Extending x-ray streak camera operation to vacuum ultraviolet wavelengths

Abstract

A major limitation in the use of x-ray streak cameras at longer wavelengths in the vacuum ultraviolet spectral region is the strong absorption of the radiation in the conductive thin films that are used for transmission photocathode substrates. Reflection photocathodes require off-axis illumination and hence do not couple easily to instruments such as flat-field spectrographs. We are investigating the use and optimization of an open-geometry photocathode structure consisting of a fine-mesh wire screen coated with the photoemissive material. Photons impinge directly onto this coated screen. Photoelectrons emitted from the side surfaces of the wires are accelerated into the streak tube by the applied field penetrating into the plane of the wire screen. Coatings of CsI and CuI are under study. Laser-produced plasmas, as well as discharge sources, are being used for the testing and optimization. A flat-field grazing-incidence spectrograph and a 1 m, normal-incidence spectrograph are used to cover the spectral region from 3 to 200 nm.