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Characterizing and correcting persistence in James Webb Space Telescope HgCdTe detectors

The persistent signal from bright sources in infrared detectors can significantly pollute subsequent images. While the persistent signal is a small fraction of the stimulus image, the high dynamic range of modern infrared detectors allows this signal to be easily detectable. In this paper we present a method of characterizing the persistence signal over time as a function of the length of time that the bright signal is left on the detector and the number of traps in each pixel. We derive the functional form for both the capture and decay of traps and show that it is analogous to radioactive decay. We show that a model with three exponential families of traps is able to explain the observed persistence. We use electronically induced persistence to simulate a flash of light and show that the observed difference between the electronically induced persistence signal and that from light induced saturation is well fit by our model. The fitted parameters for the tested part show a very fast capture rate for the tested detector. This very fast capture is significantly different than what we found for an engineering part we had tested earlier We then derive and test the capture model for the more real-world situation of the continuous accumulation of charge during an exposure. We use this model to predict the persistence from a given stimulus image that we then remove from the darks after the stimulus image. The resulting corrected darks show that over 90% of the persistence was removed.