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Radial electric field shear is crucial for turbulence suppression and transition to the H-mode, although the high shear value alone may not be sufficient for the LH-transition initiation. Temporal and spatial parameters of shear perturbation, particle source and turbulence parameters are the main factors responsible for LH-transition initiation. Different plasma discharge scenarios in two Ioffe Institute conventional tokamaks are analyzed using the model of plasma density and ion temperature evolution to clear up the role of aforementioned factors.Radial electric field shear is crucial for turbulence suppression and transition to the H-mode, although the high shear value alone may not be sufficient for the LH-transition initiation. Temporal and spatial parameters of shear perturbation, particle source and turbulence parameters are the main factors responsible for LH-transition initiation. Different plasma discharge scenarios in two Ioffe Institute conventional tokamaks are analyzed using the model of plasma density and ion temperature evolution to clear up the role of aforementioned factors.

In the H-mode discharges with the neutral beam heating (NBI) in the Globus-M tokamak the sawtooth oscillations are triggering the edge localised modes (ELM) onset. The triggered ELMs have the magnetic oscillation precursor less than 0.2 ms before the onset with the typical island rotation frequency. The paper discussing the peeling-ballooning (P-B) destabilisation caused by the current density profile broadening due to partial reconnection.

Here we report the results of the turbulence study in the high confinement mode (H-mode) with and without edge localized modes (ELMs). The study was performed by the Doppler backscattering (DBS) method on the Globus-M tokamak. It was demonstrated that the transition from the H-mode with ELMs to the ELM-free H-mode is characterized by the drop of the turbulence intensity near the periphery.

This article considers a four-frequency microwave Doppler backscattering (DBS) system in the compact spherical tokamak Globus-M. The hardware was adequate for the purposes of studying the peripheral plasma in the tokamak. The multichannel DBS system is based on duplication of a dual homodyne detection circuit for four incident Ka-band frequencies. The ray tracing results for a spherical torus are described, and specific requirements for the antenna tilt adjustment are defined. Some new experimental results are given for using DBS diagnostics on the Globus-M tokamak in order to illustrate its efficiency.