High-intensity laser-beam effects on the spatial resolution of a streak camera tube

The purpose of this paper is to present a model that explains the degradation in spatial resolution of a streak camera tube (SCT) at high laser-beam intensity. The model requires an understanding of (1) the aberration effects in the electron lens systems and (2) the surface-potential perturbation in the photocathode at high-intensity irradiation. The surface-potential perturbation in the laser-beam-irradiated spot on the photocathode gives rise to a diverging microlens (or ’’blooming’’ electrons) at the cathode-vacuum interface. Because of the electron-lens aberration, the irradiated spot at the photocathode is not perfectly focused at the SCT phosphor screen. Hence the resulting image on the screen is the magnified object of the ’’blooming’’ electrons that occur in the vicinity of the photocathode. Experiments with two different types of SCT having wide-angle and narrow-angle beam optics have demonstrated the validity of the blooming model.