Mass spectrometry is a powerful tool for gaining insights into nuclear fusion, a promising energy source that mimics the Sun's power. It's crucial for understanding the complex reactions inside experimental reactors like ITER, which aims to replicate the Sun's fusion process. These reactors heat and confine a plasma containing deuterium and tritium to extreme temperatures, aiming to fuse them into helium, releasing vast amounts of energy. However, the extreme conditions inside these reactors make direct probes impractical, necessitating the use of external diagnostics to monitor the plasma and reaction progress.
Chris Marcus and his team at Oak Ridge National Laboratory (ORNL) are developing a system that combines mass spectrometry and optical spectroscopy to analyze the light gases released during the reaction. This system, in collaboration with Hiden Analytical, focuses on detecting small concentrations of helium-4, a key product of the fusion reaction. Standard instruments struggle to distinguish helium-4 from deuterium due to their similar masses, but the Hiden team's quadrupole mass spectrometer offers a solution.
The quadrupole design, favored for its rapid scanning and compactness, ionizes gas species and separates them based on their mass-to-charge ratio. However, conventional quadrupoles have limitations in resolving helium-4 and deuterium due to their minimal mass difference. Hiden's innovation lies in their ability to operate in a different stability zone, Zone H, which enables the detection of helium-4 at the required levels while maintaining a small sensor size.
One challenge was ensuring the system's resilience to the harsh environment near the tokamak, characterized by strong magnetic fields and high radiation. Hiden addressed this by employing a coaxial cable with intermediary electronics, or a matching unit, to transmit RF power over long distances without significant power loss. This setup, tested at a fusion facility, proved immune to radiation, magnetic fields, and ground vibrations, ensuring the sensor's performance.
The mass spectrometer's resolving power was evaluated at ORNL, demonstrating its ability to detect helium-4 at 3% concentration in a deuterium-rich mixture. This fast response time, under a second, is vital for real-time fusion diagnostics. Hiden has commercialized this technology, offering the DLS-2 and DLS-2X instruments, which provide dual-zone operation for high resolving power and residual gas analysis.
The HAL 101X, another Hiden instrument, incorporates features from the ORNL project, including dual-zone operation and radiation-hard electronics. It also introduces Threshold Ionization Mass Spectrometry (TIMS) for distinguishing between ions with similar mass-to-charge ratios. Hiden is now exploring the HAL 101X's capabilities in separating light gases like neon and tritium from hydrogen deuteride, which are crucial for fusion research.
Marcus and his team are evaluating the HAL 101X at ORNL, with plans to advance it into production for a comprehensive diagnostic suite. This system will provide valuable insights into the fusion process, contributing to the development of a sustainable and abundant energy source, while also pushing the boundaries of mass spectrometry in extreme environments.
