Enhanced negative ion yields on diamond surfaces at elevated temperatures

Kumar, Pravin; Ahmad, Adeel; Pardanaud, C.; Carrère, M.; Layet, J. M.; Cartry, Gilles; Silva, F; Gicquel, A.; Engeln, Rah Richard

doi:10.1088/0022-3727/44/37/372002

Cited by 34 publications

(70 citation statements)

References 30 publications

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“…Calculations concern particles emitted by the surface, while the experiments measure negative ions that are able to reach the mass spectrometer detector. Interestingly, it also suggests that many negative ions emitted by the surface are not collected, and that carbon is probably an even better negative ion enhancer than previously thought 62 . Figure 6 also shows that above 80eV the sputtering contribution starts to decrease.…”

Section: Iii) Idf Versus Positive Ion Energymentioning

confidence: 83%

“…Experimentally, HOPG surfaces were used, but upon bombardment, some defects are created in the material and it is partially amorphized 62 up to a depth that depends on the positive ion energy. Furthermore some hydrogen (or deuterium) species are implanted in the material.…”

Section: C-srim Calculationsmentioning

confidence: 99%

“…In a real ion source structure, ion extraction apertures, focusing devices (like quadrupoles), dipole magnets (to analyze the energy) along with post slits could be used to reduce the beam emittance and energy spread. However, the primary objective of the present work is not to design a negative-ion source, but rather to understand surface production in cesium-free plasmas by analyzing negative-ion distribution functions (this work), and by comparing them for different materials 62 .…”

Section: Iii) Idf Versus Positive Ion Energymentioning

confidence: 99%

“…H-surface-production on Highly Oriented Pyrolytic Graphite (HOPG) or polycrystalline graphite has for instance been studied in 37, 38, 39 and 40. On the contrary, few works deal with negative ion surface-production in cesium-free plasmas 41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68 . Most of them are related to the industrial process of layer deposition by sputtering and concern mainly oxygen negative ions [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59].…”

Section: A-introductionmentioning

confidence: 99%

“…Our previous works were focused on H-and D-negative ion production on HOPG surfaces in H 2 and D 2 plasmas 59,60,61,62 . The positive ions impinging the surface were H 2 + and H 3 + (D 2 + and D 3 + ) with energies in the range of 10 to 150 eV.…”

Section: A-introductionmentioning

confidence: 99%

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Production of negative ions on graphite surface in H2/D2 plasmas: Experiments and srim calculations

et al. 2012

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In previous works, surface-produced negative-ion distribution-functions have been measured in H 2 and D 2 plasmas using graphite surfaces (HOPG). In the present paper we use the SRIM software to interpret the measured negative-ion distribution-functions. For this purpose the distribution-functions of backscattered and sputtered atoms arising due to the impact of hydrogen ions on a-CH and a-CD surfaces are calculated. The SRIM calculations confirm the experimental deduction that backscattering and sputtering are the mechanisms of the origin of the creation of negative ions at the surface. It is shown that the SRIM calculations compare well with the experiments regarding the maximum energy of the negative ions and reproduce the experimentally observed isotopic effect. A discrepancy between calculations and measurements is found concerning the yields for backscattering and sputtering. An explanation is proposed based on a study of the emitted-particle angulardistributions as calculated by SRIM. A-IntroductionThe ITER project and its successor DEMO (first nuclear-fusion based power plant prototype) aim at demonstrating power production by magnetic confinement nuclear fusion. Plasma start-up and continuous operation in the case of a tokamak reactor require very efficient heating and non-inductive current drive systems. Neutral beam injection (NBI) which uses high power beams of fast neutral atoms of hydrogen isotopes to heat the plasma is a promising candidate. In most existing NBI systems on contemporary fusion experiments a beam of positive ions is extracted from a conventional ion source, accelerated to energies of the order of 100 keV and neutralized via charge exchange in a background of neutral hydrogen. Due to the much larger physical dimensions the NBI systems for both ITER and DEMO require neutral beam energies in the 1 to 2 MeV range where the neutralization of positive ions becomes very inefficient and only the negative ions can be neutralized with sufficient yield. Hence the development of high current negative ion sources (50A D-beam for ITER) is crucial to the development of the ITER and DEMO NBI systems. The highcurrent-density negative-ion source for ITER 1 is currently the subject of intense research

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Section: Iii) Idf Versus Positive Ion Energymentioning

confidence: 83%

Section: C-srim Calculationsmentioning

confidence: 99%

Section: Iii) Idf Versus Positive Ion Energymentioning

confidence: 99%

Section: A-introductionmentioning

confidence: 99%

Section: A-introductionmentioning

confidence: 99%

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Production of negative ions on graphite surface in H2/D2 plasmas: Experiments and srim calculations

et al. 2012

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In‐plane and out‐of‐plane defects of graphite bombarded by H, D and He investigated by atomic force and Raman microscopies

Pardanaud

Martin

Cartry

et al. 2014

J Raman Spectroscopy

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International audienceGraphite samples exposed to H, D and He plasma at fluencies from 10(16) to 10(18)cm(-2) have been investigated by means of atomic force and Raman microscopies. The ion energy was varied between 40 and 800eV, and the ion incidence was either perpendicular (Highly Oriented Pyrolitic Graphite) or parallel (carbon/carbon composite) to the basal plane. When increasing the impinging ion energy, the growth of nanometric domes at the surface has been observed by atomic force microscopy and the incident kinetic energy has been found as the parameter determining their height. Two different Raman signatures related to (1) a graphitic nano-crystalline component similar to that of a 10(14)cm(-2) bombarded 1-, 2- and 3-layer graphene, and to (2) an amorphous component, have been evidenced. Polarization studies have revealed that these components are related to regions with either in-plane or out-of-plane disorder, coexisting in the material. These Raman studies have also revealed that both the defect-defect distance in the first case and the aromatic domain size in the second case are typically 1nm. When the number of vacancies created in the material increases, the number of in-plane defects decreases to the benefit of the out-of-plane defects. Copyright (c) 2014 John Wiley & Sons, Ltd

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Plasma Electrode for Cesium-Free Negative Hydrogen Ion Sources

Sasao

Cartry

2023

Springer Series on Atomic, Optical, and Plasma Physics

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Enhanced negative ion yields on diamond surfaces at elevated temperatures

Cited by 34 publications

References 30 publications

Production of negative ions on graphite surface in H2/D2 plasmas: Experiments and srim calculations

Production of negative ions on graphite surface in H2/D2 plasmas: Experiments and srim calculations

In‐plane and out‐of‐plane defects of graphite bombarded by H, D and He investigated by atomic force and Raman microscopies

Plasma Electrode for Cesium-Free Negative Hydrogen Ion Sources

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