The targeted plasma parameters of the compact spherical tokamak (ST) Globus-M have basically been achieved. The reasons that prevent further extension of the operating space are discussed. The operational limits of Globus-M together with an understanding of the limiting reasons form the basis for defining the design requirements for the next-step, Globus-M2. The recent experimental and theoretical results achieved with Globus-M are discussed, the operational problems and the research programme are summarized and finally, the targeted Globus-M2 parameters are presented. The magnetic field and plasma current in Globus-M2 will be increased to 1 T and 0.5 MA, respectively. The plasma dimensions will remain unchanged. With auxiliary heating at a high average plasma density, the temperatures will be in the keV range and the collisionality parameter with ν* ≪ 1 will define the operational conditions. Noninductive current drive will be a major element of the programme. The engineering design issues of Globus-M2 tokamak are discussed and the technical tokamak parameters are confirmed by thermal load and stress analysis simulations. The experimental results obtained on Globus-M2 and the limits of its performance should clarify the feasibility of an ST-based super compact neutron source.

Experimental results showing evidence for the development of filaments in plasma of the Globus-M spherical tokamak have been obtained by the method of Doppler reflectometry. The correlation between...

The results of limit cycle oscillations (LCO) studies in the spherical Globus-M tokamak are presented. The oscillations of E×B drift velocity, turbulence level, Dα light emission, plasma density and magnetic field with the LCO frequency were simultaneously observed. Properties of two LCO regimes, with and without the transition to the H-mode, are compared. The results of a correlation analysis between flows and turbulence require the use of a 1D model of the LCO development. The bicoherent analysis demonstrates that zonal flows dominate in LCO. An up–down asymmetry of the poloidal magnetic field oscillations with the LCO frequency is found.