Overview

AZURE2 is designed with two main modes of operation:

1. Data-driven mode – fitting R-matrix calculations to experimental data using least-squares minimization (MINUIT2).

2. Calculation mode – computing cross sections, S-factors, or reaction rates at user-specified energies and angles, without fitting to data. This mode can also be used to extrapolate or interpolate results from a previous fit.

GUI Organization

The graphical interface is organized into tabs, ordered from left to right in the sequence that information should be entered:

1. Particle Pairs – define the reaction participants

2. Levels and Channels – define compound nucleus levels and reaction channels

3. Segments – specify experimental data and calculation regions

4. Experimental Effects – configure target integration, convolution, and other corrections

5. Fitting – manage fit parameters and their limits

6. Calculate – select and execute the calculation

7. Plot – visualize results (requires QWT)

8. MCMC – Bayesian parameter inference via Markov Chain Monte Carlo (if enabled)

Tip

Always start by entering information in the Particle Pairs tab. AZURE2 automatically calculates allowed channels and other quantities based on the particle pair information. Changes in any tab are automatically propagated to all other tabs.

Menus

In addition to the tabs, three menus are available from the menu bar:

• File – open, save, and manage project files

• Configure – set the R-matrix formalism, check files, directories, and runtime options

• Documentation – access in-app help for the current tab

Project Files

All setup information for an AZURE2 calculation is stored in a single Input File. This file can have any name, but the convention is to use the .azr extension. The file is a text-formatted file that is normally created and edited through the GUI.

The recommended project directory structure is:

my_project/
├── my_project.azr       # Input file
├── data/                 # Experimental data files
├── output/               # Output files from calculations
└── checks/               # Debug check files

Tip

Use relative paths (relative to the Input file location) for data files and output directories. This makes it easy to share projects with collaborators.

Workflow Summary

A typical AZURE2 workflow follows these steps:

1. Define particle pairs – specify the entrance and exit channels of the reaction

2. Define levels – enter the compound nucleus levels with their energies, spins, and parities

3. Set channel parameters – enter initial values for partial widths or ANCs

4. Create data segments – link experimental data files and specify energy/angle ranges

5. Configure experimental effects – add target integration or convolution corrections if needed

6. Calculate with data – make an initial calculation to check starting parameters

7. Fit with data – perform automated least-squares fitting

8. Extrapolate – compute cross sections at energies not covered by data

9. Calculate reaction rate – integrate the cross section over a Maxwell-Boltzmann distribution