Laser-wakefield accelerators as hard x-ray sources for 3D medical imaging of human bone

A bright μm-sized source of hard synchrotron x-rays (critical energy Ecrit > 30 keV) based on the betatron oscillations of laser wakefield accelerated electrons has been developed. The potential of this source for medical imaging was demonstrated by performing micro-computed tomography of a human femoral trabecular bone sample, allowing full 3D reconstruction to a resolution below 50 μm. The use of a 1 cm long wakefield accelerator means that the length of the beamline (excluding the laser) is dominated by the x-ray imaging distances rather than the electron acceleration distances. The source possesses high peak brightness, which allows each image to be recorded with a single exposure and reduces the time required for a full tomographic scan. These properties make this an interesting laboratory source for many tomographic imaging applications

STUDIES OF DEFECT PROPERTIESAn X-ray Study of Defective Ionic Single Crystals

Les profils des réflexions (200) et (220) de la raie de diffraction CuKβ sur les monocristaux d'halogénures alcalins de dimensions (2 x 2 x 1 cm3) sont examinés. Nos mesures ont porté sur des échantillons purs et dopés, parfait et déformés. La diffraction des rayons X sur des échantillons défectueux fait apparaître expérimentalement un déplacement de la position angulaire et une déformation de la forme des raies. La variation des paramètres réticulaires de la maille cristalline et des contraintes résiduelles se rapporte inversement. Pour des cristaux fortement dopés les formes de profils sont complexes et peuvent être décomposées à proximité de l'angle de Bragg. Les systèmes NaCl.CaCl2 et NaCl.NiCl2 donnent des profils distincts déjà à l'état natif. Ces phénomènes peuvent être interprétés par une réflexion sur des grains désorientés de la matrice ou sur les phases secondaires du type Suzuki et Hosemann.The line profiles of the (200) and (220) reflections of large (2 x 2 x 1 cm3) pure and doped i.e. deformed alkali-halide single crystals were investigated with CuKβ radiation. The defective state of the crystals presents itself in the formation of a diffuse background and the shift of the Bragg angle. A negative correlation was found between the lattice parameter and residual stress values. Heavily doped crystals develop complex line profiles which can be deconvoluted in the vicinity of the Bragg peak. NaCl.CaCl2, and NaCl.NiCl2 systems yielded a number of well resolved peaks already in the as grown state. This effect might be due either to a small angle misorientation of mosaic blocks or some paracrystalline state as considered by Suzuki and Hosemann respectively