Improved large-energy-range magnetic electron-positron spectrometer for experiments with the Texas Petawatt Laser

We present the design, construction, and first use of a magnetic electron-positron spectrometer at the Texas Petawatt Laser facility. The Global Spectrometer for Positron and Electron Characterization (GSPEC) is capable of detecting electrons and positrons over a large energy range from 3-150 MeV and has been designed to diagnose the electrons and positrons accelerated by high-intensity laser interactions with over-critical targets.