Toroidal transport studies in TEXTOR using 
lithium laser blow-off injection

Kocsis, G.; Bakos, J. S.; Kálvin, S.; Könen, L.; Mank, G.; Pospieszczyk, A.

doi:10.1017/s0022377897005795

Cited by 4 publications

(3 citation statements)

References 5 publications

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“…However, there exist few studies focused on parallel or radial transport of such injected impurities with well-defined temporal and spatial localization together with minimum perturbation of the overall plasma. From these we highlight the injection of LiF by laser blowoff (LBO) in TEXTOR [6], C deposition by pellet injection in the LHD stellarator [7] and injection of various gas species by puffing in the ALCATOR-C-MOD [8]. The first of these techniques, LBO injection, has several advantages over pellets or gas puffing for impurity deposition, e.g.…”

Section: Introductionmentioning

confidence: 99%

Transport studies using laser blow-off injection of low-Z trace impurities injected into the TJ-II stellarator

Zurro¹,

Hollmann

Baciero³

et al. 2011

Nucl. Fusion

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Laser blow-off of low-Z (boron and carbon) material is used to study parallel and radial impurity ion transport, as well as radial heat transport, in the TJ-II stellarator. Toroidal transport is found to be, consistent with entrainment in edge toroidal rotation. Radial/poloidal transport and loss to the plasma edge is seen to be slower (about 5 ms) and is clearly seen to be slower for carbon than for boron, consistent with collisional (neoclassical) cross-field transport. Radial heat transport is observed to be quite rapid (0.1 ms time scale).

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Section: Introductionmentioning

confidence: 99%

Transport studies using laser blow-off injection of low-Z trace impurities injected into the TJ-II stellarator

Zurro¹,

Hollmann

Baciero³

et al. 2011

Nucl. Fusion

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“…It has been suggested that this is due to the presence of microscopic particles (pellets), which are able to penetrate into the plasma deeper than atoms. The toroidal spreading velocities are in the 10 3 to 10 4 m/s range, implying toroidal homogeneity times in the millisecond range [18]. These references indicate that radial and toroidal spreading of the injected atom burst in the plasma periphery is quite complex and unfortunately do not help to improve the usual boundary condition taken for the neutral impurity flux Φ(t) at the plasma edge: Φ(t) is tailored to follow the relative line brightnesses of the most peripheral ions monitored.…”

Section: Simulation Of the Transport Of The Injected Nickel Ionsmentioning

confidence: 93%

Enhanced transport of impurity ions and electron heat in Tore Supra ohmic discharges following nickel laser blow-off injection

et al. 1998

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Nickel has been injected into ohmic Tore Supra (TS) discharges with and without activation of the ergodic divertor (ED). The nickel ion transport is studied by means of an impurity transport code, and the radial profiles of the diffusion coefficient D and of the inward convection velocity V are obtained by simulating the soft X ray brightness and emissivity time evolutions. The simulations confirm two previously reported conclusions: the presence of a central core with reduced transport coefficients and, with the ED activated, the necessity of introducing a peripheral transport barrier (with increased inward convection and/or reduced diffusion). To make satisfactory simulations in both experimental conditions of the initial phase of the nickel ion inflow before the first inverted sawtooth, it is necessary to increase transiently the diffusion coefficient (by 1 order of magnitude or more) during the first few milliseconds after the injection. By comparison of the experimental and simulated bolometric signals, it is possible to verify quantitatively the available calculations of the global radiative losses for nickel. The observed discrepancy by a factor of 2 is discussed. The inward propagating cold wave, following the nickel injection, has been observed with a heterodyne radiometer (monitoring the electron temperature). Both with and without the ED, good simulations of the cold wave propagation are obtained using a predictive non-local transport model, previously successfully tested in JET during transient regimes. The model predicts large increases of the electron thermal diffusivity χe, by a factor of 5, immediately after the injection and describes well the electron temperature profile in the so-called heat transport dominated region outside the q = 1 surface. The experimental signals are smoothed with the 'generalized singular value decomposition' technique, reducing the effect of the sawtooth modulation; the simulation can, therefore, be more clearly compared with the measurements. It is not possible, using present experimental data, to demonstrate the existence of an electron diffusivity transport barrier inside the q = 1 region, as done for the impurity transport, because the temperature profile is strongly affected by sawteeth in this region. Similarities have been found in the time evolutions of the electron temperature and of the Abel inverted soft X ray emissivities at fixed radii, implying similar time behaviour of D and χe outside the q = 1 surface.

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“…On the other hand, the general problem of particle transport in tokamak plasmas is still an unsolved problem, either theoretically (Taguchi 1993, Lazzaro et al 1996 or experimentally (Yoshioka and Antonsen 1986, Nakamura et al 1991, Deliyanakis et al 1994, Knowlton et al 1994, Cairns et al 1995, Kocsis et al 1997, Baker et al 1998. The existing experimental database (Konings and Waltz 1997) does not permit differentiation among different models for transport.…”

Section: Introductionmentioning

confidence: 99%

Effects of radial particle diffusion on the electron cyclotron absorption coefficient in tokamak plasmas in the presence of lower hybrid waves

Rosa

Ziebell

1999

Plasma Phys. Control. Fusion

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In this paper we study the effects of particle radial transport on the electron cyclotron absorption coefficient. We consider a tokamak plasma under the combined action of lower hybrid waves, electron cyclotron waves, collisions and spatial transport of electrons across magnetic surfaces. Our results, found from the numerical solution of the diffusion equation, indicate a significant modification in the profile of the electron cyclotron absorption coefficient around the resonant surface when transport is taken into account relative to the situation when transport is absent.

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Toroidal transport studies in TEXTOR using lithium laser blow-off injection

Cited by 4 publications

References 5 publications

Transport studies using laser blow-off injection of low-Z trace impurities injected into the TJ-II stellarator

Transport studies using laser blow-off injection of low-Z trace impurities injected into the TJ-II stellarator

Enhanced transport of impurity ions and electron heat in Tore Supra ohmic discharges following nickel laser blow-off injection

Effects of radial particle diffusion on the electron cyclotron absorption coefficient in tokamak plasmas in the presence of lower hybrid waves

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