Heavy Noble Gases Research Articles

Influence of radiation damage on the thermal properties of silicon carbide implanted with heavy noble gas ions

Diffusion of heavy noble gas atoms in irradiation damaged single crystalline silicon carbide and the thermal etching of it is investigated at temperatures of 1300°C and 1400°C. For this purpose 360keV krypton and xenon ions were implanted in commercial 6H-SiC wafers at 600°C, which is far above the critical amorphization temperature of the target material. Width broadening of the implantation profiles and the retention of krypton and xenon during isothermal annealing was determined by RBS-analysis, whilst damage profiles were simultaneously obtained by α-particle channelling. No diffusion and no loss of the implanted species is detected in the implanted samples after isothermal annealing for 40h at 1400°C. However, thermal etching of the target material is observed at both annealing temperatures and leads at 1400°C to a significant shift of the implantation profile towards the surface due to sublimation. RBS analysis shows that this occurs mainly during the initial stage of isothermal annealing, while surface loss during prolonged annealing is minimal. The resulting topographical modification of the surface during annealing was studied by scanning electron and atomic force microscopy. It indicates that the observed phenomenon is due to a relatively strong dependence of thermal etching on the defect density in the surface region, while the evolving surface roughness seems not to play a decisive role.

Multidiffusion mechanisms for noble gases (He, Ne, Ar) in silicate glasses and melts in the transition temperature domain: Implications for glass polymerization

Noble gases are ideal probes to study the structure of silicate glasses and melts as the modifications of the silicate network induced by the incorporation of noble gases are negligible. In addition, there are systematic variations in noble gas atomic radii and several noble gas isotopes with which the influence of the network itself on diffusion may be investigated. Noble gases are therefore ideally suited to constrain the time scales of magma degassing and cooling. In order to document noble gas diffusion behavior in silicate glass, we measured the diffusivities of three noble gases (4He, 20Ne and 40Ar) and the isotopic diffusivities of two Ar isotopes (36Ar and 40Ar) in two synthetic basaltic glasses (G1 and G2; 20Ne and 36Ar were only measured in sample G1). These new diffusion results are used to re-interpret time scales of the acquisition of fractionated atmospheric noble gas signatures in pumices.The noble gas bearing glasses were synthesized by exposing the liquids to high noble gas partial pressures at high temperature and pressure (1750–1770K and 1.2GPa) in a piston-cylinder apparatus. Diffusivities were measured by step heating the glasses between 423 and 1198K and measuring the fraction of gas released at each temperature step by noble gas mass spectrometry. In addition we measured the viscosity of G1 between 996 and 1072K in order to determine the precise glass transition temperature and to estimate network relaxation time scales. The results indicate that, to a first order, that the smaller the size of the diffusing atom, the greater its diffusivity at a given temperature: D(He)>D(Ne)>D(Ar) at constant T. Significantly, the diffusivities of the noble gases in the glasses investigated do not display simple Arrhenian behavior: there are well-defined departures from Arrhenian behavior which occur at lower temperatures for He than for Ne or Ar. We propose that the non-Arrhenian behavior of noble gases can be explained by structural modifications of the silicate network itself as the glass transition temperature is approached: as the available free volume (available site for diffusive jumps) is modified, noble gas diffusion is no longer solely temperature-activated but also becomes sensitive to the kinetics of network rearrangements. The non-Arrhenian behavior of noble gas diffusion close to Tg is well described by a modified Vogel–Tammann–Fulcher (VTF) equation:Da2=A1a2∗exp-B1R(T-T2)-CRTwhere D is the diffusion coefficient, a the diffusion domain size (taken to be the size of the sample), A1 and C are respectively equivalent to the pre-exponential factor and to the activation energy (Ea in Jmol−1) of the classical Arrhenius equation, B1 can be interpreted as a “pseudo-activation energy” that reflects the influence of the silicate network relaxation, T2 is the temperature where the diffusion regime switches from Arrhenian to non-Arrhenian, and R is the gas constant (=8.314JK−1mol−1).Finally, our step heating diffusion experiments suggest that at T close to Tg, noble gas isotopes may suffer kinetic fractionation at a degree larger than that predicted by Graham’s law. In the case of 40Ar and 36Ar, the traditional assumption based on Graham’s law is that the ratio D40Ar/D36Ar should be equal to 0.95 (the square root of the ratio of the mass of 36Ar over the mass of 40Ar). In our experiment with glass G1, D40Ar/D36Ar rapidly decreased with decreasing temperature, from near unity (0.98±0.14) at T>1040K to 0.76 when close to Tg (T=1003K). Replicate experiments are needed to confirm the strong kinetic fractionation of heavy noble gases close to the transition temperature.

Atmospheric contamination of the primary Ne and Ar signal in mid-ocean ridge basalts and its implications for ocean crust formation

Both, terrestrial and extra-terrestrial applications of noble gases have demonstrated their importance as tracers for source identification, process characterisation and mass and heat flux quantification. However, the interpretation of noble gas isotope data from terrestrial igneous rocks is often complicated by the ubiquitous presence of heavy noble gases (Ne, Ar, Kr, Xe) with an atmospheric origin. Up to now there has been no consensus on how atmospheric noble gases are entrained into igneous rocks. Suggested processes range from contamination during sample preparation to mantle recycling through subduction. Here we present Ne, Ar, Mg, K, and Cl data of fresh glasses from the Mid-Atlantic Ridge north and south of the Ascension Fracture Zone which show that incorporation of atmospheric noble gases into igneous rocks is in general a two-step process: (1) magma contamination by assimilation of altered oceanic crust results in the entrainment of noble gases from air-equilibrated seawater; (2) atmospheric noble gases are adsorbed onto grain surfaces during sample preparation. This implies, considering the ubiquitous presence of the contamination signal, that magma contamination by assimilation of a seawater-sourced component is an integral part of mid-ocean ridge basalt evolution. Combining the results obtained from noble gas and Cl/K data with estimates of crystallisation pressures for the sample suite shows that the magma contamination must have taken place at a depth between 9 and 13km. Taking thickness estimates for the local oceanic crust into account, this implies that seawater penetration in this area reaches lower crustal levels, indicating that hydrothermal circulation might be an effective cooling mechanism even for the deep parts of the oceanic crust.

Reduction of circulation power for helium-cooled fusion reactor blanket using additive CO2 gas

Helium (He) cooling requires large circulation power to remove high heat from plasma side and nuclear heating by high energy neutron in fusion reactors due to its low density. Based on the recent findings that the heat transfer capability of the light gas can be enhanced by mixing another heavier gas, this study adds CO2 to a reference helium coolant and evaluates the cooling performance of the binary mixture for various compositions. To assess the cooling performance, computational fluid dynamic (CFD) analyses on the KO HCML (Korea Helium Cooled Molten Lithium) TBM are conducted. As a result, it is revealed that the binary mixing of helium, which has favorable thermophysical properties but the density, with a heavier noble gas or an unreactive gas significantly reduces the required circulation power by an order of magnitude with meeting the thermal design requirements. This is attributed to the fact that the density can be highly increased with small amount of a heavier gas while other gas properties are kept relatively comparable. The optimal CO2 mole fraction is estimated to be 0.4 and the circulation power, in this case, can be reduced to 13% of that of pure helium. This implies that the thermal efficiency of a He-cooled blanket system can be fairly enhanced by means of the proposed binary mixing.

Bistable solutions for the electron energy distribution function in electron swarms in xenon: a comparison between the results of first-principles particle simulations and conventional Boltzmann equation analysis

At low reduced electric fields the electron energy distribution function in heavy noble gases can take two distinct shapes. This ‘bistability effect’—in which electron–electron (Coulomb) collisions play an essential role—is analyzed here for Xe with a Boltzmann equation approach and with a first principles particle simulation method. The solution of the Boltzmann equation adopts the usual approximations of (i) searching for the distribution function in the form of two terms (‘two-term approximation’), (ii) neglecting the Coulomb part of the collision integral for the anisotropic part of the distribution function, (iii) treating Coulomb collisions as binary events, and (iv) truncating the range of the electron–electron interaction beyond a characteristic distance. The particle-based simulation method avoids these approximations: the many-body interactions within the electron gas with a true (un-truncated) Coulomb potential are described by a molecular dynamics algorithm, while the collisions between electrons and the background gas atoms are treated with Monte Carlo simulation. We find a good general agreement between the results of the two techniques, which confirms, to a certain extent, the approximations used in the solution of the Boltzmann equation. The differences observed between the results are believed to originate from these approximations and from the presence of statistical noise in the particle simulations.

Noble gases in sulfide deposits of modern deep-sea hydrothermal systems: Implications for heat fluxes and hydrothermal fluid processes

Studies of noble gases in seafloor sulfide deposits are an important tool for understanding the origin of ore-forming fluids, both enabling the determination of noble gas sources and revealing the degree of fluid–rock interaction and mantle degassing. The noble gas concentrations and isotopic compositions of 27 sulfide, 3 sulfate, and 2 opal mineral aggregate samples have been studied in different hydrothermal fields from the East Pacific Rise, Mid-Atlantic Ridge, Central Indian Ridge, Southwest Indian Ridge, and North Fiji Back-Arc Basin. The helium concentrations and isotopic ratios in the sulfide aggregate samples are variable (4He 0.12 to 22×10−8cm3 STP/g; 3He/4He ~0.6 to 10.4 Ra), and most of the sulfide helium concentrations are higher than those in the opal mineral samples (4He 0.017 and 0.028×10−8cm3 STP/g), suggesting that the low-temperature fluids have lost their mantle helium during cooling. The helium of high (>7 Ra), medium (1–7 Ra), and low (≈1 Ra) 3He/4He ratio samples is derived mainly from the MORB or OIB mantle by magma degassing, from mixing between hydrothermal fluid and seawater during ore-forming processes, and from ambient seawater, respectively. The high 3He/4He ratios (>7 Ra) of sulfides imply that high-temperature sulfides retain the helium isotopic compositions of the primary hydrothermal fluid, whereas low-temperature sulfides, sulfates, and opal minerals do not.The neon, argon, krypton, and xenon concentrations in the sulfide aggregate samples are also variable; in most of the sulfide aggregates, they are significantly lower than in the sulfate and opal mineral samples. It is known that barite and opal minerals are characteristic of low-temperature (<200°C) paragenetic associations, indicating that heavier noble gases (Ne, Ar, Kr and Xe) are enriched under low-temperature conditions. Most of the sulfide, sulfate and opal mineral aggregate samples possess heavy noble gas elemental abundances similar to those of air-saturated seawater and Ne, Ar, and Xe isotopic compositions that span narrow ranges around atmospheric values, an observation which is most easily explained by the dominance of a seawater-derived component.In addition, based on the calculated helium/heat ratios, global helium and heat fluxes to high-temperature hydrothermal vents are approximately 0.05–6×104kg per year and 0.1–12×1012W, meaning that roughly 0.3% of ocean heat is supplied by seafloor high-temperature hydrothermal activity.

Viscosity cross sections for the heavy noble gases

We have calculated viscosity cross sections for argon, krypton and xenon from zero to 1 keV using the phase shifts from our previous publication [R.P. McEachran, A.D. Stauffer, Eur. Phys. J. D 68, 153 (2014)] which presented total elastic and momentum transfer cross sections for these gases. As previously, we present simple analytic fits to our results to aid in modelling plasmas containing these atoms. By using the current results and those in reference [R.P. McEachran, A.D. Stauffer, Eur. Phys. J. D 68, 153 (2014)] the first two ‘partial cross sections’ used in the general moment method of solving the Boltzmann equation can be obtained. The agreement of our viscosity cross sections with experimentally derived results indicates the overall reliability of our calculations.

Multiple carriers of Q noble gases in primitive meteorites

AbstractThe main carrier of primordial heavy noble gases in chondrites is thought to be an organic phase, known as phase Q, whose precise characterization has resisted decades of investigation. Indirect techniques have revealed that phase Q might be composed of two subphases, one of them associated with sulfide. Here we provide experimental evidence that noble gases trapped within meteoritic sulfides present chemically and thermally driven behavior patterns that are similar to Q gases. We therefore suggest that phase Q is likely composed of two subcomponents: carbonaceous phases and sulfides. In situ decay of iodine at concentration levels consistent with those reported for meteoritic sulfides can reproduce the 129Xe excess observed for Q gases relative to fractionated solar wind. We suggest that the Q‐bearing sulfides formed at high temperature and could have recorded the conditions that prevailed in the chondrule‐forming region(s).

Numerical simulations and modeling of the stability of noble gas atoms in interaction with vacancies in silicon

In order to identify the main actors during the initial steps of the formation of noble gas filled bubbles, we have performed an extensive investigation of a single noble gas atom (helium, neon, argon, krypton, xenon) as interstitial or in interaction with a monovacancy and a divacancy in silicon. Density functional calculations in the generalized gradient approximation allowed us for determining the structure and stability of various configurations. We found that interstitial configurations are especially relevant for helium, and to a lesser extent for neon. Heavy noble gas species are predicted to form complexes with vacancies, except in out-of-equilibrium situations where an original bond-centered interstitial configuration is favored. Besides, we propose a model combining a repulsive interaction between the host local electronic density and the noble gas atom, and an elastic description of this atom as a deformable spherical inclusion into an homogeneous isotropic medium. This model is shown to provide an appropriate description, especially for light noble gas species such as helium and neon.

Effect of heavy noble gas ion irradiation on terahertz emission efficiency of InP (100) and (111) crystal planes

Emission of terahertz (THz) electromagnetic radiation from heavily-doped (5 × 1018 cm−3) (100) and (111) InP bulk materials and nanoporous honeycomb membranes, irradiated with heavy noble gas (Kr and Xe) ions, is presented. Irradiating samples with Kr or Xe improves THz emission efficiency. For (111) samples, as for unirradiated samples, the irradiated porous structures generate more THz radiation than their bulk counterparts. On the other hand, in contrast to unirradiated (100) samples, the irradiated (100) samples show a decrease in THz emission with porosity. We attribute this behaviour to changes in the local electric field due to the combined effect of the irradiation and nanoporosity.

Kr and Xe isotopic compositions of Fe-Mn crusts from the western and central Pacific Ocean and implications for their genesis

Kr and Xe nuclide abundance and isotopic ratios of the uppermost layer of Fe-Mn Crusts from the western and central Pacific Ocean have been determined. The results indicate that the Kr and Xe isotopic compositions, like that of He, Ne and Ar, can be classified into two types: low 3He/4He type and high 3He/4He type. The low 3He/4He type crusts have low 84Kr and 132Xe abundance, while the high 3He/4He type crusts have high 84Kr and 132Xe abundance. The 82Kr/84Kr ratios of the low 3He/4He type crusts are lower than that of the air, while the 83Kr/84Kr and 86Kr/84Kr ratios are higher than those of the air. The Kr isotopic ratios of the higher 3He/4He type crusts are quite similar to those of the air. The 128Xe/132Xe, 130Xe/132Xe and 131Xe/132Xe ratios of the low 3He/4He type sample are distinctly lower than those of the air, whereas the 129Xe/132Xe, 134Xe/132Xe and 136Xe/132Xe ratios are higher than those of the air. The low 3He/4He type samples have the diagnostic characteristics of the MORB, with excess 129, 131, 132, 134, 136Xe relative to 130Xe compared with the solar wind. The 128Xe/132Xe, 130Xe/132Xe and 131Xe/132Xe ratios of the high 3He/4He type samples are slightly higher than those of the air, and the 129Xe/132Xe, 134Xe/132Xe and 136Xe/132Xe ratios are qiute similar to those of the air. The noble gases in the Fe-Mn crusts are derived from the lower mantle, and they are a mixture of lower mantle primitive component, radiogenic component and subduction recycled component. The helium isotopic ratios of the low mantle reservoir are predominantly controlled by primitive He (3He) and U and Th radiogenic decayed He (4He), but the isotopic ratios of the heavier noble gases, such as Ar, Kr and Xe, are controlled to different extent by recycling of subduction components. The difference of the noble isotopic compositions of the two type crusts is the result of the difference of the noble isotopic composition of the mantle source reservoir underneath the seamounts the crusts occurred, the noble gases of the high 3He/4He type crusts are derived mainly from EM-type lower mantle reservoir, and the noble gases in the low 3He/4He type crusts are derived mainly from HIMU-type lower mantle reservoir.

Momentum transfer cross sections for the heavy noble gases

We present momentum transfer cross sections for elastic electron scattering from argon, krypton and xenon atoms over the energy range from zero to 1 keV. These have been calculated using the Dirac equations with a relativistic complex optical potential which includes polarization of the target atom by the incident electron and allows for the absorption of some of the incident electron flux into channels representing excitation and ionization of the atom. In order to aid in plasma modelling calculations, we provide simple analytic fits to these cross sections as well as to the elastic scattering cross sections. Comparisons are made with previous experimental and theoretical results.

Noble gas excimer scintillation following neutron capture in boron thin films

Far-ultraviolet scintillation signals have been measured in heavy noble gases (argon, krypton, xenon) following boron-neutron capture (10B(n,α)7Li) in 10B thin films. The observed scintillation yields are comparable to the yields from some liquid and solid neutron scintillators. At noble gas pressures of 107 kPa, the number of photons produced per neutron absorbed following irradiation of a 1200 nm thick 10B film was 14 000 for xenon, 11 000 for krypton, and 6000 for argon. The absolute scintillation yields from the experimental configuration were calculated using data from (1) experimental irradiations, (2) thin-film characterizations, (3) photomultiplier tube calibrations, and (4) photon collection modeling. Both the boron films and the photomultiplier tube were characterized at the National Institute of Standards and Technology. Monte Carlo modeling of the reaction cell provided estimates of the photon collection efficiency and the transport behavior of 10B(n,α)7Li reaction products escaping the thin films. Scintillation yields increased with gas pressure due to increased ionization and excitation densities of the gases from the 10B(n,α)7Li reaction products, increased frequency of three-body, excimer-forming collisions, and reduced photon emission volumes (i.e., larger solid angle) at higher pressures. Yields decreased for thicker 10B thin films due to higher average energy loss of the 10B(n,α)7Li reaction products escaping the films. The relative standard uncertainties in the measurements were determined to lie between 14% and 16%. The observed scintillation signal demonstrates that noble gas excimer scintillation is promising for use in practical neutron detectors.

Noble gas concentrations in fluid inclusions as tracer for the origin of coarse-crystalline cryogenic cave carbonates

The chemically inert behaviour of noble gases, their well-known solubility in water and the long-term constancy of atmospheric noble gas mixing ratios make them a unique tool for paleoclimate studies of groundwater. This concept has recently been extended to fluid inclusions in speleothems. Here we use noble gas concentrations of fluid inclusions contained in calcite crystals to constrain the formation history of coarse crystalline cryogenic cave calcites from Heilenbecker Cave (Germany).Cryogenic cave carbonates form under conditions related to the freezing of cave pools and are a new archive for paleo-permafrost timing and extent. The cryogenic origin of these carbonates is typically deduced from their crystal habit and the carbon and oxygen isotope ratios, but this can be ambiguous in some cases. A geochemical method that provides clear-cut proof of the cryogenic origin of individual crystals has been lacking so far.We examined the formation process of cryogenic cave calcites using water and noble gases extracted from inclusions in these crystals. Based on their δ13C and δ18O values, these calcite crystals could have also formed as ‘normal’, i.e. non-cryogenic, speleothems. Noble gas concentrations derived from fluid inclusions in these cryogenic calcites, however, deviate significantly from commonly observed concentrations in atmospheric air, surface water, groundwater, and stalagmites. These concentrations cannot be explained simply by a solubility component nor by the addition of various amounts of excess-air to a solubility component. The data, however, are consistent with the scenario of a slowly freezing water body lacking exchange with the cave atmosphere. The gradual freezing process leads to a partitioning of the noble gases between ice and remaining water and thereby to a pronounced over-abundance of heavy noble gases in the liquid phase recorded in the fluid inclusions of the cryogenic calcite crystals.

Heavy noble gases in solar wind delivered by Genesis mission

One of the major goals of the Genesis Mission was to refine our knowledge of the isotopic composition of the heavy noble gases in solar wind and, by inference, the Sun, which represents the initial composition of the solar system. This has now been achieved with permil precision: 36Ar/38Ar=5.5005±0.0040, 86Kr/84Kr=.3012±.0004, 83Kr/84Kr=.2034±.0002, 82Kr/84Kr=.2054 ± .0002, 80Kr/84Kr = .0412±.0002, 78Kr/84Kr=.00642±.00005, 136Xe/132Xe=.3001±.0006, 134Xe/132Xe=.3691±.0007, 131Xe/132Xe=.8256±.0012, 130Xe/132Xe=.1650±.0004, 129Xe/132Xe=1.0405±.0010, 128Xe/132Xe=.0842±.0003, 126Xe/132Xe=.00416±.00009, and 124Xe/132Xe=.00491±.00007 (error-weighted averages of all published data). The Kr and Xe ratios measured in the Genesis solar wind collectors generally agree with the less precise values obtained from lunar soils and breccias, which have accumulated solar wind over hundreds of millions of years, suggesting little if any temporal variability of the isotopic composition of solar wind krypton and xenon. The higher precision for the initial composition of the heavy noble gases in the solar system allows (1) to confirm that, exept 136Xe and 134Xe, the mathematically derived U–Xe is equivalent to Solar Wind Xe and (2) to provide an opportunity for better understanding the relationship between the starting composition and Xe-Q (and Q-Kr), the dominant current “planetary” component, and its host, the mysterious phase-Q.

Amorphous In–Ga–Zn–O thin‐film transistors prepared by magnetron sputtering using Kr and Xe instead of Ar

AbstractHeavier noble gases Kr and Xe instead of the lighter Ar during the magnetron‐sputtering deposition of amorphous indium–gallium–zinc oxide films are introduced in fabricating their thin‐film transistors (TFTs). Heavy noble gases can reduce damage to film induced by ion bombardment during the sputtering depositions. Higher field‐effect mobility with better gate bias stability can be obtained in the heavier‐noble‐gas sputtered TFTs. Raman spectroscopic analysis and X‐ray reflectometry respectively suggest that the disordered structure in the film is suppressed, and the film becomes denser by introducing heavy noble gases, corresponding to the improvement of TFT performance.

HIGHLY CONCENTRATED NEBULAR NOBLE GASES IN POROUS NANOCARBON SEPARATES FROM THE SARATOV (L4) METEORITE

The majority of heavy noble gases (Ar, Kr, and Xe) in primitive meteorites are stored in a poorly understood phase called Q. Although Q is thought to be carbonaceous, the full identity of the phase has remained elusive for almost four decades. In order to better characterize phase Q and, in turn, the early solar nebula, we separated carbon-rich fractions from the Saratov (L4) meteorite. We chose this meteorite because Q is most resistant in thermal alteration among carbonaceous noble gas carriers in meteorites and we hoped that, in this highly metamorphosed meteorite, Q would be present but not diamond: these two phases are very difficult to separate from each other. One of the fractions, AJ, has the highest 132Xe concentration of 2.1?? 10?6?cm3?STP?g?1, exceeding any Q-rich fractions that have yet been analyzed. Transmission electron microscopy studies of the fraction AJ and a less Q-rich fraction AI indicate that they both are primarily porous carbon that consists of domains with short-range graphene orders, with variable packing in three dimensions, but no long-range graphitic order. The relative abundance of Xe and C atoms (6:109) in the separates indicates that individual noble gas atoms are associated with only a minor component of the porous carbon, possibly one or more specific arrangements of the nanoparticulate graphene.

GAS-PHASE SEQUESTRATION OF NOBLE GASES IN THE PROTOSOLAR NEBULA: POSSIBLE CONSEQUENCES ON THE OUTER SOLAR SYSTEM COMPOSITION

We address the problem of the sequestration of Ar, Kr, and Xe by H in the gas-phase conditions encountered during the cooling of protoplanetary disks when H is competing with other species present in the same environment. Using high-level ab initio simulations, we try to quantify other sequestration possibilities involving He, H, H2O, and H3O+ present in the protosolar nebula. Apart from the fact that H complexes formed with heavy noble gases are found to be by far much more stable than those formed with He or H2O, we show that H2D+ and H3O+, both products of the reactions of H with HD and H2O, can also be efficient trapping agents for Ar, Kr, and Xe. Meanwhile, the abundance profile of H in the outer part of the nebula is revisited with the use of an evolutionary accretion disk model that allows us to investigate the possibility that heavy noble gases can be sequestered by H at earlier epochs than those corresponding to their trapping in planetesimals. We find that H might be abundant enough in the outer protosolar nebula to trap Xe and Kr prior their condensation epochs, implying that their abundances should be solar in Saturn's current atmosphere and below the observational limit in Titan. The same scenario predicts that comets formed at high heliocentric distances should also be depleted in Kr and Xe. In situ measurements, such as those planed with the Rosetta mission on 67P/Churyumov–Gerasimenko, will be critical to check the validity of our hypotheses.

Sputtering angle effects by Kr mixing in N+ ion beam on the lifetime of nitrided carbon stripper foils

Nitrided carbon stripper (NCS) foils with high nitrogen content were produced by ion beam sputtering of reactive nitrogen gas. Such foils seem to be very useful as strippers in high-intensity heavy ion accelerators. We have conducted comprehensive research, development, and production of such foils with high reproducibility. Krypton, a heavy noble gas, was mixed with the reaction nitrogen gas (IBSRN) in the ion beam sputtering process to produce stripper foils with short sputtering deposition time and long lifetimes in the high intensity ion beam irradiation. With the (N2 + Kr) mixed gas ions we investigated the influence of different sputtering angles (α) on the lifetime of the NCS-foils in case of poly-graphite material. The lifetime measurement of these foils of 20 ± 5 μg/cm2 was performed with a 3.2 MeV Ne+ ion beam as usual. The foils made at a sputtering angle of 15° showed a maximum of 11.0 and 7.5 C/cm2 average charge density, respectively, which corresponded to about 275 and 187 times the lifetime of the best commercially available foils.

52.4: Distinguished Paper: Electrical Properties of Amorphous InGaZnO Thin‐Film Transistors Prepared by Magnetron Sputtering with Using Kr and Xe Instead of Ar

AbstractHeavier noble gases of Kr and Xe instead of the lighter Ar during the magnetron‐sputtering deposition of amorphous indium—gallium‐zinc oxide films are introduced in fabricating their thin‐film transistors. Higher field effect mobility can be obtained by introducing heavier noble gases, while gate bias stability shows no significant difference between gas species. Raman spectroscopic analysis suggests that the disordered structure in the film is suppressed by introducing heavier noble gases. These results suggest that the introduction of heavy noble gases can reduce damage to film by ion bombardment during the sputtering depositions, resulting in the improvement of field effect mobility.