A broadband electron spectrometer and electron detectors for laser accelerator experiments

We describe the apparatus used to measure the spectrum of accelerated electrons from a laser-plasma acceleration experiment carried out a Rutherford Appleton Laboratories (RAL). The source of the broadband, energetic electrons was the forward Raman scattering instability of a high intensity (5×10¹⁸ W/cm²) laser. Here the laser beam photons decay into scattered photons and a relativistic electron plasma wave. The plasma wave subsequently accelerates plasma electrons to relativistic energies. The spectrometer and detectors were designed to give a quantitative (in energy and flux) single-shot electron spectrum over as wide a range of energies as possible. In this paper we present some calibration measurements taken prior to the RAL run which agree very well with TRACE3D runs used to model the beam transport. The silicon surface barrier detector (SBD) arrangement and fluorescer-filmpack arrangement are also described. Finally, some preliminary results are obtained which show excellent agreement between the spectra obtained with the SBDs and the film