Three-dimensional equilibria and transport in RFX-mod: A description using stellarator tools

Gobbin, M.; Bonfiglio, D.; Boozer, Allen H.; Cooper, Alfred W.; Escande, Dominique; Hirshman, S. P.; Lore, J.; Lorenzini, R.; Marrelli, L.; Martin, P.; Martines, E.; Momo, B.; Pomphrey, N.; Predebon, I.; Puiatti, M. E.; Sánchez, Raúl; Spizzo, G.; Spong, D. A.; Terranova, D.; Team, RFX-mod

doi:10.1063/1.3602083

Cited by 22 publications

(27 citation statements)

References 34 publications

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“…In the multiple helicity state the helical deformation of the plasma is localized and magnetic field lines are chaotic. The helical shape of the single helicity plasmas introduces analogies with the stellarator [16]. However the helical distortion decreases when going close to the shell, which alleviates the issue of fast particle confinement.…”

Section: Resultsmentioning

confidence: 95%

What is a Reversed Field Pinch?

Escande¹

2015

Rotation and Momentum Transport in Magnetized Plasmas

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Section: Resultsmentioning

confidence: 95%

What is a Reversed Field Pinch?

Escande¹

2015

Rotation and Momentum Transport in Magnetized Plasmas

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“…The region of maximum emissivity lies on the rational surface of the dominant mode [22]. In RFX-Mod [23] such a localized increase in SXR emissivity has also been clearly associated with an electron temperature helical structure [24,25]: magnetic topology reconstructions showed that the enhanced temperature and SXR correspond to a magnetic island.…”

Section: Introductionmentioning

confidence: 94%

Experimental investigation of electron temperature dynamics of helical states in the RFX-Mod reversed field pinch

et al. 2013

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The study of electron temperature profiles of quasi-single helical states (QSH) in RFX-Mod (and, in general, in other RFP machines) was carried out in the past mainly using Thomson scattering, thus being limited to a time resolution of the order of some milliseconds and to the collection of single, isolated cases, which displayed clear transport barriers. A new multichord double filter SXR spectrometer was developed and installed. Temperature profiles are now measured up to a frequency of some kHz, allowing one to determine the entire time evolution of electron temperature during a QSH cycle. A mapping technique, originally developed for Thomson temperature profiles, is adapted to deal with the line-integrated nature of the SXR diagnostic. In particular, temperature gradients related to the presence of transport barriers are reconstructed and analysed in a helical reference system, coherently with the underlying plasma equilibrium. The method is discussed in its capabilities and limits and then applied to a wide QSH database. As a result, a clear difference in temperature gradient behaviour between the rising phase of QSH and the saturated (or flattop) phase is observed. In the rising phase the expected correlation of temperature gradient with magnetic spectrum is confirmed, showing a positive trend between dominant mode amplitude and thermal structure dimension, as well as a negative correlation of secondary mode amplitudes and temperature gradient. On the other hand, in the flattop phase the presence of a thermal structure is intermittent, and much less influenced by the magnetic dynamics. This suggests the simultaneous presence of different mechanisms that enhance energy transport.

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“…24 The 3D nonlinear MHD codes SpeCyl 15 and PIXIE3D 25 are also being used to model the effect of 3D shaping on the MHD dynamics. [26][27][28] The same codes are also used to model helical tokamak states.…”

Section: Feedback Control Of a Helical Rfp Equilibriummentioning

confidence: 99%

RFX-mod: A multi-configuration fusion facility for three-dimensional physics studies

et al. 2013

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RFX-mod [Sonato et al., Fusion Eng. Des. 66, 161 (2003)] exploits its 192 active coils in both reversed-field pinch (RFP) and tokamak configurations with varying degrees of 3D shaping, providing also a test bed for validating stellarator codes and 3D nonlinear magnetohydrodynamic codes. This makes RFX-mod a unique and flexible facility for comparative studies on 3D shaping and control. The paper discusses how 3D fields allow access to RFP and tokamak advanced regimes. 3D fields are used to feedback control Single Helicity (SH) RFP equilibria with 1/7 helicity up to $2 MA. They also allow accessing SH regimes with higher density (Greenwald fraction up to 0.5), presently inaccessible in spontaneous SH regimes. Feedback on the 2/1 resistive-wall mode in RFX-mod tokamak plasmas allows for safe operation at qðaÞ < 2, an almost unexplored promising regime. Forcing the 2/1 mode to saturate at finite but small level, a helical tokamak equilibrium with significant n ¼ 1 modulation is produced and a new way to tailor sawteeth is found. The effects of different levels of 3D shaping on momentum transport in both RFP and tokamak helical states are discussed. [http://dx.

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Three-dimensional equilibria and transport in RFX-mod: A description using stellarator tools

Cited by 22 publications

References 34 publications

What is a Reversed Field Pinch?

What is a Reversed Field Pinch?

Experimental investigation of electron temperature dynamics of helical states in the RFX-Mod reversed field pinch

RFX-mod: A multi-configuration fusion facility for three-dimensional physics studies

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