RU211773U1 - Device for generating low-temperature plasma flow - Google Patents

Abstract

The utility model relates to plasma technology, in particular to devices generating low-temperature plasma, which can be used in medicine and biology.

The purpose of creating this device is to expand the range of its action by providing the possibility of processing uneven surfaces (surfaces with bends, with complex relief) due to the elongation of the non-thermal plasma jet. This assumes a change in the mode of excitation of the electrode system while maintaining a low gas temperature of the jet (no more than 32°C) and a low flow rate of the working gas (no more than 0.5 L/min for helium).

This goal is achieved by the fact that the device for generating a low-temperature plasma flow is additionally equipped with a pulse interrupter unit that supplies voltage to the electrodes in the form of bursts of pulses with a duration.

The block diagram of the high-voltage pulse generator of the device (Fig. 3) includes a mains rectifier 1, a transistor inverter 2, a master pulse generator 3, a step-up transformer 4, and a pulse interrupter unit 5, which temporarily stops the master pulse generator 3.

Mains rectifier 1 converts alternating mains voltage to direct voltage and serves to power transistor inverter 2. Master pulse generator 3 generates pulse signals at the control outputs of transistors of inverter 2 with the required frequency and duration. With the help of a step-up transformer 4, pulses with an amplitude of several kilovolts are formed. The pulse interrupter block 5 periodically stops the operation of the master pulse generator, due to which voltage is applied to the electrodes in the form of bursts of pulses.

The use of a voltage that excites a gas discharge in the form of bursts of high-frequency pulses with relatively long pauses between bursts makes it possible to obtain a jet up to 40 mm long at a gas temperature of not more than 32°C.

Description

The utility model relates to plasma technology, in particular to devices generating low-temperature plasma, which can be used in medicine and biology.

It is customary to divide gas-discharge plasma into two types according to the electron energy level (electron temperature): high-temperature plasma and cold plasma [1]. For example, a candle flame is considered cold plasma, since the energy of electrons in this case is relatively low, and the gas temperature is more than 1000°C. Cold plasma can be roughly divided into two subtypes: non-thermal plasma and cold plasma with a high gas temperature. The gas temperature of the nonthermal plasma does not exceed 42°C. Cold plasma with high gas temperature is observed in most types of spark discharge. Both subtypes of cold plasma are used in traditional medicine. Thus, cold plasma with a high gas temperature is generated in plasma coagulators, in plasma scalpels and in d'Arsonval apparatus.

Non-thermal plasma flows can be used for non-drug treatment of septic wounds, in dermatology (non-drug treatment of acne, eczema, various forms of dermatitis), as well as in cosmetology (non-invasive plasmolifting, postoperative rehabilitation) [3-5].

Known "Device for generating low-temperature plasma", RF patent for PM No. 167645, IPC H05N 1/24, Appl. 12/02/2015, publ. January 10, 2017 [6]. This device includes: a voltage control unit, a power generator, a high-voltage transformer, a pair of electrodes, an ionization chamber, a gas mixture formation device, magnetic and electric impact devices, a nozzle at the mixture outlet from the chamber.

The disadvantages of the above device include its limited capabilities (only smooth outer surfaces can be processed with it), structural complexity (the presence of elements of magnetic and electrical influence, a device for forming a gas mixture, as well as its low electrical safety due to possible leakage of current from a high-voltage electrode to the body person.

The closest in technical essence and the achieved result is the "Device for generating low-temperature plasma", RF patent for PM No. 202393, IPC H05N 1/24, Appl. 03/12/2020, publ. February 16, 2021 [7]. This device can serve as a prototype.

The device adopted as a prototype contains: a high-voltage power source, a nozzle with an electrode system, a device for pumping working gas through the nozzle, a mains rectifier, a transistor inverter, a master pulse generator and a step-up pulse transformer.

The main disadvantage of this device is its limited capabilities due to the small length (no more than 10 mm) of the plasma jet, which allows processing only smooth surfaces of a limited area. In addition, the use of short voltage pulses with a duration of 0.3–2 μs limits the development of gas-discharge plasma contraction in the channel, and long pauses between pulses contribute to the relaxation of the formed plasma and a decrease in the gas temperature of the flame jet. The use of a higher pulse frequency leads to an elongation of the flame jet and, at the same time, to an undesirable increase in the gas temperature of the gas discharge.

The technical result of the proposed device is to expand the spectrum of the device by providing the possibility of processing uneven surfaces (surfaces with bends, with complex relief) due to the elongation of the non-thermal plasma jet. This assumes a change in the mode of excitation of the electrode system while maintaining a low gas temperature of the jet (no more than 32°C) and a low flow rate of the working gas (for helium, no more than 0.5 l/min)

To achieve this result, a device for generating a non-thermal plasma flow, containing a high-voltage power source, a nozzle with an electrode system, a device for pumping working gas through the nozzle, a mains rectifier, a transistor inverter, a master pulse generator and a step-up pulse transformer, is additionally equipped with a pulse interrupter unit that supplies voltage electrodes in the form of bursts of pulses with a frequency of 50-1000 kHz, a duration of bursts of 50-30 μs and a pause between bursts of pulses of 200-1000 μs, moreover, the polarity of the excitation pulses can be positive, negative or alternating.

The use of a voltage that excites a gas discharge in the form of bursts of high-frequency pulses with relatively large pauses between bursts makes it possible to obtain a jet up to 40 mm long at a gas temperature of not more than 32°C (Fig. 1).

The claimed device for generating a flow of non-thermal plasma is presented in the form of a block diagram in Fig. 2.

The block diagram of the device includes: a mains rectifier 1, a transistor inverter 2, a master pulse generator 3, a step-up transformer 4, as well as a pulse interrupter unit 5, which temporarily stops the master pulse generator 3.

The operation of the device is as follows:

Mains rectifier 1 converts alternating mains voltage to direct voltage and serves to power transistor inverter 2. Master pulse generator 3 generates pulse signals at the control outputs of transistors of inverter 2 with the required frequency and duration. With the help of a step-up transformer 4, pulses with an amplitude of several kilovolts are formed. The pulse interrupter unit 5 stops the operation of the master pulse generator for a period of 50-30 μs, due to which the voltage is applied to the electrodes in the form of bursts of pulses with a pulse frequency of 50-1000 kHz, a burst duration of 50-30 μs and a pause between pulse bursts of 200-100 μs. In this case, the polarity of the excitation pulses can be positive, negative or alternating.

Due to the high pulse repetition rate, the space along the plasma jet axis is sufficiently ionized, and by the end of the pulse train, the jet length reaches its maximum value. A long pause between bursts of pulses contributes to the relaxation of the generated plasma, which prevents the formation of contracted plasma channels with high conductivity and leads to a decrease in the gas temperature of the jet.

The possibility of elongating the jet of non-thermal plasma up to 40 mm makes it possible to process uneven surfaces of the body (surfaces with bends, with complex relief). This assumes a change in the mode of excitation.

Literature:

1. Physical encyclopedia. Ch. ed. A.M. Prokhorov, editorial board: D.M. Alekseev [and others]: - Great Russian Encyclopedia, 1998

2. M. Laroussi Low-Temperature Plasmas for Medicine // IEEE transactions on plasma science, vol. 37, no. 6, 2009.

3. J. Kolb, A.H. Mohammed, R.O. Price, R.J. Swanson, A. Bowman, R.L. Chiavarini, M. Stacey, and K.H. Schoenbach Cold atmospheric pressure air plasma jet for medical applications // Applied Physics Letters 92, 241501 (2008).

4. J. Asenjo, J. Mora, A. Vargas, L. Brenes, R. Montiel, J. Arrieta, V.I. Vargas Atmospheric-Pressure Non-Thermal Plasma Jet for biomedical and industrial applications // Journal of Physics: Conference Series 591 (2015) 012049.

5.M.Y. Alkawareek, Q.Th. Algwari, G. Laverty, S.P. Gorman, W.G. Graham, D. O'Connell, B.F. Gilmore Eradication of Pseudomonas aeruginosa Biofilms by Atmospheric Pressure Non-Thermal Plasma// PLoS One. 2012;7(8):e44289.

6. Device for generating low-temperature plasma // Patent for utility model RU167645, priority from 02.12.2015.

7. Device for generating a flow of non-thermal plasma. Utility model patent RU202393, priority dated 03/12/2020.

Claims (1)

A device for generating a non-thermal plasma flow, containing a high-voltage power source, a nozzle with an electrode system, a device for pumping working gas through the nozzle, a network rectifier, a transistor inverter, a master pulse generator and a step-up pulse transformer, characterized in that it is additionally equipped with a pulse interrupter unit that supplies voltage on the electrodes in the form of bursts of pulses with a pulse frequency of 50-1000 kHz, a burst duration of 50-30 μs and a pause between pulse bursts of 200-100 μs, and the polarity of the excitation pulses can be positive, negative or alternating.

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