Study of the X-ray scattering in the silicon and CdTe XPAD

The XPAD3, a photon counting hybrid pixel detector developed in collaboration by SOLEIL Synchrotron, the Institut Neel and the Centre de Physique des Particules de Marseille (CPPM) [1], is now successfully used for a large variety of X-ray experiments on third generation synchrotron light sources [2]. Several 7.3 cm x 12.5 cm imagers composed of 8 silicon modules (7 chips per module, 9600 pixel of 130μm side per chip) are routinely used on different synchrotron beamlines at Soleil and on the CRG beamline D2AM at ESRF. Detector performances such as noiseless detection, high dynamic (27 bits) and fast framing rate (640 fps) have opened up the possibility of new or improved types of measurements. Nevertheless, above 15 keV, besides the loss of efficiency [2], the X-ray scattering in silicon sensor and the material located behind significantly increases the shape and the width of thepoint-spread function at 0.01% of the maximum. This effect prevents the study of low intensity phenomena such as diffuse scattering, which would be observed at the foot of theBragg peak and theoretically measurable with the large dynamic of the detector. This effect has been measured at different energies with monochromatic synchrotron beam (on CRISTAL and METROLOGIE Soleil beamlines) on a mono module Silicon XPAD and then compared with a Quad CdTe XPAD prototype (cf. figure 1). The results, which will be presented, demonstrate the superiority of the high Z sensor and push the investigation of the CdTe as a material sensor even at mid energy.