Measuring the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator

This paper presents a new technique to measure the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator. Measurements are performed with a stacked image plates spectrometer, capable of detecting broadband x-ray radiation up to 1 MeV. It can provide measurements of the betatron x-ray spectrum at any angle of observation (within a 40 mrad cone) and of the beam profile. A detailed description of our data analysis is given, along with comparison for several shots. These measurements provide useful information on the dynamics of the electrons are they are accelerated and wiggled by the wakefield.