XPAD3 hybrid pixel detector applications J.-F. Berar a,Ã , N. Boudet a , P. Breugnon b , B. Caillot a , B. Chantepie b , J.-C. Clemens b , P. Delpierre b , B. Dinkespiller b , S. Godiot b , Ch. Meessen b , M. Menouni b , C. Morel b , P. Pangaud b , E. Vigeolas b , S. Hustache c , K. Medjoubi c a D2AM-CRG, ESRF and Institut Neel, CNRS, 38042 Grenoble, France b CPPM, IN2P3-CNRS and Univ. de la Mediterranee, 13288 Marseille, France c Synchrotron SOLEIL, Saint-Aubin, 91192 Gif sur Yvette, France article info Available online 1 April 2009 Keywords: Pixel Detector Synchrotron Small angle X-ray scattering X-ray diffraction abstract Using Si sensors, the XPAD3 chip can be used from 4 up to 25 keV. The CdTe detector was designed to improve efficiency at higher energies (60 keV), but it still works at low energy: data were collected at 8 keV. Firstly, small detector prototypes were built and used for scattering experiments at BM02/ESRF and DIFABS/SOLEIL. Comparisons were made by collecting small angle X-ray scattering data using the same settings with the XPAD3 and the beam line CCD camera, as well as diffuse scattering from a quasi- crystal. Finally, a surface diffraction experiment was performed to characterize the strain in a few layers of GaInAs epitaxially grown on a GaAs single crystal. & 2009 Elsevier B.V. All rights reserved. 1. Introduction Third generation synchrotron sources have been of major importance for progress in materials science. Hybrid pixel detectors were developed to take full advantage of the intense monochromatic X-ray beam provided by these sources. Following on previous XPAD detectors [1,2], XPAD3 hybrid pixel detectors were designed with chips using IBM 0:25 mm technology. With a pixel size of 130 mm, the new chip consists of 80 columns of 120 pixels and peripheral functions for its operation [3]. Firstly, an acquisition test card (Fig. 1(a)) was designed for single chip characterization and used for X-ray scattering experiments (Fig. 1(b)). At present, detectors using 15  76 mm 2 Si sensors, 500 mm thick (Fig. 1(c)) are under assembly. These consist of eight ladders of seven chips (Fig. 1(d)) for an overall size of 120  76 mm 2 and more than 5  10 5 pixels. This paper will report on X-ray scattering tests carried out on single chip and single ladder Si detectors and a two chip CdTe detector (currently limited by the available CdTe sensor size, 16  21 mm 2 ). 2. From XPAD3 chips to detectors The XPAD3 chip is constructed from about 1500 transistors/ pixel: 1000 for digital and 500 for analog, and its performance has already been fully described [3]. The pixel detector can be built in a modular fashion, thus allowing improvement of the read-out system, which now consists of three major stages. Firstly, the chip was designed to ensure a 2 ms read-out time, but reduction to 1ms is expected from the chip specifications. Secondly, in the ladder, an embedded card with processor allows the seven chips to be read simultaneously and has enough memory to store 1000 images. Thirdly, an embedded concentrator designed for eight ladders is connected by an optical link to USB/OPTO cards with memory on the acquisition PC. This multi-stage system ensures data buffering of at least 1000 images at higher speed. When the exposure time increases, internal memories are liberated and continuous read-out becomes available. 3. XPAD3 detector prototypes with Si and CdTe sensors Numerous tests were carried out on small prototypes with Si and CdTe sensors, in particular to check the energy range. Using Si diodes, this can be set to operate from 5 keV up to about 25 keV. As an example, the crystal diffraction peaks of lysozyme were recorded at SOLEIL on the PIX1 beam line at 5.9 keV [3]. The lower energy limit is defined by the electronic noise of the chip, which is comparable to the number of electrons produced by a 4 keV photon in Si. The high energy limit is due to the transparency of the sensor material (at 25 keV, 500 mm Si absorbs only 21% of the incoming photons). For this reason, we decided to use CdTe sensors. The resolution and counting linearity of Si and CdTe detectors were measured: they attain similar values. At 15keV, saturation with the Si diode is reached at 9  10 5 photons=s, while linearity ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2009.03.208 Ã Corresponding author. E-mail address: berar@esrf.fr (J.-F. Berar). URL: http://www.esrf.fr/UsersAndScience/Experiments/CRG/BM02/ (J.-F. Berar). Nuclear Instruments and Methods in Physics Research A 607 (2009) 233–235