The Development of Computational Tools for Halo Analysis and Study of Halo Growth in the Spallation Neutron Source Linear Accelerator

The Spallation Neutron Source (SNS), being built at the Oak Ridge National Laboratory, utilizes a high intensity particle accelerator for neutron production. One of the challenges in SNS, as with all high intensity accelerators, is to minimize the amount of beam lost. High beam losses can cause costly damage and lead to residual activation of accelerator components, which complicates routine maintenance. One of the key components in beam loss at SNS is the development and propagation of beam halo. Halo particles are those driven to large amplitudes by space charge forces between the beam particles or by mismatch between the beam and the accelerator optics. The research presented seeks to develop computational tools to quantify the halo in a beam by analyzing beam profiles and identifying the halo using the Gaussian area ratio and kurtosis methods. Simulations of various configurations using three types of initial simulated distributions, along with an analysis of their phase space and rms properties, provides insight into the development of halo in the SNS linear accelerator. Finally, comparisons with machine beam profile data, taken at the same conditions as that of the simulated data, shows how accurately the simulations model the beam and its halo development and provides a better understanding of the best machine configuration with which to minimize beam halo and losses. Results of simulated data are independent of the initial distribution for strongly mismatched cases; however, even relatively well matched cases generate some halo. Core analysis reveals an increase in beam size as halo decreases for simulated cases. Experimental comparison with simulation results shows poor correlation between halo plots but moderate agreement in profile plots