Excitation of Lower Hybrid Oscillations at Upper Hybrid Resonance by Microwaves

Hiroe, S.; Ikegami, H.

doi:10.1103/physrevlett.19.1414

Cited by 33 publications

(6 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A PDI at the UHR was first observed in mercury vapour tube discharges through the excitation of LH oscillations by sufficiently strong microwave radiation [28]. Similar observations were reported for linear hot-cathode helium discharges [29] and the FM-I spherator [30].…”

Section: Introductionsupporting

confidence: 65%

“…shows that m e 2 is generally a small quantity of order  b the weak coupling approximation breaks down, at the UHR. The above expression is clearly maxgiving us the following m e 2 , useful for deriving the maximum γ, With (37), (47) and (49), we are now in a position to determine γ for the non-resonant PDI from(28), used in the last approximation. From this we may easily determine the non-resonant PDI threshold in a homogeneous plasma (g > 0),…”

mentioning

confidence: 99%

See 1 more Smart Citation

Parametric decay instability near the upper hybrid resonance in magnetically confined fusion plasmas

Hansen

Nielsen

Salewski

et al. 2017

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

In this paper we investigate parametric decay of an electromagnetic pump wave into two electrostatic daughter waves, particularly an X-mode pump wave decaying into a warm upper hybrid wave (a limit of an electron Bernstein wave) and a warm lower hybrid wave. We describe the general theory of the above parametric decay instability (PDI), unifying earlier treatments, and show that it may occur in underdense and weakly overdense plasmas. The PDI theory is used to explain the anomalous sidebands observed in collective Thomson scattering (CTS) spectra at the ASDEX Upgrade tokamak. The theory may also account for similar observations during CTS experiments in stellarators, as well as in some 1st harmonic electron cyclotron resonance and OX -B heating experiments.

show abstract

Section: Introductionsupporting

confidence: 65%

mentioning

confidence: 99%

Parametric decay instability near the upper hybrid resonance in magnetically confined fusion plasmas

Hansen

Nielsen

Salewski

et al. 2017

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…This is the root cause of the microwave diagnostics damage associated with such PDIs [1]. Traditionally, magnetic confinement fusion ECRH PDIs were only expected in connection with extremely high power ECRH provided by pulsed free-electron maser sources [13] or in scenarios with lower ECRH power where a significant fraction of the ECRH power would reach the upper hybrid resonance (UHR) with X-mode polarization [4,5,[9][10][11][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. PDIs are expected in the above cases due to the occurrence of electric fields with large amplitudes.…”

Section: Introductionmentioning

confidence: 99%

Parametric Decay Instabilities during Electron Cyclotron Resonance Heating of Fusion Plasmas, Problems and Possibilities

Hansen

Nielsen²,

Stober³

et al. 2023

EPJ Web Conf.

View full text Add to dashboard Cite

We review parametric decay instabilities (PDIs) expected in connection with electron cyclotron resonance heating (ECRH) of magnetically confined fusion plasmas, with a specific focus on conditions relevant for the ITER tokamak. PDIs involving upper hybrid (UH) waves are likely to occur in O-mode ECRH scenarios at ITER if electron density profiles allowing trapping of UH waves near the ECRH frequency are present. Such PDIs may occur near the plasma center in ITER full-field scenarios heated by 170 GHz O-mode ECRH and on the high-field side of half-field ITER plasmas heated by 110 GHz or 104 GHz O-mode ECRH. Additionally, 110 GHz O-mode ECRH of half-field ITER scenarios may have low ECRH absorption, due to the electron cyclotron resonance being located on the high-field side of the main plasma. This potentially allows PDIs driven by a significant amount of ECRH radiation reaching the UH resonance in X-mode to occur, as X-mode radiation can be generated by reflection of unabsorbed O-mode radiation from the high-field side wall. The occurrence of PDIs during ECRH may damage microwave diagnostics, such as the electron cyclotron emission and low-field side reflectometer systems at ITER, as well as complicate the calculation of heating and current drive characteristics. However, if PDIs are induced in a controlled manner, they may provide novel diagnostic tools and allow the generation of a moderate fast ion population in plasmas heated only by ECRH.

show abstract

“…As the dispersion relations of the involved waves are known, this has allowed investigation of various properties of the ionosphere, such as the magnetic field, 6 conditions for electron acceleration, 7 the electron temperature, 8 the ion composition, 9 and pump-generated plasma layers. 10 PDIs in the EC frequency range have also been observed in a number of laboratory plasmas, including low-temperature experiments, [15][16][17][18] inertial confinement fusion experiments, 4 and magnetic confinement fusion experiments both in tokamaks [19][20][21][22][23][24][25][26] and in stellarators. [27][28][29][30][31] PDIs in laboratory plasmas have been used to demonstrate the occurrence of O-X-B heating, 22,28,29 to provide direct heating, 4,[16][17][18]20,21,27,30 and can also deliver information about the plasma parameters, 15,19,[23][24][25][26]31 but have generally been ignored when computing ECR heating and current drive characteristics.…”

Section: Introductionmentioning

confidence: 99%

Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas

et al. 2019

View full text Add to dashboard Cite

Parametric decay instabilities (PDIs) occur for large-amplitude waves in quadratically nonlinear media, where they provide a limit of validity of linear theories and allow efficient coupling between different, well-defined wave modes. We investigate PDIs near the upper hybrid resonance in plasmas by injection of high-power electron cyclotron (EC) waves at the ASDEX Upgrade tokamak. Our measurements of PDIs have an unprecedented frequency resolution, far below the ion cyclotron frequency, allowing the first observations of secondary and tertiary PDIs during the saturation phase in a controlled laboratory setting. Furthermore, we are for the first time able to systematically compare theoretical predictions of the EC wave power thresholds, which must be exceeded to excite such PDIs, to experimental observations, validating the theory. Our findings are relevant for EC wave heating and current drive in tokamaks and stellarators, including future fusion power plants, as well as in low-temperature laboratory and industrial plasmas, inertial confinement fusion, and ionospheric modification experiments.

show abstract

Excitation of Lower Hybrid Oscillations at Upper Hybrid Resonance by Microwaves

Cited by 33 publications

References 8 publications

Parametric decay instability near the upper hybrid resonance in magnetically confined fusion plasmas

Parametric decay instability near the upper hybrid resonance in magnetically confined fusion plasmas

Parametric Decay Instabilities during Electron Cyclotron Resonance Heating of Fusion Plasmas, Problems and Possibilities

Power threshold and saturation of parametric decay instabilities near the upper hybrid resonance in plasmas

Contact Info

Product

Resources

About