Troubleshooting
While AZURE2 is fairly stable, errors can occur in certain situations. This page describes the most common issues and their solutions.
Common Issues
Kinematic Limits
Symptom: GSL error or hard crash during a pure calculation or extrapolation.
Cause: An energy or angular range was specified that is not kinematically allowed, especially when extrapolating to very low energies.
Solution: Check the energy and angle ranges in your segments. Ensure they are physically meaningful for the reaction being studied.
Threshold Effects
Symptom: GSL errors when calculating near the threshold of a reaction channel.
Cause: When multiple entrance channels are defined, the code attempts to calculate the penetrability for each channel. Very close to a threshold, the penetrability can become extremely small, causing numerical issues.
Solution: Exclude data points that are very close to the threshold. Note that this issue is exacerbated by target integration, convolution, and reaction rate routines that create sub-points near the threshold.
Unconstrained Parameters
Symptom: Crashes during fitting, especially with the Brune parameterization disabled.
Cause: One or more fit parameters are very poorly constrained by the data, causing them to be varied to unphysical values. The parameter transformation code then fails.
Solution:
Use the Brune parameterization (recommended and more numerically stable).
Fix suspected unconstrained parameters and re-run the fit to identify the problematic one(s).
Add parameter limits in the Fitting tab.
MINOS Crashes
Symptom: The MINOS error analysis routine crashes.
Cause: MINOS is very sensitive to unconstrained parameters. A crash usually indicates that the fit is not robust.
Solution: Running MINOS is itself a good test of fit quality. If it crashes, fix different parameters to isolate the unconstrained ones. A successful MINOS run is a strong indicator of a robust fit.
Reaction Rate Integration Failures
Symptom: Crashes or incorrect results during reaction rate calculation.
Cause: The numerical integration encounters a threshold or a very narrow resonance that cannot be resolved by the adaptive integration routine.
Solution: For narrow resonances (total width less than approximately 1 keV), calculate the reaction rate contribution separately using the narrow-resonance approximation. For threshold issues, create a fine energy extrapolation and perform the numerical integration externally (e.g., Simpson’s rule).
Hanging Calculations
Symptom: AZURE2 runs indefinitely without producing output or crashing.
Cause: Incorrectly formatted input data files.
Solution: Verify that data files are properly formatted with exactly four whitespace-delimited columns of numerical data. Check for extra blank lines, non-numeric characters, or missing columns.
Missing Channels
Symptom: Unexpected physics results or crashes, especially for scattering or external capture calculations.
Cause: The maximum orbital momentum (L_max) in the Levels and Channels tab is set too low, resulting in missing channels.
Solution: Increase L_max and verify that at least one channel exists for each particle pair for each \(J^\pi\). Consider adding dummy levels to include all necessary hard-sphere phase shifts.
Getting Help
For questions and support, contact the developers at: