Multi-tip floating potential probe with active compensation for fluctuation measurements

A multi-tip floating potential probe has been developed to investigate electrostatic fluctuations during pulsed flux rope mergers in the phase space mapping experiment, or PHASMA. The diagnostic features closely spaced tips (Δ = 0.68 mm) and differential signal acquisition to suppress common-mode electromagnetic pickup inherent to pulsed, reconnection-driven environments. While differential transmission and common-mode rejection are established techniques, their implementation here enables high-bandwidth, multi-direction floating potential measurements during pulsed electron-only magnetic reconnection. With a bandwidth of 10 kHz-25 MHz, the probe resolves broadband turbulence associated with the merger process. Cross correlation of floating potential signals yields two-dimensional wavenumber power spectral densities, providing spatial characterization of turbulent dynamics. To validate probe measurements, optical turbulence spectra are simultaneously obtained using a high-speed camera (Photron Nova-S9). Comparisons between electrostatic and optical spectra demonstrate the probe's capability to resolve turbulent fluctuations in pulsed electron-only reconnection experiments, offering a robust tool for studying energy dissipation and transport in flux rope interactions.