A quasi-steady-state alternating current operation assisted by lower hybrid wave (LHW) was achieved on a HT-7 superconducting tokamak with plasma current of I
p = 125 kA, line-averaged density of 1.5 × 1019 m−3, electron temperature of T
e = 500 eV and 30–50 s plasma duration. Plasma current was sustained and smoothly transferred from one direction to the other without loss of ionization. Plasma position control, LHW assistance, strong gas puffing and good wall condition are the key issues to have a smooth transition of plasma current. Our modelling results show that current reversal equilibrium configuration with two oppositely flowing currents in the high-field-side and the low-field-side during current reversal exists. This is in agreement with experimental measurements.
With the eigenvalue problem solved in the cylindrical coordinate system with a rectangular cross section, an exact analytical solution of the Grad–Shafranov–Helmhotz equation proposed by S. Wang [Phys. Rev. Lett. 93, 155007 (2004)] is found. The exact solution can describe a variety of equilibrium configurations including the current reversal equilibrium configurations, and it is valid for arbitrary aspect ratio.
Oxygen‐redox‐based‐layered cathode materials are of great importance in realizing high‐energy‐density sodium‐ion batteries (SIBs) that can satisfy the demands of next‐generation energy storage technologies. However, Mn‐based‐layered materials (P2‐type Na‐poor Nay[AxMn1−x]O2, where A = alkali ions) still suffer from poor reversibility during oxygen‐redox reactions and low conductivity. In this work, the dual Li and Co replacement is investigated in P2‐type‐layered NaxMnO2. Experimentally and theoretically, it is demonstrated that the efficacy of the dual Li and Co replacement in Na0.6[Li0.15Co0.15Mn0.7]O2 is that it improves the structural and cycling stability despite the reversible Li migration from the transition metal layer during de‐/sodiation. Operando X‐ray diffraction and ex situ neutron diffraction analysis prove that the material maintains a P2‐type structure during the entire range of Na+ extraction and insertion with a small volume change of ≈4.3%. In Na0.6[Li0.15Co0.15Mn0.7]O2, the reversible electrochemical activity of Co3+/Co4+, Mn3+/Mn4+, and O2‐/(O2)n‐ redox is identified as a reliable mechanism for the remarkable stable electrochemical performance. From a broader perspective, this study highlights a possible design roadmap for developing cathode materials with optimized cationic and anionic activities and excellent structural stabilities for SIBs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.