Control of electron dynamics, radical and metastable species generation in atmospheric pressure RF plasma jets by Voltage Waveform TailoringAtmospheric pressure capacitively coupled radio frequency discharges operated in He/N2 mixtures and driven by tailored voltage waveforms are investigated experimentally using a COST microplasma reference jet and by means of kinetic simulations as a function of the reactive gas admixture and the number of consecutive harmonics used to drive the plasma. Pulse-type ‘peaks’-waveforms, that consist of up to four consecutive harmonics of the fundamental frequency (f_0=13.56MHz), are used at a fixed peak-to-peak voltage of 400V. Based on an excellent agreement between experimental and simulation results with respect to the DC self-bias and the spatio-temporal electron impact excitation dynamics,we demonstrate that Voltage Waveform Tailoring allows for the control of the dynamics of energetic electrons, the electron energy distribution function in distinct spatio-temporal regions of interest, and, thus, the generation of atomic nitrogen as well as helium metastables, which are highly relevant for a variety of technological and biomedical applications. By tuning the number of driving frequencies and the reactive gas admixture, the generation of these important species can be optimised. The behavior of the DC self-bias, which is different compared to that in low pressure capacitive radio frequency plasmas, is understood based on an analytical model.
]]>cold atmospheric pressure plasma jetCOST jetelectron dynamicsmetastable speciesvoltage waveform tailoringPlasma Science Fundamentals574abb8b-c3c5-4648-9cf7-e1f2dbeeac932020-09-15T09:56:45+02:002021-03-21T18:54:57+01:00en-USAEPTFigure 3The base frequency and the peak-to-peak voltage of the driving voltage waveform are kept constant at 13.56MHz and 400V, respectively. The magenta stars in the left plot represent exemplary values of the DC self-bias values obtained from the analytical model for N = 4 at N_2-flows of 1sccm and 10 sccm, respectively.
Experimental data are marked as exp
Simulation data are marked as sim
x [sccm] , y[V]
(Figure3a): exp DC-Selfbias for different harmonics and N2-flows (V = Valley-function; P = Peaks-function) Left picture
(Figure3b): sim DC-Selfbias for different harmonics and N2-flows (V = Valley-function; P = Peaks-function) Left Picture
x[N], y[V]
(Figure3c): sim and exp DC-Selfbias for different harmonics and constant N2-flow [1sccm] (V = Valley-function; P = Peaks-function) Right picture
]]>2020-09-15T10:01:29+02:002020-09-15T14:33:35+02:00application/zipzip2113https://rdpcidat.rub.de/dataset/control-electron-dynamics-radical-and-metastable-species-generation-atmospheric-pressure-0Figure 4Normalized 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
]]>2020-09-15T10:05:04+02:002020-09-15T11:02:56+02:00application/zipzip452727https://rdpcidat.rub.de/dataset/control-electron-dynamics-radical-and-metastable-species-generation-atmospheric-pressure-1Figure 5Normalized 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 N2 reactive gas admixtures. The sheath widths are shown as a solid white line (second row). The data are plotted for ‘peaks’-waveforms with N=2 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]
(Figure5a-5c): exp Exc rate [a. u.]
(Figure5d-5f): sim Exc. Rate [a. u.]
(Figure5d_sheath to Figure5f_sheath): sim sheath edges of the plasma
x [ev] , y[a.u].
(Figure5g_expansion to Figure5i_expansion): sim EEPF values gained from the blue marked area in Figure5d to Figure5f
(Figure5g_collapse to Figure5i_collapse): sim EEPF values gained from the red marked area in Figure5d to Figure5f
(Figure5g_average to Figure5i_average): sim EEPF values gained from the average of Figure5d to Figure5f
x[mm], y[m-3]
(Figure5j-5l): sim time averaged helium metastable density profile
]]>2020-09-15T10:07:59+02:002020-09-15T11:03:05+02:00application/zipzip259427https://rdpcidat.rub.de/dataset/control-electron-dynamics-radical-and-metastable-species-generation-atmospheric-pressure-2Figure 6Normalized 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
]]>2020-09-15T10:10:17+02:002020-09-15T14:33:56+02:00application/zipzip434570https://rdpcidat.rub.de/dataset/control-electron-dynamics-radical-and-metastable-species-generation-atmospheric-pressure-3Figure 7Time averaged total electron impact dissociation rate of N_2 molecules obtained from PIC/MCC simulations using a cross section adopted from for different numbers of driving harmonics, N, and nitrogen admixtures, for ‘peaks’-voltage waveform with a peak-to-peak voltage of 400V. 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 [mm] , y[m^{-3}s^{-1}]
(Figure7_N1): sim Total diss. Rate for N = 1 and 1sccm N_2 admixture
(Figure7_N2): sim Total diss. Rate for N = 2 and 1sccm, 2sccm, 4sccm N_2 admixture
(Figure7_N4): sim Total diss. Rate for N = 4 and 1sccm, 4sccm, 10sccm N_2 admixture
]]>2020-09-15T10:11:05+02:002020-09-15T14:34:04+02:00application/zipzip5281https://rdpcidat.rub.de/dataset/control-electron-dynamics-radical-and-metastable-species-generation-atmospheric-pressure-4Figure 8Space and time averaged values of the helium metastable density and the electron impact dissociation rate of N_2 molecules obtained from the PIC/MCC simulations for different numbers of driving harmonics, N, and molecular nitrogen admixtures for ‘peaks’-voltage waveform with a peak-to-peak voltage of 400V. 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 [mm] , y[m^{-3}s^{-1}]
(Figure8_Diss): sim electron impact diss. Rate of N2 for N = 1, 2 and 4 and 1-10 sccm N_2 admixture
(Figure8_He): sim He* density for N = 1,2 and 4 and 1-10 sccm N_2 admixture
]]>2020-09-15T10:11:58+02:002020-09-15T14:34:12+02:00application/zipzip1393https://rdpcidat.rub.de/dataset/control-electron-dynamics-radical-and-metastable-species-generation-atmospheric-pressure-5DKANhttps://rdpcidat.rub.de