Fig. 13

Profiles of electrical potential in the circumferential direction θ at each z from measurements using an electrode array. The coordinates z and θ are defined in Fig. 12. a Profile at z1 = 16.7 mm, b at z2 = 33.3 mm, c at z3 = 50 mm, d at z4 = 66.7 mm, and e at z5 = 83.3 mm. Left panels (a1 to e1) show the measured value with elapsed time (60, 100, 200 s, etc.) from the start of the measurement at each potential electrode. The symbols indicate the data acquisition time. The reference point for the measured potential distribution used for comparison with the numerical results is the midpoint between the current electrodes. Right panels show numerical results of forward modelling (a2 to e2). The orange and blue dots, respectively, indicate the experimental and numerical results. In experimental results, error bars are smaller than the symbols. Each measured value is the potential at each electrode averaged over the last 100 s of measurement. The numerical results were calculated by using the average of all 100 s current intensity data at the corresponding timing of potential observation. The measured values were normalised by the average current for comparison