Analysis of on-line measured spectral responses of NEA photocathodes

In this paper, on the base of explaining the importance of spectral response, the way to derive characteristic parameters of NEA photocathode from its spectral response is introduced. Then, an automatic spectral response recording system is described. The system is used to take spectral response curves during the activation procedure. For the first time, on-line measured spectral response curves of GaAs:Cs-O NEA photocathodes are presented. These curves indicate the typical variation in spectral response caused by the deposition of cesium and oxygen. By the way of comparing and analyzing these curves, many important parameters of photocathodes are obtained, and the reasons that cause the bad behavior of NEA photocathodes are discussed.