High-Bandwidth Optical Detectors for Fusion Experiments

Summary form only given. Traditional nuclear diagnostics for inertial confinement fusion (ICF) experiments have relied on detectors which convert interactions with radiation to high-bandwidth electrical signals. As the power of the lasers and the nuclear yields from ICF experiments has increased, electrical background signals have become a serious problem that prevents the recording of high-quality data. A recent series of experiments at the University of Rochester Laboratory for Laser Energetics OMEGA facility studied the feasibility of using radiation-to-light converters and high bandwidth optical signal transmission as an alternate nuclear diagnostic method. The radiation to light converters (scintillators, pure glasses and plastics, and pressurized CO₂) performed well and produced predictable signal amplitudes. Fiber optic transmission lines proved to have a number of fundamental problems, with radiation sensitivity being the most serious. Simple optical light pipes have performed very well and make it possible to design high-bandwidth diagnostic systems. The light pipes are hollow stainless steel tubes with polished interior surfaces which can provide efficient signal transmission with modal dispersion of the order of 10 picoseconds. Experimental results will be discussed, and the preliminary design of a diagnostic system will be described.