Fusion-related High-heat Flux Testing On Carbon-based First Wall Materials By High-Intensity Pulsed Ion Beam Irradiation

High-intensity pulsed ion beam (HIPIB) technique was employed as a useful tool to simulate plasma-material interactions, especially material ablation and erosion in Tokamak for evaluating and developing the first-wall materials.In this study, first-wall candidate materials-C/C composite, graphite G347, glassy carbon and SiC coating were investigated in TEMP-6 HIPIB apparatus. Typical HIPIB parameters for the irradiation were heat flux parameter of 180-400 MWm-2s1/2, accelerating voltage of 300 kV, pulse width of 75 ns and 1-10 shots. Electronic balance, scanning electron microscopy, X-ray diffractometer and Raman spectroscope were used to characterize weight loss, surface morphology and phase structure, to evaluate the ablation behaviors of the carbon-based materials under high heat flux.C/C composite and graphite G347 samples were irradiated with shot angle of 45°and 90°. Fracture and exfoliation of carbon fibers were observed at first in C/C composite, obvious ablation of graphite matrix were also found and noticeable cracking occurred on the graphite matrix when increasing the shot number. The irradiated graphite G347 presented a surface of selective ablation firstly, then turned to uniform ablation on a larger scale. It is difficult to estimate the influence of shot angle on the irradiated C/C composite, but it is easier to generate damage on graphite G347 at smaller angle. X-ray diffraction analysis showed that the phase structure of both materials had little change after irradiation.The irradiated glassy carbon presented uniform ablation and many homogeneous fine particles on the whole surface at first. Surface roughness increased from nm degree toμm degree. Then blebs, some of which bursted and exfoliated, appeared because the ablation form changed into selective bubbly ablation. Surface roughness increased, then decreased. So the resistance of ablation enhanced. Raman spectroscope analysis showed that the glassy carbon seemed like to change into graphite. we found the glassy carbon has the best resistance of high heat flux in these three materials.The SiC coatings irradiated by HIPIB also. The original loose and multihole-surface presented preferential ablation on the edge of holes firstly so that the edge became smooth. Then surface was remelted on a large scale under multi-shot exposure. The porosity fall down, but a lot of small tuber formed. X-ray diffraction analysis showed that the phase structure of SiC coatings changed from C, SiC into C,SiC and Si.