JP2016004728A - Plasma generator, plasma generating body and plasma generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma generator in which a cleaned object can be cleaned surely, while suppressing impairment thereof, and to provide a plasma generating body and a plasma generating method.SOLUTION: A plasma generator 1 includes an insulating tube 2a through which a gas flows, a first electrode 2c and a second electrode 2d for generating plasma in the tube 2a, and a voltage application unit 3 which applies a first pulse for generating plasma by causing dielectric breakdown, and a second pulse for maintaining the plasma thus generated, in combination, to the first electrode 2c and second electrode 2d.

Description

  The present invention relates to a plasma generator, a plasma generator, and a plasma generation method, and more particularly to a plasma generator, a plasma generator, and a plasma generation method for generating plasma under atmospheric pressure.

  Conventionally, a cleaning method using an organic solvent or the like has been employed for cleaning the end face of an optical fiber. In this cleaning method, an operator wipes and cleans the end face of the optical fiber with a cloth soaked in alcohol or a dedicated cleaner. This wiping and cleaning work is a work that cares for the operator because the end face of the optical fiber is as small as several millimeters (for example, 2.5 mm).

  On the other hand, a cleaning device using plasma is employed for cleaning glass substrates and the like. As this cleaning device, a cleaning device has been developed that generates plasma (atmospheric pressure plasma) under atmospheric pressure and removes contaminants (organic matter) attached to the surface of the glass substrate by the plasma. This cleaning apparatus is an apparatus that generates atmospheric pressure plasma by generating an electric field with a high voltage while flowing a gas such as nitrogen in a predetermined space.

JP 2009-187862 A

  However, in the above-mentioned wiping and cleaning by the worker, since the skill varies depending on the worker, the cleaning effect varies depending on the worker, and the cloth or cleaner directly touches the end surface of the optical fiber. It can be scratched. On the other hand, when cleaning is performed using the above-described plasma, plasma is generated under atmospheric pressure using a large power source (inverter power source) such as an output of 300 W, so that the capacity is large and the optical fiber is generated by the heat of the plasma. In some cases, the end surface of the substrate may be damaged (for example, heat deterioration). For this reason, there is a demand for reliably cleaning the cleaning object while suppressing damage to the cleaning object such as an optical fiber.

  The present invention has been made in view of the above, and an object thereof is to provide a plasma generator, a plasma generator, and a plasma generation method capable of reliably cleaning an object to be cleaned while suppressing damage to the object to be cleaned. Is to provide.

  The plasma generator according to the present invention has an insulating property, a tube through which a gas flows, a first electrode and a second electrode for generating an electric field in the tube, and a first electrode and a second electrode. On the other hand, a voltage applying unit that applies a combination of a first pulse that generates plasma by causing dielectric breakdown and a second pulse that maintains the generated plasma is provided.

  The plasma generator according to the present invention further includes a metal tube inserted into the tube, and the first electrode is separated from the metal tube to the upstream side in the gas flow direction, and the outer periphery of the tube. It is desirable that the second electrode is provided on the surface and connected to the metal tube.

  The plasma generator according to the present invention further includes a metal tube inserted into the tube, and the first electrode is separated from the metal tube to the upstream side in the gas flow direction, and the outer periphery of the tube. It is desirable that the second electrode is provided on the outer peripheral surface of the tube so as to be positioned so as to face the metal tube via the tube.

  The plasma generator according to the present invention has insulating properties, a tube through which a gas flows, a metal tube inserted into the tube, and is spaced from the metal tube to the upstream side in the gas flow direction. A first electrode provided on the surface; and a second electrode connected to the metal tube.

  The plasma generator according to the present invention has insulating properties, a tube through which a gas flows, a metal tube inserted into the tube, and is spaced from the metal tube to the upstream side in the gas flow direction. A first electrode provided on the surface; and a second electrode provided on the outer peripheral surface of the tube, positioned to face the metal tube via the tube.

  The plasma generation method according to the present invention is a first method of generating plasma by causing dielectric breakdown to the first electrode and the second electrode for generating an electric field in a tube having an insulating property and through which a gas flows. And a second pulse for maintaining the generated plasma are applied in combination.

  According to the plasma generator, the plasma generator, or the plasma generation method according to the present invention, the cleaning object can be reliably cleaned while suppressing damage to the cleaning object. Specifically, the first pulse and the second pulse are combined and applied to the first electrode and the second electrode, plasma is generated by the first pulse, and the generated plasma is maintained by the second pulse. Is done. This makes it possible to stably generate plasma using a smaller power source (pulse power source) than in the past. Furthermore, when removing the contaminants attached to the object to be cleaned (for example, an optical fiber) by this plasma, the operator only has to apply the plasma to the object to be cleaned, and it is not necessary to perform wiping and cleaning. For this reason, the cleaning object can be reliably cleaned regardless of the skill of each worker, and in addition, the cleaning object can be prevented from being damaged by the wiping cleaning. In addition, since a small power source is used and its capacity is small, it is possible to suppress damage to the cleaning object due to the heat of the plasma. In this way, the cleaning object can be reliably cleaned while suppressing damage to the cleaning object.

  The apparatus further includes a metal tube inserted into the tube, and the first electrode is provided on the outer peripheral surface of the tube, separated from the metal tube on the upstream side in the gas flow direction. However, when it is connected to a metal tube, a voltage is appropriately applied and a current flows appropriately in the tube. For this reason, the formation of plasma is promoted, and the emission intensity of plasma increases. That is, since the density of plasma becomes high, it is possible to obtain a desired high-density plasma, and the object to be cleaned can be more reliably cleaned.

  The apparatus further includes a metal tube inserted into the tube, and the first electrode is provided on the outer peripheral surface of the tube, separated from the metal tube on the upstream side in the gas flow direction. However, when the metal tube is positioned so as to face the metal tube through the tube and is provided on the outer peripheral surface of the tube, a capacitance is formed by the metal tube inside the tube and the second electrode outside the tube. When the applied pulse is a short pulse, a current path is easily formed, and the current flows appropriately in the tube. Thereby, the formation of plasma is promoted, and the emission intensity of plasma is increased. That is, since the density of plasma becomes high, it is possible to obtain a desired high-density plasma, and the object to be cleaned can be more reliably cleaned.

It is a figure which shows schematic structure of the plasma generator which concerns on embodiment of this invention. It is a figure which shows schematic structure of the plasma generator which concerns on embodiment of this invention. It is a graph which shows the waveform of the applied pulse voltage which concerns on embodiment of this invention. It is a figure which shows schematic structure of the modification of the plasma generator which concerns on embodiment of this invention.

  An embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a plasma generator 1 according to this embodiment includes a plasma generator 2 that generates plasma to be irradiated on an object to be cleaned (for example, an optical fiber), and a voltage applied to the plasma generator 2. And a control unit 4 that controls the voltage application unit 3.

  As shown in FIG. 2, the plasma generator 2 has a tube 2a through which a cleaning gas (gas) flows, a metal tube 2b existing at the tip of the tube 2a, and an electric field for generating an electric field in the tube 2a. A first electrode 2c and a second electrode 2d are provided, and a support plate 2e that supports the respective portions 2a, 2b, 2c, and 2d.

  The tube 2a is positioned in the center of the support plate 2e and is fixed on the support plate 2e having an insulating property. The tube 2a has an insulating property, and includes a first insertion port H1 into which the gas tube 11 is inserted and a second insertion port H2 into which the metal tube 2b is inserted. The gas is supplied from the gas tube 11 into the pipe 2a, and flows in the pipe 2a from the top to the bottom (in FIG. 2). For example, a glass tube can be used as the tube 2a. As the supply gas, for example, helium gas can be used, and the flow rate at the time of supply is constant at, for example, 5 l / min.

  The metal tube 2b is provided by being inserted into the second insertion port H2 of the tube 2a, and a part of the metal tube 2b protrudes from the tube 2a. The metal tube 2b has a discharge port H3 for discharging plasma generated at atmospheric pressure (atmospheric pressure plasma). The allowable dimension of the metal tube 2b is equal to the inner diameter of the tube 2a, and the metal tube 2b is in close contact with the inner wall of the tube 2a. As the metal tube 2b, for example, a copper tube can be used.

  The first electrode 2c is positioned on the right side (in FIG. 2) of the tube 2a on the support plate 2e, and is fixed on the support plate 2e. A part (arm part) of the first electrode 2c is spaced from the metal tube 2b protruding from the tip of the tube 2a to the upstream side in the gas flow direction, and is wound so as to be in close contact with the outer peripheral surface of the tube 2a. It is. One end of the first cable 12 is fixed and connected to the first electrode 2c by a first fixing member 13 such as a screw. The other end of the first cable 12 is connected to the ground, and the first electrode 2c is electrically grounded. As the first electrode 2c, for example, a copper plate electrode can be used.

  The second electrode 2d is positioned on the left side (in FIG. 2) of the tube 2a on the support plate 2e, and is fixed on the support plate 2e. A part (arm portion) of the second electrode 2d is wound so as to be in close contact with the outer peripheral surface of the metal tube 2b protruding from the tip of the tube 2a, and is connected to the metal tube 2b. One end of the second cable 14 is fixed and connected to the second electrode 2d by a second fixing member 15 such as a screw. The other end of the second cable 14 is connected to the voltage application unit 3, and the second electrode 2 d is electrically connected to the voltage application unit 3. For example, a copper plate electrode can be used as the second electrode 2d. The second electrode 2d is a negative electrode.

  Returning to FIG. 1, the voltage application unit 3 includes a high voltage pulse generator 3a that generates a high voltage pulse (high voltage pulse) and a low voltage pulse generator 3b that generates a low voltage pulse (low voltage pulse). The high-pressure pulse and the low-pressure pulse are combined and applied to the pair of electrodes 2c and 2d of the plasma generator 2.

  The high-pressure pulse generator 3a is a pulse generator that generates a high-pressure pulse (first pulse) that causes dielectric breakdown to generate plasma in the tube 2a, and functions as a first pulse generator. The high voltage pulse generator 3a transmits a synchronization signal to the low voltage pulse generator 3b.

  The low-pressure pulse generator 3b is a pulse generator that generates a low-pressure pulse (second pulse) that maintains the plasma generated in the tube 2a, and functions as a second pulse generator. The low-voltage pulse generator 3b can receive a synchronization signal from the high-voltage pulse generator 3a and can synchronize with the high-voltage pulse generator 3a based on the synchronization signal.

  The control unit 4 sets various conditions such as the period (frequency) and pulse width of both the high voltage pulse generator 3a and the low voltage pulse generator 3b, and controls the high voltage pulse generator 3a and the low voltage pulse generator 3b. For example, the control unit 4 sets various conditions such as the period and pulse width of the high-voltage pulse in the high-voltage pulse generator 3a according to the input operation of the operator to an input unit (not shown) such as a keyboard and a switch, Similarly, various conditions such as the period and pulse width of the low-pressure pulse in the low-pressure pulse generator 3b are set. For example, a computer or a function generator can be used as the control unit 4.

  The predetermined high-voltage pulse is generated by the high-pressure pulse generator 3a based on the various set conditions, and the predetermined low-pressure pulse is also generated by the low-pressure pulse generator 3b based on the various set conditions. These high-pressure pulse and low-pressure pulse are combined and applied to the pair of electrodes 2 c and 2 d of the plasma generator 2.

  For example, as shown in FIG. 3, a combined pulse (pulse voltage) obtained by combining a predetermined high voltage pulse A1 and a predetermined low voltage pulse A2 is applied to a pair of electrodes 2c and 2d of the plasma generator 2. Thereby, a high voltage (high voltage) and a low voltage (low voltage) are alternately applied to the pair of electrodes 2c and 2d at each predetermined time.

  Here, in FIG. 3, as an example, the high voltage of the high voltage pulse A1 is 15 kV, the high voltage pulse width is 200 ns, the high voltage pulse frequency is about 1 kHz, and the low voltage of the low voltage pulse A2 is 0.8 kV. The width (pulse width of the entire rectangular portion) is 0.5 ms, and the cycle of the low-pressure pulse A2 (cycle of the entire rectangular portion) is the same as the cycle of the high-pressure pulse. In the application of the low-pressure pulse A2, chopper control (ON / OFF control) is performed. The width of the rectangular wave by chopper control is 0.05 ms, the frequency of the rectangular wave (low-pressure pulse frequency) is 10 kHz, the maximum value of the rectangular wave is 0.8 kV, and the minimum value is 0.6 kV. According to this chopper control (chopping), it is possible to generate a fluctuating electric field in the tube 2a as compared with the case where the applied voltage is constant (constant electric field), so that the plasma generation and maintenance ability is improved. Can be made.

  In order to determine various conditions for obtaining a plasma having a desired emission intensity (desired density), for example, as described above, the high voltage pulse has a high voltage of 15 kV, a high voltage pulse width of 200 ns, and a high voltage pulse frequency of In a state where the low pressure pulse is fixed at 0.8 kV and the low pressure pulse is fixed at 0.8 kV, the control unit 4 adjusts the low pressure pulse width, the low pressure pulse frequency, etc., and various conditions when obtaining plasma with a desired emission intensity are obtained. Ask. These various conditions are set in the high voltage pulse generator 3a and the low voltage pulse generator 3b by the control unit 4 in accordance with an input operation of the operator to the input unit.

  Here, regarding the high voltage pulse and the low voltage pulse, for example, the high voltage is within the range of 10 to 20 kV, and the low voltage is 5 kV or less. As an example, the high voltage pulse frequency is 1 kHz or less, and the high voltage pulse width is 1/100 or less of the high voltage pulse period. The low pressure pulse frequency and the low pressure pulse width are determined according to the high pressure pulse frequency and the high pressure pulse width.

  Next, the plasma generation operation of the plasma generator 1 will be described.

  First, gas is supplied from the gas tube 11 into the tube 2a of the plasma generator 2 and flows through the tube 2a. In this gas supply state, the voltage application unit 3 generates a predetermined high voltage pulse by the high voltage pulse generator 3a, generates a predetermined low voltage pulse by the low voltage pulse generator 3b in synchronization with the high voltage pulse, The high-pressure pulse and the low-pressure pulse are applied to the pair of electrodes 2 c and 2 d of the plasma generator 2. Various conditions of the predetermined high-pressure pulse and the predetermined low-pressure pulse are set in advance by the control unit 4 as described above.

  When a high voltage of a high voltage pulse is applied to the pair of electrodes 2c and 2d, an electric field is generated between the electrodes 2c and 2d, and discharge starts due to dielectric breakdown to generate plasma. This plasma is emitted from the outlet H3 of the metal tube 2b protruding from the tip of the tube 2a, collides with other molecules in the atmosphere, and is excited, dissociated, and ionized. Next, following the high voltage of the high voltage pulse, the low voltage of the low voltage pulse is applied to the pair of electrodes 2c and 2d, and the plasma generated above (the plasma state in the tube 2a) is maintained. Thereafter, a high voltage of a high voltage pulse is again applied to the pair of electrodes 2c and 2d to generate plasma, and then a low voltage of a low voltage pulse is applied to the pair of electrodes 2c and 2d to maintain the plasma. The application of the high voltage and the low voltage is sequentially performed, and generation and maintenance of the plasma are repeated.

  When the plasma emitted from the discharge port H3 is irradiated onto the cleaning object, for example, the end face of the optical fiber, active species necessary for cleaning are efficiently supplied to the end face of the optical fiber, and the optical fiber. Contaminants (organic matter) adhering to the end face of the optical fiber are decomposed and completely removed from the end face of the optical fiber. At this time, the operator may hold the plasma generator 2 and apply plasma to the end face of the optical fiber, and it is not necessary to perform wiping and cleaning. For this reason, the end face of the optical fiber can be reliably cleaned regardless of the skill of each worker, and damage to the cleaning object due to wiping cleaning can be prevented. Further, the plasma generator 2 is as small as several centimeters to several tens of centimeters, and an operator can easily carry out the cleaning work by holding the plasma generator 2.

  Further, a high voltage pulse and a low voltage pulse are used in combination, and the generation of plasma by a high voltage and the maintenance of plasma by a low voltage are repeated. Thereby, it is possible to stably generate plasma while suppressing the applied voltage. Therefore, since it becomes possible to stably generate plasma using a small power supply (pulse power supply) of about 15 W without using a large power supply (inverter power supply) of about 300 W as in the prior art, its capacity is small, Damage to the end face of the optical fiber due to the heat of the plasma (for example, thermal degradation) can be suppressed, and energy saving can be realized.

  Further, by connecting the second electrode 2d to the metal tube 2b inserted at the tip of the tube 2a, a voltage is appropriately applied, and a current flows appropriately in the tube 2a. For this reason, the formation of plasma is promoted, and the emission intensity of plasma increases. That is, since the plasma density is increased, it is possible to obtain high-density plasma, and the end face of the optical fiber can be more reliably cleaned.

  Regarding the polarity of the electrode, the second electrode 2d is a negative electrode. When helium gas is used as the gas, some helium atoms are ionized and ionized at the start of discharge to generate electrons. Next, the generated electrons are accelerated in the direction opposite to the flow direction of the helium gas, and the helium ions are accelerated toward the negative electrode side. The generated electrons collide with helium atoms, and the helium atoms are ionized and ionized. At this time, ionization of helium atoms is promoted. Thereafter, since the generated helium ions have a large inertia, some helium ions are discharged from the outlet H3 of the metal tube 2b, collide with other molecules in the atmosphere, and are excited, dissociated, and ionized. Since such a phenomenon is repeated, the emission intensity of the plasma is increased compared to the case where the second electrode 2d is a positive electrode, and a desired high-density plasma can be obtained. It can be reliably cleaned.

  Next, a modification of the above-described plasma generator 2 will be described with reference to FIG.

  As shown in FIG. 4, in the modification, a part (arm part) of the second electrode 2d is positioned so as to face the metal tube 2b inserted at the tip of the tube 2a via the tube 2a. It is wound so as to be in close contact with the outer peripheral surface of the tube 2a. In this case, since a capacitance is formed by the metal tube 2b in the tube 2a and the second electrode 2d outside the tube 2a, a current path is likely to be formed when the applied pulse is a short pulse. The current flows appropriately in the tube 2a. Thereby, the formation of plasma is promoted, and the emission intensity is increased. That is, since the density of plasma becomes high, it is possible to obtain a desired high density plasma, and the end face of the optical fiber can be more reliably cleaned.

  In the above-described embodiment, the metal tube 2b is inserted into the second insertion port H2 of the tube 2a. However, the present invention is not limited to this, for example, the second insertion port H2 of the tube 2a. The metal tube 2b may not be provided. In this case, the second insertion port H2 functions as a discharge port for discharging plasma.

  In the above-described embodiment, the metal tube 2b is inserted into the second insertion port H2 so as to protrude from the second insertion port H2. However, the present invention is not limited to this. The metal tube 2b may be inserted into the second insertion port H2 so as not to protrude from the second insertion port H2.

  Finally, the above-described embodiments are illustrative, and the scope of the invention is not limited thereto. The above-described embodiment can be variously modified. For example, some components may be deleted from all the components shown in the above-described embodiment, and further, components according to different embodiments may be appropriately combined. Also good.

DESCRIPTION OF SYMBOLS 1 Plasma generator 2 Plasma generator 2a Tube 2b Metal tube 2c 1st electrode 2d 2nd electrode 2e Support plate 3 Voltage application part 3a High voltage pulse generator 3b Low voltage pulse generator 4 Control part 11 Gas tube 12 1st Cable 13 First fixing member 14 Second cable 15 Second fixing member A1 High pressure pulse A2 Low pressure pulse H1 First insertion port H2 Second insertion port H3 Discharge port

Claims (6)

A tube having an insulating property and flowing gas;
A first electrode and a second electrode for generating an electric field in the tube;
A voltage application unit configured to apply a combination of a first pulse for generating plasma by causing dielectric breakdown to the first electrode and the second electrode and a second pulse for maintaining the generated plasma;
A plasma generator characterized by comprising: Further comprising a metal tube provided inserted into the tube,
The first electrode is provided on the outer peripheral surface of the tube, separated from the metal tube on the upstream side in the gas flow direction,
The plasma generating apparatus according to claim 1, wherein the second electrode is connected to the metal tube. Further comprising a metal tube provided inserted into the tube,
The first electrode is provided on the outer peripheral surface of the tube, separated from the metal tube on the upstream side in the gas flow direction,
2. The plasma generating apparatus according to claim 1, wherein the second electrode is provided on an outer peripheral surface of the tube so as to be opposed to the metal tube via the tube. A tube having an insulating property and flowing gas;
A metal tube provided inserted into the tube;
A first electrode provided on the outer peripheral surface of the tube, spaced from the metal tube upstream in the gas flow direction;
A second electrode connected to the metal tube;
A plasma generator characterized by comprising: A tube having an insulating property and flowing gas;
A metal tube provided inserted into the tube;
A first electrode provided on the outer peripheral surface of the tube, spaced from the metal tube upstream in the gas flow direction;
A second electrode provided on the outer peripheral surface of the tube, positioned to face the metal tube via the tube;
A plasma generator characterized by comprising:   Maintaining the first pulse for generating plasma by generating dielectric breakdown and the generated plasma for the first electrode and the second electrode for generating an electric field in a tube through which gas flows with insulation A method for generating plasma, wherein the second pulses are applied in combination.

Images