Data Integrated Neutral Beam Shinethough Calculations on C-2W

C-2W [1], TAE's current device, consists of eight neutral beam injectors (NBI) that are able to fuel, drive current, and stabilize field-reversed configuration (FRC) plasmas for up to 40 ms. An array of secondary electron emission (SEE) detectors is situated in each beam dump to measure the transmission of beam flux through the FRC. Traditionally, shinethrough is calculated by normalizing the SEE signal by the pre-plasma peak signal level and beam current of each shot. This technique, however, does not account for changes in current density due to fluctuations in beam divergence or neutralization. To amend this, two enhanced normalization techniques have been developed utilizing additional beam parameter measurements. The first method utilizes beam current density estimates derived from divergence parameters inferred from measurements on a neutral beam test stand. The second method leverages empirically determined, synthetic signals developed from over 1500 shots. The development of these techniques is detailed and compared to determine the most accurate algorithm for analysis of SEE signals to determine neutral beam shinethrough in C-2W and further devices.

1. H. Gota et al, "Overview of C-2W: High-temperature, steady-state beam-driven field-reversed configuration plasmas", Nucl. Fusion 61 106039 (2021).