Possible beneficial ponderomotive force effects on fast-wave coupling in tokamaks

1994 ◽  
Vol 51 (3) ◽  
pp. 433-440 ◽  
Author(s):  
V. A. Petržílka
Keyword(s):  
Reflection Coefficient ◽  
Electric Field ◽  
Density Gradient ◽  
Plasma Density ◽  
Ponderomotive Force ◽  
Local Electric Field ◽  
Lower Hybrid ◽  
Fast Wave ◽  
Ponderomotive Forces ◽  
Boundary Plasma

At lower-hybrid frequencies in tokamaks, ponderomotive forces at fast-wave launching typically lead in the vicinity of the launching structure to a boundary plasma density increase. This results in a decrease in the reflection coefficient, and, in detached plasmas, to the appearance of a local electric field maximum at several centimetres from the launching grill structure; this electric field maximum is connected to the reversal of the plasma density gradient near the grill mouth because of ponderomotive force effects.

Nonlinear variations of the reflexion coefficient for lower-hybrid heating

1983 ◽  
Vol 30 (2) ◽  
pp. 211-221 ◽  
Author(s):  
V. A. Petržílka ◽  
R. Klíma ◽  
P. Pavlo
Keyword(s):  
Density Gradient ◽  
Plasma Density ◽  
Harmonic Approximation ◽  
Present Theory ◽  
Lower Hybrid ◽  
Rf Power ◽  
Space Harmonic ◽  
Hybrid Heating ◽  
Reflexion Coefficient ◽  
Power Densities

The effect of the ponderomotive depression of the plasma density on the power reflexion coefficient is calculated in the first space harmonic approximation. Numerical results demonstrate a considerable growth of the reflexion coefficient when increasing the RF power. Exceptionally, the reflexion coefficient can be almost invariable up to high RF power densities (≃ 10kW cm-2), if the unperturbed plasma density gradient is high (≳ 5 × 1012 cm-4). The relation of the present theory to experiments is discussed.

Plasma waves in Rosetta electric field observations in the plasma environment of comet 67P/Churyumov-Gerasimenko

2021 ◽  
Author(s):  
Elias Odelstad ◽  
Tomas Karlsson ◽  
Anders Eriksson ◽  
Fredrik Johansson
Keyword(s):  
Electric Field ◽  
Plasma Density ◽  
Plasma Waves ◽  
Lower Hybrid ◽  
Density Gradients ◽  
Cometary Plasma ◽  
Plasma Environment ◽  
Hybrid Frequency ◽  
Drift Instability ◽  
Comet 67P

<p>We perform a comprehensive statistical study of plasma wave activity observed in the electric field measurements obtained by the Langmuir probe instrument (RPC-LAP) onboard ESA's Rosetta spacecraft, which followed the comet 67P/Churyumov-Gerasimenko in its orbit around the sun for over two years in 2014-2016. We focus on waves in the range 1-30 Hz, roughly corresponding to the lower-hybrid frequency range. Here, electric field oscillations close to the local H<sub>2</sub>O<sup>+ </sup>lower hybrid frequency are common and collocated with sharp plasma density gradients, suggesting generation by the lower hybrid drift instability. We compare statistically the properties of the waves to the theoretical predictions on lower-hybrid wave generation by the lower hybrid drift instability, regarding e.g. amplitude dependence on plasma density gradients. We also examine the data for waves that can be attributed to other instabilities, such as various velocity-space anisotropies that may occur in the cometary plasma. We correlate the comet-related parameters, (relative spacecraft position, solar distance, plasma and neutral gas density, etc.) with wave-related parameters, such as amplitude/spectral density and frequency. This investigation greatly helps to clarify the importance of the plasma waves in different regions of the cometary plasma environment. </p>

High-performance near-infrared photodetectors based on C3N quantum dots integrated with single-crystal graphene

2021 ◽  
Author(s):  
Yun Zhao ◽  
Xiaoqiang Feng ◽  
Menghan Zhao ◽  
Xiaohu Zheng ◽  
Zhiduo Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Electric Field ◽  
Single Crystal ◽  
High Performance ◽  
Near Infrared ◽  
Fast Response ◽  
Local Electric Field ◽  
Infrared Photodetectors ◽  
Photocurrent Response

Employing C3N QD-integrated single-crystal graphene, photodetectors exhibited a distinct photocurrent response at 1550 nm. The photocurrent map revealed that the fast response derive from C3N QDs that enhanced the local electric field near graphene.

scholarly journals Electron burst driven by near electric field effects of lower-hybrid launchers

2018 ◽  
Vol 58 (6-8) ◽  
pp. 465-470
Author(s):  
L. Valade ◽  
A. Ekedahl ◽  
P. Ghendrih ◽  
Y. Sarazin ◽  
Y. Asahi ◽  
...  
Keyword(s):  
Electric Field ◽  
Lower Hybrid ◽  
Electric Field Effects ◽  
Field Effects
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