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Analysis of monoenergetic proton test data reveals displacement damage degradation of charge transfer efficiency in state-of-the-art CCDs. New measurements, in combination with literature data, demonstrate good agreement between the energy dependencies of proton damage and the nonionizing energy loss (NIEL) for protons in Si. Massive shields being considered to preserve CCD perf~rman~e in satellites are then analyzed using the transport code B R Y " which quantifies both primary and secondary particle production. Using NIEL to combine the cumulative effects of both protons and neutrons reaching the CCD, we compare AI and Ta shield approaches for both trapped and flare proton environments. In general, massive Ta shields have diminished benefit owing to damage from large secondary neutron fluxes. Finally, analysis with Shockley-Read-Hall theory illustrates the importance of CCD operating conditions and transfer efficiency measurement techniques in evaluating flight performance and comparing results between devices and laboratories.

The Gaia satellite is a high-precision astrometry, photometry and spectroscopic ESA cornerstone mission, currently scheduled for launch in 2012. Its primary science drivers are the composition, formation and evolution of the Galaxy. Gaia will achieve its unprecedented positional accuracy requirements with detailed calibration and correction for radiation damage. At L2, protons cause displacement damage in the silicon of CCDs. The resulting traps capture and emit electrons from passing charge packets in the CCD pixel, distorting the image PSF and biasing its centroid. Microscopic models of Gaia's CCDs are being developed to simulate this effect. The key to calculating the probability of an electron being captured by a trap is the 3D electron density within each CCD pixel. However, this has not been physically modelled for the Gaia CCD pixels. In Seabroke, Holland & Cropper (2008), the first paper of this series, we motivated the need for such specialised 3D device modelling and outlined how its future results will fit into Gaia's overall radiation calibration strategy. In this paper, the second of the series, we present our first results using Silvaco's physics-based, engineering software: the ATLAS device simulation framework. Inputting a doping profile, pixel geometry and materials into ATLAS and comparing the results to other simulations reveals that ATLAS has a free parameter, fixed oxide charge, that needs to be calibrated. ATLAS is successfully benchmarked against other simulations and measurements of a test device, identifying how to use it to model Gaia pixels and highlighting the effect of different doping approximations.

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