Upgrades to the DARHT second axis induction cells

The dual-axis radiographic hydrodynamics test (DARHT) facility will employ two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung X-ray pulses for flash radiography. The second axis, DARHT II, features a 2.5-MeV injector and a 15.5-MeV, 2-kA, 1.6-microsecond accelerator consisting of 74 induction cells and drivers. Major induction cell components include high flux swing magnetic material (Metglas 2605SC) and a Mycalextrade insulator. The cell drivers are pulse forming networks (PFNs). The DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their operational parameters. These R&D efforts identified problems in the original cell design and means to upgrade the design, performance and reliability of the linear induction cells. Physical changes in the cell oil region, the cell vacuum region, and the cell drivers, together with different operational and maintenance procedures, have been implemented in the refurbished units resulting in greatly enhanced cell performance and reliability. All 74 cells have now been refurbished and tested for acceptance. This paper gives the results of those tests and the performance of the 26 refurbished cells in the scaled accelerator.