Nuclear Instruments and Methods in Physics Research A 513 (2003) 340–344 Ge pixel array detector for high throughput X-ray spectroscopy H. Oyanagi a, *, C. Fonne b , D. Gutknecht b , P. Dressler b , R. Henck b , M.-O. Lampert b , S. Ogawa c , K. Kasai d , S.B. Mohamed a a National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Japan b EURISYS MESURES, 1 Chemindela Roserate Lingolshem, Tanneries 67834 Cedex, France c Ogawa Consulting Engineer’s Office, 217 Famile Villa Gotennban Hihashitanaka, 1417-2 Gotennba, Shizuoka 417-0026, Japan d NE Software Co. Ltd., 9-3 Wakaba, Kakizaki-cho, Inashiki-gun, Ibaraki 300-1249, Japan Abstract For high throughput/energy-resolution fluorescence X-ray detection in X-ray absorption spectroscopy (XAS), a novel Ge pixel array detector (PAD) with 100 segments has been developed. Using a monolithic approach, a high packing density (88%) with nearly perfect commission rate (99%) were achieved, resulting in a dramatic improvement in packing density compared to the close-packed multi-element detector (57%). Two types of PAD was built with the pixel thickness of 7.5 and 10mm. Each segment has an active area of 22mm 2 . The average energy resolution at 5.9keV was ca. 220eV (6 ms shaping time) and 240 eV (0.5 ms shaping time). High efficiency in X-ray detection in a wide energy range (5–60keV) was confirmed. The present data acquisition system, CAMAC-based hybrid electronics, is capable of independent energy-analysis and recording all channels with a maximum 100kcps per channel or 10 MHz in total. Elimination of elastic and inelastic scattering improved the systematic error in XAS, as demonstrated by an XAS application to a photo-induced phase transition. r 2003 Elsevier B.V. All rights reserved. PACS: 07.85.Fv; 61.10.Ht; 87.64.Gb Keywords: Pixel array detector; X-ray absorption spectroscopy; Fluorescence detection; Synchrotron radiation 1. Introduction X-ray absorption spectroscopy (XAS), such as XANES and EXAFS, is a powerful probe of local structure routinely used in materials and biological research at synchrotron radiation facilities. For dilute systems, a fluorescence detection technique [1] is widely used to overcome limitations in sensitivity. The bulk sensitivity limit in fluores- cence XAS depends on both the flux of incident X-ray beam and detector performance, i.e., energy resolution, efficiency and throughput. For surface studies where a typical density of adsorbed atoms is in the order of 10 14 /cm 2 , a grazing-incidence geometry can provide a means of surface-sensitive measurement. Owing to the recent advances of synchrotron radiation, i.e., insertion devices such as wigglers and undulators at third-generation ARTICLE IN PRESS *Corresponding author. Tel.: +81-298-61-5394; fax: +81- 298-61-5085. E-mail address: h.oyanagi@aist.go.jp (H. Oyanagi). 0168-9002/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2003.08.059