C-AD Accelerator Physics Seminar

Many applications of accelerators, such as free electron lasers, pulsed neutron sources, and heavy ion fusion, require a good quality beam with high intensity. In practice, a major limit on the achievable intensity is often determined by the dynamics at the low energy end of the machine, which is dominated by space charge forces. Real laboratory beams at that low energy end are not in perfect equilibrium and a good understanding of their detailed evolution is needed. To address this issue, we give emphasis to the development of a simple and portable tomographic method to map the beam phase, which we extend to include effects from space charge. The technique makes no a priori assumptions of the beam distribution and is applicable to most machines. We simulate it using a particle in cell code, WARP, to ascertain accuracy of the reconstruction. Using this diagnostic we report a number of experiments conducted at the University of Maryland Electron Ring to examine emittance growth and charge homogenization of a beam with a transversely nonuniform initial density distribution. Our measurements are compared with results from theory and simulation.