This paper introduces a recent innovation in dealing with non-periodic behavior often referred to as transients. These transients can be the result from unforced response due to the initial condition and other drifts which are a source of error when performing and interpreting Fourier analysis on measurement data. Fourier analysis is particularly relevant in system identification used to build feedback controllers and the analysis of various pulsed experiments such as heat pulse propagation studies. The basic idea behind the methodology is that transients are continuous complex-valued smooth functions in the Fourier domain which can be estimated from the Fourier data. Then, these smooth functions can be approximately subtracted from the data such that only periodic components are retained. The merit of the approach is shown in two experimental examples, i.e., heat pulse propagation (core transport analysis) and radiation front movement due to gas puffing. The examples show that the quality of the data is significantly improved such that it allows new interpretation of the results even for non-ideal measurements.

VL - 62 IS - 9 U1 -FP

U2 -ESC

U5 - e00c223abaa800570057a8357cb31b33 ER - TY - JOUR T1 - Real-time plasma state monitoring and supervisory control on TCV JF - Nuclear Fusion Y1 - 2019 A1 - Blanken, T. C. A1 - Felici, F. A1 - Galperti, C. A1 - Vu, T. A1 - Kong, M. A1 - Sauter, O. A1 - M. R. de Baar A1 - EUROfusion MST1 Team A1 - TCV team AB - In ITER and DEMO, various control objectives related to plasma control must be simultaneously achieved by the plasma control system (PCS), in both normal operation as well as off-normal conditions. The PCS must act on off-normal events and deviations from the target scenario, since certain sequences (chains) of events can precede disruptions. It is important that these decisions are made while maintaining a coherent prioritization between the real-time control tasks to ensure high-performance operation. In this paper, a generic architecture for task-based integrated plasma control is proposed. The architecture is characterized by the separation of state estimation, event detection, decisions and task execution among different algorithms, with standardized signal interfaces. Central to the architecture are a plasma state monitor and supervisory controller. In the plasma state monitor, discrete events in the continuous-valued plasma state are modeled using finite state machines. This provides a high-level representation of the plasma state. The supervisory controller coordinates the execution of multiple plasma control tasks by assigning task priorities, based on the finite states of the plasma and the pulse schedule. These algorithms were implemented on the TCV digital control system and integrated with actuator resource management and existing state estimation algorithms and controllers. The plasma state monitor on TCV can track a multitude of plasma events, related to plasma current, rotating and locked neoclassical tearing modes, and position displacements. In TCV experiments on simultaneous control of plasma pressure, safety factor profile and NTMs using electron cyclotron heating (ECH) and current drive (ECCD), the supervisory controller assigns priorities to the relevant control tasks. The tasks are then executed by feedback controllers and actuator allocation management. This work forms a significant step forward in the ongoing integration of control capabilities in experiments on TCV, in support of tokamak reactor operation. VL - 59 IS - 2 U1 - FP U2 - TP U5 - 8c9a3b3c0375e6885b35e4e5874c62e0 ER - TY - JOUR T1 - Model-based real-time plasma electron density profile estimation and control on ASDEX Upgrade and TCV JF - Fusion Engineering and Design Y1 - 2019 A1 - Blanken, T. C. A1 - Felici, F. A1 - Galperti, C. A1 - Kudlacek, O. A1 - Janky, F. A1 - Mlynek, A. A1 - Giannone, L. A1 - Lang, P. T. A1 - Treutterer, W. A1 - M. R. de Baar A1 - Heemels, W. P. M. H. AB - Real-time plasma electron density profile estimation and control are essential in the operation of future tokamaks. In particular, the robustness against diagnostics failure and disturbances is important for long pulse operation. A model-based approach to profile estimation is implemented on the control systems of ASDEX Upgrade and TCV, which is able to merge information from various diagnostics for both core and edge density, as well as systematically handling diagnostic failure. The model used for profile estimation is employed to tune a feedback controller before an experiment, thereby reducing the experimental time required for tuning. Subsequently, this observer and controller have been employed in scientific experiments on ASDEX Upgrade and TCV. On ASDEX Upgrade, the density profile estimator was used in high-density pellet-fuelled discharges, providing a more reliable real-time estimate of the core density for feedback control than previously achieved. On TCV, in experiments on integrated pressure and safety factor profile control, the density profile estimator and feedback controller provide a constant density despite disturbances from time-varying ECCD power. Additionally, the real-time density profiles provide an essential input for other real-time plasma state estimation codes including Electron Cyclotron ray tracing codes, contributing to a complete real-time estimation of the entire plasma state. VL - 142 U1 - FP U2 - TP U5 - ba04f3c64979227f0173cffd3afac99f ER - TY - JOUR T1 - MANTIS: A real-time quantitative multispectral imaging system for fusion plasmas JF - Review of Scientific Instruments Y1 - 2019 A1 - Perek, A. A1 - Vijvers, W. A. J. A1 - Andrebe, Y. A1 - Classen, I. G. J. A1 - Duval, B. P. A1 - Galperti, C. A1 - Harrison, J. R. A1 - Linehan, B. A1 - Ravensbergen, T. A1 - Verhaegh, K. A1 - M. R. de Baar A1 - TCV team A1 - EUROfusion MST1 Team AB -This work presents a novel, real-time capable, 10-channel Multispectral Advanced Narrowband Tokamak Imaging System installed on the TCV tokamak, MANTIS. Software and hardware requirements are presented together with the complete system architecture. The image quality of the system is assessed with emphasis on effects resulting from the narrowband interference filters. Some filters are found to create internal reflection images that are correlated with the filters’ reflection coefficient. This was measured for selected filters where significant absorption (up to 65% within ∼70 nm of the filter center) was measured. The majority of this was attributed to the filter’s design, and several filters’ performance is compared. Tailored real-time algorithms exploiting the system’s capabilities are presented together with benchmarks comparing polling and event based synchronization. The real-time performance is demonstrated with a density ramp discharge performed on TCV. The behavior of spectral lines’ emission from different plasma species and their interpretation are qualitatively described.

VL - 90 IS - 12 U1 -FP

U2 -PEPD

U5 - 5355a89839c5513fe91f52dfac500f3d ER - TY - JOUR T1 - TORBEAM 2.0, a paraxial beam tracing code for electron-cyclotron beams in fusion plasmas for extended physics applications JF - Computer Physics Communications Y1 - 2018 A1 - Poli, E. A1 - Bock, A. A1 - Lochbrunner, M. A1 - Maj, O. A1 - Reich, M. A1 - Snicker, A. A1 - Stegmeir, A. A1 - Volpe, F. A1 - Bertelli, N. A1 - Westerhof, E. A1 - Bilato, R. A1 - Conway, G. D. A1 - Farina, D. A1 - Felici, F. A1 - Figini, L. A1 - Fischer, R. A1 - Galperti, C. A1 - Happel, T. A1 - Lin-Liu, Y. R. A1 - Marushchenko, N. B. A1 - U. Mszanowski A1 - Poli, F. M. A1 - Stober, J. A1 - Zille, R. A1 - Peeters, A. G. A1 - Pereverzev, G. V. KW - Electron cyclotron waves KW - Magnetic confinement KW - Paraxial beam tracing KW - Plasma physics KW - Wave-plasma interactions AB -The paraxial WKB code TORBEAM (Poli, 2001) is widely used for the description of electron-cyclotron waves in fusion plasmas, retaining diffraction effects through the solution of a set of ordinary differential equations. With respect to its original form, the code has undergone significant transformations and extensions, in terms of both the physical model and the spectrum of applications. The code has been rewritten in Fortran 90 and transformed into a library, which can be called from within different (not necessarily Fortran-based) workflows. The models for both absorption and current drive have been extended, including e.g. fully-relativistic calculation of the absorption coefficient, momentum conservation in electron–electron collisions and the contribution of more than one harmonic to current drive. The code can be run also for reflectometry applications, with relativistic corrections for the electron mass. Formulas that provide the coupling between the reflected beam and the receiver have been developed. Accelerated versions of the code are available, with the reduced physics goal of inferring the location of maximum absorption (including or not the total driven current) for a given setting of the launcher mirrors. Optionally, plasma volumes within given flux surfaces and corresponding values of minimum and maximum magnetic field can be provided externally to speed up the calculation of full driven-current profiles. These can be employed in real-time control algorithms or for fast data analysis.

VL - 225 U1 -FP

U2 -IMM

U5 - 0a1c01a94caffb41c92a033957ecb032 ER - TY - JOUR T1 - Profile control simulations and experiments on TCV: a controller test environment and results using a model-based predictive controller JF - Nuclear Fusion Y1 - 2017 A1 - Maljaars, B. A1 - Felici, F. A1 - Blanken, T. C. A1 - Galperti, C. A1 - Sauter, O. A1 - M. R. de Baar A1 - Carpanese, F. A1 - Goodman, T. P. A1 - Kim, D. A1 - Kim, S. H. A1 - Kong, M. A1 - Mavkov, B. A1 - Merle, A. A1 - Moret, J. A1 - Nouailletas, R. A1 - Scheffer, M. A1 - Teplukhina, A. A1 - Vu, T. AB - The successful performance of a model predictive profile controller is demonstrated in simulations and experiments on the TCV tokamak, employing a profile controller test environment. Stable high-performance tokamak operation in hybrid and advanced plasma scenarios requires control over the safety factor profile (q-profile) and kinetic plasma parameters such as the plasma beta. This demands to establish reliable profile control routines in presently operational tokamaks. We present a model predictive profile controller that controls the q-profile and plasma beta using power requests to two clusters of gyrotrons and the plasma current request. The performance of the controller is analyzed in both simulation and TCV L-mode discharges where successful tracking of the estimated inverse q-profile as well as plasma beta is demonstrated under uncertain plasma conditions and the presence of disturbances. The controller exploits the knowledge of the time-varying actuator limits in the actuator input calculation itself such that fast transitions between targets are achieved without overshoot. A software environment is employed to prepare and test this and three other profile controllers in parallel in simulations and experiments on TCV. This set of tools includes the rapid plasma transport simulator RAPTOR and various algorithms to reconstruct the plasma equilibrium and plasma profiles by merging the available measurements with model-based predictions. In this work the estimated q-profile is merely based on RAPTOR model predictions due to the absence of internal current density measurements in TCV. These results encourage to further exploit model predictive profile control in experiments on TCV and other (future) tokamaks. VL - 57 IS - 12 U1 - FP U2 - TP U5 - 11fda966ffb74ee26df776e7fcabd37d ER -