Electron beam energy spread measurements using optical klystron radiation

Abstract

In accelerators, the electron beam longitudinal dynamics critically depend on the energy distribution of the beam. Noninvasive, highly accurate measurement of the energy spread of the electron beam in the storage ring remains a challenge. Conventional techniques are limited to measuring a relatively large energy spread using the energy spread induced broadening effect of radiation source size or radiation spectrum. In this work, we report a versatile method to accurately measure the electron beam relative energy spread from 10 À4 to 10 À2 using the optical klystron radiation. A novel numerical method based on the Gauss-Hermite expansion has been developed to treat both spectral broadening and modulation on an equal footing. A large dynamic range of the measurement is realized by properly configuring the optical klystron. In addition, a model-based scheme has been developed for the first time to compensate the beamemittance-induced inhomogeneous spectral broadening effect to improve the accuracy of the energy spread measurement. Using this technique, we have successfully measured the relative energy spread of the electron beam in the Duke storage ring from 6 Â 10 À4 to 6 Â 10 À3 with an overall uncertainty of less than 5%. The optical klystron is a powerful diagnostic for highly accurate energy spread measurement for storage rings and other advanced electron accelerators.

Storage ring two-color free-electron laser

“…With proper cross-calibration, the study of the FEL power is based upon the measured extracted FEL power from the upstream FEL mirror. The direct FEL power P FEL can be written as [51][52][53][54][55][56]…”

“…where α is a numerical factor depending on the undulator configuration and FEL operational conditions; P syn is the total synchrotron radiation power emitted by the electron bunch in the entire storage ring; σ E;FEL and σ E;0 are the rms relative electron beam energy spread with FEL turned on and off, respectively. In the microwave instability region with large enough bunch current and/or with FEL lasing to increase the electron beam energy spread, the electron beam energy spread and bunch length are found to be related in a simple manner due to the longitudinal phase space rotation [55]:…”

International workshop on next generation gamma-ray source

“…A few published reviews on Compton γ-ray beams and some of the aforementioned facilities are found in [261][262][263][264][265]. Among these Compton CGS facilities, the High Intensity Gamma-ray Source (HIGS) at Duke University is the first dedicated Compton gamma-ray facility employing as the photon driver a high intra-cavity power free-electron laser (FEL) [266][267][268][269][270]. The HIGS facility is a high-flux, nearly monochromatic, and highly polarized CGS (with both linear and circular polarizations) covering a wide range of energies from about 1 to 100 MeV.…”

Measurement of the average local energy spread of electron beam via coherent harmonic generation

“…The accuracy of this method was improved by a new fitting method in Ref. [20]. The relative energy spread was measured from 6 Â 10 À4 to 6 Â 10 À3 with an overall uncertainty of less than 5% in the Duke storage ring based on this method.…”