Externally applied magnetic perturbations (MPs) provide an effective handle to control the internal dynamics of fusion plasmas. In magnetic configurations such as the tokamak and the reversed-field pinch (RFP), external coil systems are traditionally used for error field correction and feedback control of MHD instabilities like the resistive wall mode [1] and the tearing mode [2]. In the tokamak, MPs are also used for edge-localized modes (ELMs) suppression [3] and drive of neoclassical toroidal rotation [4]. More recently, MPs have been shown to govern the MHD dynamics in the RFX-mod device operated in both Ohmic tokamak and RFP configurations. In this talk, the effect of helical magnetic perturbations on the nonlinear 3D MHD modelling of fusion plasmas is discussed, with particular attention to the RFP and tokamak magnetic configurations. MHD simulation studies show that a key ingredient to capture the physics of helical self-organization observed in RFP experiments is the application of MPs consistent with the experimental helical deformation of the plasma magnetic boundary [5]. In addition, with the application of helical MPs it is possible to select the dominant helicity of helical RFP states [6], as confirmed in RFX-mod [7]. Also consistently with experimental observations, in both tokamak and RFP configurations helical MPs provide a way to mitigate the spontaneously occurring quasi periodic sawtooth oscillations. In the tokamak case, the toroidal mode coupling is shown to play an important role for the mitigation of sawteeth [8]. Finally, the use of MPs to approach realistic geometries within a circular computational domain is discussed. MHD simulations are provided by the SPECYL and PIXIE3D codes, whose nonlinear verification study is reported in Ref. [9]. [1] M. S. Chu and M. Okabayashi, Plasma Phys. Control. Fusion 52, 123001 (2010) [2] P. Zanca et al., Nucl. Fusion 47, 1425 (2007) [3] T. E. Evans et al., Phys. Rev. Lett 92, 235003 (2004) [4] A. M. Garofalo et al., Phys. Rev. Lett. 101, 195005 (2008) [5] D. Bonfiglio et al., Phys. Rev. Lett. 111, 085002 (2013) [6] M. Veranda et al., Plasma Phys. Control. Fusion 55, 074015 (2013) [7] S. Cappello et al., 24th IAEA Fusion Energy Conference, San Diego (2012) http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/199_THP216.pdf [8] D. Bonfiglio, P. Martin and P. Piovesan, 40th EPS Conference on Controlled Fusion and Plasma Physics, Espoo (2013) http://ocs.ciemat.es/EPS2013PAP/pdf/P2.145.pdf [9] D. Bonfiglio et al., Phys. Plasmas 17, 082501 (2010)
Effect of helical magnetic perturbations on the 3D MHD self-organization of fusion plasmas
Bonfiglio D;Cappello S;
2015
Abstract
Externally applied magnetic perturbations (MPs) provide an effective handle to control the internal dynamics of fusion plasmas. In magnetic configurations such as the tokamak and the reversed-field pinch (RFP), external coil systems are traditionally used for error field correction and feedback control of MHD instabilities like the resistive wall mode [1] and the tearing mode [2]. In the tokamak, MPs are also used for edge-localized modes (ELMs) suppression [3] and drive of neoclassical toroidal rotation [4]. More recently, MPs have been shown to govern the MHD dynamics in the RFX-mod device operated in both Ohmic tokamak and RFP configurations. In this talk, the effect of helical magnetic perturbations on the nonlinear 3D MHD modelling of fusion plasmas is discussed, with particular attention to the RFP and tokamak magnetic configurations. MHD simulation studies show that a key ingredient to capture the physics of helical self-organization observed in RFP experiments is the application of MPs consistent with the experimental helical deformation of the plasma magnetic boundary [5]. In addition, with the application of helical MPs it is possible to select the dominant helicity of helical RFP states [6], as confirmed in RFX-mod [7]. Also consistently with experimental observations, in both tokamak and RFP configurations helical MPs provide a way to mitigate the spontaneously occurring quasi periodic sawtooth oscillations. In the tokamak case, the toroidal mode coupling is shown to play an important role for the mitigation of sawteeth [8]. Finally, the use of MPs to approach realistic geometries within a circular computational domain is discussed. MHD simulations are provided by the SPECYL and PIXIE3D codes, whose nonlinear verification study is reported in Ref. [9]. [1] M. S. Chu and M. Okabayashi, Plasma Phys. Control. Fusion 52, 123001 (2010) [2] P. Zanca et al., Nucl. Fusion 47, 1425 (2007) [3] T. E. Evans et al., Phys. Rev. Lett 92, 235003 (2004) [4] A. M. Garofalo et al., Phys. Rev. Lett. 101, 195005 (2008) [5] D. Bonfiglio et al., Phys. Rev. Lett. 111, 085002 (2013) [6] M. Veranda et al., Plasma Phys. Control. Fusion 55, 074015 (2013) [7] S. Cappello et al., 24th IAEA Fusion Energy Conference, San Diego (2012) http://www-naweb.iaea.org/napc/physics/FEC/FEC2012/papers/199_THP216.pdf [8] D. Bonfiglio, P. Martin and P. Piovesan, 40th EPS Conference on Controlled Fusion and Plasma Physics, Espoo (2013) http://ocs.ciemat.es/EPS2013PAP/pdf/P2.145.pdf [9] D. Bonfiglio et al., Phys. Plasmas 17, 082501 (2010)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
