Intense millimetre wave bursts from plasmas well conditioned with lithium in the tokamak fusion test reactor

Intense bursts of millimetre wave emission are emitted from plasmas in TFTR when the graphite limiter is well conditioned with elemental lithium through the injection of lithium pellets. The bursts have been observed in ohmic and neutral beam heated plasmas fuelled with deuterium only, a mixture of deuterium and tritium or tritium only. The bursting is characterized by 5-10 mu s duration emission spikes of randomly varying amplitude. Spectral analysis of the millimetre wave emission reveals two components; broadband emission, which appears at frequencies below the second harmonic electron cyclotron frequency, and narrowband emission (Delta f < 3 GHz), with an equivalent radiation temperature of over 1 MeV and a frequency corresponding to the upper hybrid frequency near the low field plasma edge. The equivalent radiation temperature of the bursts increases with decreasing edge density, decreasing limiter recycling and increasing plasma stored energy.