  I-mode is a promising regime for future fusion reactors due to the high
energy confinement and the moderate particle confinement. However, the effect
of lithium, which has been widely applied for particle recycling and impurity
control, on I-mode plasma is still unclear. Recently, experiments of real-time
lithium powder injection on I-mode plasma have been carried out in EAST
Tokamak. It was found that the confinement performance of the I-mode can be
improved by the lithium powder injection, which can strongly reduce electron
turbulence (ET) and then trigger ion turbulence (IT). Four different regimes of
I-mode have been identified in EAST. The Type I I-mode plasma is characterized
by the weakly coherent mode (WCM) and the geodesic-acoustic mode (GAM). The
Type II I-mode is featured as the WCM and the edge temperature ring oscillation
(ETRO). The Type III I-mode corresponds to the plasma with the co-existence of
ETRO, GAM, and WCM. The Type IV I-mode denotes the plasma with only WCM but
without ETRO and GAM. It has been observed that WCM and ETRO are increased with
lithium powder injection due to the reduction of ion and electron turbulence,
and the enhancement of the pedestal electron temperature gradient. EAST
experiments demonstrate that lithium powder injection is an effective tool for
real-time control and confinement improvement of I-mode plasma.
