Electromagnetic wave generation device and electromagnetic wave generation method

Abstract

An electromagnetic wave generation device (100) according to the present invention is provided with: a liquid (101) accommodated in a prescribed container (105); a bubble generation means (102) for generating bubbles B in the liquid (101); and a bubble charging means (103) for electrically charging the bubbles B. The bubble charging means (103) is composed of one needle-shaped electrode (108) and a potential control means (109) for controlling the potential of the electrode (108).

Description

Electromagnetic wave generating device and electromagnetic wave generating method

[0001] This application claims priority to Japanese Patent Application No. 2024-045410, filed on March 21, 2024, the contents of which are incorporated herein by reference.

[0002] A technology for generating X-rays using an X-ray tube is known. An X-ray tube has a vacuum structure containing a filament (cathode) that generates thermoelectrons and a metal plate (anode) that generates X-rays. The filament serves as an electron source, and the thermoelectrons generated from the filament are accelerated by an electric field and collided with the metal plate to generate X-rays. Braking X-rays can also be generated by attracting the thermoelectrons generated by the electron source to the nuclei of the anode and changing the direction of travel of the thermoelectrons. Generating X-rays using an X-ray tube requires the application of a high voltage of several tens of kV or more.

[0003] X-rays are emitted from an X-ray source (X-ray focus) of a certain size. For example, if the X-ray source is wide, the resolution of the contours in the projection image obtained by irradiating a sample with the X-ray source will be low. By reducing the size of the X-ray source, the resolution of the contours can be improved. Therefore, the smaller the size of the X-ray source, the more preferable it is. In recent years, X-ray micropoint sources using X-ray tubes have been developed, and there is a demand for electromagnetic wave generators that can generate electromagnetic waves of any wavelength and that are smaller and easier to operate. Patent Document 1 discloses a technology for an electromagnetic wave generator that irradiates ultrasonic waves into a liquid to generate cavitation, and then irradiates the cavitation with microwaves to generate ultraviolet rays.

[0004] Japanese Patent Application Laid-Open No. 2008-173521

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide an electromagnetic wave generating device that has a small electromagnetic wave generating source, is capable of operating at a low voltage, and is capable of generating electromagnetic waves of any wavelength, and an electromagnetic wave generating method using the electromagnetic wave generating device.

[0006] In order to solve the above problems, the present invention employs the following means.

[0007] (1) An electromagnetic wave generating device according to one aspect of the present invention comprises a liquid contained in a specified container, a bubble generating means for generating bubbles in the liquid, and a bubble charging means for charging the bubbles, wherein the bubble charging means is composed of a needle-shaped electrode and a potential control means for controlling the potential of the electrode.

[0008] (2) Another aspect of the present invention provides an electromagnetic wave generating device comprising a liquid contained in a specified container, a substrate placed in the liquid, a bubble generating means for generating bubbles in the liquid on one surface of the substrate, and a discharge means for discharging within the bubbles, wherein the discharge means is composed of a needle-shaped electrode and a potential control means for controlling the potential of the electrode.

[0009] (3) In the electromagnetic wave generator described in either (1) or (2) above, it is preferable that the electrical conductivity of the liquid is 1 mS / cm or less, and the pressure of the liquid is 1 atm or less.

[0010] (4) In the electromagnetic wave generator described in any one of (1) to (3) above, the electrodes are preferably made of a conductive material selected from the group consisting of tungsten, chromium, and copper.

[0011] (5) In the electromagnetic wave generating device described in any one of (1) to (4) above, the liquid may be composed of a first liquid that is present in the liquid and collects therein, and a second liquid that surrounds the first liquid, and the second liquid may have insulating properties.

[0012] (6) In the electromagnetic wave generating device described in any one of (1) to (5) above, the bubble generating means may be composed of a laser light source and an optical system that guides and focuses the laser light emitted from the laser light source into the liquid.

[0013] (7) In the electromagnetic wave generator described in any one of (1) to (6) above, the bubble generating means may be an ultrasonic generator.

[0014] (8) The electromagnetic wave generator according to any one of (1) to (7) above may further include an electromagnetic wave detector disposed outside the container.

[0015] (9) An electromagnetic wave generating method according to one aspect of the present invention is an electromagnetic wave generating method that generates electromagnetic waves using an electromagnetic wave generating device described in any one of (1), (3) to (8) above, and includes a bubble generating step of generating bubbles in the liquid using the bubble generating means, and a bubble charging step of charging the bubbles using the bubble charging means.

[0016] (10) In the electromagnetic wave generating method described in (9) above, it is preferable that in the bubble charging step, the bubble is charged when the radius of the expanding bubble becomes 90% or more of its maximum value.

[0017] (11) In the electromagnetic wave generating method described in either (9) or (10) above, after the bubble charging process, it is preferable to control the sign of the electrode potential to be the same as the charged charge of the bubble until the radius of the shrinking bubble becomes 10% or less of the maximum value.

[0018] (12) In the electromagnetic wave generating method described in any one of (9) to (11) above, it is preferable that after the bubble charging process, the potential of the electrode is controlled to become ground potential after the radius of the shrinking bubble becomes 10% or less of the maximum value.

[0019] (13) Another electromagnetic wave generating method according to one aspect of the present invention is an electromagnetic wave generating method that generates electromagnetic waves using an electromagnetic wave generating device described in any one of (2) to (8) above, and includes a bubble generating step of generating bubbles on one surface of the substrate in the liquid using the bubble generating means, and a discharge step of discharging toward the one surface of the substrate using the discharge means.

[0020] According to the present invention, it is possible to provide an electromagnetic wave generating device that has a small electromagnetic wave generating source, is capable of operating at a low voltage, and is capable of generating electromagnetic waves of any wavelength, and an electromagnetic wave generating method using the electromagnetic wave generating device.

[0021] 3B is an enlarged view of a partial area of ​​the electromagnetic wave generator of FIG. 3C. FIG. 3C is an enlarged view of a partial area of ​​the electromagnetic wave generator of FIG. 3A. FIG. 3C ... 1 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 1. FIG. 2 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 1. FIG. 3 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 1. FIG. 4 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 1. FIG. 5 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 1. FIG. 6 is a graph showing the results of an experimental analysis comparing the change in bubble diameter over time for Example 2 and Comparative Example 1. FIG. 7 is a graph showing the results of a theoretical analysis comparing the change in bubble diameter over time for Reference Examples 1 to 4. FIG. 8 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 3. FIG. 9 is an image of the periphery of a bubble during the process of generating electromagnetic waves in the electromagnetic wave generation method of Example 3.

[0022] Hereinafter, an electromagnetic wave generating device and an electromagnetic wave generating method according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic parts enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the present invention.

[0023] <First embodiment> [Electromagnetic wave generator] Fig. 1 is a diagram schematically showing the configuration of an electromagnetic wave generator 100 according to a first embodiment of the present invention. The electromagnetic wave generator 100 mainly includes a liquid 101, a bubble generating means 102, and a bubble electrifying means 103. The electromagnetic wave generator 100 may further include an electromagnetic wave detector 104. In this embodiment, when a bubble B is generated in the liquid 101 using the electromagnetic wave generator 100 and expanded, the interface of the bubble B is electrified.

[0024] The liquid 101 is contained in a predetermined container 105 and is made of an insulating material with extremely low electrical conductivity. Examples of insulating materials include water and insulating oils such as silicone oil. If the electrical conductivity of the liquid 101 is high, charged particles will leak from the charged bubbles B, making it difficult to maintain the charged state of the bubbles. From the viewpoint of not interfering with the expansion and contraction of the bubbles B generated in the liquid 101, it is preferable that the viscosity of the liquid 101 be low. Both the liquid 101 and the container 105 are made of materials that transmit the generated electromagnetic waves.

[0025] The pressure of the liquid 101 is preferably 1 atm or less so as not to prevent the generation of bubbles, and may be reduced to, for example, the saturated vapor pressure. For example, if the liquid 101 is water, the pressure can be reduced to about 2 kPa by adjusting the temperature. This pressure range of the liquid 101 is preferably achieved at room temperature (about 25 to 30°C), but may also be achieved by adjusting the temperature of the liquid 101.

[0026] The bubble generating means 102 is not particularly limited as long as it is a means (device) capable of generating bubbles B in the liquid 101, and examples thereof include a laser irradiation device (mechanism) and an ultrasonic generator (mechanism). The laser irradiation device generates bubbles by irradiating the liquid 101 with a laser. The ultrasonic generator generates bubbles by applying ultrasonic waves to the liquid 101.

[0027] Here, an example will be given in which a laser irradiation device 102A is used as the bubble generating means 102. The laser irradiation device 102A includes at least a laser light source 106. The type of the laser light source 106 is not particularly limited. Furthermore, the laser irradiation device 102A may include an optical system 107 (mirrors, lenses, etc.) as needed, which guides the laser L emitted from the laser light source 106 into the liquid 101 and focuses it at a predetermined position (here, the center) in the liquid 101.

[0028] The bubble charging means 103 is mainly composed of one needle-shaped electrode 108 and a potential control means 109 that controls the potential of the electrode 108. The needle-shaped electrode 108 extends in one direction, and at least one tip 108a of the electrode 108 is sharpened so as to concentrate the electric field. From the viewpoint of emitting electrons, the angle (point angle) of the electrode tip 108a is preferably as small as possible. However, if the electrode tip 108a is too thin, the effect of erosion increases, so the angle of the tip 108a must be selected taking into consideration the operating voltage, frequency of use, etc.

[0029] In this embodiment, electromagnetic waves are generated by causing charged particles (electrons, negative ions, or positive ions) that charge the bubble B (interface) to collide with an electrode 108 made of a conductive material such as metal. Therefore, the material of the electrode 108 is appropriately selected depending on the wavelength of the electromagnetic waves to be generated. For example, when generating X-rays, the material of the electrode 108 is preferably a conductive material such as tungsten, chromium, or copper.

[0030] In either case, from a practical standpoint, electrons are preferred as the charged particles that charge the bubbles B. When electrons are used as the charged particles, the bubbles B can be charged by utilizing a discharge phenomenon, as will be described later. If there is a method for charging the bubbles B other than discharge, that method may be used, or if possible, the charged particles may be replaced with particles other than electrons.

[0031] The potential control means 109 is connected to the electrode 108 and is a device that controls the magnitude, sign, etc. of the potential of the electrode 108. The sign of the potential controlled by the potential control means 109 differs depending on whether the sign of the charged particles at the interface of the bubble B is positive or negative.

[0032] In the electromagnetic wave generating device 100 of this embodiment, electromagnetic waves E (E1) are generated when charged particles supplied into the bubble B collide with the electrode 108. The electromagnetic wave detector 104 is a device (camera, imaging device, sensor, etc.) that detects the electromagnetic waves E, and is disposed outside the container 105.

[0033] 2A to 2C and 3A to 3C are diagrams illustrating the steps of an electromagnetic wave generation method using the electromagnetic wave generator 100 of this embodiment. The electromagnetic wave generation method mainly includes a bubble generation step and a bubble charging step. The electromagnetic wave generation method may further include an electromagnetic wave detection step after the bubble charging step.

[0034] 2A, a laser beam L is irradiated into the liquid 101 using the bubble generating means 102. The liquid in the irradiated region R1 becomes hot (preferably about 10,000 K or higher) and evaporates.

[0035] 2B , a bubble B is formed in region R1 after evaporation of liquid 101. The air in bubble B has high thermal energy. Therefore, a high pressure P is applied from the inside to the outside to the interface of bubble B (hereinafter referred to as bubble interface B1), causing bubble B to expand.

[0036] (Bubble Charging Process) Next, charged particles (electrons, negative ions, or positive ions) are supplied into the bubble B to charge the bubble B (bubble interface B1). In this embodiment, a voltage V is applied to the electrode 108, and a discharge is generated at the tip 108a of the electrode as shown in FIG. 2C to supply electrons C into the bubble B. At this time, the tip 108a of the electrode is inserted into the expanded bubble B. Note that the tip 108a of the electrode may be positioned in advance at a position where the bubble B will be formed, as shown in FIGS. 2A to 2C, or may be inserted into the bubble B after the bubble B is formed.

[0037] From the viewpoint of supplying a large number of charged particles to the interior of bubble B, it is preferable that bubble B is larger when generating a discharge. When the inertial force of the liquid acting outward around bubble B as bubble B expands and the pressure around the bubble become balanced, bubble B stops expanding. The pressure inside bubble B becomes much smaller than the pressure of the surrounding liquid 101, and it is thought that the internal pressure of bubble B at its maximum diameter is saturated vapor pressure. After bubble B stops expanding, it begins to contract due to the difference between the ambient pressure and the internal pressure of bubble B. Even if the pressure inside bubble B becomes greater than the pressure of the liquid 101, bubble B continues to contract due to the inertial force of the liquid 101 around bubble B, which is moving in the direction of contraction.

[0038] This contraction continues until the inertial force and the pressure inside bubble B are balanced, resulting in an extremely high pressure inside bubble B when it collapses. When bubble B stops expanding, the radius (bubble diameter) of bubble B reaches its maximum value. It is preferable to charge bubble B when the radius of the expanding bubble B approaches this maximum value, more specifically, when it reaches 90% or more of the maximum value, and it is most preferable to charge bubble B when it reaches its maximum value.

[0039] After electrons are supplied by the discharge, the supplied electrons C are distributed at the bubble interface B1, as shown in Fig. 3A. Then, as the bubble B contracts, the electron density within the bubble B increases, and the electric field becomes stronger, resulting in the generation of streamers S around the bubble B, as shown in Fig. 3B. The generation of streamers S can be confirmed in photographs, etc., and is evidence that a high electric field is formed within the contracting bubble B.

[0040] Figure 4 is an enlarged view of region R2 in Figure 3A. Figure 5 is an enlarged view of region R3 in Figure 3B. After the bubble charging step, until the shrinking bubble B collapses, preferably until the radius of the shrinking bubble B becomes 10% or less of its maximum value, the potential of the electrode 108 is controlled using the potential control means 109 so that the sign of the potential is the same as the bubble potential due to the charge of the bubble B. In this embodiment, the charge is negatively charged electrons, and the bubble potential is negative, so the electrode potential is controlled to be a negative potential (V<0). Note that if the charge is positively charged ions and the bubble potential is positive, it is preferable that the electrode potential also be positive.

[0041] By performing such potential control, the charged charges are less likely to approach the electrode 108, and therefore it is possible to prevent the charged charges from colliding with the electrode 108 before a high electric field is created inside the bubble B. From the viewpoint of stable potential control, it is preferable that the absolute value of the potential of the electrode 108 is larger than the absolute value of the bubble potential.

[0042] Eventually, bubble B shrinks until its radius is about 10 μm, and enters a high-pressure state (collapsed state). At this time, the electric charge becomes denser, greatly increasing the electric field from the bubble interface B1 toward the central electrode 108, generating a high electric field within bubble B. Electrons accelerated by the high electric field and gaining high energy collide with the tip 108a of electrode 108, generating electromagnetic waves E as shown in FIG. 3C . The type of electromagnetic waves E generated is determined primarily by the material of electrode 108.

[0043] Fig. 6 is an enlarged view of region R4 in Fig. 3C. After the bubble charging step, once the shrinking bubble B has collapsed, preferably once the radius of the shrinking bubble B has become 10% or less of its maximum value, the potential of the electrode 108 is controlled to the ground potential (V = 0) using the potential control means 109.

[0044] By performing such potential control, the bubble potential becomes higher than the potential of the electrode 108. As a result, an extremely high electric field is generated between the bubble interface B1 and the electrode 108. Electromagnetic waves E can be generated by causing charged charges C (electrons in this case) accelerated by a high electric field to collide with the electrode 108. When generating electromagnetic waves E by causing electrons to collide with a metal member, it is generally necessary to apply a voltage of approximately several tens of kV to accelerate the electrons. In contrast, in this embodiment, the same effect can be achieved by simply applying a voltage of approximately several kV associated with discharge into the bubble B.

[0045] 7 is a diagram illustrating the change in bubble diameter (bubble radius) and bubble potential over time. As described above, bubble B repeatedly changes over time from the time of its generation, expanding, contracting, collapsing, re-expanding, and so on. Immediately after bubble B is generated, the bubble diameter increases sharply with time. As the bubble diameter approaches its maximum diameter, the change in the bubble diameter over time becomes more gradual. Thereafter, the bubble diameter decreases more gradual with time. The change in the bubble diameter over time becomes more abrupt immediately before bubble B collapses.

[0046] The bubble potential is almost constant until the bubble enters the collapse process, but once the collapse process begins, it increases rapidly, generating an extremely high electric field between the bubble interface B1 and the electrode 108. Electromagnetic waves E can be generated by causing the charged charge C accelerated by this high electric field to collide with the electrode 108.

[0047] The generated electromagnetic waves E spread radially from the vicinity of the tip 108a of the electrode 108. Therefore, as shown in FIG. 1 , the generated electromagnetic waves E can be detected by using an electromagnetic wave detector 104 disposed outside the container 105, for example.

[0048] As described above, the electromagnetic wave generator 100 of this embodiment utilizes the shrinkage phenomenon of electrically charged bubbles to create a high density of electrons and a high electric field within the bubbles. This allows sufficiently accelerated electrons to collide with the electrode 108, eliminating the need for external application of an acceleration voltage, making it possible to generate electromagnetic waves E through low-voltage operation such as discharge. For example, while conventional methods require the application of a voltage of 10 kV or more to generate X-rays, this embodiment allows the applied voltage to be reduced to around several kV.

[0049] Furthermore, the electromagnetic wave generator 100 of this embodiment can generate electromagnetic waves E from collapsed bubbles B whose radius shrinks to 10 μm or less, or to 1 / 100 (one hundredth) of the maximum diameter, thereby realizing a minimized electromagnetic wave source (micropoint source). As a result, it becomes possible to obtain high-resolution images from the generated electromagnetic waves. Miniaturization of the electromagnetic wave source also enables the electromagnetic wave generator 100 itself to be miniaturized.

[0050] Furthermore, in the electromagnetic wave generator 100 of this embodiment, by selecting the material of the electrodes 108, the voltage V to be applied to the electrodes 108, and the like, it is possible to generate electromagnetic waves of any wavelength.

[0051] Second Embodiment FIG. 8 is a diagram schematically illustrating the configuration of an electromagnetic wave generator 200 according to a second embodiment of the present invention. The liquid 101 is composed of a first liquid 110 that gathers and exists (floats) in a substantially spherical region R5 in the liquid 101, and a second liquid 111 that surrounds the first liquid 110. Bubbles B are generated in the region R5 where the first liquid 110 exists. The electromagnetic wave generator 200 may also include a droplet injection means 112 that injects droplets of the first liquid 110 into the liquid 101. The other components are similar to those of the electromagnetic wave generator 100 of the first embodiment, and at least achieve the same effects as those of the electromagnetic wave generator 100 of the first embodiment. The same reference numerals are used for components similar to those of the first embodiment.

[0052] A low-viscosity liquid such as water can be used as first liquid 110. An insulating liquid (e.g., insulating oil) such as silicone can be used as second liquid 111. The volume of region R5 where first liquid 110 exists is preferably smaller than the volume of bubble B at its maximum expansion.

[0053] In this embodiment, by irradiating the laser L onto the region R5 of the low-viscosity first liquid 110, it is possible to easily generate, expand, and contract the bubbles B and reduce the minimum diameter of the bubbles during contraction, compared to when a high-viscosity insulating liquid is used. Furthermore, because the region R5 of the first liquid 110 is surrounded by the second liquid 111, it is possible to prevent the charge on the bubble interface B1 from passing through the region R5 and leaking to the outside.

[0054] <Third embodiment> [Electromagnetic wave generator] Figure 9 is a diagram schematically showing the configuration of an electromagnetic wave generator 300 according to a third embodiment of the present invention. The electromagnetic wave generator 300 mainly includes a liquid 101, a substrate 113, a bubble generating means 102, and a discharge means 114. The discharge means 114 has a configuration similar to that of the bubble charging means 103 of the first embodiment. The configuration of the electromagnetic wave generator 300 is similar to that of the electromagnetic wave generator 100 of the first embodiment, except that it includes the substrate 113. The same reference numerals as in the first embodiment are used for components similar to or corresponding to those in the first embodiment.

[0055] The substrate 113 has a flat main surface 113a and is composed of elements that generate electromagnetic waves such as X-rays when struck by electrons, charged particles, etc., such as metal elements such as Cr, Cu, and W. The constituent elements of the substrate 113 are selected taking into consideration the energy of the electromagnetic waves to be generated. The thickness of the substrate 113 is preferably about 0.1 mm to 10 mm. When the energy of X-rays is high, it is preferable to make the substrate thick enough to prevent them from passing through.

[0056] The substrate 113 is disposed such that one surface (one main surface) 113a faces both the bubble generation means 102 and the discharge means 114. For example, the orientation of the surface 113a is adjusted so that the laser irradiated by the bubble generation means 102 can be focused on the surface 113a and so that electrons generated by the discharge means 114 can be collided with the surface 113a. The orientation of the surface 113a may be adjusted so that the surface faces only the bubble generation means 102 during bubble generation and only the discharge means 114 during discharge. In this case, the adjustment of the orientation of the surface 113a may be performed manually or by using a predetermined adjustment means (adjustment device).

[0057] 10A to 10C are diagrams illustrating the steps of an electromagnetic wave generation method using the electromagnetic wave generator 300 of this embodiment. The electromagnetic wave generation method mainly includes a bubble generation step and a discharge step. After the discharge step, the method may further include an electromagnetic wave detection step.

[0058] 10A, a laser beam L is irradiated onto one surface 113a of the substrate in the liquid 101 using the bubble generating means 102. The liquid in the region R6 near the irradiated surface 113a becomes hot (preferably about 10,000 K or higher) and evaporates.

[0059] 10B, a bubble B is formed in region R6 after evaporation of liquid 101. The air in bubble B has high thermal energy. Therefore, a high pressure P is applied from the inside to the outside to the interface of bubble B (hereinafter referred to as bubble interface B1), causing bubble B to expand.

[0060] (Discharge Process) When the bubble B reaches its maximum, a voltage V is applied to the electrode 108, causing a discharge at the tip 108a of the electrode as shown in Fig. 10C, and electrons C are caused to collide with one surface 113a of the substrate. During the discharge, the tip 108a of the electrode is inserted into the expanding bubble B. Note that the tip 108a of the electrode may be positioned in advance at a position where the bubble B will be formed, as shown in Figs. 10A to 10C, or may be inserted into the bubble B after the bubble B has been formed.

[0061] Because the inside of the bubble B has a high degree of vacuum, a high electric field is generated, which accelerates the electrons C due to the discharge, causing the high-energy electrons C to collide with the substrate 113. This collision causes electromagnetic waves E (E2) to be generated from one surface 113a of the substrate. The type of electromagnetic waves E generated varies depending on the constituent material of the substrate 113. For example, if the substrate 113 is made of metal, X-rays can be generated.

[0062] The degree of vacuum inside the bubble B is determined by the pressure of the liquid 101. The smaller the pressure of the liquid 101, the smaller the pressure inside the bubble B, and the higher the degree of vacuum can be, thereby increasing the acceleration of the electrons C.

[0063] As described above, the electromagnetic wave generator 300 of this embodiment enables discharge in a space with an increased degree of vacuum, and electrons generated by the discharge can be strongly accelerated. Therefore, high-energy electrons can be collided with a substrate, and electromagnetic waves can be generated from the substrate with high efficiency. Furthermore, like the electromagnetic wave generator 100 of the first embodiment, the electromagnetic wave generator 300 of this embodiment does not require the application of an external acceleration voltage, and therefore can generate electromagnetic waves E through low-voltage operation such as discharge. Furthermore, like the electromagnetic wave generator 100, the electromagnetic wave generator 300 of this embodiment can realize a minimized electromagnetic wave source (micropoint source), and the electromagnetic wave generator 300 itself can be miniaturized.

[0064] The effects of the present invention will be more clearly understood from the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0065] Example 1 X-rays were generated using the electromagnetic wave generator and electromagnetic wave generation method of the above embodiment. An insulating oil containing silicone oil as its main component was used as the liquid. A laser irradiation device (nanopulse laser) was used as the bubble generating means, and a laser was irradiated into the liquid, generating bubbles from a high-temperature point of approximately 10,000 K. An electrode containing tungsten as its main component and with a tip radius of approximately 15 μm was used. When the bubble reached its maximum diameter, a discharge was generated within the bubble. The discharge voltage was ±5 kV to ±30 kV, and the voltage application time was 100 ns to 1 ms.

[0066] Figures 11A to 11F show images of the area around the tip of the electrode at each stage of the electromagnetic wave generation method. The images in Figures 11A to 11F were taken when the elapsed time t from the time the laser was focused was 0 μs, 11 μs, 38 μs, 65 μs, 77 μs, and 97 μs, respectively. The bubble reached its maximum diameter 38 μs after its generation (Figure 11C). When a discharge was generated for the maximum-diameter bubble, streamers appeared 27 μs later, indicating a high electric field inside the bubble. In Figure 11D, the protrusions indicated by the arrows indicate streamers. 39 μs after the start of discharge, the bubble collapsed (Figure 11E). 20 μs after the collapse, the bubble began to re-expand (Figure 11F).

[0067] (Example 2, Comparative Example 1) Using the same electromagnetic wave generation method as in Example 1, an experimental analysis was conducted to compare the change in bubble diameter over time between when discharge was applied to the bubbles (Example 2) and when no discharge was applied (Comparative Example 1). Figure 12 is a graph showing the results. The horizontal axis of the graph represents the time elapsed since the bubbles were generated. The vertical axis of the graph represents the bubble diameter normalized by the maximum diameter (bubble diameter at maximum expansion).

[0068] (Reference Examples 1 to 4) The charge amount Q of the bubbles is 3×10 －８ When C is used (Reference Example 1), 3 × 10 －９ When C is used (Reference Example 2), 3 × 10 －１０A theoretical analysis was performed to compare the change in bubble diameter over time between the case of 0 C (Reference Example 3) and the case of 0 C (no charge) (Reference Example 4). Figure 13 is a graph showing the results. The horizontal axis of the graph represents the elapsed time since the bubbles were generated. The vertical axis of the graph represents the bubble diameter (mm).

[0069] The results of Figure 12 show that when discharge is performed on bubbles, the bubble diameter upon re-expansion tends to be larger than when discharge is not performed. On the other hand, the results of Figure 13 show that the larger the charge amount of the bubbles, the larger the pore diameter upon re-expansion tends to be. From the trends seen in Figure 13, it is believed that the result of Example 2 in which the bubble diameter upon re-expansion increases due to discharge is due to the increase in the charge amount of the bubbles caused by discharge. In other words, it is clear that discharging the bubbles causes them to become electrically charged. Therefore, as described in the above embodiment, it is believed that when the bubbles contract, the charged charges become denser and a high electric field is generated.

[0070] Example 3: Using the electromagnetic wave generator and electromagnetic wave generation method shown in Fig. 9, high-energy discharge was performed to generate X-rays. The substrate 113 was mainly made of stainless steel. The other components and conditions of use, such as the liquid 101, bubble generating means, and discharge means (bubble charging means) 114, were the same as in Example 1.

[0071] 14A to 14C are images of the area around the tip of the needle electrode 108 at each stage of the electromagnetic wave generation method. The images in Figures 14A to 14C were taken when the elapsed time from the time the laser was focused was 2 μs (immediately after convergence), 100 μs, and 146 μs, respectively.

[0072] Bubble B reached nearly its maximum diameter approximately 146 μs after its generation ( FIG. 14B ). At this time, a voltage of 10 kV was applied to needle electrode 108, causing a discharge from the tip of needle electrode 108 into bubble B. Approximately 46 μs after the start of the discharge, bubble B collapsed, and a new discharge was generated toward substrate 113 ( FIG. 14C ). The discharge voltage was 45 kV. The distance from the position where bubble B collapsed to substrate 113 was approximately 906 μm.

[0073] These results show that, according to the present invention, it is possible to output a high discharge voltage exceeding the input voltage by utilizing the space inside bubble B, which has an increased degree of vacuum. It is believed that it is possible to generate electromagnetic waves such as X-rays by colliding electrons accelerated by this discharge voltage with a metal (alloy) substrate.

[0074] The present invention can be used in a wide range of technical fields, such as next-generation cancer treatment methods that introduce micro-X-ray sources into living bodies, development of observation devices for biological tissues and cells using soft X-rays, taking ultra-high resolution X-ray images, and home health checkup devices.

[0075] 100, 200 Electromagnetic wave generator 101 Liquid 102 Bubble generating means 102A Laser irradiation device 103 Bubble charging means 104 Electromagnetic wave detector 105 Container 106 Laser light source 107 Optical system 108 Electrode 108a Electrode tip 109 Potential control means 110 First liquid 111 Second liquid 112 Droplet injection means 113 Substrate 114 Discharge means B Bubble B1 Bubble interface C Electron E Electromagnetic wave L Laser P Pressure R1, R2, R3, R4, R5 Region

Claims

1. An electromagnetic wave generating device comprising: a liquid contained in a specified container; a bubble generating means for generating bubbles in the liquid; and a bubble charging means for charging the bubbles, wherein the bubble charging means is composed of a single needle-shaped electrode and a potential control means for controlling the potential of the electrode.

2. An electromagnetic wave generating device comprising: a liquid contained in a specified container; a substrate placed in said liquid; bubble generating means for generating bubbles in said liquid on one surface of said substrate; and discharge means for discharging within said bubbles, wherein said discharge means is composed of a single needle-shaped electrode and potential control means for controlling the potential of said electrode.

3. An electromagnetic wave generating device according to claim 1 or 2, characterized in that the electrical conductivity of said liquid is 1 mS / cm or less and the pressure of said liquid is 1 atm or less.

4. The electromagnetic wave generating device according to claim 1 or 2, wherein the electrodes are made of a conductive material selected from the group consisting of tungsten, chromium, and copper.

5. An electromagnetic wave generating device as described in either 1 or 2, characterized in that the liquid is composed of a first liquid that is present in a concentrated state within the liquid and a second liquid that surrounds the first liquid, and the second liquid has insulating properties.

6. An electromagnetic wave generating device as described in either claim 1 or 2, characterized in that the bubble generating means is composed of a laser light source and an optical system that guides and focuses the laser light emitted from the laser light source into the liquid.

7. An electromagnetic wave generating device according to claim 1 or 2, wherein the bubble generating means is an ultrasonic wave generating device.

8. An electromagnetic wave generating device according to claim 1 or 2, further comprising an electromagnetic wave detector disposed outside the container.

9. An electromagnetic wave generating method for generating electromagnetic waves using the electromagnetic wave generating device described in claim 1, characterized in that it comprises: a bubble generating step for generating bubbles in the liquid using the bubble generating means; and a bubble charging step for charging the bubbles using the bubble charging means.

10. The electromagnetic wave generating method according to claim 9, characterized in that in the bubble charging step, the bubble is charged when the radius of the expanding bubble reaches 90% or more of its maximum value.

11. An electromagnetic wave generating method as described in claim 10, characterized in that after the bubble charging process, the sign of the potential of the electrode is controlled to be the same as the sign of the charged charge of the bubble until the radius of the shrinking bubble becomes 10% or less of the maximum value.

12. The electromagnetic wave generating method described in claim 10, characterized in that after the bubble charging process, the potential of the electrode is controlled to become ground potential after the radius of the shrinking bubble becomes 10% or less of the maximum value.

13. An electromagnetic wave generating method for generating electromagnetic waves using the electromagnetic wave generating device described in claim 2, characterized by comprising: a bubble generating step of generating bubbles on one surface of the substrate in the liquid using the bubble generating means; and a discharge step of discharging toward the one surface of the substrate using the discharge means.

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