Spectroscopic Measurement of Electron Temperature during Lower Hybrid Current Startup in JIPP T-IIU Tokamak

1986 ◽  
Vol 25 (Part 1, No. 3) ◽  
pp. 458-463 ◽  
Author(s):  
Mikio Mimura ◽  
Kuninori Sato ◽  
Kazuo Toi ◽  
Junji Fujita
Keyword(s):  
Electron Temperature ◽  
Spectroscopic Measurement ◽  
Lower Hybrid

Scattering of electromagnetic waves by hybrid waves in a two-electron-temperature plasma

1991 ◽  
Vol 46 (1) ◽  
pp. 99-106 ◽  
Author(s):  
S. K. Sharma ◽  
A. Sudarshan
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Stimulated Scattering ◽  
Coupled Modes ◽  
Temperature Plasma ◽  
Electrostatic Perturbation

In this paper, we use the hydrodynamic approach to study the stimulated scattering of high-frequency electromagnetic waves by a low-frequency electrostatic perturbation that is either an upper- or lower-hybrid wave in a two-electron-temperature plasma. Considering the four-wave interaction between a strong high-frequency pump and the low-frequency electrostatic perturbation (LHW or UHW), we obtain the dispersion relation for the scattered wave, which is then solved to obtain an explicit expression for the growth rate of the coupled modes. For a typical Q-machine plasma, results show that in both cases the growth rate increases with noh/noc. This is in contrast with the results of Guha & Asthana (1989), who predicted that, for scattering by a UHW perturbation, the growth rate should decrease with increasing noh/noc.

scholarly journals Analysis of Observations near the Fourth Electron Gyrofrequency Heating Experiment in EISCAT

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 191
Author(s):  
Zeyun Li ◽  
Hanxian Fang ◽  
Hongwei Gong ◽  
Zhe Guo
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Parametric Instability ◽  
Density Fluctuations ◽  
Lower Hybrid ◽  
Langmuir Waves ◽  
Ionospheric Heating ◽  
Superthermal Electron ◽  
Temperature Electron ◽  
Electron Gyrofrequency

We present the observations of the artificial ionospheric heating experiment of EISCAT (European Incoherent Scatter Scientific Association) on 22 February 2012 in Tromsø, Norway. When the pump is operating near the fourth electron gyrofrequency, the UHF radar observation shows some strong enhancements in electron temperature, electron density, ion line, and the outshifted plasma lines. Based on some existing theories, we find the following: first, Langmuir waves scattering off lower hybrid density fluctuations and strong Langmuir turbulence (SLT) in the Zakharov model cannot completely explain the outshifted plasma lines, but the data suggest that this phenomenon is related to the cascade of the pump wave and should be researched further; second, the spatiotemporal consistency between the enhancement in electron density/electron temperature reaches up to three to four times that of the undisturbed state and HF-enhanced ion lines (HFILs) suggest that SLT excited by parametric instability plays a significant role in superthermal electron formation and electron acceleration; third, some enhancements in HFILs and HF-induced plasma lines (HFPLs) are generated by parametric decay instability (PDI) during underdense heating in the third cycle, we suggest that this is due to the existence of a second cut-off in the upper hybrid dispersion relation as derived from a kinetic description.

scholarly journals Nichtlineare Welleneinkopplung in ein Plasma erhöhter Elektronentemperatur / Nonlinear Wave Coupling to a Plasma of Enhanced Electron Temperature

1976 ◽  
Vol 31 (12) ◽  
pp. 1566-1571 ◽  
Author(s):  
G. Glomski ◽  
B. Heinrich ◽  
H. Schlüter
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Nonlinear Wave ◽  
Lower Hybrid ◽  
Radio Waves ◽  
Wave Coupling ◽  
Neutral Gas ◽  
At Resonance ◽  
Parametric Effects ◽  
Lower Hybrid Resonance

Abstract Nonlinear Wave Coupling to a Plasma of Enhanced Electron Temperature In continuation of former investigations radio waves of different amplitude in the domain of lower hybrid resonance were coupled to a plasma of enhanced electron temperature. Under linear conditions no dependence of resonance behaviour on the wave amplitude was observed. Exceeding a treshhold maximum of absorption and electron density decreased significantly; both observations may be explained by onset of nonlinear and parametric effects. Increasing the amplitude the discharge only could be maintained by increasing the neutral gas pressure. In the power range of 15 to 20 kW electron density grew rapidly at resonance.

Quasimode decay of a lower-hybrid wave in a two-electron-temperature plasma

1996 ◽  
Vol 56 (2) ◽  
pp. 237-249
Author(s):  
A. Sudarshan ◽  
S. K. Sharma
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
Decay Channel ◽  
Lower Hybrid ◽  
Hybrid Wave ◽  
Lower Hybrid Wave ◽  
Temperature Plasma ◽  
Parametric Decay ◽  
Cylindrical Plasma ◽  
Ion Cyclotron

We study the quasimode decay of a lower-hybrid wave and a damped ion cyclotron wave in a plasma having two kinds of electrons. This decay channel is also investigated for a cylindrical plasma. The behaviour of the threshold and growth rate with variations in Tn/Tc and non/noc are studied, and a comparison is made with previous results. Our results show that the growth rate and the threshold for the onset of parametric decay are influenced by the presence of the second electron species.

Leistungseinkopplung in ein Plasma erhöhter Elektronentemperatur bei der unteren Hybridresonanz

1978 ◽  
Vol 33 (12) ◽  
pp. 1447-1451
Author(s):  
G. Glomski ◽  
B. Heinrich ◽  
H. Schlüter
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Reactive Power ◽  
Transfer Efficiency ◽  
Lower Hybrid ◽  
Power Transfer ◽  
Resonant Coupling

Abstract Previous investigations of lower hybrid resonant coupling to plasmas of low collision frequencies and elevated electron temperature are extended to cover a range of some mW to 1500 W of reactive power. Though resonant behaviour is observed throughout, the efficiency of power transfer is lowered when a threshold at about 1 Watt of reactive power is surpassed. Moreover there is a limited decrease of electron density. For high powers saturation in the drop of transfer efficiency is observed.

Parametric decay instability of an upper-hybrid wave in a two-temperature plasma

1994 ◽  
Vol 51 (2) ◽  
pp. 193-200 ◽  
Author(s):  
S. Konar ◽  
V. Rai
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
Density Ratio ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Hot Electron ◽  
Hybrid Wave ◽  
Temperature Plasma ◽  
Band Frequency ◽  
Parametric Decay

Parametric decay of an upper-hybrid pump into another upper-hybrid wave and a low-frequency lower-hybrid mode is considered in a two-electron temperature plasma. Expressions for the nonlinear dispersion relation and growth rate are obtained. It is found that the growth rate is quite sensitive to the hot-electron temperature and the density ratio of the hot and the cold components only when the side-band frequency is close to the second or third harmonic of the cyclotron frequency. The relevance of our investigation to Q machines and the ELMO bumpy torus is pointed out.

Three electrostatic temperature drift instabilities

1981 ◽  
Vol 25 (1) ◽  
pp. 145-159 ◽  
Author(s):  
S. Peter Gary ◽  
Barbara Abraham-Shrauner
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Electron Temperature ◽  
Lower Hybrid ◽  
Ion Temperature ◽  
Temperature Drift ◽  
Ion Temperature Gradient ◽  
Electron Temperature Gradient ◽  
Drift Instability ◽  
Electrostatic Dispersion

This paper considers temperature drift instabilities, modes which can be driven unstable solely by a temperature gradient perpendicular to a magnetic field. The linear electrostatic dispersion relation for a Vlasov plasma in a uniform magnetic field is used and propagation is assumed to be in the plane perpendicular to the gradient. Three temperature drift instabilities have been found. The ion temperature drift instability arises at frequencies much below the ion cyclotron frequency, the electron temperature drift instability propagates somewhat below that frequency and the lower-hybrid temperature drift instability has frequencies above the lower-hybrid frequency. The first of these modes is driven by an ion temperature gradient and is enhanced by increasing Te/Ti. The latter two modes are driven by an electron temperature gradient and are enhanced by a decreasing Te/Ti. Density gradients are considered as an additional source of free energy, and comparisons of temperature drift with density drift instabilities are made.

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