Optimization of the computation of total and local radiated power at ASDEX Upgrade

Radiation losses are measured as a line integrated quantity from the plasma, on ASDEX Upgrade using foil bolometers. Based on these measurements, the computation of the radiated power from either the whole volume or any sub region requires post processing including key assumptions. A new algorithm to improve this computation was recently developed and benchmarked. The algorithm is based on a routinely used tomography method and allows for local radiative events to be properly taken into account. It is compared to two other methods used at ASDEX Upgrade: the generic one based on flux tube symmetry and a more specific method using a 1D fit to compute the radiation excluding the divertor. In benchmarks with phantom radiation distributions, the new method shows a significantly better accuracy of −2.9 ± 5.2% in comparison to the previous algorithm accuracy of −27.8 ± 21.4% (average ± standard deviation on all test cases of the benchmark). The new code also allows the systematic computation of the radiated power from four sub regions, such as the divertor, the main chamber and inside the separatrix. (paper)