Impact of W Events and Dust on JET ­ ILW Operation

The occurrence of transient impurity events (TIE) leading to intense radiation spikes in JET plasma discharges has been studied since the installation of the ITER-likeWall (ILW). To generate the observed average increase in radiated power of 1.5MW, a 100µm-radius sphere of solidWdust would be required. The drop in plasma energy caused by W-TIEs is fully recovered in 90% of all cases, only 1% inducing a longer term loss in plasma energy which sometimes leads to the shut-down of plasma operation. TIEs are correlated with disruptions and with measurements of the dust mobilized by disruptions using the high resolution Thomson scattering (HRTS) diagnostic. The dust characteristics giving rise to TIEs have been studied using the dust transport code DTOKS and the 1D impurity transport code STRAHL.
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