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Experimental Target Injection and Tracking System

R. W. Petzoldt, N. B. Alexander, T. J. Drake, D. T. Goodin, K. Jonestrask, R. W. Stemke

Fusion Science and Technology / Volume 44 / Number 1 / Pages 138-141

July 2003


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Targets must be injected into an IFE power plant with an accuracy of ± 5 mm at a rate of approximately 5 to 10 each second. Targets must be tracked very accurately to allow driver beams to be aligned with defined points on the targets with accuracy ±200 m for indirect drive and ±20 m for direct drive. An experimental target injection and tracking system has been designed and is being constructed at General Atomics to investigate injection and tracking of both direct drive and indirect drive targets. The design is modular to allow testing of alternate target acceleration and tracking methods. The injector system will be used as a tool for testing the survivability of various target designs and provide feed back to the target designers. This 30 m long system will be the centerpiece of a Facility for developing IFE target fabrication and injection technologies.

A high-speed high-flow gas valve (designed and built by Oak Ridge National Laboratory) will provide helium propellant gas to the targets. To avoid target damage from excessive acceleration, an 8 m gun barrel is being built to achieve 400 m/s target speed while not exceeding 10,000 m/s2 acceleration. Direct-drive targets are protected in the barrel by sabots that are spring loaded to separate into two halves after acceleration. A sabot deflector directs the sabot halves away from the target injection path. Gas expansion chambers and orifices, keep propellant gas out of the target-tracking region. Targets will be optically tracked with laser beams and line scan cameras. High-speed computations will calculate target position in less than 2 ms based on the output from the line-scan cameras. Target position and arrival time to a plane in the reaction chamber center will be predicted in real-time based on early target position measurements. The system design, construction progress, and early testing results will be presented.

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