Low-threshold absolute parametric decay instability in the monotonous density profile region in O1-mode ECRH experimental conditions

The possibility of the low-threshold absolute parametric decay instability excitation by the ordinary wave in the presence of a monotonous plasma density profile is analyzed. It is shown that in the cases of daughter upper hybrid and ion Bernstein waves the energy circulation between two nearby deca...

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Bibliographic Details
Published in:Plasma physics and controlled fusion 2019-02, Vol.61 (2), p.25006
Main Authors: Gusakov, E Z, Popov, A Yu, Saveliev, A N
Format: Article
Language:English
Subjects:
ECRH experiments
ion Bernstein wave
microwave
ordinary wave
parametric decay
upper hybrid wave
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Summary:The possibility of the low-threshold absolute parametric decay instability excitation by the ordinary wave in the presence of a monotonous plasma density profile is analyzed. It is shown that in the cases of daughter upper hybrid and ion Bernstein waves the energy circulation between two nearby decay points can lead to an absolute instability at the pump power of less than half a megawatt. The instability saturation due to the ion Bernstein wave amplitude-dependent stochastic damping effect is considered and the rate of anomalous pump absorption is estimated. This scenario can explain the observations of anomalous scattering in the O1-mode electron cyclotron resonance heating (ECRH) experiments at the FTU (Frascati Tokamak Upgrade) tokamak in the presence of a monotonous density profile.
ISSN:0741-3335
1361-6587
DOI:10.1088/1361-6587/aaee52