Relaxation oscillations in the divertor of the ASDEX Upgrade tokamak

Relaxation oscillations found in the divertor of the ASDEX Upgrade tokamak by means of spectroscopy and probe diagnostics are reported. They are observed in both electron density and temperature with frequencies in the range from 45 to 80 Hz. In the line emission they are detected in C III, but not in Dalpha light. Interpretation of the experimental data indicates that the relaxation oscillations are associated with periodic movements of the thermal front and the power loss zone against each other