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Published online by Cambridge University Press: 02 July 2020
An event-driven 2D pixel array detector designed for protein crystallography is being tested to determine its suitability as a direct electron detector for digital imaging in electron microscopy. The detector prototype consists of an 8×8 pixel array with an 150 μm pitch. The device configuration is illustrated in Fig. 1. The detector module consists of a reverse-biased 300 μm thick monolithic silicon diode array which is bump-bonded to an Application Specific Integrated Circuit (ASIC) which instruments each diode in the array. Each pixel cell of the ASIC forms a pixel processor which consists of an amplifier, discriminator, prescalar and readout circuit.
When an incident electron enters the detector, a group of electron-hole pairs is created in the silicon. The detector bias of the diode array is such that holes are collected at the input to the amplifier where the signal is then amplified and shaped. When the output signal pulse height is greater than the discriminator threshold, the event is then registered in the prescalar, causing one count to be accumulated.