Simplified charge transfer inefficiency correction in CCDs by trap-pumping

Abstract

A major concern when using Charge-Coupled Devices in hostile radiation environments is radiation induced Charge Transfer Inefficiency. The displacement damage from non-ionising radiation incident on the detector creates defects within the silicon lattice, these defects can capture and hold charge for a period of time dependent on the operating temperature and the type of defect, or "trap species". The location and type of defect can be determined to a high degree of precision using the trap-pumping technique, whereby background charges are input and then shuffled forwards and backwards between pixels many times and repeated using different transfer timings to promote resonant charge-pumping at particular defect sites. Where the charge transfer timings used in the trap-pumping process are equivalent to the nominal CCD readout modes, a simple "trap-map" of the defects that will most likely contribute to charge transfer inefficiency in the CCD array can be quickly generated. This paper describes a concept for how such a "trap-map" can be used to correct images subject to non-ionising radiation damage and provides initial results from an analytical algorithm and our recommendations for future developments.

Proton-induced traps in electron multiplying charge-coupled devices

“…The "single trap pumping" technique allows characterization of individual defects within the transfer channel of the device, providing information on their precise location, emission time constant, energy level, and cross section. [31][32][33][34][35][36][37] A detailed description of the development of the underlying theory can be found within Ref. 18, and Ref.…”

On-ground and in-orbit characterisation plan for the PLATO CCD normal cameras

“…The use of trap pumping, which has been used successfully during on ground testing [22] and in orbit [23] to investigate specific defects and their locations is also under consideration. The technique is an excellent source of information about defect formation and evolution and it would provide a good comparison between inflight observations and the on ground radiation damage testing.…”

“…The information could also be used to create a trap map of defects present in the CCD and a Monte Carlo based model used to perform correction, however the practicality of this would be limited by the inability to identify the location of slower traps and its value will require an assessment. A simple method of using trap pumping to correct for charge loss relies on moving the charge backwards and forwards using the same operational timings as normal readout, the assessment of this method however is still at an early stage [23].…”