Effect of Poloidal Rotation on the Predictions for the Dynamics of the ITBs and Transport in JET Plasmas

Recent results from the measurements of carbon plasma rotation velocity across Internal Transport Barriers (ITBs) on JET show that the velocities are typically an order of magnitude higher than the neo-classical predictions [1]. As a consequence, the radial electric field can be very different from that calculated using the neo-classical value for vpol. This gives further rise to different wE¥B shearing rates, as normally used in transport simulations to predict the ITB dynamics, location and strength. The 1D first-principle transport models, such as the Weiland model [2] or GLF23 [3], have so far failed to reproduce satisfactorily the time dynamics, location and strength of the ITBs [4]. The Weiland model does not typically predict an ITB at all while GLF23 predicts the ITB at the wrong radial location or too weak an ITB. One of the obvious reasons is that the growth rates of the ITG/TEM modes significantly exceed the wExB shearing rates calculated from the radial electric field Er. In the present calculation of Er in transport codes, the neo-classical value for the poloidal rotation velocity is assumed. The past explanation for the failure of the Weiland model was the oversize growth rates as compared with the wExB shearing rate. However, after the recent measurements of vpol in JET, the question to be addressed in this paper is whether the failure to predict ITBs could actually be caused by the incorrectly estimated wExB shearing rates, rather than just the oversize growth rates.
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