Proton-induced CCD charge transfer degradation at low-operating temperatures

Measurements of charge transfer inefficiency (CTI) at charge-coupled device temperatures /spl sim/-100/spl deg/C show that proton-induced E-centers can be kept filled but other traps with energies 0.22-0.34 eV limit the achievable improvement in CTI. Estimates of trap energy levels and concentrations are made from CTI and emission time measurements. It is found that the CTI can be reduced for low signal levels. Implications for spaceborne astronomical instruments are discussed.