2]]>Absolute atomic oxygen densities measured space resolved in the active plasma volume of a COST microplasma reference jet operated in He/O2 and driven by tailored voltage waveforms are presented. The measurements are performed for diﬀerent shapes of the driving voltage waveform, oxygen admixture concentrations, and peak-to-peak voltages. Peaks- and valleys-waveforms constructed based on diﬀerent numbers of consecutive harmonics, N, of the fundamental frequency f0 = 13.56 MHz their relative phases and amplitudes are used. The results show that the density of atomic oxygen can be controlled and optimized by voltage waveform tailoring (VWT). It is signiﬁcantly enhanced by increasing the number of consecutive driving harmonics at ﬁxed peak-to-peak voltage. The shape of the measured density proﬁles in the direction perpendicular to the electrodes can be controlled by VWT as well. For N > 1 and peaks-/valleys-waveforms, it exhibits a strong spatial asymmetry with a maximum at one of the electrodes due to the spatially asymmetric electron power absorption dynamics. Thus, the atomic oxygen ﬂux can be directed primarily towards one of the electrodes. The generation of atomic oxygen can be further optimized by changing the reactive gas admixture and by tuning the peak-to-peak voltage amplitude. The obtained results are understood based on a detailed analysis of the spatio-temporal dynamics of energetic electrons revealed by phase resolved optical emission spectroscopy (PROES).

]]>absolute atomic oxygen densitiesCOST jetPROESreactive gasPlasma Science Fundamentalsb196cd4c-0a1a-4667-ab7d-b0e3a99012372021-01-26T12:58:23+01:002021-03-21T19:32:00+01:00en-UShttps://aept.rub.deAEPTFigure 3: 2d space resolved density oxygenMeasured 2D space resolved absolute density of atomic oxygen between the electrodes (x-direction) and the quartz walls (y-direction). The powered electrode is located at x = 0, while the grounded electrode is at x = 1 mm. The quartz walls are located at y = 0 mm and y = 1 mm. (a)-(c) Atomic oxygen density measured for diﬀerent numbers of consecutive driving harmonics, N, in the presence of “peaks” waveforms. (d) Atomic oxygen density for N = 4 and a “valleys” waveform. Note the diﬀerent ranges of the color scales. The base frequency is f0 = 13.56 MHz and the peak-to-peak value of the driving voltage waveform is kept constant at 500 V. The concentration of the O2 admixture is 0.5 %. The step resolution in x and y directions is set to 1 mm.

]]>2021-01-26T13:00:42+01:002021-03-21T13:04:48+01:00application/zipcsv14252https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-0Figure 4: spatially resolved densities atomic oxygen(a) Spatially resolved absolute densities of atomic oxygen obtained experimentally and computed from the numerical solution of eq. (8). (b) Peak and mean (spatially averaged) values of the atomic oxygen density obtained from the measured data and (c) normalized constant of proportionality used in equation (10) to relate the time averaged atomic oxygen source to the time averaged measured electron impact excitation rate as a function of the number consecutive driving harmonics, N, at y = 0.5 mm, z = -15 mm and for an O2 ﬂow corresponding to an admixture concentration of 0.5 % for “peaks”-waveforms. The normalization is performed by dividing by the proportionality constant for the N = 1 case. The powered electrode is located at x = 0, while the grounded electrode is at x = 1 mm. The base frequency is f0 = 13.56 MHz and φpp = 500 V.
Experimental data are marked as exp
Calculated data are marked as calc
Figure 4 a) exp
x (mm),y (exp atomic oxygen densities (cm-3)),
Harmonics used: 1(red), 2(olive green), 3(white) and 4(blue)
Figure 4 a) calc
x (mm),y (calc atomic oxygen densities (cm-3)),
Harmonics used: 1(red_dashed), 2(olive green_dashed), 3(white_dashed) and 4(blue_dashed)
Figure 4 b)
x (N),y (exp atomic oxygen densities (cm-3)),
Figure 4 c)
x (N),y (Normalized k)

]]>2021-01-26T13:02:17+01:002021-03-21T13:10:25+01:00application/zipcsv10083https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-1Figure 5: electron impact excitation rateNormalized 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

]]>2021-01-26T13:04:43+01:002021-03-21T19:30:19+01:00application/zipcsv92033https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-2Figure 6: 2D distribution atomic oxygen(a)-(c) 2D spatial distribution of the atomic oxygen density inside the jet obtained from the numerical solution of equation (8) for diﬀerent numbers of consecutive harmonics, N. (d)-(f) Spatially resolved atomic oxygen production rate determined from equation (10). The base frequency is f0 = 13.56 MHz and the peak-topeak value of the driving voltage waveform is kept constant at 500 V. The concentration of the O2 admixture is 0.5 %.
Experimental data are marked as exp
Calculated data are marked as calc
(Figure6a-6c):
x [mm] , y[cm^-3], z[mm]
Calc spatial distribution of the atomic oxygen density for N=1, N=2 and N=4 respectively
(Figure6d-6f):
x [mm] , y[m^-3 s^-1]
Calc spatially resolved atomic oxygen production rate for N=1, N=2 and N=4 respectively

]]>2021-01-26T13:06:18+01:002021-03-21T13:10:59+01:00application/zipcsv142004https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-3Figure 7: spatially resolved absolute densities atomic oxygen(a)-(c) Measured spatially resolved absolute densities of atomic oxygen obtained for diﬀerent oxygen admixture concentrations. (d)-(f) peak and mean (spaceaveraged) values of the atomic oxygen density obtained from the measured space resolved data at ﬁxed y = 0.5 mm and z = −15 mm. The columns show data for diﬀerent numbers of consecutive driving harmonics, N. The base frequency is f0 = 13.56 MHz and the peak-to-peak value of the driving voltage waveform is kept constant at 500 V. The concentration of the O2 admixture is varied from 0.05 % to 1.0
Experimental data are marked as exp
Calculated data are marked as calc
(Figure7a-7c): Exp absolute densities of atomic oxygen for O2 admixtures varied from 0.05 % to 1.0% with N=1, N=2 and N=4 respectively
x [mm] , y[cm^-3]

(Figure7d-7f): Exp peak and mean (spaceaveraged) values of the atomic oxygen for N=1, N=2 and N=4 respectively
x [O2 add] , y[cm^-3]

]]>2021-01-26T13:08:07+01:002021-03-21T14:46:14+01:00application/zipcsv7153https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-4Figure 8: Normalized spatio-temporal plots of the electron impact excitation Normalized spatio-temporal plots of the electron impact excitation rate from the ground state of helium into He-I 1s3s 3S1 obtained experimentally for N = 1 (ﬁrst row) and N = 4 (second row) and for diﬀerent concentrations of the O2 admixture (columns) at ﬁxed z = −15 mm. The base frequency is f0 = 13.56 MHz and the peak-to-peak value of the driving voltage waveform is kept constant at 500 V. The powered electrode is located at x = 0, while the grounded electrode is at x = 1.
Experimental data are marked as exp
Calculated data are marked as calc
x [t/TRf] , y[mm]
(Figure8a8c): Exp Exc. Rate for O2-admixtures of 0.05%, 0.2% and 0.5% respectively with N=1
(Figure8d-8f): Exp Exc. Rate for O2-admixtures of 0.05%, 0.2% and 0.5% respectively with N=4

]]>2021-01-26T13:09:29+01:002021-03-21T14:48:26+01:00application/zipcsv261011https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-5Figure 9: Measured absolute density proﬁles of He-I 1s2s 3S1 metastables Measured absolute density proﬁles of He-I 1s2s 3S1 metastables between the electrodes - (a) for N = 1 and 0.05 % of O2, (b) and (c) for N = 4 and two diﬀerent concentrations of the O2 admixture of 0.05 % and 0.2 % at ﬁxed z = −15 mm. The base frequency is f0 = 13.56 MHz and the peak-to-peak value of the driving voltage waveform is kept constant at 500 V.
Experimental data are marked as exp
Calculated data are marked as calc
x [mm] , y [cm^-3]
(Figure9a-9b): Exp absolute density proﬁles of He-I 1s2s 3S1 metastables for O2-admixtures of 0.05% and N=1 and N=4 respectively
(Figure9c): Exp absolute density proﬁles of He-I 1s2s 3S1 metastables for O2-admixtures of 0.2% for N=4

]]>2021-01-26T13:13:08+01:002021-03-21T14:45:32+01:00application/zipcsv4412https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-6Figure 10: Space and time averaged values of the atomic oxygen densitySpace and time averaged values of the atomic oxygen density obtained experimentally for diﬀerent numbers of driving harmonics, N, and molecular oxygen admixtures for “peaks”-voltage waveforms at ﬁxed z = −15 mm. The base frequency is f0 = 13.56 MHz and the peak-to-peak value of the driving voltage waveform is kept constant at 500 V.
Experimental data are marked as exp
Calculated data are marked as calc
Harmonics used: 1-4
x (N),y (exp mean atomic oxygen densities (cm-3)),

Oxygen admixtures used: 0.05 %(red), 0.1 %(blue), 0.2 %(cyan), 0.4 %(olive green), 0.6 %(dark blue), 0.8 %(green), 1.0 %(orange)

]]>2021-01-26T13:13:58+01:002021-03-21T14:44:34+01:00text/csvcsv410https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-7Figure 11: Peak and (c) mean atomic oxygen densities as a function of the peak-to-peak value of the applied voltage waveform(b) Peak and (c) mean atomic oxygen densities as a function of the peak-to-peak value of the applied voltage waveform for diﬀerent N. The data are measured at positions y = 0.5 mm and z = -15 mm. The O2 admixture concentration is ﬁxed at 0.5 %. The powered electrode is located at x = 0, while the grounded electrode is at x = 1 mm. The base frequency is f0 = 13.56 MHz. The waveform type is “peaks”.
Experimental data are marked as exp
Calculated data are marked as calc
Figure 11 a)
Harmonics used: 1(red), 2(olive green) and 4(blue)
Voltage is varied between 325 Vpp – 550 Vpp
x (Vpp),y (exp peak atomic oxygen densities (cm-3)),

Figure 11 b)
Harmonics used: 1(red), 2(olive green) and 4(blue)
Voltage is varied between 325 Vpp – 550 Vpp
x (Vpp),y (exp mean atomic oxygen densities (cm-3)),

]]>2021-01-26T13:15:04+01:002021-03-21T14:43:49+01:00application/zipcsv1520https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-8Figure 12: Spatially resolved absolute densities of atomic oxygenSpatially resolved absolute densities of atomic oxygen obtained experimentally for N = 4 as a function of the peak-to-peak value of the driving voltage waveform. The data are measured at positions y = 0.5 mm and z = -15 mm. The O2 admixture concentration is ﬁxed at 0.5 %. The powered electrode is located at x = 0, while the grounded electrode is at x = 1 mm. The base frequency is f0 = 13.56 MHz. The waveform type is “peaks”.
Experimental data are marked as exp
Calculated data are marked as calc
Figure 12 350V: (red) exp
Figure 12 450V: (white) exp
Figure 12 500V: (olive green) exp
Figure 12 550V: (blue) exp
x (mm),y (exp atomic oxygen densities (cm-3))

]]>2021-01-26T13:16:13+01:002021-03-21T14:43:07+01:00application/zipcsv2861https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-9Figure 13: Normalized spatio-temporal plots of the electron impact excitation rate 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 peakto-peak voltage amplitudes at N = 4 (“peaks”-waveforms) and z = −15 mm. The base frequency is f0 = 13.56 MHz and the O2 admixture concentration is 0.5%. The powered electrode is located at x = 0.
Experimental data are marked as exp
Calculated data are marked as calc
x [t/TRf], y[mm]
(Figure13a-13c): Exp Exc. Rate for O2-admixtures of 0.5% and N=4 with a peak-to-peak voltage of 350V, 450V and 550V respectively

]]>2021-01-26T13:17:27+01:002021-03-21T19:32:06+01:00application/zipcsv143697https://rdpcidat.rub.de/dataset/atomic-oxygen-generation-atmospheric-pressure-rf-plasma-jets-driven-tailored-voltage-10DKANhttps://rdpcidat.rub.de