First Measurement of Electron Temperature and Density Profiles for Spherical Tokamak Plasmas Sustained by Lower Hybrid Waves

Using Bayesian analysis and Gaussian processes to infer electron temperature and density profiles on the Mega-Ampere Spherical Tokamak experiment.

A unified, Bayesian inference of midplane electron temperature and density profiles using both Thomson scattering (TS) and interferometric data is presented. Beyond the Bayesian nature of the analysis, novel features of the inference are the use of a Gaussian process prior to infer a mollification length-scale of inferred profiles and the use of Gauss-Laguerre quadratures to directly calculate ...

Frequency scaling of the lower-hybrid-current-drive density limit in tokamak plasmas.

It is shown experimentally that the lower-hybrid current drive "density limit" is a function of the rf source frequency. While in previous 800MHz experiments this limit occurred at ie = 6 x 1012 cm-3. with a newly installed 2.45GHz, 100kW rf system on the Versator II tokamak fully rf-driven discharges have been achieved at densities up to i = 1.Ox 1013 cm3 , without increasing the toroidal magn...

Energetic particles in spherical tokamak plasmas

Spherical tokamaks (STs) typically have lower magnetic fields than conventional tokamaks, but similar mass densities. Suprathermal ions with relatively modest energies, in particular beaminjected ions, consequently have speeds close to or exceeding the Alfvén velocity, and can therefore excite a range of Alfvénic instabilities which could be driven by (and affect the behaviour of) fusion α-part...

Saturation of electron cyclotron maser by lower-hybrid waves

We perform a numerical study on the quasilinear relaxation of an electron cyclotron maser on the initially dominant mode. We focus thereby on a situation where the initially dominant modes are quasi-electrostatic lower hybrid (lh) waves, which have not been treated in preceding studies. To this end, we chose 0.2 ≤ ωp/ωBe < 0.5 (ωp: plasma-, ωBe: electron cyclotron frequency) and an initial loss...

Co- and Counter-current Rotation Induced by Lower Hybrid Current Drive in Tokamak Plasmas