Hot-ion modes in the high-field compact spherical tokamak Globus-M2

The development of the next generation of spherical tokamaks (STs) or fusion neutron sources based on STs depends on achieving high-temperature plasma regimes with enhanced energy confinement. Here, we report the realization of hot-ion modes in the Globus-M2 compact ST (R = 0.36 m, a = 0.24 m), where ion temperatures reach 50 million Kelvin (> 4 keV) at high plasma densities (> 10 20 m -3 ). By doubling the toroidal magnetic field from 0.5 T to 1 T, we observed a threefold improvement in thermal energy confinement. Our analysis reveals that high-torque neutral beam injection effectively suppresses ion-scale turbulence, enabling ion heat transport to approach the fundamental neoclassical limit at low collisionality. Furthermore, we demonstrate that the increased magnetic field plays a critical role in suppressing turbulent heat fluxes, ensuring robust thermal insulation. These results provide firm experimental validation for the high-field compact ST potential as a fusion neutron source or an essential testbed for fusion technology development as well as for plasma physics studies under low collisionality conditions demonstrating that record-level plasma parameters can be maintained in a compact device through the synergy of strong magnetic confinement and rotation-induced turbulence suppression.