Evaluation of a linear photodiode array detector for synchrotron small-angle x-ray scattering measurements

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Abstract
A linear photodiode array position‐sensitive detector for synchrotron small‐angle x‐ray scattering was constructed by coupling a fiber‐optic face plate coated with a thin layer (∼40 μm) of phosphor (Y2O2S:Tb) onto an electrostatically focused, intensified photodiode array detector (EG&G, PARC, Model 1422) originally designed for visible light applications. The x‐ray detector was thoroughly evaluated. It showed excellent linearity of response to the incident x‐ray intensity (less than 1%), stable pixel uniformity (an average of ±5%), good spatial linearity (±1 per 100 pixels), and a net gain of ∼17 counts/x‐ray photon at 8 keV. The detector quantum efficiency was about 1 for a signal‐to‐noise ratio of greater than ∼5%. No damage to individual pixels was found after exposure to a main beam of ∼101 0 x‐ray photons/mm2/s. A finite afterglow (≳5 s) was observed for the phosphor inside the intensifier tube. The afterglow that could limit fast time‐resolved experiments could be significantly improved by replacing the present intensifier with one using a fast‐decay phosphor. The detector usable length could be increased from the present 25 to 50 mm by replacing the fiber‐optic face plate with a 2:1 taper.

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