Abstract: In particular embodiments, anomalous plasma events, which may include formation of an electric arc in a semiconductor processing chamber, may be detected and mitigated. In certain embodiments, a method may include detecting an optical signal emitted by a plasma, converting the optical signal to a voltage signal, and forming an adjusted voltage signal. Responsive to determining that the changes associated with the adjusted voltage signal exceed a threshold, an output power of an RF signal coupled to the chamber may be adjusted. Such adjustment may mitigate formation of the anomalous plasma event occurring within the chamber.