ITER-FEAT operation

Shimomura, Y.; Aymar, R.; Chuyanov, V.A.; Huguet, M.; Matsumoto, Hiroshi; Mizoguchi, T.; Murakami, Yoshiki; Polevoi, A.; Shimada, M.; Team, Iter Joint Central; Teams, Iter Home

doi:10.1088/0029-5515/41/3/308

Cited by 75 publications

(64 citation statements)

References 4 publications

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“…In a future fusion reactor, e.g., ITER [4], the collision frequency will be much smaller than in the case of the TEXTOR RI mode discussed above. For ITER-FEAT parameters in the inductive operation stage [25], R 0 6:2 m, a 2 m, volume averaged T 9 keV, and n 10 20 m ÿ3 , we get tr 2:6 10 4 s ÿ1 , i.e., a value by a factor of 50 smaller than in the RI mode. Therefore, one might argue that DTE turbulence will be unimportant under reactor conditions.…”

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confidence: 85%

Nature of the Isotope Effect on Transport in Tokamaks

2004

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The reduction of energy and particle losses with the increasing mass of the hydrogen isotope is more pronounced under conditions of improved confinement when the dominant ion temperature gradient instability is suppressed and other channels of anomalous transport are of importance. In this Letter, we reconsider the dissipative trapped electron (DTE) instability by taking into account finite Larmor radius effects in the analysis of the ion response to perturbations. By applying the improved mixing length approximation in order to estimate the transport coefficients, it is demonstrated that DTE contribution is intrinsically dependent on the isotope mass and provides a plausible explanation for the isotope effect. Contrary to the common belief, it is shown that the DTE turbulence may be of importance for reactor plasmas of low collisionality. As observed in practically all tokamaks, the energy and particle confinement improves with increasing atomic weight of the isotope used, from hydrogen to deuterium to tritium (see, e.g., Refs. [1][2][3]). This fact is of crucial importance for the performance of future thermonuclear reactors, which will operate with a mixture of deuterium and tritium rather than present devices which normally use either hydrogen or deuterium. However, in spite of its fundamental significance, the isotope effect is still one of the least understood phenomena in the physics of tokamak transport.Analysis of the experimental database shows that the isotope effect on confinement depends essentially on the mode of tokamak operation. Thus, the most recent scalings for the energy confinement time E [4] A pattern in this puzzling picture can be found by noting that the strongest improvement with A i takes place if the ion temperature gradient (ITG) instability, which is commonly considered as the main source of anomalous transport [6], is suppressed. This is the case both for the edge barrier in the H mode and for other regimes of improved confinement where ITG is subdued by the density gradient in a large part of the plasma volume (see, e.g., analysis of the L-RI transition in Refs. [7,8]). On the contrary, under conditions where the transport is dominated by ITG modes the confinement deteriorates with increasing A i . For the case of the plasma core in the H mode, this fact was explained in Ref. [9] by applying the mixing length approximation (MLA) [6,10,11], in which max =k 2 max is used as an estimate for transport coefficients. Here max is the maximum value of the instability growth rate considered as a function of the perpendicular wave number k and k max is the k-value where max is reached. For the ITG instability both max and k max vary as A ÿ0:5 i [6,12] and the characteristic heat diffusivity A 0:5 i . Since E 1= , the scaling above is in qualitative agreement with the decrease of the core confinement in the H mode with increasing isotope atomic weight. The same result follows from the so-called improved mixing length approximation (IMLA) [6,13], which takes into account the phase shift betw...

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confidence: 85%

Nature of the Isotope Effect on Transport in Tokamaks

2004

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“…Access to high density with radiative impurity seeding is highly desirable for the construction of a profitable thermonuclear reactor [2] from the point of view of maximising the fusion power since it scales quadratically with the density.…”

Section: Introductionmentioning

confidence: 99%

Density limit of H-mode plasmas on JET-ILW

Huber

Brezinsek

Sergienko

et al. 2015

Journal of Nuclear Materials

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“…With high recycling at the plasma edge, and apparently producing plasma edge consistent with the material surfaces, this feature, at the same time, leads to substantial consequences limiting the tokamak core performance: turbulent energy losses [2], degradation of confinement with the power [3], Troyon limitations of plasma beta [4,5], possibility of sawtooth relaxations and internal collapse [6], instabilities at high edge density [7], etc.…”

Section: Introductionmentioning

confidence: 99%