Imaging with visible light today uses numerous contrast mechanisms, including bright- and dark-field contrast, phase-contrast schemes and confocal and fluorescence-based methods. X-ray imaging, on the other hand, has only recently seen the development of an analogous variety of contrast modalities. Although X-ray phase-contrast imaging could successfully be implemented at a relatively early stage with several techniques, dark-field imaging, or more generally scattering-based imaging, with hard X-rays and good signal-to-noise ratio, in practice still remains a challenging task even at highly brilliant synchrotron sources. In this letter, we report a new approach on the basis of a grating interferometer that can efficiently yield dark-field scatter images of high quality, even with conventional X-ray tube sources. Because the image contrast is formed through the mechanism of small-angle scattering, it provides complementary and otherwise inaccessible structural information about the specimen at the micrometre and submicrometre length scale. Our approach is fully compatible with conventional transmission radiography and a recently developed hard-X-ray phase-contrast imaging scheme. Applications to X-ray medical imaging, industrial non-destructive testing and security screening are discussed.
Pilatus is a silicon hybrid pixel detector system for detecting X-rays in single photon counting mode. The PILATUS II chip, fabricated in a radiation tolerant design with a standard 0.25 m CMOS process, was used to construct multichip modules with a size of 84 34 mm comprising 94'965 pixels. All calibrations and characterizations were carried out with monochromatic X-rays from a synchrotron source. In order to set any required threshold above the noise level between 2.14 keV and 22 keV the detector was calibrated with X-rays. An algorithm to adjust thresholds pixel-by-pixel and create trim files based on X-ray flat-field images was developed. The threshold dispersion was reduced from 343 eV to 36 eV by the means of trim files. An electronic noise of 447 eV has been measured. The PILATUS modules are suitable for various X-ray applications such as diffraction and imaging techniques.
We have determined the momentum p ϩ of muons from the decay ϩ → ϩ at rest, by analyzing a surface muon beam in a magnetic spectrometer equipped with a silicon microstrip detector. The result p ϩϭ (29.792 00Ϯ0.000 11) MeV/c leads to a squared muon-neutrino mass of m 2 ϭ(Ϫ0.016Ϯ0.023)MeV 2 , which corresponds to a ''laboratory'' upper limit of 0.17 MeV ͑C.L.ϭ0.9͒ for the muon-neutrino mass.The cosmological upper limit of the neutrino mass ͑65 eV͒, the muon mass, and the new value of p ϩ yield the pion mass m ϩϭ (139.570 22Ϯ0.000 14) MeV. Alternatively, if one does not use the cosmological upper limit of m , then a combined fit including the new p ϩ value, and the m ϩ and m Ϫ values from other experiments and the CPT theorem (m ϩϭ m Ϫ) leads to m Ϯϭ (139.570 37Ϯ0.000 21) MeV. As a side result, the mean kinetic energy of the pions stopped in the production target, made of isotropic graphite, immediately before their decay is found to be T ϩϭ (0.425Ϯ0.016) eV. This is consistent with the hypothesis that the pions are trapped in the potential well of a spherical harmonic oscillator, V(r)ϭV 0 ϩ 1 2 k s r 2 , with k s ϭ(1.144Ϯ0.088)ϫ10 17 eV/cm 2 .
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