Speaker
Description
A. Hjalmarsson1, L. Hägg1, S. Conroy1, J. Eriksson1, P. Ollus1, A. Jardin2, M. Rebai3, F. Scioscioli3, J. Koning4, B. Coriton5, A. Kovalev5
1. Department of Physics and Astronomy, Uppsala University, Lägerhyddsvägen1,75237 Uppsala, Sweden
2. Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, PL-31342 Krakow, Poland
3. Istituto per la Scienza e Tecnologia dei Plasmi, via Cozzi 53, Milano, Italy
4. Heemskerk Innovative Technology, Rotterdamseweg 183C, 2629 HD, Delft, The Netherlands
5. ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France
A High-Resolution Neutron Spectrometer (HRNS) system has been designed and integrated at ITER to a preliminary design level maturity. The system consists of four subsystems operating in overlapping fusion power ranges, a forward-scattering time-of-flight (fToF) neutron spectrometer, a back-scattering time-of-flight (bToF) neutron spectrometer, a neutron diamond detector (NDD), and a thin-foil proton recoil (TPR) spectrometer. In this contribution the preliminary design of the HRNS system and the methods used to validate the design will be presented.
HRNS is primarily designed to perform line-of-sight (LOS) integrated measurements of the fuel ion ratio (𝑛𝑡𝑛𝑑⁄) in the plasma core with an uncertainty of less than 20% under relevant ITER conditions. It should also provide information on the LOS integrated ion temperature (𝑇𝑖) with an uncertainty less than 10% with a data acquisition time of 100 ms.
The HRNS design is based on a performance analysis using synthetic data generated using ITER plasma transport simulations in a fusion power range of 0.5 MW to 500 MW. The synthetic neutron spectroscopy data is generated by folding the incoming HRNS neutron spectrum with a Monte-Carlo modelled detector response function, and applying a Poisson perturbation to the resulting response spectrum. For the HRNS design, neutron emission is modelled using two spectral components, a thermal component representing neutron emission from bulk plasma, and a beam-thermal component representing neutron emission from neutral beam heating ions fusing with bulk ions. These components, passed through the detector response function, are fitted to the synthetic spectroscopy data. From these fitted results the fuel ion ration and the ion temperature are evaluated for all scenarios, creating a map of how the system is expected to perform during different ITER plasma conditions.
With the current implemented design of the HRNS system, the system can estimate 𝑛𝑡/𝑛𝑑 and 𝑇𝑖, within the uncertainty requirements, in most of the operational regions of ITER investigated. For 𝑛𝑡𝑛𝑑⁄ results it is assumed that 𝑇𝑖 is supplied from another diagnostics. Without the 𝑇𝑖 as an input, 𝑇𝑖 is instead included as a free fitting parameter and the region where the HRNS can fulfill its requirements on 𝑛𝑡𝑛𝑑⁄ shrinks notably.
Acknowledgements
This work was supported by the ITER Organization and the Swedish Energy Agency (Grant No. P2023-01324), as well as the Polish Ministry of Science and Higher Education under the program entitled “international Projects Co-financed”. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.