DECLNMER
UPGRADES TO THE LLNL FLASH X-RAY INDUCTION LINEAR ACCELERATOR (FXR)The FXR is an induction linear acceleratorused for flash radiography at the Lawrence Livtmnore National Laboratory's Site 300 Test Facility. The FXR was originally completedin 1982and has been in continuoususe as a radiographictool. At that time the FXR produceda 17MeV, 2.2 kA burst of electronsfor a duration of 65 ns.An upgrade of the FXR was recentl completed. The purpose of this upgrade was to improve the performanceof the FXl by increasing the energy of the electron injector from 1.2 MeV to 2.5 MeV and the beam current from 2.2 kA to 3 kA, improving the magnetictransport system by redesigningthe solenoidaltransport fms coils, reducing the rf coupling of the electron beam to the accelerator cells, and by adding additional beam d@OStiC&We will desmibethe injectur upgradesand pdbrmanc~as well as our effbrts to tune the acceleratorby~g beam corkscrew motion and the impact of Beam Breakup Instabilityon beam centroidmotionthroughoutthe beam line as the currentis increasedto 3 kA.
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Lawrence Livermore National Laboratory has designed and constructed a test stand to improve the voltage regulation in our Flash X-Ray (FXR) accelerator cell. The goal is to create a more mono-energetic electron beam that will create an x-ray source with a smaller spot size. Studying the interaction of the beam and pulsepower system with the accelerator cell will improve the design of high-current accelerators at Livermore and elsewhere. On the test stand, a standard FXR cell is driven by a flexible pulse-power system and the beam current is simulated with a switched center conductor. The test stand is fully instrumented with high-speed digitizers to document the effect of impedance mismatches when the cell is operated under various full-voltage conditions. A time-domain reflectometry technique was also developed to characterize the beam and cell interactions by measuring the impedance of the accelerator and pulsepower component. Computer models are being developed in parallel with the testing program to validate the measurements and evaluate different design changes. Both 3D transient electromagnetic and circuit models are being used.
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