Sawtooth Activities During Impurity Injection by Laser Blow-off in HL-2A

In order to study impurity transport and their progression in the plasma,smallamount of high-Z impurities were injected into HL-2A ohmic heated plasmas by laser blow-off andtraced with good spatial temporal resolution by a soft X-ray camera.An analysis of the evolutionof the impurities’ radiation distribution in the plasma revealed that impurity transport in thecentral region was profoundly different from that outside of it.It was found that the sawteethtended to be inverted on the central soft X-ray chord signals after the impurity injection and thesoft X-ray profiles exhibited discontinuities during the movement of the impurities in the plasmacentral region.Detailed 2D visualization of the evolution of impurities’ radiation using computertomography has provided further understanding of the properties of impurity transport in theHL-2A plasma.