How to reach high temperatures of around 150 million degrees Celsius needed for fusion?

On the 15^th of April, our group leader Dr Mervi Mantsinen gave an online lecture entitled “Ion Cyclotron Resonance Frequency (ICRF) Heating in Fusion Plasmas” as part of the Fusion Technology Course of the Nuclear Engineering Master organized by the Department of Physics on Barcelona School of Industrial Engineering (ETSEIB) at Universitat Politècnica de Catalunya (UPC), Barcelona, Spain.

This course offers the students an overview on selected key topics in Fusion Technology, delivered by specialist lecturers from F4E, UPC and our Fusion group at Barcelona Supercomputing Center (BSC). The course is coordinated at UPC by Dr Shimpei Futatani who moved from our Fusion group to UPC two years ago.

In her lecture, Mervi first introduced the basic principles of electromagnetic wave propagation in plasmas. Thereafter, she focused on the use of electromagnetic waves in the ion cyclotron range of frequencies for plasma heating and current drive in fusion devices.

ICRF heating is one of the three external heating systems together with electron-cyclotron resonance heating and neutral beam injection that will be implemented on ITER. In ICRH heating, radiofrequency waves are injected into the plasma to transfer energy to the charged particles, or ions, that make up the fusion fuel.

By generating waves at a frequency that matches the oscillation of the ions perpendicular to the magnetic lines, i.e. the so-called ion cyclotron frequency, ICRH waves resonate with plasma ions, which leads to energy transfer from the radio waves to the plasma, analogous to heating food in a microwave oven.

The temperatures inside ITER must reach 150 million degrees Celsius, that is ten times the temperature at the core of the Sun, in order for the gas in the vacuum chamber to reach the plasma state and for the fusion reaction to occur. The hot plasma must then be sustained at these extreme temperatures in a controlled way in order to extract energy.

Ultimately, researchers aim to achieve a “burning plasma” where the energy of the helium nuclei produced by the fusion reaction is enough to maintain the temperature of the plasma. The external heating can then be strongly reduced or switched off altogether.