Abstract
A laser-wire transverse electron beam size measurement system has been constructed and operated at the Accelerator Test Facility (ATF) extraction line at KEK. The construction of the system is described in detail along with the environment of the ATF related to the laser wire. A special set of electron beam optics was developed to generate an approximately $1\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ vertical focus at the laser-wire location. The results of our operation at the ATF extraction line are presented, where a minimum rms electron beam size of $4.8\ifmmode\pm\else\textpm\fi{}0.3\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ was measured, and smaller electron beam sizes can be measured by developing the method further. The beam size at the laser-wire location was changed using quadrupoles and the resulting electron beam size measured, and vertical emittance extracted.
Highlights
Electron-positron accelerators such as a linear collider and other low emittance accelerator facilities, like light sources, will generate beams with transverse beam sizes of the order of 1 m [1]
The normal techniques of beam size measurement, for example, wire scanners and screens which intersect the charged particle beam, are not applicable when the bunch charge density is sufficiently large to damage the material placed in the beam
A number of Compton scattering diagnostics have already been developed for beam size measurement, such as the Stanford Linear Collider (SLC) laser wire [4,5], Accelerator Test Facility (ATF) damping ring laser wire [6], and PETRA laser wire [7]
Summary
Electron-positron accelerators such as a linear collider and other low emittance accelerator facilities, like light sources, will generate beams with transverse beam sizes of the order of 1 m [1]. The normal techniques of beam size measurement, for example, wire scanners and screens which intersect the charged particle beam, are not applicable when the bunch charge density is sufficiently large to damage the material placed in the beam. In these scenarios noninvasive techniques must be used such as optical diffraction radiation [2] or methods based on laser interactions with electron beams. A number of Compton scattering diagnostics have already been developed for beam size measurement, such as the Stanford Linear Collider (SLC) laser wire [4,5], ATF damping ring laser wire [6], and PETRA laser wire [7]. We report on the operation with the extraction line laser wire, including a custom made short focal length final focus lens, interaction chamber mover system, and knife edge vacuum manipulator, and on results obtained using this system, including the ATF extracted beam emittance measurement
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