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

Abstract

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-ray sources facility at Duke University, we have successfully determined the electron beam energy with a relative uncertainty of about 3 Â 10 À5 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 Â 10 À5) of the electron beam by varying the storage ring dipole field can be directly detected using the Compton scattering technique.

Theoretical and simulation studies of characteristics of a Compton light source

“…The energy spread of a Compton gamma-ray beam is mainly determined by the degree of the collimation of the gamma beam, energy spread, and angular divergence of the electron beam [21]. The contributions of these parameters to the gamma-ray beam energy spread are summarized in Table I.…”

“…Because of the nonideal response of the detector, the measured spectrum has a structure of a full energy peak, a single and double escape peaks, and a Compton plateau. To unfold the measured energy spectrum, a novel end-to-end spectrum reconstruction method has been recently developed [21]. The comparison of the measured gamma spectrum and calculated spectrum using the CCSC code is shown in Fig.…”

“…In some literature [22,23], a simple quadratic sum of individual contributions was used to estimate the energy spread of the Compton scattering gamma-ray beam. Since the electron-beam angular divergence and the gammabeam collimation introduce non-Gaussian broadening effects on the gamma-beam spectrum [21], causing the spectrum to have a long energy tail (Figs. 10 and 11), the energy spread of the gamma-ray beam cannot be given simply by the quadrature sum of different broadening mechanisms.…”

“…More applications of using CCSC and MCCMPT codes to study characteristics of Compton gamma-ray beams can be found in [21,25,26].…”

Electron beam energy spread measurements using optical klystron radiation

“…Furthermore, with high undulator fields, the off-axis harmonic content can corrupt the fundamental spectrum. In fact, the APS method is analogous to the technique of measuring the electron beam energy spread using the measured Compton x-ray or gamma-ray beam spectrum [9,10]. Both of these techniques used at ESRF and APS are not suitable for measuring a very small energy spread when the spectrum broadening is small.…”