Plasma wall interaction and energy fluxes in RFX

Antoni, V.; Bagatin, M.; Bergsåker, Henric; Mea, G. Della; Desideri, Daniele; Martines, E.; Rigato, V.; Serianni, G.; Sonato, P.; Tramontin, L.; Zandolin, S.

doi:10.1016/0022-3115(94)00558-3

Cited by 20 publications

(7 citation statements)

References 7 publications

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“…The energy flux asymmetry, defined as the ratio between the parallel energy fluxes measured on the electron and on the ion drift sides, is found to be about three at the extreme edge of the plasma (for r/a > 0.95), decreasing towards unity deeper inside, as reported in figure 4(c). The values of the asymmetry factor observed at the edge are in agreement with previous energy flux measurements, averaged over the entire discharge duration, obtained from calorimetric probes [23]. The decrease in the asymmetry towards unity inside the plasma is in agreement with the results of a Fokker-Planck code developed to study the superthermal electron population at the edge of RFPs [24].…”

Section: Experimental Conditions and Resultssupporting

confidence: 90%

Magnetic fluctuations and energy transport in RFX

Serianni¹,

Murari²,

Fiksel

et al. 2001

Plasma Phys. Control. Fusion

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In thermonuclear fusion plasmas, transport losses are usually believed to be caused by turbulent fluctuations. Particularly in the outer region of tokamaks, stellarators and reversed field pinches, electrostatic turbulence accounts for particle transport. In tokamaks, electrostatic fluctuations can also be responsible for the radial energy flux; in reversed field pinches, energy transport cannot be ascribed to electrostatic turbulence only. In the plasma edge of the reversed field experiment device, identified as the region between the toroidal field reversal and the first wall, an extensive study of magnetic fluctuations and of the related radial energy flux has been performed. It is found that magnetic fluctuations carry most of the radial flux of energy. However, close to the wall the magnetic fluctuation-driven energy flux decreases abruptly, so that another mechanism must be invoked. There are indications that the energy flux channel in this region is the macroscopic magnetic deformation due to the phase locking of magnetic modes.

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Section: Experimental Conditions and Resultssupporting

confidence: 90%

Magnetic fluctuations and energy transport in RFX

Serianni¹,

Murari²,

Fiksel

et al. 2001

Plasma Phys. Control. Fusion

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“…The SOL created by limiters or plasma-column displacement reveals properties similar to those in tokamaks. In particular the decay length of density λ n is found to be [8,9] shorter than that of temperature λ T as shown in the example of figure 2. The diffusion coefficient D obtained from equating the parallel and perpendicular fluxes (i.e.…”

Section: Edge Regionmentioning

confidence: 85%

“…As a consequence it is found in most experiments that the ionization length of the main impurities is comparable to or shorter than their ion Larmor radius, as shown in figure 4, so that the plasma is screened to a large extent from the impurity neutrals released with thermal velocity by localized erosion and chemical sputtering. In RFX [9] evidence of prompt redeposition has been reported from the analysis of the first wall and in ETA BETA II [26] from the decay length of the impurities measured with sample probes. The same wall cleaning and conditioning techniques used in tokamaks are also routinely applied to RFP devices in order to control the impurity content of the plasma.…”

Section: Antonimentioning

confidence: 99%

Edge physics in reversed-field pinch and tokamak: similarities and differences

Antoni¹

1997

Plasma Phys. Control. Fusion

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The edge-region properties of a reverse-field pinch (RFP) configuration are reviewed and a comparison with those of tokamaks is attempted. Despite the different magnetic configurations, many similarities have been observed. Among the similarities is the electrostatic nature of the particle transport and the structure of the plasma potential. In particular the radial electric field changes sign across the last closed flux surface and gives rise to an E × B velocity shear layer. The anomalous transport driven by electrostatic and magnetic fluctuations is addressed and the regimes of improved confinement recently observed in RFPs are reviewed. The role of the velocity shear on turbulence stabilization in these regimes is discussed.

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“…The radial behaviour of the energy fluxes qe and qi measured on the electron and on the ion drift sides has already been presented elsewhere [40]. The asymmetry A = qe/qi is plotted in Fig.…”

Section: Energy Fluxmentioning

confidence: 88%

Stochastic magnetic and ambipolar electric fields in the plasma edge region of RFX

Antoni¹,

Martines²,

Bagatin³

et al. 1996

Nucl. Fusion

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The edge region of the reversed field pinch experiment RFX has been investigated with Langmuir and calorimetric probes. The energy flux measurements reveal a spatial structure that is consistent with the presence of a superthermal tail in the energy distribution function of the electrons, as expected according to the kinetic dynamo theory (KDT). In the framework of this model, the value of the magnetic field line diffusion coefficient in the edge region has been derived. The radial electric field obtained from the plasma potential gradient is opposite in sign to the ambipolar electric field expected in a stochastic magnetic field. The discrepancy is discussed in terms of particle recycling at the wall.

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Plasma wall interaction and energy fluxes in RFX

Cited by 20 publications

References 7 publications

Magnetic fluctuations and energy transport in RFX

Magnetic fluctuations and energy transport in RFX

Edge physics in reversed-field pinch and tokamak: similarities and differences

Stochastic magnetic and ambipolar electric fields in the plasma edge region of RFX

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