Measurement of an electron beam size with a laser wire beam profile monitor

Hiroshi Sakai,Toshiyuki Okugi,Takashi Taniguchi,Yousuke Honda,Yasuo Higashi,Mikio Takano,Sakae Araki,Junji Urakawa,Noboru Sasao

doi:10.1103/physrevstab.4.022801

Hiroshi Sakai, Toshiyuki Okugi + Show 7 more

Open Access

https://doi.org/10.1103/physrevstab.4.022801

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Abstract

We describe the first measurement of an electron beam size in the accelerator test facility damping ring at KEK with a laser wire beam profile monitor. This monitor is based upon the Compton scattering process of electrons with a laser light target, which is produced by injecting a cw laser beam into a Fabry-P\'erot optical cavity. We have observed clear signals of the Compton scattered photons and confirmed that the observed energy spectrum as well as the count rate agree with the expected ones. From the measurement, we have deduced the vertical beam size ${\ensuremath{\sigma}}_{b}$ to be $9.8\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\pm\else\textpm\fi{}0.4\ensuremath{\mu}\mathrm{m}$, where the first (second) error represents statistical (systematic) uncertainty. Various improvements are in progress to enhance the signal-to-noise ratio, which is essential for the detailed study of the beam dynamics.

Highlights

Production of low emittance beams is one of the important techniques of an electron accelerator and storage ring
We describe the first measurement of an electron beam size in the accelerator test facility damping ring at KEK with a laser wire beam profile monitor
We have observed clear signals of the Compton scattered photons and confirmed that the observed energy spectrum as well as the count rate agree with the expected ones

Summary

INTRODUCTION

Production of low emittance beams is one of the important techniques of an electron accelerator and storage ring. In order to develop technologies for such a low emittance beam, an accelerator test facility (ATF) was built at KEK [1] It consists of an electron linac, a damping ring in which the beam emittance is reduced, and an extraction line. Of crucial importance is a vertical emittance measurement in the damping ring itself For this purpose, we have been developing a new type of beam profile monitor, which is based on the Compton scattering process of electrons with laser light. In order to achieve both good spatial resolution and fast response for the monitor, the target light must be very thin and intense These requirements are realized by injecting a cw laser beam into a Fabry-Pérot optical cavity.

EXPERIMENTS

Optical cavity

Rm 1 2 Rm

DATA TAKING AND ANALYSIS

Findings

SUMMARY AND DISCUSSION