Presentation is loading. Please wait.

Presentation is loading. Please wait.

ION ENERGY DISTRIBUTIONS TO PARTICLES IN CORONA DISCHARGES

Similar presentations


Presentation on theme: "ION ENERGY DISTRIBUTIONS TO PARTICLES IN CORONA DISCHARGES"— Presentation transcript:

1 ION ENERGY DISTRIBUTIONS TO PARTICLES IN CORONA DISCHARGES
Natalia Yu. Babaeva and Mark J. Kushner University of Michigan Department of Electrical Engineering and Computer Science Ann Arbor, MI USA 36th IEEE International Conference on Plasma Science San Diego, California May 31 – June 5, 2009  ICOPS2009_Natalie_01

2 University of Michigan Institute for Plasma Science & Engr.
AGENDA Ion energy and angular distributions (IEADs) to particles and surfaces in corona discharges Description of the model IEAD on particles Effects of particles on streamer dynamics Particle permittivity Streamer polarity IEADs to polymer surfaces Summary University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_02

3 ION ENERGY AND ANGULAR DISTRIBUTIONS (IEAD)
There is interest in adapting commodity corona-streamer discharges to high value processing – including functionalization of polymer beads for biomedical applications. Ion energy and angular distributions (IEAD) to particles suspended in atmospheric pressure plasma are important to activating surface chemistry. Example: Biodegradable porous beads are used for drug delivery and gene therapy. Beads are 10s µm in diameter Functionalized Porous Bead for Protein Binding sites ( University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_03

4 University of Michigan Institute for Plasma Science & Engr.
GOALS OF PRESENT STUDY Evaluate ability of atmospheric pressure corona streamer discharges to activate surfaces through ion bombardment. Investigate typical ion activation energies (i.e., IEADS) delivered to surfaces of particles and polymer sheets. “Particle” can be in the form of a bacterium…Required ion energies for sterilization typically  3 eV(?) Investigation performed with results from 2-dimensional plasma hydrodynamics model with kinetic simulation of ion transport. C. violaceum bacterial cells exposed to plasma K. G. Vandervoort, N. Abramzon and G. Brelles-Mariño, Trans. Plasma Science (2008) University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_04

5 MODELING PLATFORM: nonPDPSIM
Poisson’s equation: Transport of charged and neutral species: Surface Charge: Electron Temperature Radiation transport and photoionization: University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_05 5 5

6 DESCRIPTION OF THE PCMC MODULE
IEADs to surfaces are derived using the Plasma Chemistry Monte Carlo Module – a kinetic simulation of ion transport. Pseudo-particles (ions and neutrals) are launched from sites near the particle in the streamer channel determined by electron impact and heavy particles production rates. Monte Carlo techniques are used to advance their trajectories in time varying electric fields while accounting for elastic and inelastic collisions. The energy and angles of particles as they strike surfaces are recorded to provide a time averaged IEAD. Electric potentials computed on the unstructured nonPDPSIM mesh are interpolated onto a rectilinear structured mesh that overlays the unstructured mesh. University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_06

7 GEOMETRY AND CONDITIONS
0.5 mm 50 µm Positive and negative corona - rod (rc= 0.07 cm) to grounded metal (gap = 2 mm), 2-d unstructured mesh. Humid air: N2/O2/H2O = 79.5/19.5/1.0 , particle: 45 m University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_07

8 POSITIVE STREAMER INTERSECTING PARTICLE
Space Charge (2 x 1013 cm-3,1 dec) Close-up Positive streamer is a conductive channel outlined by positive space charge. Streamer envelopes small particle. Some amount of charge is removed from the streamer by particle. Positive corona, N2/O2/H2O = 79.5/19.5/1.0, particle: 45 m, /0=2 1 mm [O2+] (5 x 1013 cm-3, 3 dec) Close-up MIN MAX Cathode Animation Slide-GIF University of Michigan Institute for Plasma Science & Engr. 0-2.5 ns ICOPS2009_Natalie_08

9 CHARGE ON PARTICLE AND E-FIELD LINES (/0=2)
Charge (-2x1014 to 4x1013 cm-3) CHARGE ON PARTICLE AND E-FIELD LINES (/0=2) E-field Double layer of negative and positive charge is formed at the bottom of the particle. Electric field lines terminate at the bottom negative charges until positive and negative charges dissipate. Wake forms above particle. Positive corona, N2/O2/H2O = 79.5/19.5/1.0, particle: 45 m, /0=2 Animation Slide-GIF MIN MAX ns University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_09

10 IEAD ALONG PARTICLE SURFACE
O2+ Flux Lines O2+ Upper surfaces receive higher ion energy. Two group of ions: Thermalized (low energy and high angle) and fast (up to 8-10 eV, accelerated by corona fields near local normal). Grazing angles for ions to bottom surfaces. Positive corona in air, particle 45 m, /0=2 Animation Slide-GIF University of Michigan Institute for Plasma Science & Engr. MIN MAX ICOPS2009_Natalie_10

11 University of Michigan Institute for Plasma Science & Engr.
/0 = 2 Close-up PARTICLE DYNAMICS /0 = 2 vs /0 = 80 E/N (8 to 800 Td) 1 mm Low permittivity particle is enveloped by streamer. Secondary streamers can be launched from underside of high /0 particle due to high polarization. Positive corona, N2/O2/H2O = 79.5/19.5/1.0, particle: 45 m /0 = 80 Close-up Animation Slide-GIF MIN MAX University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_11 0-2.5 ns ns

12 CHARGE ON PARTICLE AND E-FIELD LINES (/0= 80)
Charge (-2x1014 to 4x1013 cm-3) E-field CHARGE ON PARTICLE AND E-FIELD LINES (/0= 80) For high /0 particle positive charges envelope the particle partially shielding electric field. High refraction of electric field lines at the particle boundary. Double layer of positive and negative charge is formed at the bottom of the particle. Positive corona, N2/O2/H2O = 79.5/19.5/1.0, particle: 45 m, /0=80 Animation Slide-GIF MIN MAX University of Michigan Institute for Plasma Science & Engr. ns ICOPS2009_Natalie_12

13 University of Michigan Institute for Plasma Science & Engr.
IEAD on PARTICLE /0=2 vs /0=80 O2+ Flux /0=2 /0=80 More energetic and more symmetric distribution of ions for particle /0=80. Effect is attributed to ion striking the surface at near normal angles . Positive corona, N2/O2/H2O = 79.5/19.5/1.0, particle: 45 m O2+ O2+ ns Animation Slide-GIF University of Michigan Institute for Plasma Science & Engr. MIN MAX ICOPS2009_Natalie_13

14 NEGATIVE STREAMER INTERSECTING PARTICLE
Charge (-4x1014 to 7x1013 cm-3) E-field [O2+ ] (4x1013 cm-3 , 3 dec) 1 mm More diffusive and wider negative streamer. Wake forms underneath the particle. All process are analogous but in reverse direction to positive corona. Negative corona, N2/O2/H2O = 79.5/19.5/1.0, particle: 45 m, /0=2 Animation Slide-GIF ns University of Michigan Institute for Plasma Science & Engr. MIN MAX ICOPS2009_Natalie_14

15 IEADs FROM NEGATIVE AND POSITIVE STREAMERS
O2+ flux O2+ IEAD, Positive corona, /0=2 IEAD, negative corona, /0=2 O2+ flux Animation Slide-GIF O2+ Mirror distributions of ion energies. University of Michigan Institute for Plasma Science & Engr. MIN MAX ICOPS2009_Natalie_15

16 University of Michigan Institute for Plasma Science & Engr.
CORONA DISCHARGE TREATERS Pulsed atmospheric corona discharges treat commodity polymers [e.g., poly-propylene] Low capital cost High volume Low product value High reliability Tantec, Inc. Streamers 10s – 100s mm (Ref: Enercon) University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_16

17 POSITIVE CORONA POLYMER TREATMENT
Geometry [O2+ ] (5x1013 cm-3 , 3 dec) 1 mm /0=2.2 Streamer plasma is filamentary and treats surface uniformly only due to the spatial averaging of many discharges. Streamer spreads on polymer as charges shield potential. Positive corona, N2/O2/H2O = 79.5/19.5/1.0 Animation Slide-GIF University of Michigan Institute for Plasma Science & Engr. MIN MAX ICOPS2009_Natalie_17

18 IEAD ON POLYMER SURFACE
Electric field (kV/cm) 1 2 3 High energy ions (up to 30 eV) strike the polymer surface due to compression of potential and surface charges. Positive corona, N2/O2/H2O = 79.5/19.5/1.0 Animation Slide-GIF University of Michigan Institute for Plasma Science & Engr. MIN MAX ICOPS2009_Natalie_18

19 University of Michigan Institute for Plasma Science & Engr.
CONCLUDING REMARKS The IEAD on particles in the channel of positive and negative corona discharges in humid air were investigated. Large sheath potential generated as the streamer passes the particle. Two groups of ions strike the particle: Thermal low energy-high angle ions Energetic ions up to 10 eV can strike the particle The polarity of discharge and permittivity of particle determine the character of the IEAD. The ion energy to polymer surfaces can be as high as 30 eV due to sheath formation…large enough for surface activation. University of Michigan Institute for Plasma Science & Engr. ICOPS2009_Natalie_19


Download ppt "ION ENERGY DISTRIBUTIONS TO PARTICLES IN CORONA DISCHARGES"

Similar presentations


Ads by Google