Bayesian inferences of radial current losses and symmetry in multi-terawatt magnetically insulated transmission lines via photonic doppler velocimetry*

Assessments of the electrical current delivered by 20-30 MA pulsed power facilities has historically been enabled by bdot measurements at large-radius and at a limited number of azimuthal locations [1]. This sparsity, and that bdot data is unreliable for some configurations [2] precludes realizing the full design potential of sophisticated (but under-constrained) particle-in-cell simulations, and slows efforts to optimize magnetically insulated transmission line geometries. Relying on the Z machine at Sandia National Laboratories, we collected photonic doppler velocimetry (PDV) data at 8 radii and each of 3 azimuths within 55 mm. Using these PDV velocimetry traces together with Bayesian inference, we estimate delivered current vs. radius vs. time, and will discuss radial current losses and azimuthal asymmetries for a short-circuit synchronous Z pulse. This data will be compared with PIC modeling of the experiment.

 

[1] H. M. Hess, et al, PoP 25 042702 (2018)

[2] T. M. Hutchinson, et al, JAP, 134, 155901 (2023).