JP2015125906A - X-ray generator and X-ray imaging system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable X-ray generator in which bubbles generated in insulation oil provided for cooling are reliably captured and which has high heat dissipation properties and high pressure resistant performance.SOLUTION: In an X-ray generator including a bubble chamber for reserving bubbles in insulation oil, at the inside of a housing container, the inner surface of the bubble chamber has a region having a larger contact angle with the insulation oil than the inner surface of the housing container at the outside of the bubble chamber.

Description

  The present invention relates to an X-ray generator that emits X-rays emitted from an X-ray generator tube to a subject, and an X-ray imaging system that detects X-rays passing through the subject with an X-ray detector.

  As an X-ray generator that generates X-rays by irradiating a target with an electron beam bundle emitted from an electron source, an X-ray generator provided with an X-ray generator tube is known.

  The X-ray generator operates by applying a tube voltage of 30 kV or more and 150 kV between the anode and the cathode. In addition, the X-ray generation efficiency of a target that generates X-rays by electron irradiation is as low as 1% or less, and most of the kinetic energy of electrons is converted into thermal energy, leading to an increase in the temperature of the X-ray generation tube.

  An X-ray generating tube to which a tube voltage is applied during operation is accommodated in a metal container from the viewpoint of protecting an operator and shielding leaked X-rays. The storage container is filled with insulating oil for the purpose of suppressing discharge between the X-ray generation tube and the storage container and further cooling the X-ray generation tube. The insulating oil is stored in the storage container together with the X-ray generation tube so as to come into contact with the inner surface of the storage container and the outer surface of the X-ray generation tube. Heat is transferred to

  The X-ray generator is a gas dissolved in insulating oil as a result of heat generated by the X-ray generating tube, gas obtained by thermally decomposing the insulating oil, and residual gas that could not be purged when the storage container was sealed. In some cases, bubbles may be generated.

  In the X-ray generator, heat transfer is limited at a portion in contact with the generated bubbles. In addition, the generated bubbles move without being stationary in the storage container due to the convection of the insulating oil, the attitude of the radiation generator, and the like, which has been a problem from the viewpoint of suppressing discharge and reducing the cooling performance.

  In an X-ray generator, it is known to provide a bubble chamber for introducing and retaining bubbles in a predetermined region. Patent Document 1 discloses providing a bubble chamber in a storage container as a structure for capturing bubbles generated in insulating oil of an X-ray generator. Patent Document 1 further discloses that by providing a protrusion at the opening of the bubble chamber, it is difficult for the trapped bubbles to escape from the bubble chamber even when the posture of the X-ray generator is changed. ing.

JP2013-149368

  Even in the X-ray generation apparatus provided with the bubble chamber as in Patent Document 1, there are cases where the trapped bubbles cannot be stably retained.

  It is an object of the present invention to provide a highly reliable X-ray generator that makes it difficult to escape air bubbles trapped in a bubble chamber, stabilizes the cooling action and discharge suppressing action of insulating oil. Moreover, it aims at providing the X-ray imaging system which can image | photograph an X-ray imaging image with a high SN ratio stably.

The present invention is an X-ray generator having an X-ray generator tube and insulating oil, and a storage container for storing the X-ray generator tube and the insulating oil,
The storage container has a main chamber for storing the X-ray generation tube, and a bubble chamber having an interior communicating with the interior of the main chamber through an opening,
In the contact angle with the insulating oil, the inner surface of the bubble chamber has a region exhibiting a larger contact angle than the inner surface of the main chamber.

  According to the present invention, the bubble chamber has a region on the inner surface that exhibits a high contact angle with the insulating oil, thereby improving the adhesion of the trapped bubbles to the inner surface of the bubble chamber and the escape of the bubbles trapped in the bubble chamber. Can be suppressed. Thereby, it becomes possible to stabilize the cooling action and the discharge suppressing action of the insulating oil, and to provide a highly reliable X-ray generator.

It is a cross-sectional schematic diagram which shows embodiment (a) and the operation state (b) of the X-ray generator of this invention. 1 is a schematic configuration diagram showing an embodiment of an X-ray imaging system to which an X-ray generator of the present invention is applied. 1 is a schematic configuration diagram showing an embodiment of an X-ray imaging system having a mechanism for rotating an X-ray generator of the present invention. It is a flowchart in tomography by the X-ray imaging system of this invention. It is a schematic diagram explaining the effect of the X-ray generator of this invention. It is a cross-sectional schematic diagram which shows the relationship between a bubble chamber and a bubble accompanying the attitude | position change of the X-ray generator of this invention. It is a cross-sectional schematic diagram which shows other embodiment (a), (b) of the X-ray generator of this invention.

  The X-ray generator and X-ray imaging system of the present invention will be described below with specific embodiments.

  1 (a) and 1 (b) show an embodiment of an X-ray generator of the present invention and an embodiment of an X-ray generator tube applied to the X-ray generator.

<X-ray generator tube>
An X-ray generator tube 2 shown in FIG. 1B includes a cathode 3 having an electron emission source and an anode 4 having a transmission type target 32. In this embodiment, X-rays are generated by irradiating the target 32 with the electron beam bundle 5 emitted from the electron emission source. For this reason, the electron emission source is arranged to face the target 32. In the present embodiment, the target 32 also serves as an X-ray extraction window of the X-ray generation tube 2.

  The electrons contained in the electron beam bundle 5 are incident energy necessary for generating X-rays at the target 32 by the acceleration electric field formed in the internal space of the X-ray generation tube 2 sandwiched between the cathode 3 and the anode 4. It is accelerated until it becomes.

  The internal space of the X-ray generator tube 2 is evacuated for the purpose of ensuring the mean free path of the electron beam bundle 5. The degree of vacuum inside the X-ray generation tube 2 is preferably 1E-8 Pa or more and 1E-4 Pa or less, and more preferably 1E-8 Pa or more and 1E-6 Pa or less from the viewpoint of the lifetime of the electron emission source. preferable.

  The internal space of the X-ray generation tube 2 can be evacuated by sealing the exhaust pipe after evacuation using an exhaust pipe (not shown) and a vacuum pump. Further, a getter (not shown) may be disposed in the internal space of the X-ray generation tube 2 for the purpose of maintaining the degree of vacuum.

  The X-ray generator tube 2 is provided with an insulating tube 19 in the body for the purpose of electrical insulation between the electron emission source defined by the cathode potential and the target 32 defined by the anode potential. The insulating tube 19 is made of an insulating material such as a glass material or a ceramic material. In the present embodiment, the envelope 111 is configured by the cathode 3, the insulating tube 19, and the anode 4.

  The envelope 111 is preferably composed of a member having hermeticity for maintaining a degree of vacuum and fastness having atmospheric pressure resistance.

  As the electron emission source provided in the cathode 3, for example, a hot cathode such as a tungsten filament or an impregnated cathode, or a cold cathode such as a carbon nanotube can be used. The electron emission source can be configured to include a grid electrode (not shown) and an electrostatic lens electrode for the purpose of controlling the beam diameter, electron current density, on / off timing, and the like of the electron beam bundle 5.

<X-ray generator>
The X-ray generation device 1 includes an X-ray generation tube 2 including a transmission type target 32, an insulating oil 8, and a storage container 6 that stores the X-ray generation tube 2 and the insulating oil 8. The X-ray generating tube 2 of the present embodiment is fixed inside the storage container 6 using a support body (not shown) arranged so as not to disturb the flow of the insulating oil 8.

  The storage container 6 may be configured to store therein a tube voltage circuit that is electrically connected to the X-ray generation tube 2 and outputs a tube voltage. The tube voltage circuit does not have to be arranged inside the storage container 6 and may be arranged outside the storage container 6.

  By storing the tube voltage circuit inside the storage container 6, the tube voltage output is stabilized by receiving the cooling action by the convection of the insulating oil 8, and the high-voltage feeder is routed by a short distance. The discharge breakdown voltage can be increased, and the reliability of the X-ray generator is improved.

  The insulating oil 8 contacts the outer surface of the X-ray generation tube 2 and the inner surface of the storage container 6 and is stored so as to reduce the temperature difference between the high temperature portion of the X-ray generation tube 2 and the low temperature portion of the storage container 6. Convection occurs inside the container 6. Since the insulating oil 8 performs cooling and electrical insulation of the X-ray generator tube 2, it is preferable that the insulating oil 8 has high cooling capacity and high electrical insulation. Moreover, since the target 4 becomes high temperature due to heat generation, and the heat is transferred to the insulating oil 8, a target that is less affected by heat is preferable. Therefore, as the insulating oil 8, an electrical insulating oil, a fluorine-based insulating oil, or the like can be used.

  An X-ray extraction window 7 is disposed at a position facing the target 32 of the storage container 6. As a material for the X-ray extraction window 7, a material having a small amount of X-ray attenuation such as beryllium or aluminum is applied.

<X-ray imaging system>
Next, a configuration example of an X-ray imaging system 60 to which the X-ray generator 1 of the present invention is applied will be described with reference to FIG. FIG. 2 shows a basic configuration example of an X-ray imaging system 60 that acquires an X-ray transmission image captured at a predetermined exposure angle with respect to the subject 204.

  The system control unit 202 integrally controls the X-ray generator 1 and the X-ray detector 206. The drive circuit 103 outputs various control signals to the X-ray generation tube 2 under the control of the system control unit 202. The drive circuit 103 includes at least a tube voltage circuit, and includes a tube current circuit that is connected to the electron emission source and controls the tube current as necessary. In the present embodiment, the drive circuit 103 is stored outside the storage container 6 together with the X-ray generation tube 2, but may be disposed inside the storage container 6. The emission state of the X-ray bundle 34 emitted from the X-ray generator 1 is controlled by the control signal output from the drive circuit 103.

  The X-ray bundle 34 emitted from the X-ray generation device 1 is emitted to the outside of the X-ray generation device 1 with the irradiation range adjusted by a collimator (not shown), transmitted through the subject 204 and detected by the X-ray detector 206. Is done. The X-ray detector 206 converts the detected X-ray into an image signal and outputs it to the signal processing unit 205. The signal processing unit 205 performs predetermined signal processing on the image signal and outputs the processed image signal to the system control unit 202.

  The system control unit 202 outputs a display signal for displaying an image on the display device 203 to the display device 203 based on the processed image signal. The display device 203 displays an image based on the display signal on the screen as a captured image of the subject 204.

  Next, another configuration example of the X-ray imaging system 60 to which the X-ray generator 1 of the present invention is applied will be described with reference to FIG. FIG. 3 shows a basic configuration example of an X-ray imaging system 60 that acquires an X-ray tomographic image by imaging the subject 204 at a plurality of exposure angles around the rotation axis Ac.

  An X-ray detector 206 is disposed on the emission side of the X-ray generation apparatus 1 of the present embodiment via the subject 204. The subject 204 includes the whole body or a specific part of the subject.

  The X-ray generator 1 and the X-ray detector 206 are mechanically connected to the rotation drive device 54 via a source support part 55 and a detector support part 56, respectively, and a common rotation axis Ac. Are configured to rotate synchronously in the same direction. Therefore, it can be said that the rotation drive device 54 is a mechanism that changes the posture of the storage container 6 with respect to the vertical direction.

  The subject 204 is disposed between the X-ray generator 1 and the X-ray detector 206 so as to overlap the rotation axis Ac.

  The output of the X-ray detector 206 includes X-ray transmission image data, and is connected to the display panel 60 via the data processing circuit 57, the image processing circuit 58, the system control unit 202, and the reconstruction unit 59. The data processing circuit 57 and the image processing circuit 58 correspond to the signal processing unit 205 in the embodiment of FIG.

  The output of the system control unit 202 is connected to the drive circuit 103, the X-ray generator 1, the rotation drive device 54, the data processing circuit 57, and the image processing circuit 58, and the output of the operation panel 62 is sent to the system control unit 202. It is connected.

  In the present embodiment, the subject 204 is stationary and the X-ray generator 1 and the X-ray detector 206 rotate, but the imaging system (X-ray generator 1, X-ray detector 206) and the subject 204 rotate. What is necessary is just to rotate with an angular velocity relatively around an axis. Therefore, the subject 204 may rotate about the rotation axis Ac, and the X-ray generator 1 and the X-ray detector 206 may be stationary.

  In the X-ray imaging system of the present embodiment, the X-ray generator 1 and the X-ray detector 206 are arranged to face each other, and are different from the subject 204 by rotating synchronously about the rotation axis Ac. A transmission image can be acquired for each shooting angle.

  Next, a tomographic sequence involving rotational scanning of the line generator 1 in the X-ray imaging system 60 shown in FIG. 3 will be described with reference to FIG.

  FIG. 4 is a flowchart of the imaging operation of the X-ray imaging system 60. When a command to start imaging (step S101) is input from the operation panel 62, the X-ray generator 1 and the X-ray detector 206 connected to the rotation drive device 54 via the system control unit 202 are set to a predetermined rotational speed. Then, the rotation is started (step S102). Here, the system control unit 202 monitors an encoder signal (not shown) generated from the rotary drive device 54 and confirms whether a predetermined constant speed and angle are reached.

  When the predetermined speed and angle are reached, the system control unit 202 sends a signal to the X-ray generator 1 via the drive circuit 105 and starts X-ray exposure (step S103). Be exposed to. At the same time, image data is collected by the X-ray detector 206 via the data processing circuit 57 (step S104).

  The X-ray generator 1 and the X-ray detector 206 rotate synchronously at a predetermined rotation angle, and imaging is continued until a predetermined number of image data is collected. When the collection of the image data captured at every predetermined angle is completed, the synchronous rotation between the X-ray generator 1 and the X-ray detector 206 is ended (step S105).

  Next, the reconstruction unit 59 reconstructs the image data to construct two lines of reconstructed image data. Here, in the reconstruction, the first reconstructed image data is configured based on the electric signal output from the high resolution area of the X-ray detector 206, and based on the electric signal output from the low resolution area. Second reconstructed image data is constructed (step S106).

  Next, the corresponding first reconstructed image data and second reconstructed image data are synthesized at a certain ratio. Specifically, the first reconstructed image data is multiplied by a coefficient k1, and the second reconstructed image data is multiplied by k2. Then, the multiplied image data is added (step S107).

  In this manner, a tomographic image is acquired from a plurality of transmitted X-ray images of the subject 204 and angle information. The X-ray imaging system 60 can be used for non-destructive inspection of industrial products and pathological diagnosis of human bodies and animals.

<Bubble chamber>
Next, the bubble chamber which is a feature of the present invention will be described with reference to FIGS.

  As shown in FIG. 1A, the X-ray generator 1 of this embodiment includes a bubble chamber 13 that captures bubbles generated in the insulating oil 8.

  Bubbles generated inside the storage container 6 are more likely to float due to the influence of buoyancy due to a rise in temperature during operation of the X-ray generator tube 2, and the viscosity of the insulating oil decreases. .

  The bubble chamber 13 has an interior communicating with the interior of the main chamber 14 accommodating the X-ray generation tube 2 and the opening in order to capture bubbles moving inside the storage container 6. For this reason, the bubble chamber 13 of the present embodiment is adapted to allow the bubbles generated in the vicinity of the X-ray generation tube 2 to flow in by the convection of the insulating oil 8 and the buoyancy received by the bubbles.

  The inside of the bubble chamber 13 of the present embodiment is surrounded by a wall disposed in a portion other than the opening. The wall of the bubble chamber 13 is constituted by a part of the outer peripheral wall of the storage container 6 and the partition plate 15. In the present specification, the inside of the wall constituting the bubble chamber 13 is hereinafter referred to as the inner surface of the bubble chamber.

  The inner surface of the bubble chamber 13 of the present embodiment has a larger contact angle with the insulating oil 8 than the inner surface of the storage container 6 outside the bubble chamber 13.

  In the present embodiment, in the main chamber 14, a glass epoxy resin plate 18 made of a laminate of a glass resin cloth and an epoxy resin is disposed in a region excluding the opening between the bubble chamber 13 and the X-ray extraction window 7. And exposed to the inner surface of the main chamber 14. The glass epoxy plate of this embodiment has a surface free energy of 43 mN / m, and the surface exhibits lipophilicity.

  On the other hand, the partition wall 15 made of brass and the storage container 6 are exposed on the inner surface except for the opening between the bubble chamber 13. The brass of this embodiment has a surface free energy of 1000 mN / m, and the surface exhibits hydrophilicity, that is, oil repellency.

  The effect of making the inner surface of the bubble chamber 13 larger at the contact angle θc with the insulating oil 8 than the inner surface of the main chamber 14 will be described with reference to FIGS.

  FIG. 5A shows a solid-liquid interface between the solid 28 having the inner surface whose surface free energy is higher than that of the insulating oil 8, the insulating oil 8, and the bubbles 27. Similarly, FIG. 5B shows a solid-liquid interface between the solid 29 having the same inner surface free energy as the insulating oil 8, the insulating oil 8, and the bubbles 27. Further, similarly, FIG. 5C shows a solid-liquid interface between the solid 29 having the inner surface whose surface free energy is lower than that of the insulating oil 8, the insulating oil 8 and the bubbles 27.

  5C, since the solid 30 has a low affinity for the insulating oil 8 and has a lipophilic surface, the insulating oil 8 is easily wetted by the solid 30, and the contact angle θc between the bubble 27 and the solid 30 increases. The bubbles 27 at the solid-liquid interface shown in FIG. 5C are weakly adherent to the solid 30 and easily float.

  On the other hand, in FIG. 5A, since the solid 28 has a hydrophilic surface with low affinity for the insulating oil 8, the insulating oil 8 is difficult to wet the solid 28, and the contact angle θc between the bubble 27 and the solid 28 is small. Become. The bubbles 27 at the solid-liquid interface shown in FIG. 5A have strong adhesion to the solid 28 and are difficult to move.

  5A to 5C exemplify the case where the lower part of each figure is downward in the vertical direction, but the relationship between the contact angle of the adhesiveness of the bubbles is not necessarily shown in FIG. It is not limited to arrangement. The solid-liquid interface formed by each of the solids 28 to 30 may form an arbitrary angle with respect to the vertical straight direction.

  Accordingly, since the inner surface of the bubble chamber 13 has a higher surface free energy region than the inner surface of the main chamber 14, the bubbles 12 flowing into the bubble chamber 13 are difficult to escape from the bubble chamber 13. As a result, the bubbles generated by the X-ray generator 1 are stably captured in the bubble chamber, and the cooling performance and discharge resistance performance of the X-ray generation tube 2 can be stably maintained.

  The member constituting the inner surface of the bubble chamber 13 may be made of a material having a large contact angle with the insulating oil 8 relative to the main chamber 14. The inner surface of the bubble chamber 13 preferably has a hydrophilic material, and the inner surface of the storage container 6 outside the bubble chamber 13 preferably has a lipophilic material.

  As the material exhibiting hydrophilicity, a material exhibiting a surface free energy of 100 mN / m or more is selected. Specific examples of the material exhibiting hydrophilicity include pure metals such as copper, aluminum, zinc, and tin, and alloys such as stainless steel and brass. The aforementioned metal group exhibits a surface free energy of 500 to 1200 mN / m.

  Moreover, as a material exhibiting lipophilicity, a material exhibiting surface free energy of less than 100 mN / m is selected. Specific examples of the material exhibiting lipophilicity include fluororesin, silicone resin, epoxy resin, acrylic resin, polyethylene resin, polyimide resin, and polyimidazole resin. The aforementioned resin group exhibits a surface free energy of 10 to 80 mN / m.

  Maintaining the state where the trapped bubbles are held by using the bubble chamber 13 having an inner surface that exhibits a higher contact angle with the insulating oil 8 than the contact angle between the inner surface of the main chamber 14 and the insulating oil 8. Is possible. As a result, the X-ray generator 1 of the present invention can secure a contact area between the storage container 6 and the insulating oil 8 in the main chamber 14, and the cooling performance and the discharge resistance performance of the insulating oil 8 are reduced. It is difficult and has high reliability.

  For example, when an X-ray generator having a bubble chamber is applied to an X-ray CT apparatus as an X-ray source as in the X-ray imaging system 60 shown in FIG. Depending on the position, bubbles could escape from the bubble chamber. FIG. 6 shows an X-ray imaging system 60 including the X-ray generator 1 that is rotated and scanned in the angle range of 0 to 360 degrees around the rotation axis Ac shown in the vertical direction of the drawing.

  3 and 6 are illustrated in the same manner as in FIG. 5 with the lower part of each figure being vertically downward. In FIG. 6, the attitude of the X-ray generator 1 is defined based on the angle formed by the partition plate 15 between the main chamber 14 and the bubble chamber 13 and the vertical direction. , 180 degrees and 270 degrees are shown as representatives.

  In the X-ray imaging system 60 shown in FIG. 6, since the rotation axis Ac is not parallel to the vertical direction, the storage container 6 and the bubble chamber 13 are moved relative to the vertical direction as the X-ray imaging apparatus 1 rotates. Take different postures. However, since the inner surface of the bubble chamber 13 of the present embodiment has a surface with a smaller contact angle with the bubble 12 than the main chamber 14, the X-ray generator 1 takes a different posture around the rotation axis Ac. In addition, the floating of the bubbles 12 in the bubble chamber 13 is suppressed. As a result, in the X-ray generator 1 provided with the bubble chamber 13 of the present embodiment, escape of the trapped bubble 12 from the bubble chamber 13 is reduced. The feature regarding the difference in surface free energy between the bubble chamber 13 and the main chamber 14 of the present invention is that the bubble chamber 13 is arranged in the storage container 6 apart from the rotation axis Ac as shown in FIG. In particular, the effect is exhibited.

  In addition, the convection behavior of the insulating oil may change depending on the fluctuating parameters such as the ambient temperature of the X-ray generator and the operating time of the X-ray generator tube, and the trapped bubbles may escape from the bubble chamber. . That is, the X-ray generator provided with the bubble chamber of the present invention is an X-ray imaging apparatus that does not include the rotation axis Ac as in the embodiment shown in FIG. 2, or an X that has the rotation axis Ac parallel to the vertical direction. Even in the X-ray apparatus, the effect of suppressing escape of bubbles from the bubble chamber is exhibited.

  Next, a modification of the embodiment of the X-ray generator 1 shown in FIG. 1 (a) will be described with reference to FIGS. 7 (a) and 7 (b).

  In the X-ray generator 1 shown in FIG. 7A, a copper foil is formed on one surface on the inner surface of the bubble chamber 13 on the point that the glass epoxy plate 18 is used for the inner surface of the storage container 6 and the partition plate 15. The difference from the X-ray generator 1 shown in FIG.

  In the present embodiment, since the inner surface of the main chamber 14 is made of a glass epoxy plate 18 and the inner surface of the bubble chamber 13 is made of copper, the bubbles 12 captured in the bubble chamber 13 are free to surface. Based on the energy difference (43 <1100 mN / m), it continues to be captured stably.

  On the other hand, in the X-ray generator 1 shown in FIG. 7B, the region 17 in which the copper foil is formed on the glass epoxy plate is provided in a part of the inner surface of the bubble chamber 13, as shown in FIG. This is different from the embodiment shown in FIG. Also in the present embodiment, since the inner surface of the main chamber 14 is made of the glass epoxy plate 18 and the inner surface of the bubble chamber 13 is made of copper, the bubbles 12 captured in the bubble chamber 13 are free to surface. Based on the energy difference (43 <1100 mN / m), it continues to be captured stably.

<Contact angle measurement>
The inner surface of the bubble chamber 13 provided in the X-ray generator 1 of the present invention has a region 17 having a larger contact angle with the insulating oil 8 than the inner surface of the main chamber 14 that houses the X-ray generating tube 2. Configured to do. Therefore, the member constituting the inner surface of the storage chamber 6 can be determined even for a member whose surface free energy is not known by identifying the contact angle with the droplet of the insulating oil 8.

  If the size of the droplet at the time of contact angle measurement is too small, an error will occur in the direction of decreasing the contact angle due to the effect of evaporation from the surface of the droplet to the measurement atmosphere, and if too large, the contact angle will be reduced due to gravity deformation of the droplet. An error occurs in the increasing direction. By acquiring correlation data between a plurality of droplet sizes and contact angles in advance for the members constituting the storage chamber, the droplet size that maximizes the contact angle is determined based on the correlation data. Is preferable in order to reduce errors in contact angle identification.

  Insulating oil usually exhibits a sufficiently low vapor pressure with respect to the measurement atmosphere. Therefore, it is possible to set the droplet size by giving priority to the mitigation of the influence of gravity deformation. It is preferable that

  Moreover, it is preferable that the solid surface serving as the specimen is a cleaning surface from which metal ions, organic substances, and the like are removed.

<Surface free energy measurement>
Next, a method for measuring the surface free energy of the members constituting the inner surface of the storage container will be described. The method for measuring the surface free energy of a member includes <measurement of the contact angle of a solid-liquid interface performed using a reagent droplet> and the relationship between the contact angle of the solid-liquid interface and the surface free energy <Duple-Young equation > And <Fowkes formula> that handles the work of adhesion.

As the reagent, a reagent set comprising a plurality of reagents having different surface free energy components is used. Components of the surface free energy is meant a dispersion term gamma _Lid and polar term gamma _{Li p} and the components of the hydrogen bond gamma _Lih. As a specific example of the reagent set, three liquids of α-bromonaphthalene, methylene iodide, and pure water are used. The reagent set is not limited to the above-described three liquids, and other combinations of reagents having different surface free energy components are applied.

Here, it is assumed that the reagent Li has surface free energy γ _Li (mN / m) in the same manner as a solid surface serving as a specimen to be described later. Here, i is a number indicating the type of reagent. The surface free energy gamma _Li reagents Li has a dispersion term gamma _Lid and polar term gamma _Li p and components of the hydrogen bond term gamma _Lih. A reagent set consisting of three liquids with reagent numbers i of 1 to 3 can define a square matrix having 3 × 3 = 9 parameters as a matrix G. In addition, a square matrix having nine elements that match the 0.5th power of each element of the square matrix G is defined as a matrix A.

  The solid surface serving as the specimen is defined by the total value of the three components of the dispersion term γsd, the polar term γsp, and the hydrogen bond term γsh as unknown surface free energy γs. In terms of ensuring the measurement accuracy of the fixed surface free energy γs, it is desirable to combine the reagents so that the determinant of the matrix A of the reagent set becomes larger.

The matrix G, matrix A, inverse matrix A ^{−1 of} the matrix A, and surface free energy γ _L corresponding to the reagent set Y consisting of α-bromonaphthalene, methylene iodide, and pure water are shown in Tables 1 to 4, respectively. Street. Therefore, the determinant of the matrix A of the reagent set Y is 55.9 (mN / m) ^1.5 . The value of the determinant of the matrix A is preferably 20 (mN / m) ^1.5 or more.

Here, the surface free energy γs of the solid specimen S has a dispersion term γ _Sid , a polar term γ _Sip, and a hydrogen bond term γ _Sih , and θ _SL1 , θ _SL2 , Consider the case where the contact angle of the solid-liquid interface of _θSL3 is obtained by contact angle measurement. At this time, the surface free energy γs of the solid S is uniquely identified by the following general formulas 1 to 4.

Note that A ⁻¹ (p, q) included in each right side of the general formulas 2 to 4 means an element of (p row, q column) of the inverse matrix A ⁻¹ . Further, each right side of the general formulas 2 to 4 is defined by a <Duple-Young formula> that handles the relationship between the contact angle of the solid-liquid interface and the surface free energy, and a <Fowkes formula> that handles the work of adhesion. Yes. As a method for measuring the surface free energy, the Fowkes equation may be appropriately replaced with the Zisman method, the Owens and Wendt method, the Van Oss method, or the like.

DESCRIPTION OF SYMBOLS 1 X-ray generator 2 X-ray generator tube 3 Electron emission source 5 Electron bundle 6 Storage container 7 X-ray extraction window 8 Insulating oil 12 Captured bubble 13 Bubble chamber 14 Main chamber 17 Area with a large contact angle with insulating oil 8 32 targets

Claims (10)

An X-ray generator tube, insulating oil, and a storage container for storing the X-ray generator tube and the insulating oil;
An X-ray generator having
The storage container has a main chamber for storing the X-ray generation tube, and a bubble chamber having an interior communicating with the interior of the main chamber through an opening,
The X-ray generator according to claim 1, wherein an inner surface of the bubble chamber has a region exhibiting a larger contact angle than an inner surface of the main chamber at a contact angle with the insulating oil.   The X-ray generator according to claim 1, wherein the region of the inner surface of the bubble chamber exhibits a surface free energy larger than the inner surface of the storage container outside the bubble chamber.   The X-ray generator according to claim 1, wherein the region on the inner surface of the bubble chamber has a surface free energy of 100 mN / m or more.   The X-ray generator according to any one of claims 1 to 3, wherein the region of the inner surface of the bubble chamber has a metal.   The X-ray generator according to any one of claims 1 to 4, wherein an inner surface of the storage container outside the bubble chamber has at least a resin.   The X-ray generation according to claim 5, wherein the resin is selected from at least one of a fluororesin, a silicone resin, an epoxy resin, an acrylic resin, a polyethylene resin, a polyimide resin, and a polyimidazole resin. apparatus.   An X-ray generator according to claim 1, and an X-ray detector that detects X-rays emitted from the X-ray generator and transmitted through a subject. X-ray imaging system. A rotation drive device connected to the storage container and changing the attitude of the storage container with respect to the vertical direction;
The X-ray generator generates X-rays at different angles of the storage container changed by the rotation driving device, and the X-ray detector detects X-rays transmitted through the subject. A system control unit for integrating and controlling the X-ray detector and the X-ray detector;
The X-ray imaging system according to claim 7, comprising: The X-ray generator is arranged to form the different angle with respect to a vertical direction by rotating around a rotation axis,
The X-ray imaging system according to claim 8, wherein the bubble chamber is disposed in the storage container so as to be separated from the rotation shaft. Reconstruction for reconstructing a tomographic image of a subject by a signal processing unit connected to the X-ray detector and acquiring an image signal output from the X-ray detector, and the plurality of acquired images and angle information The X-ray imaging system according to claim 8 or 9, further comprising: a unit.