Development of a Thomson-type Mass and Energy Spectrometer for High-energy Plasma Beams with the Geant4 Monte Carlo Toolkit

Thomson-type spectrometers characterize particle beams using parallel magnetic and electric fields to separate and detect ions of different mass, energy, and charge state. Traditionally, the output of these spectrometers is calibrated against particle beams of known species and energy, or less accurately, using particle trajectory calculations assuming uniform fields. We present the design and calibration of a Thomson spectrometer using the Geant4 Monte Carlo toolkit. By running Monte Carlo simulations using the precise spectrometer geometry, including the measured non-uniform magnetic field and two dimensional electric field simulations, it is possible to accurately predict and calibrate the output of the spectrometer without a known particle beam. We will describe the application of this spectrometer to the output of an electromagnetic plasma accelerator operating in a gas-puff mode, and quantify the error associated with calibrating the spectrometer assuming uniform fields.