| 1. |
- Davidsson, D. W., et al.
(författare)
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Limitations to flat-field correction methods when using an X-ray spectrum
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; , s. 146-150
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Tidskriftsartikel (refereegranskat)abstract
- Flat-field correction methods are implemented in order to eliminate non-uniformities in X-ray imaging sensors. If the compensation is perfect, then the remaining variations result from noise over the detector area. The efficiency of the compensation is reduced when an object is placed in the beam. A principle cause of this effect is believed to be the spectrum hardening caused by the object. In a normal application the correction factors are calculated for a certain spectrum, meaning that the average of the correction for the individual photon energies are used. If the composition of the spectrum changes the correction factor will also change. In this paper, we present a theory for the sensitivity of the gain constants on X-ray spectra. The theory is supported by experimental data obtained with X-ray spectra and monochromatic X-rays.
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| 2. |
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| 3. |
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| 4. |
- Marchal, J, et al.
(författare)
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Active pixel detector for ion beam profiling
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 487:1-2, s. 224-231
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Tidskriftsartikel (refereegranskat)
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| 5. |
- O'Shea, J. N., et al.
(författare)
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Molecular ordering in isonicotinic acid on rutile TiO2(110) investigated with valence band photoemission
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:20, s. 10203-10208
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of isonicotinic acid on rutile TiO2(110) has been investigated using synchrotron-based valence band photoemission. Structural ordering in multilayer films of the molecules is found to give rise to a strong angular dependence in the valence band intensities when measured using linearly polarized radiation. Molecular ordering in this case is proposed to be induced by intermolecular hydrogen bonding which is found to be highly dependent upon the deposition rate of the isonicotinic acid. Through comparison of the experimental data with density functional calculated valence band spectra of hydrogen-bonded isonicotinic acid molecules, we can account for the angular dependence in terms of the spatial distribution of the molecular orbitals.
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| 6. |
- Pellegrini, G., et al.
(författare)
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Technology development of 3D detectors for high-energy physics and imaging
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 487:02-jan, s. 19-26
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Tidskriftsartikel (refereegranskat)abstract
- Various fabrications routes to create '3D' detectors have been investigated and the electrical characteristics of these structures have been compared to simulations. The geometry of the detectors is hexagonal with a central anode surrounded by six cathode contacts. A uniform electric field is obtained with the maximum drift and depletion distance set by electrode spacings rather than detector thickness. This should improve the ability of silicon to operate in the presence of the severe bulk radiation damage expected in high-energy colliders. Moreover, 3D detectors made with other materials (e.g. GaAs, SiC) may be used, for example, in X-ray detection for medical imaging. Holes in the substrate were made either by etching with an inductively coupled plasma machine, by laser drilling or by photochemical etching. A number of different hole diameters and thickness have been investigated. Experimental characteristics have been compared to MEDICI simulations.
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