Thick , fully depleted p-channel charge-coupled devices ( CCDs ) have been developed at the Lawrence Berkeley National Laboratory ( LBNL ) .
These CCDs have several advantages over conventional thin , n-channel CCDs , including enhanced quantum efficiency and reduced fringing at near-infrared wavelengths and improved radiation tolerance .
Here we report results from the irradiation of CCDs with 12.5 and 55 MeV protons at the LBNL 88-Inch Cyclotron and with 0.1 - 1 MeV electrons at the LBNL ^ { 60 } Co source .
These studies indicate that the LBNL CCDs perform well after irradiation , even in the parameters in which significant degradation is observed in other CCDs : charge transfer efficiency , dark current , and isolated hot pixels .
Modeling the radiation exposure over a six-year mission lifetime with no annealing , we expect an increase in dark current of 20 e ^ { - } /pixel/hr , and a degradation of charge transfer efficiency in the parallel direction of 3 \times 10 ^ { -6 } and 1 \times 10 ^ { -6 } in the serial direction .
The dark current is observed to improve with an annealing cycle , while the parallel CTE is relatively unaffected and the serial CTE is somewhat degraded .
As expected , the radiation tolerance of the p-channel LBNL CCDs is significantly improved over the conventional n-channel CCDs that are currently employed in space-based telescopes such as the Hubble Space Telescope .