Conceptual research on meeting tomographic reconstruction and measurement accuracy requirements: Key factors in the development of a radiated power diagnostics for DEMO

Abstract

This work addresses the development of diagnostics for core plasma radiated power and soft x-ray intensity measurements, which will be useful in future fusion reactors to ensure reliable plasma control (by monitoring the power loss across the separatrix) in accordance with the DEMO control requirements. For this purpose, we look into the development of such a detection system that will provide the required information via soft x-ray diagnostics. The target photon range for such a detecting system is considered to be 3–50 keV. The aspects of the development have included detailed diagnostics design, physics, engineering and integration studies, as well as an investigation into the feasibility and performance of the diagnostics and its components. The development is currently in the design phase. Nevertheless, the answer is already needed regarding the fulfillment of system requirements. In order to monitor the power crossing the separatrix, a precise estimation of the plasma radiation is needed to maintain the high-efficiency plasma. This requires strict measurement accuracy criteria, with 3% accuracy margin for the core plasma radiated power estimate and 5% noise for a single measurement of a single detector within the detector array. Here, an initial estimation of the detecting system's accuracy was provided based on an analysis of both the tomography reconstruction and detector measurement capabilities. The optimal number of lines of sight for tomography reconstruction was found for the considered plasma field of view. Additionally, the initial concept for a photon-sensitive chamber of the detecting system was developed. This allowed for the assessment of the predicted measurement accuracy of the detector for horizontal and vertical lines of sight.