Modulator charging system upgrade for a 5-MeV electron acceleration

The Lawrence Livermore Laboratory is currently constructing a new linear induction accelerator with a higher beam current than the Astron [1] accelerator. The new accelerator, called the Experimental Test Accelerator (ETA) will be a 5-MeV, 10-kA accelerator with a pulsewidth of 50 ns. Like the Astron, the principle of magnetic induction is used to obtain a linear accelerator. The modular accelerating cavities form essentially a 1:1 transformer and the change in flux in the ferrite core induces an axial electric field for the acceleration of electrons. Since the total energy storage for the ETA is much greater than the requirement for Astron, the power system, the capacitor bank, and the modulator charging system all had to be modified to provide an overall regulation of 0.1 percent. This strict regulation of the charging voltage is necessary for pulse-to-pulse repeatability.