Build a Nachamkin plasmoid on purpose

Why the library suggests it

Jack Nachamkin, writing for the Air Force's Phillips Laboratory, works the spherically symmetric time-harmonic case and finds two things worth building against: a critical frequency below which the current can no longer be carried by the electrons and the object stays stable, and resonant sizes at which the plasmoid's boundary conditions are met by ordinary vacuum solutions, so no energy flows in or out. A stable vortical motion of the plasma exactly cancels the dominant electromechanical stress, and what is left falls away steeply as frequency rises (Force-Free Time-Harmonic Plasmoids, 1992). A separate line asks what holds many nanometre-scale plasmoid kernels together as one visible object, and finds a quantum exchange force between dipole-carrying ions that reaches a few per cent of the electromagnetic energy at liquid-water ion densities (Quantum exchange interaction of spherically symmetric plasmoids, 2012). The relaxation argument that says why any such object settles into one shape is Magnetic Helicity, Spheromaks, Solar Corona Loops, and Astrophysical Jets (2017).

The experiment or build

Build a radio-frequency discharge cell whose drive frequency and chamber dimensions are set from Nachamkin's own critical-frequency and resonant-size formulas, in a partially ionised gas at the pressure the analysis assumes. Sweep the frequency through the predicted critical value and sweep the cavity dimension through the predicted resonance. The settling measurement is plasmoid lifetime as a function of drive frequency and cavity size, with a peak appearing at the predicted resonant size and a stability threshold appearing at the predicted critical frequency. A lifetime peak that lands where a 1992 calculation said it would is a strong result; a lifetime peak that lands somewhere else is a better one, because it corrects the theory.