Experimental study of an ion-temperature-gradient driven instability in a linear machine

Greaves, R. G.; Chen, J; Sen, A. K.

doi:10.1088/0741-3335/34/7/006

Cited by 35 publications

(27 citation statements)

References 33 publications

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“…In addition, due to the small size of CLM and the range of unstable linearly unstable poloidal modes, there are only a few modes present in the experiment. 30,32 Here we extend the calculations of Ref. 50 to take into account that the system here ͑both experiment and simulation͒ is radially bounded and three dimensional.…”

Section: Theory Of Nonlinear Saturationmentioning

confidence: 89%

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Simulation of cylindrical ion temperature gradient modes in the Columbia Linear Machine experiment

Parker¹,

Sen²

2002

Physics of Plasmas

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A comparison of the Columbia Linear Machine experiment [A. K. Sen, J. Chen, and M. Mauel, Phys. Rev. Lett. 66, 429 (1991)] with three-dimensional nonlinear electrostatic gyrokinetic simulation results is given, as well as comparisons with linear theory and simple theoretical predictions of nonlinear saturation. Linear theory is in reasonable agreement with the both experimental and simulation results. An analysis of the radial mode width which is localized by variation in the ion temperature gradient is given and compares well with both experiment and simulation. The theoretical estimate of the nonlinear saturation level is within a factor of 2 of what is observed in experiment and in simulation. In addition, both experiment and simulation show excitation of longer wavelength modes with poloidal mode numbers smaller than the linearly most unstable mode.

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Section: Theory Of Nonlinear Saturationmentioning

confidence: 89%

“…This is accomplished by a dc ion acceleration scheme 30 or a rf heating technique, which consists of two meshes: a disk mesh excited by a rf signal and an annular mesh biased by a dc voltage. 32 In this paper we focus on the experiments done using the first method of dc acceleration.…”

Section: Itg Modes Found In Clmmentioning

confidence: 99%

Simulation of cylindrical ion temperature gradient modes in the Columbia Linear Machine experiment

Parker¹,

Sen²

2002

Physics of Plasmas

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“…5,6 We now discuss the clear identification of the low frequency ͑ 2 ͒ mode of the triad discussed above. Its azimuthal mode number is determined from the azimuthal phase shift measured via cross-correlation of two Langmuir probes, displaced azimuthally 90°͑180°͒ apart to yield m 2 = 0.…”

Section: ͑2͒mentioning

confidence: 97%

“…4 The mode with a frequency of f ϳ 120 kHz satisfied the characteristics of the slab ITG mode with m =2, k ʈ ϳ 2 / 400 cm −1 . 5 We focus on maintaining the most important parameters rigorously constant for both gases. In the case of ITG modes in the CLM it is iʈ .…”

Section: Introductionmentioning

confidence: 99%

A new paradigm for plasma transport and zonal flows

2006

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Most tokamak experimental results indicate dependence of the ion thermal conductivity on the isotopic mass close to χ⊥∼mi−0.5, i.e., inverse gyro-Bohm. This is in stark contradiction to most present theoretical models predicting Bohm (mi0) or gyro-Bohm (mi0.5) scaling. A basic physics isotopic scaling experiment [V. Sokolov and A. K. Sen, Phys. Rev. Lett. 89, 095001 (2002)] on the anomalous ion thermal conduction due to ion temperature gradient (ITG) instabilities in two different gases (hydrogen and deuterium) closely confirms the tokamak results. Another series of experiments designed to explore the physics basis of this scaling appears to lead to a new model for this scaling based on 3-wave coupling of two ITG radial harmonics and an IA wave. The resulting isotopic scaling of transport is ∼mi−0.5 dictated primarily by the IA damping. This basic physics may be extrapolated to tokamaks resolving the paradox [V. Sokolov and A. K. Sen, Phys. Rev. Lett. 92, 165002 (2004)]. Last, the much discussed theoretical role of zonal flows in transport regulation is critically examined by another set of experiments. A novel diagnostic has been developed on the basis of the observation that the effect of zonal flow can be seen in the FM modulation (at zonal flow frequency) of the carrier frequency of the large equilibrium Doppler shift frequency of ITG modes both in tokamaks and in the Columbia Linear Machine [V. Sokolov, X. Wei, and A. K.Sen, APS DPP meeting, Savannah (2004)]. The present results indicate zonal flow levels close to the theoretical prediction, but its shear is much lower than that predicted by theory for transport regulation.

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“…Low-frequency density fluctuations are also easily observed in cylindrical magnetized plasma columns. [5][6][7][8][9] These cylindrical machines are of fundamental interest and can provide a testing ground for comparisons of numerical simulations with experiments.…”

Section: Introductionmentioning

confidence: 99%

Kinetic water-bag model of global collisional drift waves and ion temperature gradient instabilities in cylindrical geometry

Gravier

Plaut

2013

Physics of Plasmas

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Équipe 107 : Physique des plasmas chaudsInternational audienceCollisional drift waves and ion temperature gradient (ITG) instabilities are studied using a linear water-bag kinetic model [P. Morel et al., Phys. Plasmas 14, 112109 (2007)]. An efficient spectral method, already validated in the case of drift waves instabilities [E. Gravier et al., Eur. Phys. J. D 67, 7 (2013)], allows a fast solving of the global linear problem in cylindrical geometry. The comparison between the linear ITG instability properties thus computed and the ones given by the COLUMBIA experiment [R. G. Greaves et al., Plasma Phys. Controlled Fusion 34, 1253 (1992)] shows a qualitative agreement. Moreover, the transition between collisional drift waves and ITG instabilities is studied theoretically as a function of the ion temperature profile

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Experimental study of an ion-temperature-gradient driven instability in a linear machine

Abstract: An ion-tcmpcraturc~gradient driven instability is investigated in the Columbia Linear Machinc (CLM). A transit-time r.f. techniquc is used to heat the core of the plasma column. This produces the

Cited by 35 publications

References 33 publications

Simulation of cylindrical ion temperature gradient modes in the Columbia Linear Machine experiment

Simulation of cylindrical ion temperature gradient modes in the Columbia Linear Machine experiment

A new paradigm for plasma transport and zonal flows

Kinetic water-bag model of global collisional drift waves and ion temperature gradient instabilities in cylindrical geometry

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