The European Domestic Agency for ITER, Fusion for Energy, has signed a four-year Framework Partnership Agreement with a consortium formed by European research centres—DTU Denmark and IST-IPFN Portugal—for the development and design of the Collective Thompson Scattering diagnostic for ITER.
The primary objective of the Collective Thomson Scattering (CTS) diagnostic is to monitor fast ion behaviour across the plasma radius in seven locations. Fast ions are elusive particles that are a natural consequence of the fusion process and plasma heating techniques. Although they represent less than five percent of plasma density, fast ions carry up to one-third of the plasma’s kinetic energy. Optimizing their confinement within the plasma is important as they play a major part in sustaining the high plasma temperatures required for fusion by colliding with—and transferring their energy to—the 'bulk' particles in the plasma.
However, fast ions behave unpredictably; while some remain within the magnetic field, others escape the plasma and reduce confinement, or ’cause mischief' by contributing their energy to and amplifying plasma disturbances.
The CTS diagnostic system will consist of mirrors and antennas integrated into one of the equatorial ports of the ITER machine. The upper antenna and mirrors will launch a powerful, single and high frequency microwave beam (1 MW at 60 GHz, equivalent to 1,000 microwave ovens at full power) into the plasma and record the scattered electromagnetic waves through the lower mirrors and receiver antennas. These measurements will allow scientists to establish the dynamics and distribution of the ions in the plasma—in particular the fast ions.