Ruolo delle instabilità localizzate al bordo del plasma di JET nel confinamento delle impurezze pesanti

The purpose of this thesis is to evaluate how efficaciously edge localized mode (ELM) can control heavy impurity (W) in JET's plasma. To do this we studied some plasma pulses' sets made at JET (each pulse had a different ELM's frequency), using blometry and spettrography to select those which were stable enough. Once we had a new set of stable shots, using a softwere (which make a deconvolution of Soft X Rays data) made by T. Puttrich, we have computed the W's concentration in the plasma for each different ELM's frequency taking advantage of sawtooth's profile to achive higher precision. The results suggest that higher ELM's frequency are correlated to lower concentration of W. Looking for other proof for ours data, we studied the Kr behavior and W SXR emission directly and both of them confirmed ours results. In addition, we computed the W's fluxes from the divertor, using photon's ones, reciving an additional confirmation. In conclusion we can say that ELMs can be used for heavy impurities' control.