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Retention of 200 eV H þ 2 ions ðE i ¼ 100 eV=nuclÞ in fine grain graphite of MPG-8 type, graphite of RGT type ðC þ 3:5% TiCÞ; CFC of N11 type, crystalline boron carbide and hydrocarbon films was investigated by means of thermal desorption spectrometry. The implantation dose varied between 5 Â 10 21 and 6 Â 10 24 H=m 2 : Temperature of the samples during implantation was 470 AE 10 K: The measurements showed that hydrogen retention at high fluences increased in the following order: B 4 C; MPG-8 and CFC, RGT, CHfilms. The main part of trapped hydrogen and CH 4 molecules are collected in deep layers beyond the kinetic ion range.Slowing down of the retention rate in graphites at fluences around 5 Â 10 23 H=m 2 may account for the approach of the hydrogen trapping rate and the rate of the hydrogen release from the sputtered surface. Hydrogen retention in B 4 C saturates near the fluence 10 24 H=m 2 : Saturation of the CH 4 release was observed in all graphites and in boron carbide at fluences around 10 24 H=m 2 : The features of the hydrogen retention in deep layers of materials under low energy ion implantation are discussed.Ã

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