Researchers from Milan, Italy, have made a significant leap in understanding the fundamental properties of matter at the staggering temperature of 150 million degrees, a feat that could reshape our approach to nuclear fusion. This breakthrough hinges on measuring the intrinsic radiation emitted from fusion plasma, a hot ionized gas that is the key to harnessing the power of nuclear fusion for energy production. Nuclear fusion, the process that fuels the stars, releases an immense amount of energy when light nuclei combine to form heavier nuclei. The energy release, described by Einstein’s famous equation E=Δmc², underscores why scientists are so eager to replicate this process on Earth.
Achieving nuclear fusion requires meeting several stringent conditions. The plasma’s core must reach temperatures approximately ten times higher than those found at the core of the Sun. Additionally, the plasma must maintain a high density to ensure sufficient fuel undergoes fusion, and the energy produced must remain within the system long enough to sustain the reaction with minimal external input. This intricate balance is what makes measuring the properties of a fusion reactor’s core so critical.
One of the most pressing challenges is how to measure temperatures and other properties at such extreme conditions without destroying the measuring instruments. Traditional probes are out of the question; they would be obliterated by the plasma. Instead, researchers have turned their attention to the intense electromagnetic and nuclear radiation emitted by the fusion process itself. This radiation includes neutrons, which serve as energy carriers, and gamma rays produced during various nuclear reactions.
The neutron and gamma-ray diagnostics group at the University of Milano-Bicocca and the Institute for Plasma Science and Technology has emerged as a leader in designing instruments that can measure this radiation. Neutrons, in particular, pose a unique challenge for detection due to their uncharged nature and the fact that they interact infrequently with matter. However, the energy spectrum of the neutrons released during deuterium-tritium fusion reactions provides valuable insight into the plasma’s properties, acting as a “fingerprint” of the fusion process.
To capture these elusive neutrons, researchers are developing specialized spectrometers tailored for specific applications. Some instruments, like small detectors made from inorganic scintillators or synthetic diamonds, are designed for easy integration into the complex environments of tokamaks. Others, such as time-of-flight or magnetic proton recoil instruments, require more intricate designs but offer heightened sensitivity for detecting subtle changes in fuel properties.
In addition to neutrons, the presence of energetic particles, including fast ions and runaway electrons, complicates diagnostics. These particles emit high-energy gamma rays, which can provide further insights into fusion reactions. However, detecting these gamma rays is also challenging, as they interact sporadically with matter and often release only a fraction of their energy during detection.
As the field moves towards achieving burning plasma conditions—where the fusion process is self-sustaining—advancements in nuclear diagnostics become even more critical. Projects like ITER in Europe, SPARC in the United States, and BEST in China are at the forefront of this pursuit. The success of these initiatives hinges on our ability to accurately measure and understand the complex dynamics of fusion plasma.
The implications of this research extend far beyond the laboratory. If scientists can successfully harness nuclear fusion, it could revolutionize energy production, providing a nearly limitless, clean source of power. As the world grapples with climate change and dwindling fossil fuel resources, the quest for fusion energy has never been more urgent. This latest breakthrough in measuring plasma properties at extreme temperatures not only enhances our understanding of fusion but also brings us one step closer to realizing its potential as a viable energy source.
