Abstract
8 keV 3He ions have been implanted into edge-oriented pyrolytic graphite at temperatures of 120 K and 295 K. The retention behavior observed by nuclear reaction and residual gas analyses differs markedly from that observed in metals. Despite the negligible reflection coefficient, the mean re-emission coefficient at low fluence amounts to ~30% at room temperature, with a relative maximum at a fluence of 1.5 × 10 17 cm −2. Saturation is observed at fluences above 5 × 10 17 cm 12. The implanted He is completely removed by annealing to 750 K. Reimplantation at room temperature shows an enhanced retention (~90%) at low fluences. The experimental results are discussed in terms of He diffusion, trapping at damage sites and possible structural changes of the material.
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