Real-time control of the beam attenuation with XPAD hybrid pixel detector

Abstract

In order to fully benefit from a beam produced by modern synchrotron light sources, characterised by a wide and continuous energy spectrum, high brightness and a very high intensity, advancement in detector technology has been made over the last decades. However, one of the main limitations of the state-of-the-art counting hybrid pixel detectors is the maximum count-rate that is very often few orders of magnitudes lower than of the incident, reflected or diffracted beam flux. Therefore, direct beam attenuation is mandatory in order to perform the measurements according to the detector's characteristics. In this work we present a major upgrade of a fast attenuation system developed at Synchrotron SOLEIL, which allows for a dynamical change of the beam attenuation as a function of the photon flux received by XPAD S140 photon counting detector. The system performs a cyclic real-time estimation of the flux received by every pixel during acquisition of an image and searches for clusters of at least two pixels that exceed user defined levels of counts/s. The beam attenuation is immediately and automatically changed in order to guarantee that the detector will always operate in its linear range even during a long continuous scan, by acting on the direct attenuators.

Resolving the structure of the striped Ge layer on Ag(111):Ag2Ge surface alloy with alternate fcc and hcp domains

“…The sample was analyzed with 18.46 keV X-rays at a grazing incidence angle of 0.2°. Scattered X-rays were detected with a X-ray Pixel chips with Adaptive Dynamics hybrid pixel detector [14]. Diffracted intensity was measured by performing a series of rocking scans around diffraction.…”

In situ X-ray measurements over large Q-space to study the evolution of oxide thin films prepared by RF sputter deposition

“…According to the experimental setup, the beamline energy was chosen to be 11.9 keV and the focus size was set to 1 (h)  0.04 (v) mm 2 . Therefore, we followed the surface evolution by GISAXS with the 2D detector (XPAD3 Hybrid Pixel Detector, pixel size 130 lm  130 lm) [24] and detected GIXRPD and XRR with the point detector (Model Cyberstar, Echirolles cedex, France) (see Fig. 2).…”

High-energy x-ray diffraction from surfaces and nanoparticles

“…4(a) in the case of a Pd(100) single crystal with low mosaicity. A sample rotation is still needed to record the whole reciprocal space, which is traditionally performed at lower photon energies using a smaller 2D detector, involving a time-consuming point-topoint movement of the sample and detector arm, which can be significantly speeded up by a continuous movement of the detector arm and synchronized readout of the detector and automatized absorber system [25,26]. Alternatively, also at lower, conventional photon energies a stationary, large 2D detector could also be employed for fast data recording, together with fast online data analysis to create distortion-free cuts through reciprocal space, as they are directly delivered in very good approximation in the high-energy case.…”