UC Davis PDG:ECE Imaging Diagnostics

Electrons that gyrate around magnetic field lines give rise to emission at harmonics of the electron cyclotron frequency. If the electrons are sufficiently hot and sufficiently dense, then the plasma is considered optically thick. Under these conditions, the electron cyclotron emission (ECE) is directly proportional to the electron temperature and independent of all other plasma parameters.

In tokamak plasmas, the total magnetic field decreases monotonically with radius. As the electron cyclotron frequency is proportional to the total magnetic field, the emissions at a given frequency are emitted from a very specific layer of the plasma corresponding to a given magnetic field. Measuring the emission power as a function of frequency allows the electron temperature to be computed as a function of plasma radius. Spatially imaging the emission onto an array of detectors expands the capabilities of ECE radiometry to include ECE imaging.

High temporal and spatial resolution ECE imaging systems have been developed to measure the electron cyclotron emission of tokamak plasmas. The novel diagnostic systems can measure the plasma electron temperature profiles with a spatial resolution of about 1 cm. The power spectral densities and dispersion relations of electron temperature fluctuations can be measured by applying correlation techniques. ECE imaging diagnostics can perform 2D measurements of electron temperature profiles and fluctuations, and poloidal correlation measurements of electron temperature fluctuations. 

The unique features of the ECE Imaging diagnostics derive from the use of wideband, low cost monolithic and hybrid Schottky diode mixer arrays. Follow the links below to learn more about both the technogy and the techniques employed in ECE Imaging. 

Imaging array design and fabrication
Correlation Measurements

UC Davis has fabricated and installed multichannel ECE Imaging systems on a number of fusion plasma tokamaks across the world. Follow the links below for a description of the systems involved, and to sample data collected with these systems. 

ECE Imaging on the TEXT-U tokamak in the U.S.A.
ECE Imaging on the RTP tokamak in the Netherlands
ECE Imaging on the TEXTOR tokamak in Germany

Comments to: Calvin Domier