F. Aumayr

TU Wien

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Herbert Biber

TU Wien

A. Mutzke

Max Planck Institute for Plasma Physics - Greifswald

André Galli

University of Bern

Reinhard Stadlmayr

TU Wien

P. Wurz

University of Bern

Paul Stefan Szabo

University of California, Berkeley

Elisabeth Gruber

Universität Innsbruck

Daniel Primetzhofer

Uppsala University

Klaus Mezger

University of Münster

Martina Fellinger

TU Wien

Cooperative Institutions

TU Wien

Centre National de la Recherche Scientifique

Chinese Academy of Sciences

Institute of Modern Physics

University of Vienna

University of Chinese Academy of Sciences

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Universität Innsbruck

Université de Caen Normandie

Centre de Recherche sur les Ions, les Matériaux et la Photonique

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Experimental Insights Into Space Weathering of Phobos: Laboratory Investigation of Sputtering by Atomic and Molecular Planetary Ions

Journal of Geophysical Research Planets (2020)

Paul Stefan Szabo Herbert Biber Noah Jäggi Markus Wappl Reinhard Stadlmayr

Abstract Investigating the space weathering of the Martian moon Phobos represents an important step toward understanding the development from its origin to its present‐day appearance. Depending on Phobos’ orbital position, its surface is continuously sputtered by the solar wind and planetary ions that originate in the Martian atmosphere. Based on Mars Atmosphere and Volatile Evolution measurements, it has been proposed that sputtering by planetary O + and O 2 + ions dominates in the Martian tail region, where the planet mostly shadows Phobos from the solar wind. In these models, uncertainties for sputtering yield inputs still exist due to the lack of sufficient analog experiments. Therefore, sputtering measurements with O + , O 2 + , C + , and CO 2 + ions between 1 and 5 keV were performed using augite samples as Phobos analogs. The experimental results for O + irradiations show smaller mass changes than predicted by SDTrimSP simulations, which probably can be attributed to O implantation enabled by the Fe content of the target. Sputtering with O 2 + and CO 2 + in the low keV range shows no deviations in the sputtering yields attributable to molecular effects. Therefore, CO 2 + ions will most likely be negligible for the sputtering of Phobos according to the current understanding of ion fluxes on the Martian moon. Ultimately, our experiments suggest that the sputtering contribution on Phobos by O ions is about 50% smaller than previously assumed. This does not change the qualitative outcome from previous modeling stating that planetary O ions are by far the dominant sputtering contribution on Phobos in the Martian tail region.

Space weathering

Regolith

10.1029/2020je006583

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Citations (16)

Creation of Lunar and Hermean analogue mineral powder samples for solar wind irradiation experiments and mid-infrared spectra analysis

Icarus (2021)

Noah Jäggi André Galli P. Wurz Herbert Biber Paul Stefan Szabo

The surfaces of airless planetary bodies are subject to a barrage of charged particles, photons, and meteoroids. This high-energy space environment alters the surfaces and creates a tenuous atmosphere of ejected particles surrounding the celestial bodies. Experiments with well characterized analogue materials under controlled laboratory conditions are needed to interpret the observations of these atmospheres and improve composition models of such bodies. This study presents methods to create and analyze mineral powder pellets for ion irradiation experiments relevant for rocky planetary bodies including the Moon and Mercury. These include the pyroxenes diopside and enstatite, the plagioclase labradorite and the non-analogue pyroxenoid wollastonite. First ion irradiation experiments with diopside, enstatite and wollastonite pellets were performed under UHV with 4 keV He+ at fluences of several 1021 ions m−2 (~100 and ~1000 years for Mercury and the Moon, respectively). The pellet's thermal IR reflectance properties were compared before and after irradiation showing monotonously shifting IR spectral features between 7 − 14 μm towards higher wavelengths. For all irradiated pellets, Reststrahlen bands shifted by ~0.03 μm. Surface abrasion was found to remove the sputter effect, which is restricted to the top few tens of nm of the surface. Additionally, ion irradiation experiments were performed in a quartz crystal microbalance catcher setup, where the mass sputtered from pellets was monitored. This proves, that the presented sample preparation method allows the study of irradiation induced sputtering and surface alteration on the surfaces of rocky planets under laboratory conditions.

Enstatite

Diopside

Regolith

10.1016/j.icarus.2021.114492

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Formation of beryllium-hydrogen ions in chemical sputtering from 20 to 420eV

Nuclear Materials and Energy (2019)

Lorenz Ballauf Faro Hechenberger Reinhard Stadlmayr T. Dittmar Matthias Daxner

The formation of BeD+ in collisions of deuterium molecular ions with a beryllium surface at hyperthermal energies is investigated, using a purpose-built tandem mass spectrometer setup, "SurfTOF". In the manifold of products, hydrogen-containing molecules are of special interest in fusion devices. Our experiments show, that they can be formed in nearly all conditions comparable to plasma and wall temperature, with two mechanisms involved: First, BeD+ is formed directly in a reaction of the D2+ projectiles with the Be surface, which is the main aspect of this work. There was no evidence found, that this particular mechanism relies on D implanted in the bulk Be. BeD2+ was not detected. The second reaction pathway produces BeH+. It is efficiently formed when H2O molecules are adsorbed on the surface, much less abundant for hydrocarbon adsorbates. The yield of Be+, BeH+ and BeD+ products, is measured as a function of several parameters: Scanning the impact energy from 20 to 426 eV reveals that the molecular BeD+ is preferably produced at low energies. At 20 eV, its abundance is three times higher than that of pure Be+. When the surface temperature is raised from 298 to 673 K, sputtering yields increase two orders of magnitude for both, Be+ and BeD+.

10.1016/j.nme.2019.100722

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Erosion of Fe-W model system under normal and oblige D ion irradiation

Nuclear Materials and Energy (2017)

Bernhard M. Berger Reinhard Stadlmayr D. Blöch Elisabeth Gruber K. Sugiyama

The dynamic erosion behaviour of iron-tungsten (Fe-W) model films (with 1.5 at% W) resulting from 250 eV deuterium (D) irradiation is investigated under well-defined laboratory conditions. For three different impact angles (0°, 45° and 60° with respect to the surface normal) the erosion yield is monitored as a function of incident D fluence using a highly sensitive quartz crystal microbalance technique (QCM). In addition the evolution of the Fe-W film topography and roughness with increasing fluence is observed using an atomic force microscope (AFM). The mass removal rate for Fe-W is found to be comparable to the value of a pure Fe film at low incident fluences but strongly decreases with increasing D fluence. This is consistent with earlier observations of a substantial W enrichment at the surface due to preferential Fe sputtering. The reduction of the mass removal rate is initially more pronounced for irradiation under oblique angles as compared to normal incidence, but the differences vanish for fluences > 2·1023 D/m². High resolution AFM images reveal that continued ion irradiation leads to significant surface roughening and (depending on ion impact angle) formation of nanodots or nano-ripples. This may indicate that the W enrichment at the surface due to preferential sputtering of Fe is not exclusively responsible for the observed reduction in erosion with increasing D fluence.

Quartz Crystal Microbalance

10.1016/j.nme.2017.03.030

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Absence of synergistic effects in quasi-simultaneous sputtering of tungsten by Ar and D ions

Nuclear Materials and Energy (2023)

C. Cupak Florian Brandstätter R. Cserveny F. Troneberger Herbert Biber

A quartz crystal microbalance was used to experimentally study the erosion of tungsten during rapidly alternating bombardment with 2 keV argon and deuterium projectiles. A key goal was to investigate whether the mean sputtering yield of the alternating irradiation can be predicted from data for sputtering yields of single ion species. In addition, influences by residual gas pressure in the UHV experiment and variable ion fluxes have been studied. Our results show that the mean sputtering yield of irradiations with alternating ion species can be well predicted for a range of different fluence ratios as a simple superposition of individual sputtering yields, weighted by the respective relative fluences. This finding supports that no synergistic sputtering effects were relevant in the investigated low-flux regime.

Quartz Crystal Microbalance

10.1016/j.nme.2023.101435

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The effect of temperature on guiding of slow highly charged ions through a mesoscopic glass capillary

Journal of Physics Conference Series (2012)

R J Bereczky G. Kowarik F. Ladinig Dominik Schrempf K. Tőkési

We present first temperature dependent transmission measurements of slow highly charged ions through a single, straight Duran glass capillary with a high aspect ratio. By changing the temperature of the glass capillary the electrical conductivity of the Duran can be varied by several orders of magnitude. This held the promise to investigate the effect of conductivity on particle transport (build-up and removal of charge patches) through capillaries in more details.

Mesoscopic physics

10.1088/1742-6596/388/13/132031

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Deducing Lunar Regolith Porosity From Energetic Neutral Atom Emission

Geophysical Research Letters (2022)

Paul Stefan Szabo A. R. Poppe Herbert Biber A. Mutzke Jessica Pichler

Abstract The porosity of the upper layers of regolith is key to the interaction of an airless planetary body with precipitating radiation, but it remains difficult to characterize. One of the effects that is governed by regolith properties is Energetic Neutral Atom (ENA) emission in the form of reflected and neutralized solar wind protons. We simulate this process for the surface of the Moon by implementing a regolith grain stacking in the ion‐solid‐interaction software SDTrimSP‐3D, finding that proton reflection significantly depends on the regolith porosity. Via comparison with ENA measurements by Chandrayaan‐1, we derive a globally averaged porosity of the uppermost regolith layers of . These results indicate a highly porous, fairy‐castle‐like nature of the upper lunar regolith, as well as its importance for the interaction with impacting ions. Our simulations further outline the possibility of future regolith studies with ENA measurements, for example, by the BepiColombo mission to Mercury.

Regolith

Lunar soil

10.1029/2022gl101232

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Solar wind sputtering of wollastonite as a lunar analogue material – Comparisons between experiments and simulations

Icarus (2018)

Paul Stefan Szabo Rimpei Chiba Herbert Biber Reinhard Stadlmayr Bernhard M. Berger

10.1016/j.icarus.2018.05.028

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Citations (37)

Ultrafast electronic response of graphene to a strong and localized electric field

Nature Communications (2016)

Elisabeth Gruber R. Wilhelm Rémi Pétuya Valerie Smejkal Roland Kozubek

Abstract The way conduction electrons respond to ultrafast external perturbations in low dimensional materials is at the core of the design of future devices for (opto)electronics, photodetection and spintronics. Highly charged ions provide a tool for probing the electronic response of solids to extremely strong electric fields localized down to nanometre-sized areas. With ion transmission times in the order of femtoseconds, we can directly probe the local electronic dynamics of an ultrathin foil on this timescale. Here we report on the ability of freestanding single layer graphene to provide tens of electrons for charge neutralization of a slow highly charged ion within a few femtoseconds. With values higher than 10 12 A cm −2 , the resulting local current density in graphene exceeds previously measured breakdown currents by three orders of magnitude. Surprisingly, the passing ion does not tear nanometre-sized holes into the single layer graphene. We use time-dependent density functional theory to gain insight into the multielectron dynamics.

Charge carrier

10.1038/ncomms13948

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Citations (138)

Sputtering yield reduction for nano-columnar W surfaces under D ion irradiation

Nuclear Materials and Energy (2023)

Johannes Brötzner C. Cupak Martina Fellinger Herbert Biber A. Lopez-Cazalilla

This study investigates the sputtering properties of nano-columnar tungsten surfaces under 2 keV D2+ irradiation. It was conducted both by performing experiments in a highly sensitive quartz crystal microbalance setup as well as by numerical methods using two simulation codes called SPRAY and SDTrimSP-3D. A key question was whether the strong sputtering yield reduction observed in previous studies under 2 keV Ar+ irradiation is maintained when using a much lighter ion species like deuterium. For the latter, a substantially larger projected range in the material has to be expected. Therefore, a total confinement of the ion-solid interaction within the W nano-columns cannot be assumed a priori. However, both the experiments and the numerical simulations showed in good agreement that the geometrically induced sputtering yield reduction is still observed to the same extent despite the increased range of ions in the material. Thus, a potential application of such nano-columnar tungsten surfaces as plasma facing components in future nuclear fusion devices is not affected.

Quartz Crystal Microbalance

10.1016/j.nme.2023.101507

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Citations (2)