Internal transport barrier formation in experiments with reverse magnetic shear in T-10 tokamak

Kirneva, N.; Esipchuk, Yu. V.; Borschegovskij, A A; Chistyakov, V. V.; Gorbunov, E.P.; Venisov,; Dremin, M. M.; Kakurin, A. M.; Khimchenko, L. N.; Kislov, D. A.; Krylov, S.V.; Krupin, V.A.; Myalton, T.B.; Novikov, Alexander; Orlovskij, I I; Pavlov, Yu.D.; Petrov, D.P.; Ploskirev, G.N.; Roy, I. N.; Ryjakov, D. V.; Shelukhin, D. A.; Skovoroda, A. A.; Skosirev, Yu V; Slepneva, L I; Sushkov, A. V.; Trukhin, V. M.; Trukhina, E.V.

doi:10.1088/0741-3335/47/10/011

Cited by 9 publications

(6 citation statements)

References 23 publications

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“…We focus here only on very recent results on electron ITBs created with dominant electron heating. The main studies on eITBs have been reviewed in [52] and can be found for the different tokamaks as follows: ASDEX Upgrade [53,54], DIII-D [55], FTU [56,57], JET [58,59], JT-60U [60,61], Tore Supra [62,63], TCV [64][65][66] and T-10 [67,68] . Electrons ITBs are obtained at very low densities, with cold ions, and lead to central electron temperatures up to 20 keV.…”

Section: Transport In Electron Internal Transport Barriermentioning

confidence: 99%

Electron heat transport studies

Ryter

Camenen

DeBoo

et al. 2006

Plasma Phys. Control. Fusion

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Electron transport in fusion plasmas is intensively studied in coordinated experiments and great progress in physics understanding has been achieved during the past years. A threshold in normalized gradient explains most of the observations, both in steady-state and transient conditions. The results convincingly suggest that trapped electron modes (TEM) dominate electron transport at low and moderate collisionality, with electron heating. The stabilization of these modes at high collisionality predicted by theory is found in the experiments. Electron transport is then driven by the ion temperature gradient modes. At low collisionality, if TEM are stabilized by negative shear and Shafranov shift effects, electron internal transport barriers may develop.

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Section: Transport In Electron Internal Transport Barriermentioning

confidence: 99%

Electron heat transport studies

Ryter

Camenen

DeBoo

et al. 2006

Plasma Phys. Control. Fusion

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“…Reverse magnetic shear discharges are a possible operational scenario of nuclear fusion reactors because these configurations have good MHD stability properties and energy confinement at high β [1][2][3][4][5][6][7], although Alfvén Eigenmode stability and energetic particle confinement are still an open issue [8][9][10][11][12][13][14]. MHD stability of interchange and ballooning modes is improved in high β discharges by combining reverse shear operation (the plasma is in the second stable regime [15,16]) and fast toroidal rotation [17].…”

Section: Introductionmentioning

confidence: 99%

Subdominant modes and optimization trends of DIII-D reverse magnetic shear configurations

et al. 2019

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Alfvén Eigenmodes (AE) and magneto-hydrodynamic (MHD) modes are destabilized in DIII-D reverse magnetic shear configurations and may limit the performance of the device. We use the reduced MHD equations in a full 3D system, coupled with equations of density and parallel velocity moments for the energetic particles (with gyro-fluid closures) as well as the geodesic acoustic wave dynamics, to study the properties of instabilities observed in DIII-D reverse magnetic shear discharges. The aim of the study consists in finding ways to avoid or minimize MHD and AE activity for different magnetic field configurations and neutral beam injection (NBI) operational regimes. The simulations show at the beginning of the discharge, before the reverse shear region is formed, a plasma that is AE unstable and marginally MHD stable. As soon as the reverse shear region appears, ideal MHD modes are destabilized with a larger growth rate than the AEs. Both MHD modes and AEs coexist during the discharge, although the MHD modes are more unstable as the reverse shear region deepens. The simulations indicate the destabilization of Beta induced AE (BAE), Toroidal AE (TAE), Elliptical AE (EAE) and Reverse Shear AE (RSAE) at different phases of the discharges, showing a reasonable agreement between the frequency range of the dominant modes in the simulations and the diagnostic measurements. A further analysis of the NBI operational regime indicates that the AE stability can arXiv:1904.01193v1 [physics.plasm-ph] 2 Apr 2019Optimization of DIII-D reverse shear configurations 2 be improved if the NBI injection is off axis, because on-axis injection leads to AEs with larger growth rate and frequency. In addition, decreasing the beam energy or increasing the NBI relative density (the ratio between the energetic particle and thermal plasma density) leads to AEs with larger growth rate and frequency, so an NBI operation in the weakly resonant regime requires higher beam energies than in the experiment (V th,f /V A0 > 0.3). The MHD linear stability can be also improved if the reverse shear region and the q profile near the magnetic axis are in between the rational surfaces q = 2 and q = 1, particularly if there is a region in the core with negative shear, avoiding a flat q profile near the magnetic axis. The simulations also show a smooth transition between MHD modes and low frequency AE, no critical β f , pointing out an overlap between MHD and AE activity for modes with frequencies lower than 30 kHz. This is in the range of Beta Acoustic Alfven Eigenmodes (BAAE) and BAE.

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“…It has been put forward for several machines (e.g. JET, DIII-D, JT-60U, TCV, T-10) that regions of enhanced confinement develop when q min reaches a rational value, mainly due to resonant modes stabilization [16][17][18][19][20][21][22]. The results of the exploration of this possibility are summarized in figure 8 (right): the q min values in our database are homogeneously spread from q min ∼ 1.1 to q min ∼ 1.65, and they do not seem to accumulate around rational surfaces (for the sake of completeness, in the plot the q = 4/3 surface is also represented by the dashed red line).…”

Section: A General Featurementioning

confidence: 99%

Internal transport barrier formation in the Tore Supra tokamak

Turco¹,

Giruzzi²,

Artaud³

et al. 2009

Plasma Phys. Control. Fusion

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The characteristics of the safety factor profile (q) have been studied for a database of discharges featuring internal transport barrier phenomena under different heating and current drive conditions in the Tore Supra tokamak. The presence of a recurrent link between the time of formation of an internal barrier and the central safety factor (q 0 ) crossing a low order rational surface is reported on and discussed for a database of ∼40 discharges. Other relevant features of the current profile (e.g. the minimal q value, the magnetic shear and the presence of magnetic islands in the plasma) have been investigated, yielding to little or no correlation with the time and location of the barrier.

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Internal transport barrier formation in experiments with reverse magnetic shear in T-10 tokamak

Cited by 9 publications

References 23 publications

Electron heat transport studies

Electron heat transport studies

Subdominant modes and optimization trends of DIII-D reverse magnetic shear configurations

Internal transport barrier formation in the Tore Supra tokamak

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