Slow-wave antenna coupling to ion Bernstein waves for plasma heating in ICRF

Sy, W. N. C.; Amano, Tsuneo; Ando, R.; Fukuyama, A.; Watari, T.

doi:10.1088/0029-5515/25/7/004

Cited by 14 publications

(21 citation statements)

References 14 publications

(23 reference statements)

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“…The question is then what the expected range of N| is when the IBW is launched by the antenna. It was not a priori obvious that Type-in antennas [8] excite IBW preferentially; this was then demonstrated by Sy et al [16]. Their model provides a simple estimate of an N| spectrum of IBW with a peak around six, as shown in Fig.…”

Section: Discussionmentioning

confidence: 91%

“…For a detailed analysis, the wave N| spectrum of the Mode-II regime must be known; the present code [16] PTE ~ with (6) , K) = -iP H 2 sinhPd i£iH 2 cosh pa + P sinhpa 2 coshP(a+d) + P sinhP(a+d)…”

Section: Discussionmentioning

confidence: 99%

“…[18] is: Wave N t spectrum for the Mode-l regime, computed with the model of Ref. [16] and with partition of the wave energy into electron and ion parts. It is predicted that not only ion heating occurs but also electron heating.…”

Section: Discussionmentioning

confidence: 99%

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Characteristics of ion Bernstein wave heating on the JIPP T-IIU tokamak

Ogawa¹,

Kawahata²,

Ando³

et al. 1987

Nucl. Fusion

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Ion Bernstein Wave (IBW) heating has been examined on the JIPP T-IIU tokamak under two different conditions referred to as Mode-I and Mode-II. In the Mode-I regime, a wave is launched on an IBW branch between the third and fourth cyclotron harmonics of deuterium ions. In the Mode-II regime, a wave is launched on a branch between the second and third cyclotron harmonics. These two modes show quite different heating characteristics. The causes of this difference are analysed by using a simple model to determine the k, spectrum of the excited wave and by applying a ray tracing code. In connection with the Mode-I experiment as discussed in a previous report (1985), two important new experimental results are obtained. It is shown that an IBW heats the core of the plasma rather than causing plasma-edge interaction, as anticipated. It is also shown that the energy tail of the hydrogen ions is higher than that of the deuterium ions, which indicates that the responsible heating mechanisms are different.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Characteristics of ion Bernstein wave heating on the JIPP T-IIU tokamak

Ogawa¹,

Kawahata²,

Ando³

et al. 1987

Nucl. Fusion

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“…Indeed, it has been shown that a drop in density at the plasma edge can help facilitate coupling to electrostatic modes that have non-zero (though small) components of k || . 28,29 …”

Section: B Excited Modes In Bwx IImentioning

confidence: 99%

Variable dual-frequency electrostatic wave launcher for plasma applications

Jorns

Sorenson

Choueiri

2011

Review of Scientific Instruments

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A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example--generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently--with a high adaptability to a number of plasma dynamics and heating applications.

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“…,49 The mcxtification of IBWH antenna coupling due to tile ponderomotive force lead tc) fmlher non-linear effects to set in, On the other hand, the ponderomotive density reduction could perhaps help reduce the rf power loss due to the slmath related processes fSc,cs 4.3, 1 to 4,3,3), For this reason, to maintain an optimum wave launching condition, it may be qt_ite tb important to adjust the plasma boundary position at a given power level to account for tt'_e density profile mcxtification by the ponderomotive force, II, the coupling is dominated by the EPW physics since in both regimes, EPW is excited at the antenna-plasma interface, Also, the wave reflection, ii' any, should take place mainly in the EPW layer (as discussed in the prevtous section), For this reason, the _mtenna coupling theory developed for Lt-HI could be applied directly here,4, 92 A multi-step model was used to simulate arbimu'y plasma profiles, 66 In these EPW dominated regimes, the magnetic field delxmdence for the antenna loading, like LHH case, is therefore relatively weak, The simplest model was used by W,N,-C, Sy et al, whe, e a step model (with an optional vacuum interface region) where the wave fields were matched at the plasma boundary was used to coupled directly to IBW 93. Brambilla has used the finite-Larmor-radius expanded wave differential equations to solve tor the surface impedance for the 2-0i launching case.43, 94 F. Skiff, et.…”

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confidence: 99%

Ion Bernstein wave heating research

Ono¹

1992

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Ion Bernstein wave heating (IBWH) utilizes the ion Bernstein wave (IBW), a hot plasma wave, to carry the radio frequency (rf). power to heat tokamak reactor core. Earlier wave accessibility studies have shown that this finite-Larm0r-radius (FLR) mode should penetrate into a hot dense reactor plasma core without significant attenuation. Moreover, the IBW's low phase velocity (m / kt,= VTi << Va) greatly reduces the otherwise ,serious wave absorption by the 3.5 MeV fusion ox-particles. In addition, the property of IBW's that k±p i = 1 make:; l(xcalized bulk ion heating possible at the ion cyclotron harmonic layers. Such bulk ion heating can prove useful in optimizing fusion reactivity. In another vein, with proper selection of parameters, IBW's can be made subject to strong localized electron Landau damping near the major ion cyclotron harmonic resonance layers. This property can be useful, for example, for rf current drive in the reactor plasma core,. IBW's can be excited with loop antennas or with a lower-hybrid like waveguide launcher at the plasma edge, the latter structure being one that is especially compatible with reactor application. In either case, the mode at the plasma edge is an electron plasma wave (EPW). Deeper in the plasma, the EPW is mode-transformed into an [BW. Such launching and mode-transformation of IBW's were first demonstrated in experiments in the ACT-1 plasma torus and in particle simulation calculations. These and other aspects of IBW heating physics have been investigated through a number of experiments performed on ACT-1, JIPPTII-U, TNT, PLT and Alcator-C. In these experiments both linear and nonlinear heating processes have been observed, Interestingly, improvement of plasma confinement was also observed in the PLT, Alcator-C, and JIPPTII-U experiments, opening up the possible use of IBW's for the active control of plasma transport. Two theoretical explanations have been proposed: one ba_d on tour-wave-mixing of IBW with low frequency turbulence, the other on the noninear generation of a velocity-shear laver. Both models are consistent with the observed threshold power level of a few hundred kW in the experiments.. Experiments on lower field plasmas on JI-:I'II-M and DII!-D have raised some concern with the IBW wave-launching process. The experiments showed serious impurity release from the walls but little or no core heating, a combination of circumstances strongly suggestive of edge heafingl Possible parasitic channels could include the excitation of short wavelength modes by the Faraday shield's fringing fields, antenna sheath-wave excitation, an axial convective loss " channel, and nonlinear processes such as parametric instability and ponderomotive effects. Suggested remedies include changes in the antenna phasing, the use of low-Z insulators, operating at higher frequencies, positioning the plasma differently with respect to the antenna, eliminating the Faraday shields, and using a waveguide launcher. The recent JIPPTII-U experiment, employing a ()-rcphased antenna array with a ...

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Slow-wave antenna coupling to ion Bernstein waves for plasma heating in ICRF

Cited by 14 publications

References 14 publications

Characteristics of ion Bernstein wave heating on the JIPP T-IIU tokamak

Characteristics of ion Bernstein wave heating on the JIPP T-IIU tokamak

Variable dual-frequency electrostatic wave launcher for plasma applications

Ion Bernstein wave heating research

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