Status of testing and characterization of the Speedster-EXD550 x-ray hybrid CMOS detector

Abstract

The novel Speedster-EXD550 is a 550×550-pixel X-ray hybrid CMOS detector (HCD) with event-driven readout capabilities and 40-micron pixel pitch. In event-driven readout mode, only the pixels that contain sufficient liberated charge from the absorption of an x-ray will be read out. Event-driven readout allows for even faster readout speed than other HCDs, reaching readout speeds up to 10,000 frames/sec. The high frame rate of the Speedster-EXD550 is desirable for future missions as the effects of dark current and x-ray pile-up will be reduced. The readout circuitry within the ROIC for the Speedster-EXD550 contains a high-gain capacitive transimpedance amplifier, in-pixel correlated double sampling, and an in-pixel comparator enabling event-driven readout. The Speedster-EXD550 also utilizes column-parallel on-chip digitization. The ability of the Speedster-EXD550 will be demonstrated on BlackCAT, a funded NASA CubeSat mission. Testing and characterization of the Speedster-EXD550 has been done by the Penn State High Energy Astrophysics Detector and Instrumentation lab in both full-frame and event-driven readout modes. A radioactive 55 Fe source was used for the measurements presented. Here, we discuss the methods and recent results for the characterization of the Speedster-EXD550 dark current, read noise, gain, and gain variation.