Asymmetric cold pulse perturbation has been observed by means of electron–cyclotron emission (ECE) and soft-x-ray array during pulse-modulated molecular beam injection (MBI) experiments on HL-2A. The perturbation depth is about 30 cm from the low field side and only about 10 cm from the high field side. The cold pulses cannot propagate to the plasma centre from either the low or high field side. The electron temperature in the plasma centre does not change during MBI, but electron density pulse perturbations can be observed in the plasma centre from the ECE 3rd harmonic measurements, which corresponds to the results of the far-infra-red laser interferometer. The experimental results indirectly provide evidence of the shielding mechanisms of the MBI physics.
Generation of high-charge electron beam in a subcritical-density plasma through laser pulse self-trapping