Normalized spatio temporal plots of the electron impact excitation rate from the ground state into the He-I 1s3s 3S1 level (d-f), measured for different numbers of consecutive harmonics N (“peaks”- waveforms) at fixed z = −15 mm. The base frequency is f0 = 13.56 MHz, φpp = 500 V, and the O2 admixture concentration is 0.5%.
Experimental data are marked as exp
Calculated data are marked as calc
x [t/TRf] , y[mm]
(Figure5a-5c): Exp Exc. Rate for O2-admixtures of 0.5% and N=1, N=2 and N=4 respectively