From Simulation to Reality: How JOREK Is Shaping the Future of Fusion Energy

The Power of Prediction

Fusion energy represents the pinnacle of clean energy solutions, but the road to making it a reality is fraught with technical challenges. At the heart of overcoming these challenges lies the JOREK code, a powerful computational tool that simulates the complex dynamics of plasma within magnetic confinement fusion devices such as the tokamak and stellarator. JOREK’s predictive capabilities are crucial for designing and operating next-generation tokamaks like ITER. Its simulations of pedestal dynamics, edge-localized mode (ELM) suppression, and disruption mitigation strategies provide vital insights that inform the construction and operation of these massive fusion reactors.

For instance, JOREK’s detailed models of ELM suppression by resonant magnetic perturbations (RMPs) have shown that it’s possible to stabilize the plasma edge and avoid the damaging bursts of energy that ELMs can produce. These simulations not only predict the behaviour of plasma under different conditions but also help in developing strategies to mitigate these potentially harmful events.

Spotlight on Recent Findings

The recent review paper published in Nuclear Fusion highlights several breakthroughs achieved using JOREK. One significant advancement is the simulation of shattered pellet injection (SPI) for disruption mitigation in ITER with an unprecedented accuracy. These simulations have demonstrated that injecting pellets of frozen deuterium or other materials can rapidly cool the plasma, reducing negative disruption consequences such as heat loads that could otherwise damage the reactor​​.

Additionally, JOREK has provided insights into the mechanisms behind vertical displacement events (VDEs) and how impurity injection is able to reduce the forces acting onto machine components. Understanding these mechanisms is critical for designing effective mitigation strategies that can protect the reactor from mechanical stresses.

The research also delves into detailed modelling of the plasma and scrape-off layer in normal operation. A recent result focusses on the formation of so-called high-field side high-density (HFSHD) regions in ITER, shedding light on how these structures influence plasma stability and performance. These findings are instrumental in fine-tuning the design and operational parameters of future tokamaks to maximize their efficiency and safety.

JOREK in Action

Validation against experimental data is a cornerstone of JOREK’s development. The code’s predictive accuracy has been rigorously tested through comparisons with real-world experiments. For example, JOREK’s simulations of ELM suppression by RMPs have been validated with data from the ASDEX Upgrade tokamak, showing a strong correlation between predicted and observed behaviours. This validation reinforces confidence in JOREK’s models and their applicability to future reactors like ITER.

Moreover, JOREK’s role in understanding the dynamics of runaway electron (RE) beams, which can pose significant risks during disruptions, has been validated e.g. through experiments in the JET and KSTAR tokamaks. These studies provide indications of how RE beams can be controlled and mitigated, preventing damage to the reactor walls. “This area will remain a major focus of our research in the coming years, since the protection of large tokamaks from REs is essential, but also a particularly challenging task” says Matthias Hoelzl, group leader at Max Planck Institute for Plasma Physics and coordinator of the JOREK code development.

The Role of EUROfusion

The development and success of JOREK would not have been possible without the continuous support from EUROfusion. Through enabling research projects and the current theory and simulation projects on “MHD Transients” and “Runaway electrons in disruptions”, EUROfusion has been pivotal in turning initial efforts into a worldwide activity that significantly impacts fusion research. This collaboration has fostered the development of innovative solutions and attracted numerous talented researchers to the field.

Looking Ahead

The future applications of JOREK are vast and promising. As research progresses, JOREK will continue to play an essential role in ongoing and future tokamak projects. Its ability to simulate complex plasma behaviours with high accuracy makes it an invaluable tool for ensuring the success of fusion energy as a sustainable power source. A key to further progress is the development of efficient hybrid models, which capture effects not accessible in pure fluid simulations. Looking ahead, JOREK’s capabilities will be expanded to include more detailed kinetic models and enhanced integration with other simulation tools. “Combining traditional fluid models and kinetic models is instrumental in the struggle to understand all aspects of large-scale plasma dynamics and provide accurate predictions” says Guido Huijsmans, the original author of the code. These advancements will enable even more precise predictions and control strategies for plasma behaviour in fusion reactors. And these inputs are desperately needed as researchers around the world push forward reliable protection strategies of future fusion devices from major disruptions or edge localized modes.

In conclusion, JOREK is not just a simulation code; it is a cornerstone of fusion research, turning theoretical predictions into practical solutions. As we move closer to achieving sustainable fusion energy, JOREK will undoubtedly be at the forefront of this revolutionary journey, ensuring the safety, efficiency, and viability of future fusion power plants.

References:

1. Non-linear MHD modelling of transients in tokamaks: A review of recent advances with the JOREK code.
   • Link to the paper
     This paper reviews recent progress in non-linear MHD (magnetohydrodynamic) modelling of transient events in tokamaks using the JOREK code. It highlights key advancements and applications in fusion research.
2. Hoelzl, Matthias. Recent LinkedIn post announcing the publication of the review paper on JOREK.
   • Link to LinkedIn post
     Matthias Hoelzl’s LinkedIn post provided an update on the latest research and publication on non-linear MHD modelling with the JOREK code.
3. MHD Simulations of Neutral and Impurity Transport in ELM-controlled Plasmas.
   • Link to the paper
     Sven Korving’s thesis discusses MHD simulations focusing on neutral and impurity transport within edge-localized mode (ELM) controlled plasmas, providing insights into plasma behaviour and control mechanisms in tokamaks.

Read the previous article in the JOREK series: Unlocking the Mysteries of Plasma Dynamics: The Role of the JOREK Code in Fusion Energy Research