Saturday 01 March 2025
Researchers at the Institute for Plasma Research in India have made a significant breakthrough in understanding and controlling sawtooth oscillations in tokamaks, devices designed to mimic the conditions of fusion reactions.
Sawtooth oscillations are a common phenomenon observed in tokamaks, where the plasma core temperature suddenly increases, followed by a crash. This instability can lead to disruptions in the plasma confinement, which can ultimately prevent the achievement of sustained fusion reactions.
To control sawtooth oscillations, researchers have traditionally relied on external heating methods, such as electron cyclotron resonance (ECR) or lower hybrid (LH) heating. However, these methods require complex equipment and are not always effective.
In this study, scientists from India used a novel approach to control sawtooth oscillations by injecting short pulses of gas into the plasma edge. The injected gas creates a cold pulse that propagates towards the core of the plasma, modifying its density profile and suppressing the growth of trapped electron modes (TEMs), which are responsible for the sawtooth instability.
The researchers used the ADITYA-U tokamak to conduct their experiments, observing a significant delay in the onset of sawteeth following gas injection. The observed delay was found to be proportional to the amount of gas injected, indicating that the method is effective and can be controlled.
Furthermore, the study revealed that the temperature profile inside the q=1 surface, where the sawtooth instability is most prominent, plays a crucial role in determining the stability of the plasma. By modifying this profile through gas injection, researchers were able to delay the onset of sawteeth and achieve more stable plasma conditions.
The findings of this study have significant implications for the development of fusion energy. By controlling sawtooth oscillations using novel methods like gas injection, researchers can improve the confinement and stability of plasmas, ultimately paving the way for the achievement of sustained fusion reactions.
The success of this approach also highlights the importance of understanding the complex interactions between plasma and external heating sources. As researchers continue to explore new methods for controlling sawtooth oscillations, this study demonstrates the potential benefits of considering novel approaches that can be integrated into existing tokamak designs.
Cite this article: “Controlling Sawtooth Oscillations in Tokamaks through Gas Injection”, The Science Archive, 2025.
Tokamaks, Plasma, Fusion, Sawtooth Oscillations, Instability, Confinement, Stability, Gas Injection, Electron Cyclotron Resonance, Lower Hybrid Heating
