Beam injector and transport calculations for ITS

The Integrated Test Stand at Los Alamos National Laboratory (LANL) is addressing issues in high-brightness electron beam generation, acceleration, and transport. The machine consists of a 3 kA, 3.5 MV injector, eight induction acceleration gaps, a drift section and a final-focus magnet which focuses the beam onto diagnostic targets. One of the goals of the program is to test and improve the predictive capability of numerical models. We have carried out detailed simulations of the diode and initial drift region with the particle-in-cell codes IVORY and SPROP, obtaining good agreement with experimental streak-camera data at several axial locations. Transport through the accelerating cells to the target 10 m from the cathode is modeled with the envelope codes LAMDA and XTR. The magnet settings for minimum spot-size are close to the experimental values. From the measured value of the minimum spot-size we infer a normalized Lapostolle emittance of about 0.2 cm-rad. We have characterized the sensitivity of the spot-size to variation in the machine parameters