Dimensionless experiments test the invariance of plasma physics to changes in the dimensional plasma parameters, when the canonical dimensionless parameters, such as rho_star, nu_star, β, q, ... are conserved [1], [2]. In particular, isotope identity experiments exploit the change in isotope ion mass A = mi/mp to obtain plasmas with identical dimensionless profiles in the same tokamak. In...
Transition between isotope-mixing and non-mixing states in hydrogen-deuterium mixture plasmas is observed for the first time in the world in the isotope (hydrogen and deuterium) mixture plasma in Large Helical Device. In the non-mixing state, the isotope density ratio profile is un-uniform when the beam fueling isotope species differs from the recycling isotope species and the profile varies...
Wendelstein 7-X (W7-X) is an optimized stellarator of the HELIAS type. ASDEX Upgrade is a medium sized tokamak. In electron cyclotron heated (ECRH) hydrogen plasmas the central ion temperature is clamped at Ti,0 ~ 1.5 keV in both W7-X (Figure-1) and AUG. These findings are found to be virtually independent of heating power and electron density, and for W7-X, independent of magnetic...
Simultaneous high ion temperature ($T_i$) and high electron temperature ($T_e$) regime has been significantly extended due to the optimized heating scenario in the LHD deuterium (D) campaign. Such high-temperature plasmas were realized by the simultaneous formation of an electron ITB (e-ITB) and an ion ITB (i-ITB) by the combination of high power NBI and ECRH. In the high $T_i$ operation the...
Positive plasma potential was observed for the first time in a core tokamak plasmas, conventionally characterized by negative potential. Direct measurement of the electric potential in the core plasma is of paramount importance for the understanding of the role of radial electric field E_r in the mechanisms regulating the toroidal plasma confinement. New experimental observations and...
Diverted discharges at negative triangularity on the DIII-D tokamak (figure [1]a) sustain normalized confinement and pressure levels typical of standard H-mode scenarios ($H_{98,y2}\simeq 1$, $\beta_N\simeq 3$) without developing an edge pressure pedestal (figure [1]b), despite the auxiliary power far exceeding the L→H power threshold expected from conventional scaling laws. The power...
Introduction – Negative triangularity discharges were first studied on TCV to examine the effect of plasma shaping on energy confinement in ohmic, L-mode discharges [1]. Subsequent experiments, using ECRH to stabilize MHD instabilities, showed an improvement of energy confinement in negative triangularity as compared to similar positive triangularity discharges [2]. Modulated ECRH to allow...
