Experimental data are marked as exp

Simulation data are marked as sim

(Figure4a-4d): x (mm), exp Helium metastable densities (cm-3)

(Figure4e-4h): x (mm), sim He metastable densities (cm-3)

(Figure4i-4l): x (mm), sim averaged Helium metastable densities (cm-3)

(Figure4m-4p): x (mm), sim Source (cm-3 s-1) Singlets and Triplets

(Figure4r-4u): x (mm), sim exc. Rate (cm-3 s-1)

Harmonics:

N = 1: a, e, i, m, r

N = 2: b, f, j, n, s

N = 3: c, g, k, o, t

N = 4: d, h, l, p, u

Experimental data are marked as exp

Simulation data are marked as sim

x [t/TRf] , y[mm]

(Figure5a-5c): sim Metastable source [a. u.]

(Figure5d-5f): sim Exc. Rate [a. u.]

(Figure5a_5d_Sheath to Figure5c_5f_Sheath): sim sheath edges of the plasma. These sheaths are the same for each corresponding metastable source and Exc. rate ]]>

Experimental data are marked as exp

Simulation data are marked as sim

x[mm]

(Figure6a): Exp absolute helium metastable density [cm^{-3}]

(Figure6b): Exp and sim space and time averaged densities of helium metastables [cm^{-3}] ]]>

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*] ]]>

Experimental data are marked as exp

Simulation data are marked as sim

x[mm]

(Figure8a-8d): exp Helium metastable densities [cm^{-3}]

(Figure8e-8h): sim He metastable densities [cm^{-3}]

(Figure8i-8l): sim averaged Helium metastable densities [cm^{-3}]

(Figure8m-8p): sim Source [cm^{-3} s^{-1}] Singlets and Triplets

(Figure8r-8u): sim exc. Rate [cm^{-3} s^{-1}]

Peak-to-peak Voltage:

350V: a, e, i, m, r

400V: b, f, j, n, s

450V: c, g, k, o, t

500V: d, h, l, p, u ]]>

Experimental data are marked as exp

Simulation data are marked as sim

x [t/TRf] , y[mm]

(Figure9a-9c): Sim Metastable source [a. u.]

(Figure9d-9f): Sim Exc. Rate [a. u.]

(Figure9a_9d_Sheath to Figure9c_9f_Sheath): Sim sheath edges of the plasma. These sheaths are the same for each corresponding metastable source and Exc. rate ]]>

Experimental data are marked as exp

Simulation data are marked as sim

[V]

(Figure10a): Sim of Space- and time-averaged helium metastable densities and electron impact excitation [cm^{-3}]

(Figure10b): Sim of Ratio of the normalized space- and time-averaged excitation rate and the helium metastable density [Norm. Exc. Rate / n

(Figure10b_fit): fit for the normalized space- and time-averaged excitation rate and the helium metastable density [Norm. Exc. Rate / n

Experimental data are marked as exp

Simulation data are marked as sim

x[mm]

(Figure8a-8d): exp Helium metastable densities [cm^{-3}]

(Figure8e-8h): sim He metastable densities [cm^{-3}]

(Figure8i-8l): sim averaged Helium metastable densities [cm^{-3}]

(Figure8m-8p): sim Source [cm^{-3} s^{-1}] Singlets and Triplets

(Figure8r-8u): sim exc. Rate [cm^{-3} s^{-1}]

Nitrogen admixture:

a, e, i, m, r: 0.05% nitrogen admixture

b, f, j, n, s: 0.1% nitrogen admixture

c, g, k, o, t: 0.2% nitrogen admixture

d, h, l, p, u: 0.4% nitrogen admixture ]]>

Experimental data are marked as exp

Simulation data are marked as sim

x [t/TRf] , y[mm]

(Figure12a-12c): Sim Metastable source [a. u.]

(Figure12d-12f): Sim Exc. Rate [a. u.]

(Figure12a_12d_Sheath to Figure12c_12f_Sheath): Sim sheath edges of the plasma. These sheaths are the same for each corresponding metastable source and Exc. rate ]]>

Experimental data are marked as exp

Simulation data are marked as sim

Nitrogen concentrateion[%]

Figure13a: Sim and exp data for time averaged helium metastable dens [cm^{-3}]

Figure13a_fit: sim fit [cm^{-3}] ]]>