A spectroscopic scheme to measure the expansion velocity of ablation plasmas formed by high intensive pulsed ion beam

This paper presents a spectroscopic scheme to measure the expansion velocity of the ablation plasma formed on the surface of a polyethylene target, which is impacted by the high intensity pulsed ion beam (HIPIB) generated in the TEMP-II accelerator of our laboratory. The temporal emission profiles of the ablation plasma pulses are obtained by a SP-305 spectrometer and depicted by a TDS3052B digital oscilloscope at different positions along the direction of the plasma expansion with the aid of optical fibers. The distinguished differences of the average arrival-time of the emission maximums to different positions are used to determine the expansion velocity of the ablation plasma. Some spectral peak emissions from different species existed in the ablation plasmas are chosen to determine the expansion velocity of the ablation plasmas by the above-mentioned arrival-time scheme. The results from different species show the expansion velocity in same order of 1000 m/s when the average energy of each HIPIB pulse is about 12J and the duration is 70 ns. (C) 2004 Elsevier Ltd. All rights reserved.