Designing an Energy Analyzer for the PHAse Space MApping (PHASMA) Experiment

The PHAse Space MApping experiment is designed to investigate distribution functions in magnetic reconnection events arising from the merger of two flux ropes generated by two pulsed plasma guns. PHASMA is also employed for helicon plasma studies which require measurements of particle velocity and energy distribution functions. To that end, a compact retarding field energy analyzer (RFEA) is constructed with four wire-mesh grids of Debye-scale resolution (0.125mm per grid hole) to measure electron energy distribution functions. Electric potential gradients within the RFEA are set to reject ion collection and minimize secondary electron generation (via photoelectric and electron impact effects) with the use of a suppressor grid. All currents are collected with a circuit designed to minimize perturbations to the energies of incoming particles while providing fast amplification for non-pulsed experiments where the discriminator potential can be swept with a programmable power supply. Here we describe the development of the diagnostic along with the related electronics.