title: Intrinsic beam emittance of laser-accelerated electrons measured by x-ray spectroscopic imaging.
abstract: The recent combination of ultra-intense lasers and laser-accelerated electron beams is enabling the development of a new generation of compact x-ray light sources, the coherence of which depends directly on electron beam emittance. Although the emittance of accelerated electron beams can be low, it can grow due to the effects of space charge during free-space propagation. Direct experimental measurement of this important property is complicated by micron-scale beam sizes, and the presence of intense fields at the location where space charge acts. Reported here is a novel, non-destructive, single-shot method that overcame this problem. It employed an intense laser probe pulse, and spectroscopic imaging of the inverse-Compton scattered x-rays, allowing measurement of an ultra-low value for the normalized transverse emittance, 0.15 (±0.06) π mm mrad, as well as study of its subsequent growth upon exiting the accelerator. The technique and results are critical for designing multi-stage laser-wakefield accelerators, and generating high-brightness, spatially coherent x-rays.
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: G
authors.initials: G
authors.lastname: Golovin
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: S
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: S
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: B
authors.initials: B
authors.lastname: Zhao
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: P
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science &Innovation Campus, Didcot OX11 0QX, UK.
authors.forename: M
authors.initials: M
authors.lastname: Veale
authors.affiliation: Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science &Innovation Campus, Didcot OX11 0QX, UK.
authors.forename: M
authors.initials: M
authors.lastname: Wilson
authors.affiliation: Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science &Innovation Campus, Didcot OX11 0QX, UK.
authors.forename: P
authors.initials: P
authors.lastname: Seller
authors.affiliation: Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588, USA.
authors.forename: D
authors.initials: D
authors.lastname: Umstadter