Åpne denne publikasjonen i ny fane eller vindu >>2006 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]
Control of MHD instabilities using a conducting wall together with external magnetic fields is an important route to improved performance and reliability in fusion devices. Active control of MHD modes is of interest for both the Advanced Tokamak and the Reversed Field Pinch (RFP) configurations. A wide range of unstable, current driven MHD modes is present in the RFP. An ideally conducting wall facing the plasma can in principle provide stabilization to these modes. However, a real, resistive wall characterized by a wall field diffusion time, cannot stabilize the ideal MHD modes unless they rotate with Alfvénic velocity, which is usually not the case. With a resistive wall, the ideal modes are converted into resistive wall modes (RWM) with growth rates comparable to the inverse wall time. Resistive wall modes have been studied in the EXTRAP T2R thin shell RFP device. Growth rates have been measured and found in agreement with linear MHD stability calculations. An advanced system for active control has been developed and installed on the EXTRAP T2R device. The system includes an array of 128 active saddle coils, fully covering the torus surface. Experiments on EXTRAP T2R have for the first time demonstrated simultaneous active suppression of multiple independent RWMs. In experiments with a partial array, coupling of different modes due to the limited number of feedback coils has been observed, in agreement with theory. Different feedback strategies, such as the intelligent shell, the rotating shell, and mode control have been studied. Further, feedback operation with different types of magnetic field sensors, measuring either the radial or the toroidal field components have been compared
sted, utgiver, år, opplag, sider
Stockholm: KTH, 2006. s. viii, 46
Serie
Trita-EE, ISSN 1653-5146 ; 2006:005
Emneord
Resistive wall modes, RWM, active control, feedback, MHD modes, Reversed-Field pinch, RFP, intelligent shell, mode control
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-3867 (URN)91-7178-285-0 (ISBN)
Disputas
2006-03-17, H1, Teknikringen 33, Stockholm, 10:30
Opponent
Veileder
Merknad
QC 201009292006-03-082006-03-082022-06-22bibliografisk kontrollert