Analysis of charge transfer efficiency noise on proton-damaged CCDs for the Hubble Space Telescope Wide Field Camera 3

Abstract

Proton induced charge transfer efficiency (CTE) degradation has been studied in the large format charge-coupled device (CCD) flight-like candidates for Wide Field Camera 3 for the Hubble Space Telescope. These detectors were irradiated with different proton fluences. This paper focuses on the statistical nature of CTE degradation due to damage on one of the irradiated devices with exceptional initial CTE characteristics. In radiation damaged CCDs, CTE noise can be the dominant noise component. In contrast to other noise sources, CTE noise has a component of fixed pattern noise that can be removed by the appropriate calibration technique. A large set of data was acquired and analysis of it confirms the expectation that CTE damage is a local phenomenon and it varies widely across the CCD surface. Possible mitigation solutions and their practicality are discussed in some detail.