Design and construction of a imaging instrument for studying ion emission from pure ion emitters

摘要

The development of new ion sources is important in the area of surface analysis to make it easier to perform more sensitive and accurate analyses. In surface analysis a primary ion beam composed of a single species can help when predicting and interpreting the results. Therefore, much interest and effort has been focused on producing pure ion emitters. An instrument has been designed and constructed to view the current densities of the ions being emitted from pure ion emitters. The instrument electrostatically accelerates and focuses the ion beam onto a microchannel plate detector equipped with a phosphor screen for viewing the images. These images are used to identify areas of enhanced ion emission. Once these areas are identified, the investigator can use other instruments to analyze them, and hopefully develop a better understanding of the chemistry and physics involved in the ion emission process. A computer based control system has been integrated into the system to simplify the operation of the instrument and provide safety features to protect the hardware from damage. A closed-circuit video camera system is used to allow the images to be remotely viewed during imaging procedures. Experiments show that the instrument has a lower detection limit of 7.45 (times) 10(sup 3) ions/sec/mm(sup 2) and a spatial resolution of approximately 3 (minus) 4 (mu)m. Results from imaging cesium zeolite and perrhenate ion sources indicate that the ions are primarily being emitted from the surface of the sources and not from the interfacial region between the substrate and the emitter material.