Time integrated phosphor behavior in gated image intensifier tubes

New flow analysis applications of MCP image intensifier tubes require faster image repetition rates. When coupled to CCD readout chips their time-integrated behavior determines the overall system's response concerning the intensity of unwanted "ghost" images. Previously published experimental data as well as manufacturer's literature provide only time resolved response information. New data for the widely used high-efficiency, slow-decay P20 and P43 phosphors are determined as functions of both exposure (excitation) time and interframe time. Previously reported dependency of decay time being determined solely by the preceding exposure time is not supported by new data. Data herein show an increase of decay time by more than a factor of 100, especially for short excitation times. This is caused by intensity integration on the CCD chip. The P20 shows a very long non-exponential decay. Though being faster during the initial 200 to 500 mus, the P20's decay extends over a substantially longer time as compared to the P43 phosphor. This is in clear contradiction to earlier results, which could lead to the expectation of the P20 being more than an order of magnitude faster than P43 for very short exposure times.