Energy loss, range, path length, time-of-flight, straggling, multiple scattering, and nuclear interaction probability

Measurements of the excitation and ionization of helium, neon, and argon by positrons of energies between threshold and 50 eV, utilising time-of-flight energy loss spectrometry, are reported. Scattering into forward angles up to 60° is observed and the measurements suggest that sharp forward lobes exist in the angular distributions of positrons scattered following atomic excitation. Multiple scattering corrections to the measurements are described. Comparison is made with the inelastic scattering of electrons by the same atoms, and connections drawn between the present results and those of the recent complementary studies of Griffith et al. and Charlton et al.

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Background Fitting in the Low-Loss Region of Electron Energy Loss Spectra

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133874 ◽

1990 ◽

Vol 48 (2) ◽

pp. 56-57

Author(s):

C P Scott ◽

A J Craven ◽

C J Gilmore ◽

A W Bowen

Keyword(s):

Energy Loss ◽

Multiple Scattering ◽

Simple Form ◽

Single Scattering ◽

Low Loss ◽

Characteristic Energy ◽

Normal Method ◽

Fitting In ◽

Electron Energy Loss ◽

Electron Energy Loss Spectra

The normal method of background subtraction in quantitative EELS analysis involves fitting an expression of the form I=AE-r to an energy window preceding the edge of interest; E is energy loss, A and r are fitting parameters. The calculated fit is then extrapolated under the edge, allowing the required signal to be extracted. In the case where the characteristic energy loss is small (E < 100eV), the background does not approximate to this simple form. One cause of this is multiple scattering. Even if the effects of multiple scattering are removed by deconvolution, it is not clear that the background from the recovered single scattering distribution follows this simple form, and, in any case, deconvolution can introduce artefacts.The above difficulties are particularly severe in the case of Al-Li alloys, where the Li K edge at ~52eV overlaps the Al L2,3 edge at ~72eV, and sharp plasmon peaks occur at intervals of ~15eV in the low loss region. An alternative background fitting technique, based on the work of Zanchi et al, has been tested on spectra taken from pure Al films, with a view to extending the analysis to Al-Li alloys.

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Stray light characterization with ultrafast time-of-flight imaging

Scientific Reports ◽

10.1038/s41598-021-89324-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

L. Clermont ◽

W. Uhring ◽

M. Georges

Keyword(s):

Path Length ◽

Imaging System ◽

Time Of Flight ◽

Optical Path Length ◽

Optical Path ◽

Stray Light ◽

Laser Source ◽

Space Telescopes ◽

Characterization Methods ◽

Instance Space

AbstractUnderstanding stray light (SL) is a crucial aspect in the development of high-end optical instruments, for instance space telescopes. As it drives image quality, SL must be controlled by design and characterized experimentally. However, conventional SL characterization methods are limited as they do not provide information on its origins. The problem is complex due to the diversity of light interaction processes with surfaces, creating various SL contributors. Therefore, when SL level is higher than expected, it can be difficult to determine how to improve the system. We demonstrate a new approach, ultrafast time-of-flight SL characterization, where a pulsed laser source and a streak camera are used to record individually SL contributors which travel with a specific optical path length. Furthermore, the optical path length offers a means of identification to determine its origin. We demonstrate this method in an imaging system, measuring and identifying individual ghosts and scattering components. We then show how it can be used to reverse-engineer the instrument SL origins.

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