Ultrafast Gated Intensifier Design for Laser Fusion X-Ray Framing Applications

Abstract

The transmission line imager described above is now in fabrication and some of the important characteristics of its components have been tested. The design of the device addresses all of the stringent requirements for ICF framing applications and proposes solutions to many of the problems limiting the performance of other designs in use and described in the literature. The two most important features of this device are its very short gating time and its high image quality. The high speed results from the integral photoconductive-switch pulse generator, matched vacuum transmission line geometry, and small high-conductivity photocathode. The small photocathode is made possible because of the high resolution of the proximity focused imager and the special high contrast phosphor screen. The phosphor screen incorporates the unique feature of an electron collimator which serves both to: 1) increase the shutter ratio by attenuating x-rays which reach the screen, and 2) prevent Rutherford scattered electrons from re-impacting the screen in another location, impairing the image contrast ratio and edge response. The resolution and edge response of the screen is also enhanced by the narrow transverse electron energy distribution of the photocathode and the isolation between the islands of phosphor at the end of each fiber of the screen. If this design is successful in all respects it will make possible short frame time quantiative images of ICF phenomenon of unprecedented quality.