A New High Spatial Resolution Streak Tube

Abstract

A new high spatial resolution electrostatically focused streak tube is described. Previous streak tube design work emphasized shorter time resolutions with little regard for the amount of spatial information that could be obtained. The design goals of the initial version of this tube included a time resolution of only 100 ps, but 500 line pairs of spatial resolution across the 25-mm diameter of the photocathode (about twice the number of spatial resolution elements ,previously available). Computer programs were used in the tube design to simulate electron trajectories in the three-dimensional azimuthally symmetric electric imaging fields. Both tangential and sagittal trajectories were considered so that the tangential and sagittal focal surfaces could be designed to be in close proximity to each other for off-axis points, thus affording better spatial resolution. Test results obtained with the prototype tube are presented. The tube is limited in time and spatial resolution by the spread in the energy distribution of photoelectrons leaving the photocathode. The addition of an accelerator electrode close to the cathode is predicted by computer analysis to improve the time resolution to a few picoseconds and to double the useful diameter of the photocathode--doubling the number of spatial resolution elements. A modified version of the tube that includes an accelerator electrode is presently being fabricated.