Metallic work function measurement in the range 2–3.3 eV using a blue light-emitting diode source

Schletti, R.; Würz, Peter; Fröhlich, T

doi:10.1063/1.1150231

Cited by 11 publications

(2 citation statements)

References 9 publications

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“…Then, one proceeds with the application of a fresh alkali or alkaline-earth metal layer. In addition to heating the surface to substantial temperatures, the handling of a dispenser introduces some complexity, as well as monitoring the WF of the surface [28].…”

Section: Detection Via Surface Ionizationmentioning

confidence: 99%

Particle Scattering off Surfaces: Application in Space Science

Würz

Scheer

Wieser

2006

e-J. Surf. Sci. Nanotechnol.

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In many applications of remote sensing of plasma populations in space science a high detection efficiency of energetic neutral atoms (ENAs) is necessary because the sources of these ENAs are very faint. In the recent years surface science processes occurring during particle scattering off specialized surfaces have been successfully used to detect these ENAs with high efficiency. The relevant processes are kinetic secondary electron emission and surface ionization. When secondary electron emission is used an ENA hits a so-called start surface where it releases a secondary electron, which initiates the measurement sequence. Being scattered off the start surface, the ENA continues its flight until it is absorbed at the stop detector. The time difference between the release of the secondary electron and the detection of the particle at the stop detector is measured and with the path length the velocity of the particle is obtained. Surface ionization, i.e., the formation of negative ions, is the well-known charge transfer process where an atom receives an electron from the scattering surface during the scattering process. In modern space science applications mostly insulating surfaces are used as conversion surfaces since these do not need any preparation in space to be operable and at the same time have very stable performance over years. In this paper we will show the current status of surface-science-based detection technology that is used in present space missions of the European Space Agency (ESA) and the U.S. American space agency (NASA).

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Section: Detection Via Surface Ionizationmentioning

confidence: 99%

Particle Scattering off Surfaces: Application in Space Science

Würz

Scheer

Wieser

2006

e-J. Surf. Sci. Nanotechnol.

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“…Furthermore, the formation of a dipole layer on the surface of the metal can lower the work function under high vacuum conditions (p < 10 -6 Pa) and a clean caesium layer to a value as low as 1.4 -1.7 eV at a thickness below one monolayer [6]. Due to the high chemical reactivity of caesium layers small amounts of impurities, for example the residual gas, can cause a degradation of the caesium layer and thus of the work function [7,8]. Besides the time dependence of the work function in the vacuum phase of pulsed plasma operation, the plasma itself may modify the work function by plasma surface interaction processes and eventually decrease the thickness of the layer until the layer is removed.…”

Section: Introductionmentioning

confidence: 99%

Optimizing the laser absorption technique for quantification of caesium densities in negative hydrogen ion sources

Fantz¹,

Wimmer²

2011

J. Phys. D: Appl. Phys.

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To cite this version:U Fantz, C Wimmer. Optimizing the laser absorption technique for quantification of caesium densities in negative hydrogen ion sources. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (33) Abstract. The performance of negative hydrogen ion sources, which rely on the formation of negative hydrogen ions on a surface with low work function, depends strongly on the caesium dynamics in the source. A quantitative measurement of the amount of caesium in the source during plasma-on and plasma-off (vacuum phase) is highly desirable. The laser absorption technique is optimized for the diagnostics of neutral caesium densities close to the extraction surface on which the negative hydrogen ions are generated. The setup has been simplified as much as possible utilizing also an automatic data evaluation for online measurements at high power rf sources. The setup has been tested and calibrated in a small scale laboratory experiment. The system and the analysis of the D 2 caesium line at 852.1 nm is described in detail, including effects of line saturation and density depletion. The system is sensitive in the density range of 10 13 -10 17 m -3 (path length of about 15 cm), allowing also for a temporal resolution of 40 ms. First very promising results from the negative hydrogen ion source are presented, such as the increase of the caesium density due to the caesium evaporation and time traces before, during, and after the discharge indicating a strong caesium redistribution.

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Surface Plasma Negative Ion Sources

Dudnikov

2019

Springer Series on Atomic, Optical, and Plasma Physics

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Metallic work function measurement in the range 2–3.3 eV using a blue light-emitting diode source

Cited by 11 publications

References 9 publications

Particle Scattering off Surfaces: Application in Space Science

Particle Scattering off Surfaces: Application in Space Science

Optimizing the laser absorption technique for quantification of caesium densities in negative hydrogen ion sources

Surface Plasma Negative Ion Sources

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