EFDA-JET-CP(09)05/02

Impurity Radiation for Detecting Arcs during High Lower Hybrid Power Transmission at JET

During high power commissioning of the JET LH launcher, the radiation and impurity release has been analyzed from various diagnostics: VUV and visible spectroscopy, bolometry. These two last diagnostics have lines-of-sight viewing the launcher and can provide information about the electron and/or impurity source localisation. Using a database of 800 plasmas, it is concluded that the iron contamination (FeXV and FeXXIII) is very low for 94% of the pulses and increases linearly with LH power. During arcs, a strong and fast increase of the radiation along the line-of-sight viewing the launcher is observed. This diagnostic could provide a tool for arc detection complementary to the RF measurements aiming at reducing the metal contamination in the plasma.
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EFDC090502 1.39 Mb