When a neutron source becomes the sample
10 Sep 2026 - Stephanie Richardson
A team from Tokamak Energy recently visited ISIS to carry out an unusual user experiment: bringing a neutron source as a sample.
Based in Oxfordshire, not far from ISIS and the Rutherford Appleton Laboratory, Tokamak Energy is developing technologies to help make commercial fusion energy a reality.
Fusion, the process that powers the Sun, works by heating hydrogen isotopes to form a plasma at temperatures over 100 million degrees Celsius. When the nuclei fuse, they release large amounts of energy, with the majority carried by the neutrons produced in the reaction. These neutrons not only enable the capture of fusion energy but also provide valuable information about conditions inside the plasma, including how effectively fusion reactions are taking place, making neutron measurements an important tool in fusion research.
The visiting team from Tokamak Energy included Margarita Iliasova, Kamya Chandrasekhar, Mayank Rajput and Reza Mirfayzi. The group specialises in fusion diagnostics and neutronics, developing and using instruments to measure neutrons produced in fusion plasmas. These measurements help researchers understand what is happening inside the plasma and assess the performance of fusion experiments.
To ensure accurate measurements on ST40, the world’s highest-field spherical tokamak, neutron detectors must be calibrated against sources with known properties. These sources must also be compact enough to fit inside the tokamak vessel for in-vessel calibration. As part of this work, the Tokamak Energy team used NILE to characterise their neutron generator, which will be used both for in-vessel calibration and to calibrate ST40’s neutron diagnostics ahead of the device’s planned restart next year.
“We first learned about ISIS’s capabilities during a visit a few years ago, and this project provided the opportunity to work with them directly,” said Margarita. “The facilities and expertise available at NILE, combined with access within the timescales we needed, made ISIS an ideal place to carry out these measurements.”
The facilities and expertise available at NILE, combined with access within the timescales we needed, made ISIS an ideal place to carry out these measurements.
Margarita Iliasova, Tokamak Energy
Working with ISIS Instrument Scientists Carlo Cazzaniga and Maria Kastriotou, the team used NILE’s detector systems to measure the neutron output of their generator. Since the Tokamak Energy team’s generator has similar characteristics to the NILE source, it could be integrated directly into the existing experimental setup, allowing the team to take advantage of the facility’s instrumentation and shielding infrastructure.
“It’s not every day that a neutron source becomes the sample,” remarked Carlo. “As a standalone instrument, NILE operates independently of the ISIS accelerator, giving users more flexible access to this specialist facility when they need it.”
The project highlights how ISIS facilities and expertise can support a wide range of industrial and research challenges, from advanced detector development to the technologies needed for future fusion energy systems.
