What ECE measures
Plasma electrons radiate at harmonics of the cyclotron frequency. Where the plasma is optically thick, the emission gives a local measurement of the electron temperature along the radius, and the time/spectral analysis of the signal also lets us detect MHD modes — both essential for controlling the plasma. Turning this into a working diagnostic on DEMO is mostly a matter of architecture, waveguides and integration.
Why DEMO is hard
Unlike present machines, DEMO combines an intense neutron/gamma environment with tight integration constraints: limited access ports, qualified materials, mirror durability, and lines shared with ECRH and reflectometry. The design answers with robust waveguides, careful front-end choices and a redundant line-of-sight layout.
Characterizing the antennas (microwave tests)
To pin down the front-end, we characterise candidate antennas on the bench with microwave techniques — work carried out here in the DEMO context. We measure the horn pattern from near- to far-field and check the behaviour of pseudo-CPC concentrators against a 140 GHz source.
Where the work stands
The current effort revises the ECE Design Description Document (DDD) against the new DEMO baseline and reports the conceptual-design studies (deliverables D001 — revised DDD, and D002 — final report). A companion, exploratory line — a multifunctional THz-TDS diagnostic tested on the WEST tokamak — feeds the same competences (see the THz and Reflectometry pages).
Key publications
- M. Alonzo, M. Zerbini, G. Rocchi, “Electron Cyclotron Emission Diagnostics for Next Generation Nuclear Fusion Experiments, such as DEMO”, IRMMW-THz (2023).
- M. Zerbini, “Plasma diagnostic techniques based on terahertz radiation”, Applied Physics Reviews 12 (2025).