| 1. |
- Aoyagi, M., et al.
(författare)
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Systematic effects on a Compton polarimeter at the focus of an X-ray mirror
- 2024
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- XL-Calibur is a balloon-borne Compton polarimeter for X-rays in the ∼15–80 keV range. Using an X-ray mirror with a 12 m focal length for collecting photons onto a beryllium scattering rod surrounded by CZT detectors, a minimum-detectable polarization as low as ∼3% is expected during a 24-hour on-target observation of a 1 Crab source at 45° elevation. Systematic effects alter the reconstructed polarization as the mirror focal spot moves across the beryllium scatterer, due to pointing offsets, mechanical misalignment or deformation of the carbon-fiber truss supporting the mirror and the polarimeter. Unaddressed, this can give rise to a spurious polarization signal for an unpolarized flux, or a change in reconstructed polarization fraction and angle for a polarized flux. Using bench-marked Monte-Carlo simulations and an accurate mirror point-spread function characterized at synchrotron beam-lines, systematic effects are quantified, and mitigation strategies discussed. By recalculating the scattering site for a shifted beam, systematic errors can be reduced from several tens of percent to the few-percent level for any shift within the scattering element. The treatment of these systematic effects will be important for any polarimetric instrument where a focused X-ray beam is impinging on a scattering element surrounded by counting detectors.
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| 2. |
- Lockyer, Nicholas P., et al.
(författare)
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Secondary ion mass spectrometry
- 2024
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Ingår i: Nature Reviews Methods Primers. - 2662-8449. ; 4
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Forskningsöversikt (refereegranskat)abstract
- Secondary ion mass spectrometry (SIMS) is a technique for chemical analysis and imaging of solid materials, with applications in many areas of science and technology. It involves bombarding a sample surface under high vacuum with energetic primary ions. The ejected secondary ions undergo mass-to-charge ratio (m/z) analysis and are detected. The resulting mass spectrum contains detailed surface chemical information with sub-monolayer sensitivity. Different experimental configurations provide chemically resolved depth distribution and 2D or 3D images. SIMS is complementary to other surface analysis techniques, such as X-ray photoelectron spectroscopy; chemical imaging techniques, for example, vibrational microspectroscopy methods such as Fourier transform infrared spectroscopy and Ramanspectroscopy; and other mass spectrometry imaging techniques, including desorption electrospray ionization and matrix-assisted laser desorption ionization. Features of SIMS include high spatial resolution, high depth resolution and broad chemical sensitivity to all elements, isotopes and molecules up to several thousand mass units. This Primer describes the operating principles of SIMS and outlines how the instrument geometry and operational parameters enable different modes of operation and information to be obtained. Applications, including materials science, surface science, electronic devices, geosciences and life sciences, are explored, finishing with an outlook for the technique.
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| 3. |
- Stark, T. H., et al.
(författare)
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Generalization of Classic Question Order Effects Across Cultures
- 2020
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Ingår i: Sociological Methods & Research. - : SAGE Publications. - 0049-1241 .- 1552-8294. ; 49:3, s. 567-602
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Tidskriftsartikel (refereegranskat)abstract
- Questionnaire design is routinely guided by classic experiments on question form, wording, and context conducted decades ago. This article explores whether two question order effects (one due to the norm of evenhandedness and the other due to subtraction or perceptual contrast) appear in surveys of probability samples in the United States and 11 other countries (Canada, Denmark, Germany, Iceland, Japan, the Netherlands, Norway, Portugal, Sweden, Taiwan, and the United Kingdom;N= 25,640). Advancing theory of question order effects, we propose necessary conditions for each effect to occur, and found that the effects occurred in the nations where these necessary conditions were met. Surprisingly, the abortion question order effect even appeared in some countries in which the necessary condition was not met, suggesting that the question order effect there (and perhaps elsewhere) was not due to subtraction or perceptual contrast. The question order effects were not moderated by education. The strength of the effect due to the norm of evenhandedness was correlated with various cultural characteristics of the nations. Strong support was observed for the form-resistant correlation hypothesis.
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