Normalized spatio-temporal plots of the electron impact excitation rate from the ground state into He I 3S1 obtained experimentally (first row) and from PIC/MCC simulations, for different N_2 reactive gas admixtures. The positions of the sheath edges are shown as a solid white line (second row). The data are plotted for ‘peaks’-waveforms with N=4 and Vpp=400V. The third 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 fourth row shows the time averaged helium metastable density profiles 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.
Experimental data are marked as exp
Simulation data are marked as sim
x [t/TRf] , y[mm]
(Figure6a-6c): exp Exc rate [a. u.]
(Figure6d-6f): sim Exc. Rate [a. u.]
(Figure6d_sheath to Figure6f_sheath): sim sheath edges of the plasma
x [ev] , y[a.u].
(Figure6g_expansion to Figure6i_expansion): sim EEPF values gained from the blue marked area in Figure6d to Figure6f
(Figure6g_collapse to Figure6i_collapse): sim EEPF values gained from the red marked area in Figure6d to Figure6f
(Figure6g_average to Figure6i_average): sim EEPF values gained from the average of Figure6d to Figure6f
x[mm], y[m-3]
(Figure6j-6l): sim time averaged helium metastable density profile