Hard x-ray detectors for OMEGA and NIF

Laser-plasma instabilities that produce an unacceptably high level of hot e lectrons are potentially dangerous for both direct-drive and indirect-drive inertial confinement laser fusion. The hot electrons preheat the fuel and prevent compression of the capsule to the requisite conditions for ignition . Fast electron generation and preheat can be inferred from the hard x-ray radiation generated by the interaction of the hot electrons with the target . On the University of Rochester's OMEGA laser system, time-resolved hard x -ray detectors have been operating in an energy range from 10 to 500 keV. I n this article we will present initial results for the yield and spectrum o f the hard x-ray radiation. The concept used on OMEGA can be easily extende d to infer the amount of laser energy coupled to suprathermal electrons and to the target for both direct- and indirect-drive implosions on the upcomi ng National Ignition Facility, as well as to measure the conversion efficie ncy in high-x-ray-yield experiments. (C) 2001 American Institute of Physics .