Experimental investigation of memory effects in intensified photodiode-array spectrograph detectors

The use of intensified linear photodiode arrays as spectrograph detectors can, in certain applications, be subject to interference by several side effects. The widely used P-20 phosphor of the image intensifier exhibits both phosphorescence decay (persistence) and thermoluminescence memory effects together with an inherent nonlinear response to incident light, whereas the photodiode array exhibits a readout-lag memory effect. During characterization of any one of these effects, it was important to ensure that the measurements were not influenced by the other side effects. This was particularly true for the phosphorescence and readout-lag effects, and for the thermoluminescence and inherent phosphor nonlinearity effects. These side effects become significant in applications where spectra that exhibit large changes in shape and intensity on a pulse-by-pulse basis are being recorded individually at rates > 0.1 Hz. A determination should then be made to either correct, circumvent, or ignore these potential sources of error.