arXiv subjects

M. van Berkel

Publications and source records attributed to M. van Berkel.

5 recordsLinked to original sources

arXiv2026

Detachment dynamics and disturbance rejection in the TCV X-Point Target divertor

The X-Point Target divertor is an alternative divertor configuration with a secondary X-point in its divertor volume. In this work, we investigate the dynamic response and disturbance rejection capacity of the XPT configuration on the TCV tokamak, comparing it to a single null (SN) divertor. We employ a system identification approach using multi-sine perturbations to measure the dynamic response of the detached state in both Ohmic and auxiliary-heated L-mode scenarios upon D$_2$ fuelling, N$_2$ seeding and Electron Resonance Cyclotron Heating (ECRH) power modulations. We demonstrate an inherent disturbance rejection capacity of the XPT at its secondary X-point compared to a SN configuration for all perturbation scenarios. Upstream of its secondary X-point, the dynamic response of the detached state between the XPT and SN appears similar. The disturbance rejection capacity of the XPT could be highly beneficial for passively buffering disturbances that cannot be effectively managed by power exhaust controllers. At the same time, it presents a challenge for monitoring the detached state close to the secondary x-point.

physics.plasm-ph↗

arXiv2026

Fuelling fusion plasmas with pellets: Can neuromorphic control outperform Sigma-Delta modulation?

Nuclear fusion is a promising clean energy source in which deuterium and tritium fuse inside a magnetically confined plasma in a tokamak, releasing energy. A key challenge on the route to practical nuclear fusion is the control of the plasma density which has to be done through adding fuel in the form of deuterium and tritium to the plasma. Pellet injection, firing frozen fuel into the plasma, is used to accomplish this. Since the injection of a pellet causes an almost instantaneous increase in particle density compared to the time scales of the plasma dynamics, the problem is of a hybrid nature in which continuous plasma dynamics are interrupted by discrete bursts of particles. In this paper, we propose a formal hybrid model for this fuelling process and we propose a new, neuron-inspired control method that treats pellets much like spikes as in a brain-like system. The neuromorphic controller offers a lightweight solution that naturally fits the hybrid character of pellet fuelling. For comparison, we also develop a hybrid model of sigma-delta modulation, which is used in current tokamaks. For both the neuromorphic controller and the sigma-delta modulation we present formal analysis results for this control problem in nuclear fusion. We derive explicit actuator and controller parameter constraints, key for controller tuning, that lead to practical stability guarantees. Numerical simulations compare the different controller variants and validate the theoretical results.

eess.SY↗

arXiv2025

Nuclear fusion plasma fuelling with ice pellets using a neuromorphic controller

In reactor-grade tokamaks, pellet injection is the best candidate for core plasma fuelling. However, density control schemes that can handle the hybrid nature of this type of fuelling, i.e., the discrete impact of the pellets on the continuously evolving plasma density, are lacking. This paper proposes a neuromorphic controller, inspired by the integrate-and-fire neuronal model, to address this problem. The overall system is modelled as a hybrid system, and we analyse the proposed controller in closed loop with a single-input single-output linear time-invariant plasma model. The controller generates spikes, representing pellet launches, when the neuron variable reaches a certain threshold. Between the control actions, or spikes, the system evolves in open loop. We establish conditions on the controller variables and minimum actuator speed, depending on the reference value for the desired density, the pellet size and the time-constant of the plasma density, that guarantee a practical stability property for the closed-loop system. The results are illustrated in a numerical example.

eess.SY↗

arXiv2024

First demonstration of Super-X divertor exhaust control for transient heat load management in compact fusion reactors

Nuclear fusion could offer clean, abundant energy. However, managing the immense power exhausted from the core fusion plasma towards the divertor remains a major challenge. This is compounded in emerging compact reactor designs which promise more cost-effective pathways towards commercial fusion energy. Alternative divertor configurations (ADCs) are a potential solution to this challenge. In this work, we demonstrate exhaust control in ADCs for the first time, on MAST-U. We employ a novel diagnostic strategy for the neutral gas buffer which shields the target. Our work shows that ADCs tackle key risks and uncertainties in realising fusion energy: 1) an enlarged operating window which 2) improves exhaust control through the absorption of transients which can remove the neutral shield and damage the divertor, 3) isolation of each divertor from other reactor regions, enabling combined control. This showcases real-world benefits of alternative divertors for effective heat load management and control in reactors.

physics.plasm-ph↗

arXiv2021

Model-based electron density profile estimation and control, applied to ITER

In contemporary magnetic confinement devices, the density distribution is sensed with interferometers and actuated with feedback controlled gas injection and open-loop pellet injection. This is at variance with the density control for ITER and DEMO, that will depend mainly on pellet injection as an actuator in feed-back control. This paper presents recent developments in state estimation and control of the electron density profile for ITER using relevant sensors and actuators. As a first step, Thomson scattering is included in an existing dynamic state observer. Second, model predictive control is developed as a strategy to regulate the density profile while avoiding limits associated with the total density (Greenwald limit) or gradients in the density distribution (e.g. neo-classical impurity transport). Simulations show that high quality density profile estimation can be achieved with Thomson Scattering and that the controller is capable of regulating the distribution as desired.

physics.plasm-ph↗