Kalman filter density reconstruction in ICRH discharges on ASDEX Upgrade

•Kalman filter and a heuristic model are used to identify false diagnostics.•False interferometry signals can reliably be detected in real-time on AUG.•States of a nonlinear distributed system are estimated amid corrupted diagnostics. Plasma density is one of the key quantities that need to be contr...

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Bibliographic Details
Published in:Fusion engineering and design 2021-09, Vol.170, p.112510, Article 112510
Main Authors: Bosman, T.O.S.J., Kudláček, O., Fable, E., van Berkel, M., Felici, F., Bock, A., Luda, T., de Baar, M.R.
Format: Article
Language:English
Subjects:
Algorithms
AUG
Bremsstrahlung
Cyclotron resonance
Density reconstruction
Discharge
Extended Kalman filter
Interferometers
Kalman filter
Plasma density
Prediction models
Real time
Reconstruction
Time measurement
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Summary:•Kalman filter and a heuristic model are used to identify false diagnostics.•False interferometry signals can reliably be detected in real-time on AUG.•States of a nonlinear distributed system are estimated amid corrupted diagnostics. Plasma density is one of the key quantities that need to be controlled in real-time as it scales directly with fusion power and, if left uncontrolled, density limits can be reached leading to a disruption. On ASDEX Upgrade (AUG), the real-time measurements are the line-integrated density, measured by the interferometers, and the average density derived from the bremsstrahlung measured by spectroscopy. For control, these measurements are used to reconstruct the radial density profile using an extended Kalman filter (EKF). However, in discharges where ion cyclotron resonance heating (ICRH) is used, the measurements from the interferometers are corrupted and the reconstructed density is false. In this paper, the existing EKF implementation is improved, implemented and experimentally verified on AUG. The new EKF includes a new particle transport model in the prediction model RAPDENS as well as a new representation of ionization and recombination. Furthermore, an algorithm was introduced that is capable of detecting the corrupt diagnostics; this algorithm is based on the rate of change of the innovation residual. The changes to the RAPDENS observer resulted in better density reconstruction in ICRH discharges where corrupt measurement occur. The new version has been implemented on the real-time control system at AUG and functions properly in ICRH discharges.
ISSN:0920-3796
1873-7196
DOI:10.1016/j.fusengdes.2021.112510