Development of a Cold Cathode Electron Source Based on Gold Cathode MCP

In this study, cold cathode electron sources using deep-UV photons to excite gold cathode and microchannel plate (MCP) were employed to configure a high-quality electron impact ion source (EI) in a mass spectrometry. As an electron multiplying device, MCP can amplify weak signal by thousands of times. Gold was used as a photocathode and it had the characteristics of simple excitation, stable photoemission, and uniform photocurrent density distribution. Combining the characteristics of the two, a series of research were carried out. The gold cathode JGS2 was formed by evaporation gold film on JGS2 quartz glass, and the gold-cathode MCP was formed by evaporation gold film on the input surface of MCP, respectively. The two were assembled in different combinations to develop two kinds of cold cathode electronic sources. Firstly, the deep-UV excited gold cathode MCP was used as the electron source, the output electron beam current range was 10^-11-10^-6 A. When the excitation light source was stable, the electron source could reach a stable state quickly and maintain a stable output for a long time (>5 h). Under the interaction of gold cathode MCP and gold cathode JGS2, the maximum output electron beam current of electron source could reach 10-5 A. At the same time, the contributions of reflected photoelectrons and transmitted photoelectrons generated by the gold cathode to the output current under different electric fields were discussed, as for the deeper working mechanism to be solved. In addition, the output electron beam current could be continuously adjusted by changing the working voltage of MCP, so that the cold cathode electron source could be flexibly and quickly adjusted and responded within a certain range. Finally, a fluorescent screen was used to observe the imaging quality of the output current generated by the above system, and the RGB image captured by the high-definition camera was converted into a grayscale image, and the non-uniformity of the image was calculated to be about 6.5%. Therefore, the imaging uniformity of the cold cathode electron source developed in this paper on the phosphor screen was good. The above results showed that the cold cathode electron source composed of gold cathode MCP excited or combined with gold cathode JGS2 by deep ultraviolet light had the characteristics of long working stability, good uniformity, wide and continuously adjustable beam current range. It can realize the functions of photoelectric conversion and electron multiplication, and is expected to provide a new alternative for the development of electron sources in EI sources in the future.