Atmospheric Non-thermal Plasma Jet and its Applications Dr. Eng./ Kamal M. A. Ahmed Assistant Professor Egyptian Atomic Energy Authority
Introduction 1 Outline Plasma, sources & configurations 2 Plasma Jet Design, components & diagnostics 3 Measurements Electrical & temperature& wettability 4 Plasma Applications 2
Introduction 1 Outline 2 Plasma Jet 3 Measurements 4 Plasma Applications 3
Introduction A ➢ Plasma in our life B ➢ Plasma classifications C ➢ Electrical safety & Plasma sources D ➢ Plasma configurations 4
Plasma definition • plasmas are mostly generated by electrical discharges 5
Plasma in our life Plasmas occur naturally comprise the majority of the universe (95 or 99). Natural Plasma Plasmas in astrophysics ➢ Well-known examples : ▪ the Sun ▪ stars ▪ the ionosphere ▪ Lightning Plasmas in Aurora يبطقلا قفشلا 6 Lightning (U. of Alaska) Solar physics
Plasma in our life but also can be manmade . Artificial Plasma Melting • Lighting Plasma display Cutting • Spray 7 Coatings Biomedical
Plasma classifications -kHz - 13.56 MHz 8 2.54 GHz
How to produce plasma (1) Power supply HV (2) (3) 9 What voltage and current are dangerous for humans?
Electrical safety Electricity in touch Current < 30 mA Voltage < 50 V AC, 50 Hz ✓ Earthing 10
Earthing Charged device Device Earthing rod 11
For the measurements devices Should be isolated from the plasma source and the power supply 220 V Power 50 Hz Plasma supply chamber Isolation Measure devices transformer 12 ✓ The coaxial cables should be 50 ohm
Plasma Configurations ✓ Corona discharge ✓ DBD ✓ Glow discharge 13
Plasma Configurations ✓ MHCD ✓ Plasma focus ✓ Gliding arc discharge ✓ Plasma torch 14
Plasma Jet Configurations MHCD Coaxial discharge Pin-to-ring discharge Floating 15 electrode
Introduction 1 Outline 2 Plasma Jet 3 Measurements 4 Plasma Applications 16
Plasma Jet 01 Design Goals 1 03 02 Dia iagno nosti stics cs 3 Device 2 Components 17
Design goals Advantages of Atmospheric plasma 1 NON-thermal (Cold) Plasma Ch/cs 2 Gas selection ection 3 Power source’s choice; Neon Power supply 4 Factors affect the plasma operation 5 Electrode & insulators 6 18
Advantages of Atmospheric plasma Atmospheric plasma ➢ No Vacuum equipment's Required ➢ Lower Purchase and Maintenance Costs ➢ Can be operated in open air with large treatment areas. ➢ Minimum cooling is required ➢ Different configurations and geometries are available 19
NON-thermal (Cold) Plasma ch/cs ✓ The majority of the electrical energy deposited in the Non-thermal (cold) plasma heats the electrons instead of heating the background gas. ➢ Because the ions and the neutrals remain relatively cold, cold plasmas is used for the treatment of heat sensitive materials including polymers and biological tissues. ➢ Its characteristics include a strong thermodynamic non- equilibrium nature, low gas temperature, presence of reactive chemical species and high selectivity offer a tremendous potential to utilize these cold plasma sources in a wide range of applications. 20
Factors affecting the plasma operation (Supply frequency, working voltage, gas type, flow rate, working pressure, electrode spacing and electrode material) Power supply ❑ V? ❑ I? ❑ f(Hz)? Electrodes ❑ Material HV ❑ Dimensions : spacing & hole ❑ Configuration Gas ❑ Type? ❑ P? 21 Insulator ❑ Flow rate
Gas selection ➢ Gas can be Air, H 2 , He, O 2 , N 2 , Ar, CH 4 ,..etc. Using Air is an advantageous • Low cost • Portability • Ozone generation Endless Air 50% cost reduction ➢ Higher flow rates helps in Cooling of the system 22
I-V Ch/s V = Vdc - RI 23
Power source’s choice B ( p . d ) = V − + b ln[ A ( p . d )] ln[ln( 1 1 )] se d=1cm The breakdown voltage must exceed d=500 m MHCD depends on the pressure, p ❑ Atmospheric and electrode spacing, d . ❑ Vb will exceed hundred kV for atmospheric pressure ❑ Solution is : MHCD (d in micrometer range) 24
➢ To reduce breakdown voltage, the power supply frequency is increased. ➢ So RF is favored over DC ➢ Low frequency RF is favored due to : • Higher Ion Density. • Increased Efficiency. • Better Uniformity. What about higher cost of RF Supply 25
Neon Power supply ✓ A neon power supply is chosen as a low- cost power supply. Output 10 kV, 30 mA and 20 kHz 26
Electrode selection Electrode’s material can be ⚫ Stainless steel, ⚫ Aluminum, ⚫ Graphite deposition, ⚫ Copper ⚫ Tungsten ⚫ …. etc 27
Insulator selection Melting point( C) Material Alumina 2072 ❑ Sustain HV ❑ Stand for high Porcelain 1400 T (melting Glass 1500 point) Mica 1250 Teflon 335 Mylar 254 Silicon rubber 200 PVC 160 28 Acrylic 160
ANPJ Atmospheric Nonthermal Plasma Jet 29
Plasma jet Power Envelope supply Gas inlet Electrodes 30
Plasma jet in our lab. Envelope Electrodes PS Mylar Teflon Gas inlet 31
ANPJ-II 32
ANPJ-II Power supply 33
Comparison Previous New ANPJ Device ANPJ-II Device 100% Only 6 cm 3 156 cm 3 4%
Flow system Air N 2 ❑ The flow rate in the range from 3 to 25 L/min. 35
Plasma jet length 36
Diagnostics tools 37
Diagnostic devices Plasma jet device N 2 gas Neon Voltage Power supply probe Optical fiber cables To oscilloscope Variac Spectrometer Thermometer 38 DC power supply PMT
Diagnostics devices ✓ Voltage divider ✓ Rogowski coil ✓ Photomultiplier Tube ✓ Optical Emission Spectroscopy ✓ Gas and components’ temperature 39
Voltage divider Scale the voltage to be suitable for the measurement device 40
Rogowski coil 41
Temperature measurements Thermometer ✓ thermocouple or IR used to measure the gas temperature Thermocouples act as a transducer converting thermal energies into electrical Thermocouples are flexible, inexpensive, and provide fairly accurate temperature measurements. 42
Introduction 1 Outline 2 Plasma Jet 3 Measurements 4 Plasma Applications 43
Electrical measurements Current, voltage and power measurements 44
Electric circuit i(t) 5 nF Plasma jet 25 Ω device 21:1 Variac voltage probe Gas inlet V c (t) V d (t) Neon power supply 1000:1 10kV, 30 mA, 0-220 V voltage 20kHz probe 45
Electrical Ch/s 1 = 46 P i ( t ) V ( t ) dt d T
Electric Ch/cs Lissajous figure Method Charge 1 = P V ( t ) dQ Discharge voltage d 47 T
Plume electrical measurements (b) R 3 = 1 k Ω Cathode Dielectric Probe Plasma jet R 2 = 9 M Ω Anode Oscilloscope R 1 = 20 k Ω Voltage divider (a) Z=0 mm 48
Plume electrical measurements A safely plasma dose is generated from the plasma jet device even when the exposure time is relatively long (220h). 49 Plasma power density equals 0.17 mW/cm 2 << 135 J/cm 2
Temperature measurements Gas and electron temperature measurements 50
Gas temperature <50 o C Gas T ✓ Cold plasma For heat- sensitive treatments Polymer & biomedical Axial distance 51
Spectroscopy- photomultiplier − ( E E ) = 1 2 k T in eV exc g A I 2 2 1 1 ln ( ) g A I 1 1 2 2 52
Plume intensity N 2 Intensity Axial distance 53
Species emission from plasma jet ✓ Ozone ✓ NO ✓ OH Stephan Reuter, J. Phys. D: Appl. Phys. 51 (2018) 233001 54
Spectroscopy- Spectrometer Envelope Electrodes Plasma jet 5 mm Gas flow Cable 5m Optical fiber support cable Slider OceanView 45 0 software Glass slide for protection 55 USB cable Spectrometer
Excitation Electron Temperature ( Alg lgorit orithm hm for or spectrometer) Data System Background Acquistion Equalization Subtraction 3500 3000 2500 Output Data 2000 from 1500 1000 Spectrometer 500 0 00 400 500 600 700 800 900 1000 Temperature Estimation Peak Peak Peak Identification Detection Modeling E − k kT exc I ln 56 A g ki k
Spectrum https://www.nist.gov/ 57
Electron vs gas temperature <400 K 11680 T gas T e ~ 1 eV ✓ Cold plasma 58
Sine vs pulsed wave comparison Advantages of pulsed ✓ Less temperature ✓ Higher velocity ✓ Less energy consumption Xiong et al., PHYSICS OF PLASMAS 17, 043506 (2010) 59
Wettability Contact angle measurements 60
Contact angle & wettability Smaller Contact angle Larger Better Wettability Worse Better adhesiveness Worse 61
Contact angle Measurements spherical cap approach h − h α = tan 1 θ ( ) ; Substrate a a = 2 = + 2 2 V h ( h 3 a ) 6 ➢ V is known , a is computed, h is calculated ➢ Contact angle is measured 62
Contact angle Measurements LBADS approach 63
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