Real-time estimation and control of the electron density with a novel multi-rate observer on TCV*

The estimation and control in real time of the electron density for tokamaks is fundamental for its operation in many experimental conditions and scenarios. A precise assessment of the electron density profile during the discharge enables a more accurate control of various derived quantities, such as core, edge and line-averaged electron density within the LCFS.

Building on the integration of RAPDENS into the TCV plasma control system [1], this follow-up study explores its application to density control for detachment studies and high-performance H-mode scenarios.

The RAPDENS-based density profile observer combines the spatial resolution of Thomson Scattering with the high time resolution of the FIR to obtain a reliable density profile estimate, which is then employed to control the normalized edge density [2] for advanced tokamak scenarios in H-mode plasmas.

Experiments demonstrated the observer’s capability to support detachment studies in complex divertor geometries by accurately controlling the line-averaged density within the LCFS while avoiding divertor pick-up of the FIR signal.

Unknown plasma parameters can be estimated and adapted in real-time through the Kalman filter algorithm, such as fuelling efficiency and particle transport coefficients, for enhanced model robustness.

[1] F. Pastore et al., Fus. Eng. Des vol.192, p.113615,doi:10.1016/j.fusengdes.2023.113615, 2023.

[2] M. Bernert et al 2015 Plasma Phys. Control. Fusion 57 014038, doi: 10.1088/0741-3335/57/1/014038