Experimental measurement of ion distribution function during magnetic reconnection

The Magnetic Reconnection Experiment (MRX) investigates the process of magnetic reconnection in a laboratory setting. Efficient heating of electrons and ions has been detected and documented during fast reconnection. In order to explore acceleration of charged particles beyond their thermal speeds, seen in space satellite measurements and numerical kinetic simulations, a five-electrode retarding-field energy analyzer was developed to measure the electron and ion distributions in MRX. All electrodes are referenced to the plasma-facing aperture by capacitors to accommodate the dynamically varying plasma potential. An in-line isolation amplifier was placed into the probe shaft to avoid possible picking up electric noise. All electrodes but the collector are electroformed grids of nickel, of which the aperture and rejecter grids have sub-Debye-length spacing. A first version of this probe is designed to measure ions entering the probe aperture perpendicular to local magnetic field. Initial data will be presented and compared with the numerical predictions by kinetic simulations.