Normalized spatio-temporal plots of the electron impact excitation rate from the ground state into He I3S1 obtained experimentally (first row) and from PIC/MCC simulations, for different numbers of consecutive harmonics (‘peaks’-waveform). The positions of the sheath edges are shown as a solid white line (second row). The data are plotted for different driving voltage waveforms shown in row 3. The fourth row shows EEPFs averaged over different spatio-temporal regions of interest marked in row 2. The black solid line corresponds to the EEPF averaged over the entire electrode gap and RF period of the fundamental driving frequency. The fifth row shows the time averaged helium metastable density profile extracted from the PIC/MCC simulation. The powered electrode is located at x = 0, while the grounded electrode is at x = 1mm. The base frequency is f = 13.56MHz, the flow ratio is He/N2 = 1000/1 (1 sccm N2 flow).
Experimental data are marked as exp
Simulation data are marked as sim
x [t/TRf] , y[mm]
(Figure4a-4c): exp Exc rate [a. u.]
(Figure4d-4f): sim Exc. Rate [a. u.]
(Figure4d_sheath to Figure4f_sheath): sim sheath edges of the plasma
x [t/TRf] , y[V]
(Figure4g-i): exp Voltage waveform
(Figure4g_to_i_sim): sim corresponding Voltage waveform
x[eV], y[a. u,]
(Figure4j_expansion to Figure4l_expansion): sim EEPF values gained from the blue marked area in Figure4d to Figure4f
(Figure4j_collapse to Figure4l_collapse): sim EEPF values gained from the red marked area in Figure4d to Figure4f
(Figure4j_average to Figure4l_average): sim EEPF values gained from the average of Figure4d to Figure4f
x[mm], y[m-3]
(Figure4m-4o): sim time averaged helium metastable density profile