Low-emittance electron bunches from a laser-plasma accelerator measured using single-shot X-ray spectroscopy

Abstract

The presence of low emittance beams in laser-plasma accelerators is indicated by single-shot spectroscopic measurements of betatron X-rays. By matching the X-ray betatron spectra to analytical and numerical models of betatron radiation, the electron bunch radius inside the plasma is estimated to be close to 0.1 micron. Correlations of the bunch radius with electron beam parameters are presented. Photon-counting spectra and statistical fitting are used to establish confidence ranges. Combined with simultaneous electron spectrum and divergence measurements, the normalized transverse emittance is estimated to be as low as 0.1 mm mrad consistent with three-dimensional particle-in-cell simulations. © 2012 American Institute of Physics.