Measurement of electromagnetic waves from runaway electrons

Area of Science:

• Plasma physics
• Fusion energy research
• Electromagnetic wave propagation

Background:

• Tokamak discharges generate electromagnetic waves through coupling with plasma waves.
• Runaway electrons in tokamaks emit signals carrying information about kinetic instabilities.
• Radio frequency (RF) emissions offer a unique diagnostic for studying fast particle behavior.

Purpose of the Study:

• To investigate RF emissions from runaway electron scenarios in tokamak plasmas.
• To analyze the frequency scaling of kinetic instabilities in the lower hybrid range.
• To estimate the radial location of runaway electron beam and plasma wave interactions.

Main Methods:

• Experiments conducted at the Frascati Tokamak Upgrade (FTU).
• Exploration of frequencies in the lower hybrid and whistler wave ranges.
• Simplified analysis of frequency scaling with respect to density profiles and wave vector coupling.

Main Results:

• Observed pronounced sensitivity of RF measurements in detecting driven instabilities.
• Demonstrated the potential of RF emissions as a monitor for instability processes.
• Provided a method for estimating the radial location of wave-particle interactions.

Conclusions:

• RF emission analysis is a valuable tool for studying fast electron activity in tokamaks.
• Understanding these emissions aids in monitoring plasma instabilities during discharge.
• The study offers insights into the interaction dynamics between runaway electrons and plasma waves.