Speaker
Description
A versatile R-matrix module for multi-channel reaction calculations was developed which allows not only phenomenological R-matrix analyses, but also extensions to new and non-standard formulations of R-matrix theory such as the Reduced R-matrix formulation and the hybrid R-matrix concept. An important feature of the module is the capability to combine standard R-matrix analysis with the result of calculable R-matrix calculations an important aspect for the realisation of the hybrid R-matrix approach [1]. The calculable R-matrix allows the solution of potential-based coupled-channel problems in terms of R-matrix parameters using the Lagrange-mesh technique [2]. The R-matrix module can be coupled with parameter optimization frameworks like the DAKOTA-package [3] and allows the analysis of experimental data in terms of R-matrix parameters. The flexible code structure enabled the development of several approaches such as the hybrid R-matrix using pseudo-potentials instead of background poles or the reduced R-matrix method which inherently accounts for threshold energies of channels not explicitly included in the analysis.
The new R-matrix module provides the collision matrix and can easily be included into the multi-channel code GECCCOS (GEneral Coupled-Channel COde System) which has been developed by the nuclear data group at TU-Wien to perform nuclear reaction calculations especially for light nuclear systems. Aiming at maximum flexibility regarding the inclusion of new or enhanced modules a clear structure regarding the calculation flow and the data transfer between modules was an important design goal. This ensured easy development and inclusion of new reaction modules as well as compatibility with existing codes for ENDF file generation. Furthermore the output of observables follows the scheme of the TALYS [4] code thus simplifying the combined use in nuclear data evaluation.
A successful run of the code yields the complete S-matrix (collision matrix) as well as observables for unpolarised beams, angle-differential cross sections, excitation functions, and angle-integrated cross sections (if existing). Recently an extension for obtaining the analysing power of spin 1/2 particles was successfully implemented and tested. The inclusion of polarisation observables for higher spin values is in progress. For phenomenological R-matrix analyses a separate module automatically assembles calculated and available experimental values, automatically performs reference frame transformations if necessary and calculates chi-square values as feedback for the parameter fitting process. In the presentation an overview of the design concept, implemented functionality and current status of development will be given together with an outlook on envisaged future developments.
Acknowledgement: The work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
References
[1] Th. Srdinko, H. Leeb, EPJ Web of Conferences 146, 12030 (2017).
[2] P. Descouvemont, D. Baye, Rep. Prog. Phys. 73, 036301 (2010).
[3] B.M. Adams, W.J. Bohnhoff, et al., Dakota, A Multilevel Parallel Object-Oriented Framework for Design Optimization, Parameter Estimation, Uncertainty Quantification, and Sensitivity Analysis (Version 6.12, User’s Manual, Sandia Technical Report SAND2020-12495, Nov. 2020).
[4] A.J. Koning, S. Hilaire and M.C. Duijvestijn, “TALYS-1.0”, Proc. of the Int. Conf. on Nuclear Data for Science and Technology, April 22-27, 2007, Nice, France, Eds.: O.Bersillon, F.Gunsing, E.Bauge, R.Jacqmin, and S.Leray, EDP Sciences, 2008, p. 211-214.