Charge transfer efficiency (CTE) is a measure of the ability of the device to transfer charge from one potential well to the next. CTE is defined as the ratio of charge transferred from the target pixel to the initial charge stored in the target pixel. The transfer process is amazingly efficient. Typically, for well-made buried-channel scientific CCDs, the CTE will be between 0.99999 and 0.999999 for large charge packets (< 1000 eâ). Assuming a CTE of 0.999999, this means that for a CCD of 1000 pixels on the side, 99.8% of the charge will remain in the pixel farthest removed from the output after it has been transferred to the output (i.e., 2000 pixel transfers). The lost charge from the target pixel dribbles out as a deferred charge in trailing pixels. For computational purposes CTE is specified in terms of charge transfer inefficiency (CTI).
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