Comparison of Supersonic Molecular Beam Injection from both low field side and high field side of HL-2A

SMBI (supersonic molecular beam injection), as an effective fueling method for fusion plasmas, has been widely used on the HL-2A tokamak and other fusion devices. Two different types of SMBI system are now installed on HL-2A. One is an electromagnetic valve injector on the low field side (LFS), and the other is a pneumatic valve injector on the high field side (HFS). A new electron density record, which exceeds both the Greenwald density limit and the maximum density obtained by gas puffing (GP), was obtained on HL-2A with single-null-divertor operation. The HFS injection system is still under test, however, its outstanding fueling characteristics have already been observed, e.g. it has higher fueling efficiency compared to the LFS system. This excellent feature is still preserved during the process of ECRH.