Fig. 1. Relationship between allowable and forbidden component center wavelength difference and electric field strength of helium spectral line Stark splitting

Fig. 2. Atmospheric pressure nanosecond pulse discharge experiment

Fig. 3. Measurement and peak composition analysis of He 447.1 nm spectral lines under different high voltages at the needle tip

Fig. 4. Effect of data fitting

Fig. 5. Comparison of theoretical electric field between needle plate and electric field obtained from spectral line experimental data