We propose an extensive analysis of the various phenomena involved in the overall photoconductive lag (carrier trapping in the bulk, injection at the interfaces, hole collection through diffusion in the low field portions of the target) in an a-Si:H vidicon target. We have developed a new a-Si:H target which shows a photoconductive lag as low as 1.2% under light bias. The advantages of amorphous silicon as a target material (high sensitivity, absence of after-image or burning) are maintained. A comprehensive model of photoconductive lag is discussed. Experimental results on an improved pick-up tube are given. Industrial applications are described.