Recent progress in lower hybrid current drive theory and experiments

Barbato, Emanuele

doi:10.1088/0741-3335/40/8a/006

Cited by 19 publications

(26 citation statements)

References 26 publications

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“…These limits of the LH spectrum in N -space are obtained from a well known propagation model which assumes several back and forth trips of the LH waves before complete absorption due to Landau damping [8,11,12]. The use of this propagation model is one of the main differences between the investigation developed in the present paper and the approach adopted in Ref.…”

Section: The Fokker-planck Equation and The Numerical Schemementioning

confidence: 99%

Efficiency of LH+EC current drive in tokamaks featuring an internal transport barrier

Rosa¹,

Ziebell²,

Oliveira³

et al. 2005

Braz. J. Phys.

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In the present paper we study the effects due to the occurrence of radial transport of particles in a tokamak on the efficiency of current drive due to combined action of lower hybrid waves and electron cyclotron waves, in the presence of an internal transport barrier. The results are obtained by numerical solution of the Fokker-Planck equation which rules the evolution of the electron distribution function. We assume that the radial transport of particles can be due to magnetic or to electrostatic fluctuations, and compare the two situations. In both cases the efficiency of current drive is shown to increase with the increase of the fluctuations which originate the transport. The current drive efficiency is shown to depend weakly on the radial position of the barrier, with a slightly more pronounced dependence in the case of magnetic fluctuations.

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Section: The Fokker-planck Equation and The Numerical Schemementioning

confidence: 99%

Efficiency of LH+EC current drive in tokamaks featuring an internal transport barrier

Rosa¹,

Ziebell²,

Oliveira³

et al. 2005

Braz. J. Phys.

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“…A wide class of waves can be launched in the plasma yet, for current drive purposes, the excitation of superthermal electrons has been the most successful method, in accordance with theoretical predictions [1]. Lower Hybrid Current Drive (LHCD) is a well-tested and efficient method [3,4,5], based on Landau damping of the wave power. Its main drawback is that in the so-called multi-pass regime, the current profile remains difficult to control and calculations still lack full reliability.…”

Section: Introductionmentioning

confidence: 99%

“…Its main drawback is that in the so-called multi-pass regime, the current profile remains difficult to control and calculations still lack full reliability. Note, however, that in very hot plasmas, the wave is expected to be absorbed without relying on any subtle upshift mechanism (single-pass absorption), which makes the LH wave a serious candidate to drive off-axis current in future experiments [4]. On the other hand, Electron Cyclotron (EC) waves exploit the resonance with the electron gyro-motion and are characterized by a narrow deposition, thus providing a means to induce a local modification of the current profile.…”

Section: Introductionmentioning

confidence: 99%

Theory of synergy between electron cyclotron and lower hybrid waves

Dümont

Giruzzi

2004

Physics of Plasmas

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A theoretical study of the improvement of the Electron Cyclotron Current Drive (ECCD) efficiency in regimes where most of the current is driven by Lower Hybrid (LH) waves is presented. A perturbation technique is employed to solve the adjoint equation and derive the response function including both collisional and LH effects in the limit where the former dominate. An alternative treatment of the problem, involving a numerical solution of the Langevin equations is proposed to gain insight into the current drive mechanism and confirm the obtained results. The existence of a cross-effect between the two waves is demonstrated and the conditions for the synergy, i.e. significant enhancement of the ECCD efficiency in the presence of LH power, are identified.

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“…Also, the change in q itself affected the propagation domain [20] and the ray trajectory of the LH waves. Both of these effects tended to direct more LH power at the ITB, and the off-axis j LH , in turn, reinforced the reversal of magnetic shear.…”

mentioning

confidence: 99%

Evolution of Lower-Hybrid-Driven Current during the Formation of an Internal Transport Barrier

Naito¹,

Ide³

et al. 2002

Phys. Rev. Lett.

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Evolution of the lower-hybrid(LH)-driven current profile was measured during the formation of an internal transport barrier (ITB) in a reversed magnetic shear discharge. As the ITB developed, the initially centrally peaked LH-driven current profile gradually turned hollow and was sometimes accompanied by an off-axis peak in the electron temperature profile. These observations indicate the concentration of LH power deposition to the ITB for this case as a result of nonlinear coupling between the LH waves and the target plasma.

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Recent progress in lower hybrid current drive theory and experiments

Cited by 19 publications

References 26 publications

Efficiency of LH+EC current drive in tokamaks featuring an internal transport barrier

Efficiency of LH+EC current drive in tokamaks featuring an internal transport barrier

Theory of synergy between electron cyclotron and lower hybrid waves

Evolution of Lower-Hybrid-Driven Current during the Formation of an Internal Transport Barrier

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