Ion-induced synergistic effects for CH4 production from carbon under H+, H0 and H2 impact

Haasz, A.A.; Auciello, O.; Stangeby, P.C.; Youle, I.S.

doi:10.1016/0022-3115(84)90417-3

Cited by 38 publications

(4 citation statements)

References 4 publications

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“…The observed synergism recalls another synergism in a-C:H erosion, namely, that between ion bombardment and atomic hydrogen [22,23,[28][29][30]. In this case, the proposed explanation [23] was that ion bombardment creates dangling bonds at and below the surface which become passivated by H. By repeated such events hydrocarbon molecules are formed which leave the surface.…”

supporting

confidence: 58%

Chemical sputtering of carbon films by argon ions and molecular oxygen at cryogenic temperatures

Hopf

Schlüter

Jacob

2007

Applied Physics Letters

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The experiments demonstrate the existence of a synergistic interaction of molecular oxygen and energetic ions with amorphous carbon leading to enhanced erosion; although the samples, amorphous hydrogenated carbon films, are not gasified by O 2 at room temperature, additional ion bombardment at the same temperature leads to erosion rates that drastically exceed those of physical sputtering. Investigation of the temperature dependence from 400 down to 113 K shows that the erosion rate increases with decreasing temperature.

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supporting

confidence: 58%

Chemical sputtering of carbon films by argon ions and molecular oxygen at cryogenic temperatures

Hopf

Schlüter

Jacob

2007

Applied Physics Letters

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“…An explanation for the stronger release of 3 He from C during H bombardment compared with W is that in our experiment the targets are exposed to H + ion and H 0 atom fluxes. While at a bias of 100 eV (corresponding to 33 eV per H for the dominant H + 3 plasma species) W is not eroded, the combination of H + ion and H 0 atoms leads to a strong chemical sputtering of the 3 He implantation zone in C [16]. This leads to the release of the implanted 3 He from the eroded regions of the implantation zone.…”

Section: Particle-induced He Releasementioning

confidence: 99%

The implications of high-Z first-wall materials on noble gas wall recycling

et al. 2007

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Recent experiments in ASDEX Upgrade (AUG) have experienced surprisingly high He plasma impurity concentrations. Such high He concentrations have not been observed with C walls, they were only observed since the increase of the W firstwall coverage of ASDEX Upgrade to 85%. The high He plasma concentration appears to be linked to the fraction of W surfaces open to plasma contact that are not covered by boronization layers and to the number of He glow discharges performed for wall conditioning prior to normal plasma operation. This points to the different retention and release properties of W and C for He. To elucidate these differences dedicated laboratory experiments have been performed. To study the retention, different types of W and C targets, including those used in ASDEX Upgrade, were implanted with 3 He at 200 eV and 600 eV and the amount of retained He was determined through thermal effusion spectroscopy (TES) and ion beam analysis (IBA) methods. These experiments showed that W can retain up to 10 times more He than C depending on the energy of the implanted 3 He. he TES measurement showed that both W and C start to out gas He at ≈ 400K which is not reached at the first wall in AUG. Therefore the differences in the release of He from W and C surfaces due to particle bombardment was investigated. 3 He implanted W and C substrates were exposed to 4 He or H 2 plasmas and the loss of 3 He was measured. For an H 2 plasma and 100 eV bias, three times more He is released from W than from C. For 4 He and 100 eV bias between 2 and 10 times more 3 He was released from W than from C depending on the type of W and C. The release rate of He from W and C through particle induced release was found to be equal. Therefore the stronger release of He from W can be explained by the higher retention of He in W.

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“…Thermal hydrogen irradiation of pure carbon or a-C:H leads to the bonding of H to the surface carbon atoms. In the case of pure carbon, a simultaneous irradiation or preirradiation by energetic ions [21][22][23][24] is usually required in order to produce bonding sites for the incoming thermal ions. Since carbon favors structures with threefold-or fourfoldcoordinated carbon sites, it seems plausible that hydrogen atoms implanted into a-C:H bond to carbon atoms with coordinations of 3 or less.…”

Section: B Model Studies For Carbon Erosion From A-c:hmentioning

confidence: 99%

Swift chemical sputtering of amorphous hydrogenated carbon

et al. 2001

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Ion bombardment of carbon materials is known to cause erosion with energies far below the threshold energy of physical sputtering, as well as at temperatures below the threshold of thermal desorption. Generally regarded as chemical sputtering, this effect, and factors contributing to it, are not well understood. We use classical molecular-dynamics simulations, capable of realistically describing bond formation and breaking, to study amorphous hydrogenated carbon surfaces under low-energy hydrogen bombardment. We present a swift chemical sputtering mechanism which can explain the experimentally observed characteristics of erosion by low-energy ion irradiation. We also show how the difference in the surface hydrogen concentration and carbon coordination fractions at various temperatures affect the carbon sputtering yield.

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Ion-induced synergistic effects for CH4 production from carbon under H+, H0 and H2 impact

Cited by 38 publications

References 4 publications

Chemical sputtering of carbon films by argon ions and molecular oxygen at cryogenic temperatures

Chemical sputtering of carbon films by argon ions and molecular oxygen at cryogenic temperatures

The implications of high-Z first-wall materials on noble gas wall recycling

Swift chemical sputtering of amorphous hydrogenated carbon

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