Upgrades and characteristics of the compact torus injector for central fueling of the EAST tokamak

The compact torus injector (CTI) for the central fueling of the EAST tokamak has undergone significant upgrades to enhance its injection capability. During the initial phase of the platform testing phase, EAST-CTI demonstrated relatively low performance, with a maximum velocity of 150 km s⁻¹ and a single compact torus (CT) plasma mass of 90 μg Kong D et al 2023 Plasma Sci. Technol. 25 065601. These parameters were insufficient for conducting central fueling experiments on the EAST tokamak. Consequently, extensive upgrades were carried out to improve the performance of the EAST-CTI system. The compression region was extended from 280 mm to 700 mm to prevent rapid compression and deceleration of the CT plasma, along with an extension of the acceleration region to further increase the plasma acceleration. The power supply system has also been upgraded. These improvements elevated the operating voltage from 8 kV to 15 kV, increased the discharge current from 120 kA to 300 kA and enabled repetitive operation at a maximum rate of 2 Hz. As a result, significant advances in EAST-CTI performance were achieved, with the maximum velocity increasing to 330 km s⁻¹ and the CT plasma density reaching 1.5×10²² m⁻³, thereby enhancing the system capability for future fueling experiments on EAST. This study offers valuable insights into CTI modification and the improvement of central fueling systems for prospective fusion reactors.