Energy and energy spread measurements of an electron beam by Compton scattering method

A gamma-ray beam produced by Compton scattering of a laser beam with an electron beam can be used to measure the electron beam parameters. In several published works, a simple fitting model has been applied to determine the electron beam energy and energy spread without considering the gamma beam collimation and electron beam emittance effects. This fitting model is rederived in this work, and the underlying assumptions and resultant limitations are discussed. To overcome these limitations, a new fitting model is proposed, which takes into account the collimation and emittance effects. Using the new model and a gamma-ray beam produced at the high intensity gamma-ray sources facility at Duke University, we have successfully determined the electron beam energy with a relative uncertainty of about 3 X 10(-5) around 460 MeV as well as the electron beam energy spread. We also experimentally demonstrated for the first time that a small relative energy change (about 4 X 10(-5)) of the electron beam by varying the storage ring dipole field can be directly detected using the Compton scattering technique.