JP6061288B2 - Power supply for plasma generator and plasma generator - Google Patents

Description

  The present invention relates to a power source for a plasma generation apparatus and a plasma generation apparatus.

  The plasma jet is a kind of atmospheric pressure non-equilibrium plasma. As a major feature, the plasma jet has a high electron temperature of several tens of thousands of K, while the gas temperature is about room temperature, so it is possible to perform a plasma process with chemically active radicals without applying a heat load to the irradiation target. It is. In recent years, the application of atmospheric pressure non-equilibrium plasma to various fields such as medical treatment, biological field, fuel reforming, plasma CVD, nanotube synthesis, etc. is rapidly progressing. Many devices for generating atmospheric pressure non-equilibrium plasma have been proposed so far (for example, Patent Documents 1 to 3).

International Publication No. 2008/072390 JP 2008-10373 A JP 2004-14494 A

  Factors for efficiently generating plasma at atmospheric pressure include high frequency power supply, steep voltage change, reduction of plasma region, and the like. In the conventional atmospheric pressure plasma generation apparatus, in order to generate plasma efficiently, generally, a high frequency power supply with a relatively complicated configuration (that is, an expensive) is used to achieve a high frequency power supply and a steep voltage change. Yes.

  Under such circumstances, there is a great demand for a power supply suitable for plasma generation and having a simpler configuration (that is, less expensive), but as a power supply for a plasma generator, a power supply that is simple in configuration and can generate plasma efficiently. Is not known so far.

  Therefore, the present invention provides a power source that has a simpler configuration than the prior art and that can efficiently generate plasma.

In order to solve the above-described problem, one aspect of the disclosed power source is a power source for supplying power to a plasma reactor as a load, and includes a step-up transformer, the step-up transformer, and the load. And a plurality of high voltage AC silicon diodes connected in series.

According to the aspect of the power supply according to the present disclosure, a step-up transformer (for example, a neon transformer) generates a high voltage from a commercial power supply having a low frequency of about several tens Hz and about 100 V to 200 V, and the generated high voltage In addition, waveform distortion (that is, high-frequency component) due to the non-linear characteristics of the high-voltage AC silicon diode can be applied. Thereby, a high voltage including a steep voltage change suitable for plasma generation can be obtained. Since the step-up transformer and the high-voltage AC silicon diode are both inexpensive and readily available, the power supply can be configured very simply. Experiments by the inventors have confirmed that a plasma jet can be generated efficiently using such a simple power source.

The schematic diagram which shows an example of the structure of the plasma production apparatus which concerns on embodiment The graph which shows an example of the voltage waveform and current waveform which concern on embodiment The graph which shows an example of the voltage waveform and current waveform which concern on embodiment The graph which shows an example of the voltage waveform and current waveform which concern on embodiment The graph which shows an example of the voltage waveform and current waveform which concern on embodiment The image which shows an example of the production | generation condition of Ar plasma jet which concerns on embodiment The graph which shows an example of the result of spectroscopic analysis of Ar plasma jet concerning an embodiment The graph which shows an example of the result of spectroscopic analysis of Ar plasma jet concerning an embodiment The image which shows an example of the production | generation state of He plasma jet which concerns on embodiment The graph which shows an example of the result of the spectroscopic analysis of He plasma jet concerning an embodiment The graph which shows an example of the result of the spectroscopic analysis of He plasma jet concerning an embodiment The graph which shows an example of the change of the surface temperature of the plasma irradiation object which concerns on embodiment The graph which shows an example of the change of the surface temperature of the plasma irradiation object which concerns on embodiment

One aspect of the disclosed power source is a power source for supplying power to a plasma reactor as a load, and includes a step-up transformer and a plurality of high voltages connected in series between the step-up transformer and the load. And an AC silicon diode .

According to this aspect, with a step-up transformer (for example, a neon transformer), a high voltage is generated from a commercial power source having a low frequency of about several tens Hz and about 100 V to 200 V, and the generated high voltage is used for high voltage AC. Waveform distortion (that is, high-frequency components) due to the nonlinear characteristics of the silicon diode can be given. Thereby, a high voltage including a steep voltage change suitable for plasma generation can be obtained. Since the step-up transformer and the high-voltage AC silicon diode are both inexpensive and readily available, the power supply can be configured very simply. Experiments by the inventors have confirmed that a plasma jet can be generated efficiently using such a simple power source.

The power supply may further include a switch for switching the number of high-voltage AC silicon diodes connected in series between the step-up transformer and the load.

According to this aspect, the emission intensity of plasma can be adjusted by switching the number of high-voltage AC silicon diodes .

Further, one aspect of the disclosed plasma generating apparatus, a step-up transformer, and the plasma reactor, and a plurality of high-voltage AC silicon diode connected in series between the step-up transformer and the plasma reactor The plasma reactor generates plasma using a high voltage supplied from the step-up transformer via the plurality of high-voltage AC silicon diodes . The plasma reactor is composed of a quartz tube, a gas introduction part that guides a source gas to the quartz tube, an internal electrode that is passed through the quartz tube, and an external electrode that covers the outer periphery of the quartz tube, Plasma may be generated by a dielectric barrier discharge generated by applying the high voltage between the internal electrode and the external electrode .

According to this aspect, it is possible to obtain a plasma generation apparatus that can efficiently generate plasma by using a simple power source including a step-up transformer and a high-voltage AC silicon diode .

  Hereinafter, a plasma generation apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  The embodiment described below shows a specific example of the present invention. Numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of constituent elements, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Embodiment)
FIG. 1 is a schematic diagram showing an example of the structure of a plasma generation apparatus according to an embodiment of the present invention.

  The plasma generation apparatus 1 includes a power supply 10 and a plasma reactor 20.

The power supply 10 is a power supply that generates a high voltage including a steep voltage change suitable for plasma generation from a commercial power supply 11, and includes a transformer 12 and a plurality of high-voltage AC silicon diodes 13. The plurality of high-voltage AC silicon diodes 13 are connected in series between the transformer 12 and the plasma reactor 20 as a load. Here, the transformer 12 is an example of a step-up transformer.

The power supply 10 may further include a switch 14 for switching the number of high-voltage AC silicon diodes 13 connected between the transformer 12 and the plasma reactor 20. The switch 14 may be capable of directly connecting the transformer 12 and the plasma reactor 20 without using the high-voltage AC silicon diode 13.

  The transformer 12 may be a neon transformer, for example. The neon transformer is a step-up transformer that is generally used to light a neon tube and is configured by using a porcelain leakage transformer or an inverter circuit. The input voltage is 100V or 200V, and the output voltage is 6000V to 15000V. There are such types. Neon transformers are usually available for several thousands to tens of thousands of yen.

As an example, SIDAC (Silicon Diode for Alternating Current) (registered trademark) may be used for the high-voltage AC silicon diode 13. SIDAC is a bidirectional voltage trigger type semiconductor element that is energized by applying a voltage that exceeds a specified threshold, and is widely used as a switch element or a pulse generation element. SIDAC is usually available for several hundred yen / piece.

  As an example, the plasma reactor 20 is a reactor that generates a plasma jet 32 from a source gas 31 by dielectric barrier discharge, and includes a gas introduction unit 21, a quartz tube 22, a bond 23, an internal electrode 24, and an external electrode 25. ing. For the source gas 31, for example, rare gases (Ar, He) are used.

  The gas introduction unit 21 is a member that guides the source gas 31 to the quartz tube 22, and is joined to the quartz tube 22 by an airtight bond 23.

  As an example, the quartz tube 22 has an outer diameter of 3.0 mm and an inner diameter of 1.6 mm.

  The internal electrode 24 is an electrode passed through the quartz tube 22 and may be, for example, a copper wire.

  The external electrode 25 is an electrode that covers the outer periphery of the quartz tube 22, and may be, for example, an aluminum foil.

  In the plasma generating apparatus 1 configured as described above, the source gas 31 is introduced from the gas introduction part 21 of the plasma reactor 20 into the quartz tube 22. Then, by applying a high voltage including a steep voltage change between the internal electrode 24 and the external electrode 25 from the power supply 10, the internal electrode 24 and the external electrode 25 in the source gas 31 in the quartz tube 22. A dielectric barrier discharge occurs between them and a plasma jet 32 is generated from the source gas 31.

  In the above, a plasma reactor that generates a plasma jet by dielectric barrier discharge has been illustrated. However, for example, an atmospheric pressure plasma generation apparatus that does not require the use of a rare gas or the like is known (for example, (Patent document 4: Japanese translations of PCT publication No. 2003-514114, Patent document 5: Japanese translations of PCT publication No. 2003-518317).

  In devices that generate plasma using a high voltage, not limited to dielectric barrier discharge, it is generally important to pulse the power supply, and changing the frequency is considered important for controlling plasma characteristics. ing. Therefore, according to the power source 10, for example, a plasma reactor that generates plasma using a high voltage in general is preferably driven widely without being limited by a specific plasma generation method such as dielectric barrier discharge. Can do.

  That is, the plasma reactor driven by the power supply 10 may use any plasma generation method such as dielectric barrier discharge or thermal plasma method, and can generate plasma in atmospheric pressure, reduced pressure, or water. It may be generated. Typically, a non-equilibrium atmospheric pressure plasma jet may be generated, such as the plasma reactor 20 described above.

  The inventors conducted an experiment in which a plasma jet was actually generated by the plasma generator 1 and irradiated on the object. Hereinafter, this experiment will be described in detail.

In this experiment, the secondary voltage of the transformer 12 is 40 kVpp, the frequency is 60 Hz, the gas type of the source gas 31 is Ar and He, and the flow rate is 4 slpm, and the secondary winding of the transformer 12 and the plasma reactor 20 When the number of high-voltage AC silicon diodes 13 connected in series between the internal electrodes 24 is four, 0, 10, 20, and 30, the gas type and the number of high-voltage AC silicon diodes 13 The plasma jet 32 was generated in the eight combinations. The generated plasma jet 32 was irradiated to pork that was supposed to be close to human skin.

2A to 2D are graphs showing examples of voltage waveforms and current waveforms according to the embodiment. 2A to 2D respectively show the case where the secondary winding of the transformer 12 and the internal electrode 24 of the plasma reactor 20 are directly connected (that is, zero high-voltage alternating current silicon diodes 13), and the secondary winding of the transformer 12. When 10, 20, and 30 high voltage AC silicon diodes 13 are connected in series between the line and the internal electrode 24 of the plasma reactor 20, the output voltage (upper stage) and output current (lower stage) of the power source 10 are Show.

By connecting a plurality of high-voltage alternating current silicon diodes 13 in series between the secondary winding of the transformer 12 and the internal electrode 24 of the plasma reactor 20, the voltage waveform is transformed into a stepped waveform, resulting in a current waveform. The result was that the number of appearing pulses increased.

This deformation of the waveform indicates that the high voltage generated by the transformer 12 is given waveform distortion (that is, a high frequency component) due to the non-linear characteristics of the high voltage AC silicon diode 13. As described above, the simple power source 10 including the transformer 12 and the plurality of high-voltage AC silicon diodes 13 can obtain a high voltage including a steep voltage change suitable for plasma generation from the commercial power source 11. It was confirmed.

FIG. 3 is an image showing an example of an Ar plasma jet generation state according to the embodiment. In the image, Ar plasma jets generated in accordance with the number of connected plasma reactors 20 before discharge and high voltage AC silicon diodes 13 are shown from the left.

4A and 4B are spectra showing an example of a result of spectral analysis of the Ar plasma jet according to the embodiment. 4A and 4B, the Ar plasma jet is observed at a point of 2 mm outward from the exit of the quartz tube 22 when the number of high voltage AC silicon diodes 13 connected is 0, 10, 20, and 30, respectively. A spectrum obtained by (spectral analysis) is shown. A hatched area is a spectrum when the high-voltage AC silicon diode 13 is not used (zero). 4A and 4B show that the use of the high-voltage alternating current silicon diode 13 increases the emission intensity of plasma (particularly the emission intensity derived from OH and Ar).

FIG. 5 is an image showing an example of the generation state of the He plasma jet according to the embodiment. In the image, from the left, a He plasma jet generated according to the number of connected plasma reactors 20 before discharge and high voltage AC silicon diodes 13 is shown. From FIG. 5, when the source gas is He, as the number of high voltage AC silicon diodes 13 is increased, a significant increase in light emission is recognized not only in the jet section but also between the internal electrode 24 and the external electrode 25. It is done.

6A and 6B are spectra showing an example of a result of spectral analysis of the He plasma jet according to the embodiment. 6A and 6B, the He plasma jet is observed at a point of 2 mm outward from the exit of the quartz tube 22 when the number of high voltage AC silicon diodes 13 connected is 0, 10, 20, and 30, respectively. A spectrum obtained by (spectral analysis) is shown. A hatched area is a spectrum when the high-voltage AC silicon diode 13 is not used (zero). 6A and 6B, as in the case of the Ar plasma jet, as the number of high voltage AC silicon diodes 13 connected is increased, the emission intensity of the plasma (particularly, emission intensity derived from N2, He, O) increases. I understand that.

7A and 7B are graphs showing an example of changes in the surface temperature of the plasma irradiation target according to the embodiment. For each of 0, 10, 20, and 30 high voltage AC silicon diodes 13 connected, Ar plasma jet (FIG. 7A) and He plasma jet (FIG. 7B) were continuously applied to the target pork for 600 seconds. The time change of the maximum temperature observed on the pork surface is shown.

From FIG. 7A, when the Ar plasma jet is irradiated, there is no significant difference in the temperature rise amount on the target surface according to the number of connected high-voltage AC silicon diodes 13. Further, from FIG. 7B, it is recognized that when the He plasma jet is irradiated, the temperature rise amount on the target surface tends to increase as the number of connected high-voltage AC silicon diodes 13 increases.

  Table 1 shows the average value of the target surface temperature between 500 seconds and 600 seconds.

From Table 1, the difference in the temperature rise due to the difference in the number of connected high voltage AC silicon diodes was hardly observed in the case of Ar, and a difference of about 3 ° C. was observed in the case of He.

  From this data, it was confirmed that the Ar plasma jet and He plasma jet generated by the plasma generator 1 can directly irradiate an object having a relatively small allowable thermal load.

As described above, the high voltage generated from the commercial power supply 11 by the power supply 10 constituted by the transformer 12 and the plurality of high voltage AC silicon diodes 13 is used, compared with the case where the high voltage AC silicon diode 13 is not used. It was also confirmed that a plasma jet with high emission intensity can be generated. The amount of increase in heat load received by the plasma jet irradiation object due to the use of the high-voltage alternating current silicon diode 13 is little or slight depending on the gas type.

  Therefore, the power supply 10 can provide a power supply that is suitable as a power supply for the plasma generation apparatus, has a simple configuration, and can generate plasma efficiently.

  While the plasma generation apparatus according to the aspect of the present invention has been described based on the embodiment, the present invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, one or more of the present invention may be applied to various modifications that can be conceived by those skilled in the art, or forms constructed by combining components in different embodiments. It may be included within the scope of the embodiments.

  For example, a plasma generation apparatus that generates plasma in a plurality of plasma reactors and irradiates the target can be considered. In such a plasma generation apparatus, a high voltage generated by a single power source may be branched and supplied to a plurality of plasma reactors. Such a plasma generation apparatus is suitable for processing a large area object.

  Moreover, you may provide the power supply of this invention separately in each of several plasma reactor. Even in such a case, since the individual power supplies are simply and inexpensively configured, a large increase in cost is unlikely to occur. In addition, since each plasma reactor can be independently driven by an individual power source, the controllability is good, and it is suitable for a plasma generation apparatus in a production facility, for example.

  The present invention can be used as a power source for a plasma generation apparatus. In particular, since a plasma can be efficiently generated by a simple and inexpensive power source, it has great applicability to widely spread a plasma generation apparatus in many application fields.

DESCRIPTION OF SYMBOLS 1 Plasma generator 10 Power supply 11 Commercial power supply 12 Transformer 13 High voltage alternating current silicon diode 14 Switch 20 Plasma reactor 21 Gas introduction part 22 Quartz tube 23 Bond 24 Internal electrode 25 External electrode 31 Source gas 32 Plasma jet

Claims (5)

A power source for supplying power to a plasma reactor as a load,
A step-up transformer,
A power supply comprising a plurality of high-voltage AC silicon diodes connected in series between the step-up transformer and the load. The power supply according to claim 1, further comprising a switch for switching the number of high-voltage AC silicon diodes connected in series between the step-up transformer and the load. The power supply according to claim 1, wherein the step-up transformer is a neon transformer. A step-up transformer,
A plasma reactor,
A plurality of high voltage alternating current silicon diodes connected in series between the step-up transformer and the plasma reactor ,
The plasma reactor generates plasma using a high voltage supplied from the step-up transformer via the plurality of high voltage alternating current silicon diodes . The plasma reactor is
A quartz tube,
A gas introduction part for introducing a source gas to the quartz tube;
An internal electrode passed through the quartz tube;
An external electrode covering the outer periphery of the quartz tube;
The plasma generation apparatus according to claim 4, wherein plasma is generated by dielectric barrier discharge generated by applying the high voltage between the internal electrode and the external electrode .