The DARHT Phase 2 Linac

The second phase accelerator for the Dual Axis Hydrodynamic Test facility (DARHT) is designed to provide an electron beam pulse that is 2{mu}s long, 2kA, and 20 MeV in particle energy. The injector provides 3.2 MeV so that the linac need only provide 16.8 MeV. The linac is made with two types of induction accelerator cells. The first block of 8 cells have a 14 in. beam pipe compared to 10 in. in the remaining 80 cells. The other principal difference is that the first 8 cells have reduced volt-sec in their induction cores as a result of a larger diameter beam pipe. The cells are designed for very reliable high voltage operation. The insulator is Mycalex. Results from prototype tests are given including results from solenoid measurements. Each cell contains a solenoid for beam transport and a set of x-y correction coils to reduce corkscrew motion. Details of tests to determine RF mode impedances relevant to BBU generation are given. Blocks of cells are separated by intercells some of which contain transport solenoids. The intercells provide vacuum pumping stations as well. Issues of alignment and installation are discussed.