Tokamak MHD equilibrium generation by narrow-spectrum fast-wave current drive

Ehst, D.A.; Evans, K.; Ignat, D.

doi:10.1088/0029-5515/26/4/006

Cited by 23 publications

(29 citation statements)

References 18 publications

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“…This is consistent with the previous results (Ref. [6][7][8][9] that the fast wave damping is proportional to the plasma beta times the wave number. However, a curious observation is that the damping is not nearly as strongly dependent on the plasma density.…”

Section: Htch Harmonic Fast Wave Dispersion Relationsupporting

confidence: 94%

“…8 This condition together with the decreasing temperature (though the decreasing density may help offset this trend) tends to make the rf-based current drive near the plasma periphery not practical. The higher electron temperature also increases the bootstrap and other forms of pressure driven currents through higher electron pressure and lower collisionality.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…[7][8][9][10][11]. The experimental evidence of direct fast wave current drive FWCD is relatively limited.…”

Section: Master Distribution Of This Document Is Unlimited^mentioning

confidence: 99%

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High harmonic fast waves in high beta plasmas

Ono¹

1995

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High hannonic fast magnetosonic wave in high beta / high dielectric plasmas is investigated including the finite-Larmor-radius effects. In this regime, due to the combination of group velocity slow down and the high beta enhancement, the electron absorption via electron Landau and electron magnetic pumping becomes significant enough that one can expect a strong (= 100%) single pass absorption. By controlling the wave spectrum, the prospect of some localized electron heating and current drive appears to be feasible in high beta low-aspect-ratio tokamak regimes. Inclusion of finite-Larmor-radius terms shows an accessibility limit in the high ion beta regime (pi = 50% for a deuterium plasma) due to mode-conversion into an ionBernstein-wave-like mode while no beta limit is expected for electrons. With increasing ion beta, the ion damping can increase significantly particularly near the beta limits. The presence of energetic ion component expected during intense NBI and a-heating does not appear to modify the accessibility condition nor cause excessive wave absorption.

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Section: Htch Harmonic Fast Wave Dispersion Relationsupporting

confidence: 94%

Section: Conclusion and Discussionmentioning

confidence: 99%

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High harmonic fast waves in high beta plasmas

Ono¹

1995

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“…Furthermore, we want to ensure that the total {bootstrap + RF) current needed for maintaining the steady-state equilibrium is self-consistent with the equilibrium. In other words, the objective of the calculation is to establish a steady-state two-dimensional tokamak equilibrium that is is [8] where < > denotes the average over a flux surface, [4,9] and j? F and jNC are the Narallel (to the magnetic field) current density due to RF waves and neoclassical transport, respectively.…”

Section: Model For the Calculationsmentioning

confidence: 99%

Bootstrap currents in radiofrequency driven tokamak equilibria

1989

Self Cite

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As a result of certain experimental observations, interest in the bootstrap current arising from neoclassical transport in tokamaks has increased recently. In this study, the bootstrap current is calculated for a number of radiofrequency (RF) current driven tokamaks. Two-dimensional, self-consistent, steady state tokamak MHD equiJibria are obtained by including both the transport driven bootstrap current and the externally driven RF current. Self-consistency is accomplished by iterating the two-dimensional MHD equilibrium calculation and the current calculation (including bootstrap current and RF ray tracing). The parameter Γ = 1 −(γ/γB) is defined as a measure of the RF current drive power reduction achieved when bootstrap currents are included in the calculation (γ = n̄e R0I/PCD is the current drive efficiency without the benefit of bootstrap current and γB = n̄eR0I/PCD is the higher efficiency obtained when bootstrap effects are included). For INTOR-type reactor parameters with n̄e = (0.7−1.4) × 1020 m−3, Γ ≈ 0.4−0.9 (40-90% reduction of RF power) is obtained. Calculations for other reactor parameters of interest are also carried out. It is found that for reactor-grade plasmas, the bootstrap current contribution to the toroidal current is, in general, important. In some cases, it is even found that the bootstrap current density locally exceeds the required current density of the initial target equilibrium. An approximate scaling law for P, based on the parametric survey performed, is also obtained.

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“…Several researchers have studied the effect of trapped electrons on current-drive efficiency [1][2][3][4][5][6]. In kinetic theory, the bounce-averaging procedure enables us to consider the effect of trapped electrons on RF current drive [7][8][9]. In tokamak, a particle orbit can transit from one orbit class to the other.…”

Section: Introductionmentioning

confidence: 99%

Change of Resonant Electron Orbits from Trapped to Passing in Fast Wave Current Drive

Yao

Zhao

2010

Plasma and Fusion Research

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In fast wave current drive, fast waves accelerate resonant electrons in the direction parallel to the static magnetic field, causing parallel velocity to increase. The trajectory of a trapped resonant electron is calculated by computer code in which fast wave induced diffusion in velocity space is accounted for by a quasi-linear operator. Simulations show that the orbit of a trapped resonant electron transits from trapped to passing in some cases, reducing the effect of trapped electrons on current drive and improving current-drive efficiency. We determined the conditions under which this type of transition occurs.

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Tokamak MHD equilibrium generation by narrow-spectrum fast-wave current drive

Cited by 23 publications

References 18 publications

High harmonic fast waves in high beta plasmas

High harmonic fast waves in high beta plasmas

Bootstrap currents in radiofrequency driven tokamak equilibria

Change of Resonant Electron Orbits from Trapped to Passing in Fast Wave Current Drive

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