In this work, we have developed and successfully fabricated a high frequency (30-70 KHz), high voltage generator (2-6 kV) as a power supply to generate a plasma jet. Effect of the oscillating frequency, the applied voltage on the output voltage and the plasma jet’s stability were studied.
Research DEVELOPMENT AND FABRICATION OF A TUNABLE HIGH FREQUENCY, HIGH VOLTAGE POWER SUPPLY FOR ATMOSPHERIC-PRESSURE PLASMA JET GENERATION Le Thi Quynh Xuan1, Nguyen Nhat Linh1,2, Dao Nguyen Thuan1,* Abstract: More recently, the innovative non-thermal plasma (NTP) technology has drawn considerable attention in various fields, from applied research to industry In this work, we have developed and successfully fabricated a high frequency (30-70 KHz), high voltage generator (2-6 kV) as a power supply to generate a plasma jet Effect of the oscillating frequency, the applied voltage on the output voltage and the plasma jet’s stability were studied A stable plasma jet with a maximum length of 1.5-1.8 cm could be achieved at output voltage ~ kV and oscillating frequency ~ 55 KHz We showed that this plasma jet system could be applied as a quick, chemical-free and effective method to enhance seed germination and seedling growth of black turtle bean Keywords: Cold plasma; Plasma jet; Dielectric Barrier Discharge; High voltage; High frequency; Push-pull circuit INTRODUCTION Non-thermal plasma (NTP) or cold plasma is an ionized gas at non-thermal equilibrium while the temperature of ions and gas (~300K) is much lower than electron’s temperature (>104K) Cold plasma caries charged particles (electrons, ions), radicals (reactive oxygen species - ROS, reactive nitrogen species - RNS) and irradiated UV which strongly interacts and have effects on many objects In recent decades, cold plasma have been studied extensively and is widely applied in various fields from research to industry including material science (surface modification and functionalizing (1)), agriculture (killing virus/bacterial (2), enhancing seed germination and seedling growth (3,4)…), medicine (sterilization (5), wound healing (6), plastic surgery (7)…), environment (water treatment (8), waste treatment…), and food safety (decontamination (9)) In recent years, several devices have been presented that are able to generate a cold plasma plume at atmospheric pressure in air They employs different methods using microwaves, radio frequency, pulsed or alternative current in various setups such as dielectric barrier discharge (DBD), atmospheric pressure plasma jet (APPJ), and corona discharges All of these discharges have their own unique features In this work, we aim to develop an atmospheric pressure plasma jet (APPJ) system This configuration has an advantage that there will be a dielectric barrier (quartz tube) between the plasma emitting electrode and the outer electrode, hence minimizing risk of sparks and arcs between theses electrodes In order to build a plasma jet system, we need to develop and fabricate a tunable high frequency, high voltage (~ few kV) power supply to generate the plasma jet Typical high voltage DC (direct current) power supply are availed commercialized, however, it is not suitable for plasma jet generation The charge on the electrodes need to be altered in order for the plasma jet to operate It is important to emphasize that the electrodes will be eroded overtime when the discharge is continuous (with a low frequency high voltage power supply) This Journal of Military Science and Technology, Special Issue, No.57A, 11 - 2018 79 Physics leads to the instability of the plasma discharge Therefore, by using a high voltage, high frequency power source, the two electrodes are constantly changing their charge very fast (high frequency) which will help to minimize eroding effect significantly, hence allowing stable and long operation of the plasma system MATERIALS AND METHODS 2.1 Development of a tunable high frequency, high voltage power supply The tunable high frequency, high voltage power supply consisted of main units: a power unit, a duty-cycle PWM controller, a PWM high frequency generator and a high voltage transformer (Figure and 2) The function of each unit was as the following: The power unit (8-14V) supplied a stable power for the system The duty-cycle controller unit using an IC NE555 to generate pulses to control the operation of the following high frequency generator unit The duty-cycle controller unit also allowed the system to run steadily at the upper range of the output voltage (~6 kV) while limiting the circuit’s current, hence avoiding overheat on electrical components, especially on the MOSFET transistors The rate of the duty-cycle controller was defined as f = 1⁄ ln2 C (R + 2R ) Duty cycle ON duration (state 1) in one cycle t = ln2 C (R + R ) Duty cycle OFF duration (state 0) in one cycle t = ln2 C R The high frequency generator unit used a PWM IC SG3525 to generate reverse tunable high frequency pulses in order to operate MOSFET IRFP250 transistors in push-pull configuration This block generated a high frequency square voltage (few hundred V) to feed in the input of the following high voltage transformer unit The high frequency output signal at pin 11 and 14 could be defined as: C + (0.7 R + 3R ) The high voltage transformer unit was employed to amplify the input voltage (a few hundred V) to very high output voltage (~ 2-6 kV) This high voltage transformer was made of ferrite core with (5+5) turns on the primary winding and 3000 turns on the secondary winding The core and windings were immersed in electrical insulating oil to prevent any electrical sparks and arcs f= Figure Diagram of main component units of the tunable high frequency, high voltage power supply 80 L T Q Xuan, N N Linh, D N Thuan, “Development and … plasma jet generation.” Research Figure Circuit diagram of the duty-cycle control unit, the high frequency generator unit and the high voltage transfomer unit Although some reports on high voltage, high frequency power supply using a phase-shifted PWM full bridge inverter (10), or a parallel-resonant push-pull inverter (11), or an input-series two-transistor flyback (12) were described elsewhere Our circuit had an advantage that allowed tuning various parameters as the applied voltage, the high frequency, and the duty cycle independently The optimization of our circuit also minimized heat loss on most power-consumed ICs, hence allowed the circuit to work for very long operation time without overheating on the MOSFET transistors as well as the high voltage transfomer 2.2 Configuration and fabrication of a plasma jet emitter The plasma jet emitter consisted of a stainless steel syringe inserted inside a quartz capillary tube of 1.5mm internal diameter following a set up as reported (13) The needle was shortened and covered with an insulating rubber, then attached to a quartz tube by adhesive epoxy Copper electrode outside the quartz tube was made by wrapping a copper tape around the tube Various quartz tubes with different internal diameters and metal needle with different diameters were tested Generally, with smaller and shorter needles, the plasm jet beams were longer However, if the needle was small, the jet beam had a small cross section, which was difficult to use in many applications In our setup, the tube length was cm while the needle length was 3cm This configuration gave the jet beam with a maximum length of 1.5-1.8 cm and was highly stable 2.3 Characterization of the plasma jet system A Tektronix P6015 Voltage Probe (1000:1) connected to a Tektronix TBS1154 oscilloscope to measure output voltage of our power supply The output voltage was varied between kV and 6kV to study its impact to the plasma jet The Argon gas was connected to a flow controller to vary the gas flow rate conditions, from 200 sccm to 900 sccm The optical emission of the plasma jet discharge in 3001000 nm range was collected at 10 mm away from the nozzle and focused on the input of an IHR550 spectrometer (Figure 3) Journal of Military Science and Technology, Special Issue, No.57A, 11 - 2018 81 Physics Figure Setup for electrical and optical characterization of the plasma jet system RESULTS AND DISSCUSION 3.1 Plasma jet’s operating condition condition:: Minimum voltage for electrical discharge To create a plasma jet, it is necessary to have an electr electrical ical discharge between the two electrodes inside the quartz tube The minimum breakdown voltage required to initiate electrostatic discharge between two electrodes is determined by Paschen's law with VB is the breakdown voltage [V]; p is the pressure [[pascal]; pascal]; d is is the distance between two electrodes [m]; γse is is the secondary secondary electron electron electron emission emission coefficient (the number of secondary electrons produced per incident positive ion), A, B are constant coefficient depends on gas type With Ar gas, at p = 2.0 [Torr], [Torr], the minimun breakdown voltage is 215 [V] at pd = 0.7 [Torr.cm] (14) (14) The distance between the metal tip and copper ring in our setup is 0.5 cm m With this distance, the minimum potential for a breakdown discharge in Ar gas is VB ~ [kV] However, it should be noted that as one of the two electrodes is a sharp electrode, the minimum voltage for a breakdown discharge is lower because the charge density at the tip is higher When applying a high-voltage highvoltage high high frequency frequency voltage on the metal syringe and copper electrode, and with Ar gas flow, it will produce a plasma jet (15) (15) 3.2 Effect of the oscillating frequency on the output voltage and stability In order to determine the optimal operating frequency of the plasma jet system, we varied the oscillating frequency of the power supply from 30 KHz to 70 KHz (Figure 4) The error bar at each monitoring frequency was determined by the 82 L T Q Xuan, N N Linh, D N Thuan, “Develop Development and … plasma jet generation Development generation.” ” Research difference of output voltage between loaded (plasma emission) and unloaded (no plasma emission) operating condition Figure showed that maximum output voltage can be achieved by our power supply is ~ kV at oscillating frequency f ~ voltage 50 KHz The balanced sinusoidal output voltage represented the stability of the power supply and the high frequency transformer when operating in push push-pull pull mode (Figure 5) In lloaded oaded condition, the jet beam reached a maximum length of 1.8 cm and the plasma jet was stable at this condition Figure Dependence of output voltage Vpp vs oscillating frequency of the power supply Figure 55 Characterization of output voltage waveform from our power supply 3.3 Effect of the applied voltage on the output voltage and the maximum 3.3 current Table showed the dependence of high output voltage and current when changing the input voltage from 8V to 114V 4V (the oscillation frequency was 556.4 6.4 kHz) With maximum current varying from to (A), the circuit was stable and the heat loss was low (the IRF250 MOSFET transistors were not overheated) The output voltage could vary between - kV when changing the input in the range of - 14 V Journal of Military Science and Technology, Special Issue, No No.57A 57A, 11 - 2018 2018 83 Physics Table Dependence of the output voltage and the maximum current vs the input voltage when the power supply operated at 54.6 KHz Input Voltage Vin (V) 10 11 12 13 14 Output Voltage Vpp (kV) 2.1 2.8 3.3 3.9 4.5 5.3 6.1 Imax (A) 0.96 1.12 1.32 1.45 1.54 1.68 1.78 3.4 Emission spectra of the plasma jet Figure was the optical emission spectrum (OES) of the plasma jet ranging from 300 to 1000 nm There were spectral regions: the 700-900 nm spectral region was due to the electron displacement of 2pi to 1si of the Ar atom In the vicinity of ultraviolet light at 300-400 nm were the emission lines of the N2 atom Under the plasma arc discharge, water molecules inside the quartz tube were irradiated into OH- radicals and contributed an emission band around 300 nm An analysis of gas flow rate ranging from 200 sccm to 900 sccm showed that our system could generate stable plasma jet, with the full spectra of OH- and N2 characteristic peaks The plasma temperature measured by a digital thermometer at the end of the quartz tube was 25 - 29 °C, which was suitable to be applied in various life science researches Figure Emission spectra of the plasma jet in 300 - 1000 nm range 3.5 Application of the atmospheric-pressure plasma jet in agriculture: an example of enhancing seed germination and seedling growth of black turtle bean The effects of cold plasma (CP) treatment on seed germination of black turtle bean was investigated The seeds were pre-selected to ensure germination capability and had similar size and shape (Figure 7-A) Seed germination and seedling root were significantly enhanced after only 2-minutes plasma treatment (Figure 7-B) The mechanism of this enhancement could be folds First, the 84 L T Q Xuan, N N Linh, D N Thuan, “Development and … plasma jet generation.” Research plasmas directly induced changes in the seed coating, which could lead to better water absorption on the surface of treated seeds (16) Second, other works suggested oxygen and nitrogen reactive species (RONS) and radicals could penetrate into the seed and enhanced the metabolic process of plant growth (3,4) TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) spectroscopy shown a significant increase in the concentration of oxygen- and nitrogencontaining groups on the surface of the plasma treated lentil, beans and wheat seeds (17) Our results showed that cold plasma treatment could be used as a quick and effective method to enhance seed germination and seedling growth of black turtle bean This method could be applied to various vegetable’s seeds Figure Effect of cold plasma treatment time on seeds’ germination and seedling growth of black turtle bean (A) Cold plasma treatment on black turtle bean (B) Photo of batches of 10 black turtle bean seeds after 24 hours sowing on paper on a petri dish with no plasma treatment (left) and with 2-minutes plasma treatment (right) CONCLUSION We have developed and successfully fabricated a high frequency (30-70 KHz) high voltage generator (2-6 kV) as a power supply for a plasma jet system Effect of the oscillating frequency, the applied voltage on the output voltage and the plasma jet’s stability were studied A stable plasma jet with a maximum length of 1.5-1.8 cm could be achieved at output voltage ~ 6kV and oscillating frequency ~ 55 KHz The plasma jet operated steadily at room temperature and atmospheric pressure could be used for agricultural and biological applications We have demonstrated an application of this plasma jet system as a quick, chemical-free and effective method to enhance seed germination and seedling growth of black turtle bean Acknowledgement: This research was supported by IMS, VAST under grant number CSCL04.18 REFERENCES [1] Reichen, P., Sonnenfeld, A and Rudolf von Rohr, P (2009) "Remote Plasma Device for Surface Modification at Atmospheric Pressure" Plasma Processes and Polymers, Vol 6, pp S382-S386 Journal of Military Science and Technology, Special Issue, No.57A, 11 - 2018 85 Physics [2] Liu, F., Sun, P., Bai, N., Tian, Y., Zhou, H., Wei, S., Zhou, Y., Zhang, J., Zhu, W., Becker, K et al (2010) "Inactivation of Bacteria in an Aqueous Environment by a Direct-Current, Cold-Atmospheric-Pressure Air Plasma Microjet" Plasma Processes and Polymers, Vol 7, pp 231-236 [3] Ji, S.-H., Choi, K.-H., Pengkit, A., Im, J.S., Kim, J.S., Kim, Y.H., Park, Y., Hong, E.J., Jung, S.k., Choi, E.-H et al (2016) "Effects of high voltage nanosecond pulsed plasma and micro DBD plasma on seed germination, growth development and physiological activities in spinach" Arch Biochem Biophys., Vol 605, pp 117-128 [4] Bafoil, M., Jemmat, A., Martinez, Y., Merbahi, N., Eichwald, O., Dunand, C and Yousfi, M (2018) "Effects of low temperature plasmas and plasma activated waters on Arabidopsis thaliana germination and growth" PLOS ONE, Vol 13, pp e0195512 [5] Laroussi, M (2005) "Low Temperature Plasma-Based Sterilization: Overview and State-of-the-Art" Plasma Processes and Polymers, Vol 2, pp 391-400 [6] Isbary, G., Stolz, W., Shimizu, T., Monetti, R., Bunk, W., Schmidt, H.U., Morfill, G.E., Klämpfl, T.G., Steffes, B., Thomas, H.M et al (2013) "Cold atmospheric argon plasma treatment may accelerate wound healing in chronic wounds: Results of an open retrospective randomized controlled study in vivo" Clinical Plasma Medicine, Vol 1, pp 25-30 [7] von Woedtke, T., Metelmann, H.R and Weltmann, K.D (2014) "Clinical Plasma Medicine: State and Perspectives of in Vivo Application of Cold Atmospheric Plasma" Contributions to Plasma Physics, Vol 54, pp 104-117 [8] Samanta, K.K., Jassal, M and Agrawal, A.K (2009) "Improvement in water and oil absorbency of textile substrate by atmospheric pressure cold plasma treatment" Surf Coat Technol., Vol 203, pp 1336-1342 [9] Pankaj, S.K., Bueno-Ferrer, C., Misra, N.N., Milosavljević, V., O'Donnell, C.P., Bourke, P., Keener, K.M and Cullen, P.J (2014) "Applications of cold plasma technology in food packaging" Trends in Food Science & Tech., Vol 35, pp 5-17 [10] Hothongkham, P and Kinnares, V (2010), The 2010 International Power Electronics Conference - ECCE ASIA -, pp 1560-1567 [11] Alonso, J.M., Garcia, J., Calleja, A.J., Ribas, J and Cardesin, J (2005) "Analysis, design, and experimentation of a high-voltage power supply for ozone generation based on current-fed parallel-resonant push-pull inverter" IEEE Transactions on Industry Applications, Vol 41, pp 1364-1372 [12] Meng, T., Song, Y., Wang, Z., Ben, H and Li, C (2018) "Investigation and Implementation of an Input-Series Auxiliary Power Supply Scheme for HighInput-Voltage Low-Power Applications" IEEE Transactions on Power Electronics, Vol 33, pp 437-447 [13] Hong, Y., Lu, N., Pan, J., Li, J., Wu, Y and Shang, K (2013) "Electrical and Spectral Characteristics of a Low-Temperature Argon–Oxygen Plasma Jet With Syringe Needle-Ring Electrodes" IEEE Transactions on Plasma Science, Vol 41, pp 545-552 86 L T Q Xuan, N N Linh, D N Thuan, “Development and … plasma jet generation.” Research [14] Torres, C., Reyes, P.G., Castillo, F and Martínez, H (2012) "Paschen law for argon glow discharge" Journal of Physics: Conference Series, Vol 370, pp 012067 [15] Muyang, Q., Congying, Y., Sanqiu, L., Xiaochang, C., Gengsong, N and Dezhen, W (2016) "Gas flow dependence of atmospheric pressure plasma needle discharge characteristics" Japanese Journal of Applied Physics, Vol 55, pp 046101 [16].Zhou, R., Zhou, R., Zhang, X., Zhuang, J., Yang, S., Bazaka, K and Ostrikov, K (2016) "Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth" Sci Rep-Uk, Vol 6, pp 32603 [17] Bormashenko, E., Grynyov, R., Bormashenko, Y and Drori, E (2012) "Cold radiofrequency plasma treatment modifies wettability and germination speed of plant seeds" Sci Rep-Uk, Vol 2, pp 741-741 TÓM TẮT NGHIÊN CỨU PHÁT TRIỂN VÀ CHẾ TẠO BỘ NGUỒN CAO ÁP TẦN SỐ CAO SỬ DỤNG LÀM NGUỒN PHÁT PLASMA JET Ở ÁP SUẤT KHÍ QUYỂN Gần đây, cơng nghệ plama nhiệt độ thấp nhận nhiều quan tâm nghiên cứu phát triển mạnh mẽ để ứng dụng nhiều lĩnh vực, từ nghiên cứu đến lĩnh vực nông nghiệp, y tế, môi trường… Trong nghiên cứu này, phát triển chế tạo phát cao áp (2-6 kV) tần số cao (30-70 Khz) làm nguồn cho thiết bị phát plasma jet Ảnh hưởng tần số dao động, điện áp đầu vào tới cao áp đầu độ ổn định tia plasma khảo sát Kết cho thấy tia plasma jet đạt chiều dài ổn định tối đa 1.5-1.8 cm với điện áp đầu ~ kV tần số dao động ~ 55 KHz Hệ plasma jet chế tạo được sử dụng để kích thích hạt đỗ đen nảy mầm phát triển cách nhanh chóng, hiệu mà khơng cần sử dụng hóa chất Từ khóa: Plasma lạnh; Plasma dạng tia; Phóng điện qua hàng rào điện mơi; Cao áp; Tần số cao; Mạch đẩy kéo Received 8th September 2018 Revised 20 th October 2018 Accepted 1st November 2018 Author affiliations: Institute of Materials Sciences (IMS), VAST; Plasma Bioscience Research Center, Kwangwoon University, South Korea *Corresponding author: thuandn@ims.vast.ac.vn Journal of Military Science and Technology, Special Issue, No.57A, 11 - 2018 87 ... significantly, hence allowing stable and long operation of the plasma system MATERIALS AND METHODS 2.1 Development of a tunable high frequency, high voltage power supply The tunable high frequency, high. .. (30-70 KHz) high voltage generator (2-6 kV) as a power supply for a plasma jet system Effect of the oscillating frequency, the applied voltage on the output voltage and the plasma jet s stability... Bafoil, M., Jemmat, A. , Martinez, Y., Merbahi, N., Eichwald, O., Dunand, C and Yousfi, M (2018) "Effects of low temperature plasmas and plasma activated waters on Arabidopsis thaliana germination