Measurement of electric flux emission: a new diagnostic for the dense plasma focus

Abstract This paper presents a novel diagnostic technique for investigating the symmetry of the plasma formation process in the Dense Plasma Focus (DPF) device. The DPF, a scalable laboratory plasma device developed in the 1960s, has been extensively studied with various gas fills and considered for a broad range of applications—including commercial fusion energy, short-lived radioisotope production for medical imaging and brachytherapy, nano-scale industrial coatings, and deep-space propulsion. However, achieving reliable and reproducible operation of the DPF remains a significant challenge. Plasma initiation occurs via a surface discharge across an insulating sleeve between the two coaxial electrodes of the DPF device. Typically, a series of ‘training’ shots is required before symmetric plasma formation is achieved, yet the mechanisms underlying this process remain poorly understood. Numerical simulations have revealed that plasma formation involves complex atomic and radiative phenomena spanning wide spatial and temporal scales, rendering predictive modelling nearly impossible. The diagnostic technique introduced here provides new empirical insights—unavailable through existing methods—into the physics and phenomenology of plasma formation. It utilizes three symmetrically arranged, absolutely calibrated, and identical D-dot probes to measure the electric flux emitted by the plasma, potentially offering a pathway toward more reproducible DPF operation through a better understanding of the plasma formation process.