2025 at the IAEA Headquarters in Vienna.

Participants will discuss progress in evaluations of charged-particle and neutron-induced reactions of light elements at low energies relevant to energy and non-energy applications. 

The main topics to be covered are: i) comparison of the evaluations of ⁷Be system produced with the R-matrix analysis codes AZURE2, GECCCOS, SAMMY, ii) evaluations of ¹⁰Be and ¹⁷O systems using RAC code, iii) measurements and evaluation of ¹⁵N system, and iv) developments in uncertainty quantification in R-matrix analysis.

Meeting report, INDC(NDS)-0931, 2025

Tuesday 18 November

7Be evaluation

12:30 Lunch break

Day 1

1 Differential cross-section measurement of the 14N(n, p)14C reaction in the 0.1-6.0 MeV energy region

Accurate cross sections and differential cross sections of the 14N(n, p)14C reaction are of significant importance for research in Boron Neutron Capture Therapy as well as astrophysical element synthesis. From the last century to the present, several measurements have been conducted, and cross sections have been obtained. However, on one hand, present experimental measurements show considerable discrepancies in the keV neutron energy region; on the other hand, there is a severe lack of differential cross sections for the 14N(n, p)14C reaction across the entire energy spectrum, with a shortage of measurement results. Based on the Back-n white neutron beamline at China Spallation Neutron Source, this research utilized wide-spectrum neutrons and employed charged particle detectors for experimental measurements. Through simulation and multiple beam test experiments, the experimental conditions and methods were explored, and a successful 400-hour beam time experiment was conducted. For the first time internationally, the differential cross sections of the 14N(n, p)14C reaction in the 0.1-6.0 MeV neutron energy range was measured, and differential cross sections as low as 0.1mb in the 0.1-0.45 MeV neutron energy range were provided, which are expected to clarify the discrepancies in previous measurements and different evaluation databases in this energy region.

Speaker: Wei JIANG

INDEN-LE_14N(n, p)14C_WeiJiang.pdf

2 Continued progress on the $^{15}$N system

Previous work has been preformed to fit $^{14}$N+n, $^{14}$C+p and $^{11}$B+$\alpha$ data for the $^{15}$N system up to about 2 MeV above the their respective thresholds, which are similar in energy. This past work found that there were apparent discrepancies in the fitting, expecially with the $^{11}$B$(\alpha,n)^{14}$N and $^{14}$N$(n,p)^{14}$C data sets. By implementing energy shifts, resolution effects, improved handeling of the Coulomb functions near thresholds and increase in code speed, some of these apparent discrepancies were resolved. However, other discrepancies, including some rather large normalization factors for the data and some data with very small uncertainties, are still resulting in conflicting results.

Speaker: Richard deBoer (University of Notre Dame)

deBoer_INDEN-LE_2025_2.pdf

3 Comprehensive new evaluation of the 8Be system

Updates from ongoing work for the new evaluation of the 8Be system using EDA code will be presented.

Speaker: Som Paneru (Los Alamos National Laboratory)

INDEN-LE_2025.pdf

Wednesday 19 November

7Be evaluation

12:30 Lunch break

Day 2

4 The improved evaluation of the n+16O system

In recent years, the improved global fitting of the Reduced R-Matrix theory for n+16O system has been carried out using the RAC. The cross sections for the 16O(n, α0)13C reaction in the 6.8-11.7 MeV neutron energy region have been measured recently, which have been added into the fitting. In addition, the measured data for the 16O(n, α0)13C reaction of Lee et al. have been also added into the fitting. The evaluation of the 16O(n, α0)13C reaction have been improved.

Speaker: Mr Cong Xia (Peking University)

5 2025-ENSDF Evaluation of $^{17}$O

The 2021-ENSDF evaluation of $^{17}$O was updated in 2025 as part of $A=17$ mass evaluation, which is in progress. I will briefly present the changes with an emphasis on the astrophysical region of interest.

Speaker: Kiana Setoodehnia (Duke University)

Setoodehnia.pdf

6 R-matrix based evaluation with GENEUS_R: current status of application to n+Be-9 and p-Li-6

Speaker: Helmut Leeb

Dinner

Thursday 20 November

7Be evaluation

12:30 Lunch break

Day 3

7 A new python-based phenomenological R-matrix code

We have recently begun developing a new phenomenological R-matrix code with the aims of exploring (a) how to optimize the evaluator’s use of the code, and (b) how to integrate machine learning approaches to assist with R-matrix analysis.

We use the Wigner-Eisbund parameterization of the R-matrix [1], with a user-adjustable boundary condition [2]. The data included in the calculation can be filtered using a flexible system, similar to the data segments used in AZURE [3], with calculations performed only for the currently selected subset of data. The entire calculation object can be serialized and saved to (or loaded from) a compressed JSON format file. This includes the particle pairs and channels, the R-matrix pole parameters, the data sets being analysed, and all the required Coulomb wave functions (which then only need to be calculated once).

The code is written in python and can be used interactively via jupyter notebooks. A graphical user interface has been written to allow editing of the R-matrix pole energies and widths, with real-time updates to the calculations and plotting of the results. The use of python means the calculations can be very easily scripted to add, edit and remove poles. This allows, for example, easy generation of training data for machine-learning-based models such as convolutional neural networks.

We will give an overview of the code, its design, preliminary results and benchmarking, and future plans.

[1] A. M. Lane and R. G. Thomas, Rev. Mod. Phys. 30, 257 (1958)
[2] F. C. Barker, Aus. J. Phys 25, 341 (1972)
[3] R. E. Azuma, Phys. Rev. C 81, 045805 (2010)

Speaker: Dr Edward Simpson (Australian National University)

Ed Simpson - INDEN-LE Meeting.pdf

8 The improved evaluation of the n+9Be system

The global fitting for n+9Be system using RAC have been reported in 2022. In recent years, the improved Global fitting of the Reduced R-Matrix theory for n+9Be system has been carried out using the RAC. More detailed fitting for the cross section of the 9Be(n, tot) has been conducted. New measurement data of the differential cross sections for the 9Be(n, el) from China have been added into the fitting. Thus, the evaluation of the 9Be(n, 2n) have been improved.

Speaker: Mr Wenkai Ren (Peking University)

9 Recent Developments in AZURE2: Enhanced R-Matrix Analysis with Application to the 7Be Compound System

AZURE2 has undergone significant enhancements to improve its analytical capabilities and uncertainty quantification. This presentation will describe recent upgrades implemented in the code and demonstrate their application to updated analyses of the 7Be compound system.

Key developments include the implementation of energy shift parameters for systematic treatment of data uncertainties, enabling more rigorous handling of experimental energy calibration effects. The Coulomb wavefunction calculations have been substantially improved to enhance numerical accuracy and stability across a broader range of reaction conditions. The possibility of using the infinitely thick target data was added in the code. A significant methodological advancement is the integration of a preliminary Markov Chain Monte Carlo (MCMC) sampling capabilities alongside new frequentist minimization algorithms. Finally, progress is being made on the addition of a hybrid potential model.

These upgrades are demonstrated through an updated R-matrix fit of the $^{7}$Be compound system, which incorporates the enhanced treatment of systematic uncertainties and improved wavefunctions, alongside the $^{12}$C(p,γ)$^{13}$N and $^{13}$C(α,n)$^{16}$O examples. The enhanced AZURE2 framework represents a substantial step forward in R-matrix analysis capabilities, offering the nuclear physics community improved tools for precise reaction rate determinations and uncertainty quantification.

Speaker: Jakub Skowronski (Università degli Studi di Padova)

2025_INDEN_Skowronski.pdf

Friday 21 November

Day 4

Drafting recommendations - Future perspectives