(a) Space- and time-averaged helium metastable densities and electron impact excitation rate from the ground state into He-I (3s)3S1 normalized by the respective values at N = 1 obtained from the PIC simulation as a function of the number of applied consecutive harmonics for two different concentrations of N_2 and φpp = 500 V. (b) Ratio of the normalized space- and time-averaged excitation rate and the helium metastable density as a function of N for different combinations of N_2 concentrations and peak-topeak driving voltages (PIC simulation data). The base frequency is f_0 = 13.56 MHz
Experimental data are marked as exp
Simulation data are marked as sim
x[N]
(Figure7a): Sim of Space- and time-averaged helium metastable densities and electron impact excitation [Nrom. Exc. Rate n]
(Figure7b): Sim of Ratio of the normalized space- and time-averaged excitation rate and the helium metastable density [Nrom. Exc. Rate / n]
(Figure7b_fit): fit for the normalized space- and time-averaged excitation rate and the helium metastable density [Nrom. Exc. Rate / n*]