Speaker
Description
The construction of nuclear level schemes from γ-ray spectroscopy data is a long-standing and computationally challenging problem, especially for complex nuclei with a large number of observed transitions. Despite its fundamental importance for the interpretation of nuclear structure experiments, only a limited number of dedicated algorithmic approaches have been proposed [1,2], leaving considerable scope for further methodological development. In this work, we present a new algorithmic approach for the automatic reconstruction of nuclear decay schemes based solely on γ–γ coincidence information.
The input to the algorithm consists exclusively of coincidence relations, i.e. information on which γ-ray transitions are observed in mutual coincidence, without any prior knowledge of level ordering. The output is a complete decay scheme, including all reconstructed excited states and all γ-ray transitions connecting them. A naive brute-force approach based on random assignment of transitions to levels leads to a combinatorial explosion, with computational complexity worse than factorial in the number of transitions. For example, even assuming the generation of one billion candidate schemes per nanosecond, reconstructing a correct scheme for a system with only 32 transitions would require a time comparable to the age of the Universe.
By introducing a dedicated recursive algorithm that systematically exploits coincidence constraints, we reduce the effective complexity of the problem by many orders of magnitude. As a result, decay schemes containing up to 200 γ-ray transitions can be reconstructed in less than one second on standard personal computing hardware. Due to the stochastic nature of certain algorithmic choices, repeated runs may give a different decay schemes that all satisfy the coincidence conditions. This feature allows the use of additional experimental observations, such as transition intensities, to select the most physically plausible solution. In cases where an exact solution satisfying all coincidence relations cannot be found, the algorithm returns the best approximate scheme along with a clear indication of which coincidence requirements are violated.
We hope that this approach will help to streamline and accelerate nuclear spectroscopy studies. The developed program can be further extended by taking into account additional experimental information, such as γ-ray transition intensities, to select the most physically probable scheme and to supplement the decay scheme with additional nuclear quantities, which will further improve the analysis process.
References
[1] I. Adam, A. A. Byalko et al., Measurement Techniques, Vol. 40, No. 6 (1997).
[2] K. Jansson, D DiJulio et al., Nuclear Instruments & Methods in Physics Research. Section A, Vol. 654, No. 1 (2012)
| Contribution category | Experiment |
|---|---|
| Presenter status | Student |