Observation and analysis of maser activity in a tokamak plasma

High-resolution spectral measurements of electron plasma-frequency emission from alcator C tokamak reveal a level of coherence indicative of maser activity (Δω/ω=6×${10}^{\mathrm{-}6}$). A full-wave theoretical analysis yields the complete mode structure of the electromagnetic fields as well as the dispersion relation. This analysis shows that for wave frequencies near the central plasma frequency the waves are highly localized and thereby the plasma forms a high-Q cavity for these waves.