JP2010244834A - X-ray generator and x-ray measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray generator attaining a stable X-ray generating position, without affecting the irradiating position of electron beams, by installing a small high-voltage power source without electromagnetic leakages in the inside of an X-ray tube. <P>SOLUTION: The small high-voltage power source has a drive circuit for transforming input AC or DC power into high-frequency AC power of 10-200 kHz; a plurality of piezoelectric step-up transformers, provided in parallel to step up the transformed high frequency AC power while suppressing heat generation and electromagnetic radiation noise; and a plurality of voltage step-up rectifying circuits for rectifying each stepped-up AC power, to obtain high voltage of 30-100 kV and to load it to the X-ray tube. The small high-voltage power source is installed inside the X-ray tube. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention aims to reduce the size of the X-ray generator with a small high-voltage power source using a piezoelectric step-up transformer, and configure the high-voltage power source inside the X-ray tube, thereby reducing the power supply to the X-ray tube. The present invention relates to an X-ray measurement apparatus that realizes improvement in design freedom and safety of use of an X-ray measurement apparatus by eliminating external wiring of a high-voltage cable.

  Japanese Unexamined Patent Application Publication No. 2002-359967 (Patent Document 1) is known as a prior art of a stabilized DC high-voltage power source using a piezoelectric step-up transformer. Patent Document 1 describes that it can be used for an X-ray fluorescent image intensifier tube for X-ray detection used in X-ray tomography or a DC high-voltage power source for supplying power to an imaging plate.

  Ricoh Technical Report No.31.December, 2005, pp.59-66 (Non-Patent Document 1) describes a power-saving inverter for liquid crystal backlights using a piezoelectric transformer.

JP 2002-359967 A Ricoh Technical Report No.31.December, 2005 published pp.59-66

  A general high-frequency high-voltage power supply uses a boosting electromagnetic transformer in part. Although small size and high performance have been achieved with recent advances in parts, a high voltage power source cannot be inserted into the X-ray tube. When an electromagnetic transformer is used for boosting, when the electromagnetic transformer is used in the power supply circuit, the leakage flux affects the trajectory of the electron beam in the X-ray tube. The stability is greatly affected. A microfocus X-ray tube has an X-ray generation area of about 10-50 μm and is affected by movement of the X-ray generation part of about several μm due to the influence of an electromagnetic transformer. It was difficult to do.

  Further, the above Patent Document 1 does not consider the application of a piezoelectric step-up transformer as a high-voltage power supply circuit for an X-ray tube for generating X-rays.

  In addition, the piezoelectric step-up transformer is small and highly efficient. However, since the power handled is generally small, it is used as a backlight power source for LCDs and a high-voltage power source for air purifiers as described in Non-Patent Document 1. I just came.

  The object of the present invention is to achieve a stable X-ray generation position without affecting the irradiation position of the electron beam by installing a small high-voltage power source without electromagnetic leakage inside the X-ray tube in order to solve the above problems. Another object of the present invention is to provide an X-ray generation apparatus and an X-ray measurement apparatus including the X-ray generation apparatus.

  In the present invention, since the voltage is boosted by using the vibration of the piezoelectric ceramic, a small high voltage power source is configured by using a piezoelectric step-up transformer that essentially does not generate a leakage magnetic field. It is possible to mount inside.

  Further, the present invention uses a final booster by connecting a cockcroft circuit (voltage boosting rectifier circuit) to each piezoelectric transformer in the construction of a high-frequency power source that cannot be handled by a single piezoelectric step-up transformer. The output voltage is ensured by alternatingly connecting in parallel by shifting the phase of the low voltage and high frequency for each piezoelectric transformer. As a result, even if there is some variation in the characteristics of the piezoelectric transformer, it is possible to secure output power by using a plurality of piezoelectric transformers. According to this method, the pulsating flow rectified by multi-phase rectification is added, and since the frequency of the ripple component mixed in the high-voltage direct current that is output is high, it is easy to remove, and the direct current high-voltage that is smaller and superior in electrical characteristics than the conventional power supply. Power supply is possible.

  The present invention also includes an X-ray generator having an electron source and an X-ray target irradiated with a converged electron beam obtained from the electron source, and comprising an X-ray tube for generating X-rays A drive circuit that converts input AC or DC power into high-frequency AC power of 10 to 200 kHz and boosts the high-frequency AC power converted by the drive circuit while suppressing heat generation and electromagnetic radiation noise. A compact having a piezoelectric step-up transformer and a voltage step-up rectifier circuit that rectifies AC power boosted by the piezoelectric step-up transformer to obtain a high voltage of 30-100 kV and loads between the electron source and the X-ray target. A high-voltage power supply is installed inside the X-ray tube, and a high-voltage cable connecting the high-voltage output of the voltage boosting rectifier circuit and the load is not provided outside the X-ray tube. To do.

  The present invention is characterized in that a plurality of the piezoelectric step-up transformers in the compact high-voltage power supply are used in parallel. Further, the present invention is characterized in that each of the plurality of piezoelectric step-up transformers in the small high-voltage power supply generates electric power by controlling and using the phase of the high-frequency power obtained from the drive circuit. The present invention is characterized in that the voltage boosting rectifier circuit is connected to each of the plurality of piezoelectric step-up transformers in the small high-voltage power supply.

  According to the present invention, it is possible to connect a plurality of small and highly efficient piezoelectric step-up transformers in parallel by phase control of input power, which enables excellent electrical characteristics as a high-voltage power supply for a microfocus X-ray tube. . This makes it possible to insert a high-voltage power supply inside the X-ray tube. The voltage on the input side can be as low as about 12-100V, and the high voltage of 30-100 kV of the conventional X-ray tube can be in the form of being inserted inside the X-ray tube. In other words, by placing a small high-voltage power supply inside the X-ray tube, cost reduction, downsizing, high reliability, and high stability can be achieved, and the degree of freedom in designing an X-ray measuring device using a microfocus X-ray tube is increased. It becomes possible to provide an easy-to-use X-ray measuring apparatus.

  An X-ray generator (microfocus X-ray tube) using a small and high-efficiency piezoelectric transformer according to the present invention as a small high-voltage power source, and an X-ray measuring apparatus (X-ray analyzer, X-ray) provided with the X-ray generator An embodiment of a transmission image measuring apparatus, an X-ray interferometer, or the like will be described with reference to the drawings.

[Embodiment]
FIG. 1 is a perspective view showing an embodiment in which a small high voltage power source according to the present invention is mounted. FIG. 1 shows a microfocus X-ray tube (X-ray generator) 2 in which a primary power source 1 and a small high-voltage power source 21 are mounted in order to supply AC or DC primary power to a small high-voltage power source 21 of the present invention. Yes. In other words, an X-ray tube (X-ray generator) 2 having a small high-voltage power supply 21 according to the present invention mounted therein is provided with an electron source (filament) in an X-ray tube main body 2 made of stainless steel and ceramics that can be evacuated. ) 22 and an X-ray target 25 for forming an anode. The electron source 22 is heated by direct current power from the filament power supply 211 via the high-voltage insulating transformer 212, emits thermoelectrons and functions as a cathode, and is an electrostatic electron lens (Wernelt) installed close to the electron source 22. ) 24, the electrons emitted from the electron source 22 are formed into a focused electron beam, and the X-ray target 25 is irradiated.

  In the present embodiment, the primary power source 1 is, for example, a 12-100 V DC or AC power source. The power of the primary power source 1 is connected to a small high voltage power source 21 mounted inside the microfocus X-ray tube 2 via a connection cable 11. The internal circuit of the small high voltage power source 21 has a filament power source 211 for heating the filament 22 for emitting thermoelectrons and a high voltage insulation transformer 212. The converged electron beam 29 is irradiated onto the X-ray target 25 and X-rays 27 are emitted through an X-ray transmission window 26 provided in a part of the microfocus X-ray tube 2.

  Since the small high-voltage power supply 21 in this embodiment is installed inside the microfocus X-ray tube 2, the high-voltage power supply 21 is installed on the filament 22 side in the configuration in which the filament 22 side is set to a negative high voltage. And the filament 22 can be connected by a short-distance internal high-voltage wiring 12, and the high-voltage portion is installed inside the X-ray tube, so that the high-voltage portion does not exist outside the tube. In the present embodiment, the connection voltage between the primary power source 1 and the small high-voltage power source 21 inside the X-ray tube is, for example, 12-100 V direct current or alternating current. Therefore, it is not necessary to supply an applied voltage directly from an external high-voltage power supply unlike a conventional X-ray tube, and electrical wiring parts such as connection cables and connectors can be of a normal voltage grade. In addition, one ground electrode of the small high-voltage power supply 21 is connected to the X-ray target 25 using the metal sheath of the microfocus X-ray tube 2.

  In addition to the high voltage application method used in the above embodiment, when the filament 22 side is set to the ground potential and the X-ray target 25 side is set to the positive high-voltage potential side, a small high-voltage power source 21 is connected to the X-ray target 25 side. It is also possible to install.

  FIG. 2 is a perspective view showing an embodiment in which a small high-voltage power supply 21 is installed on the X-ray target 25 side. FIG. 2 shows a microfocus X-ray tube (X-ray generation) in which the primary power source 1 and the small high voltage power source 21 are mounted inside the X-ray target 25 in order to supply AC or DC primary power to the small high voltage power source 21 of the present invention. Device) 2. The difference from the above embodiment is that the electron source 22 can be connected from the filament power source 211 that heats the electron source 22 with direct-current power without going through the high-voltage insulating transformer 212. Even in such a configuration, the filament 22 emits thermoelectrons and functions as a cathode, and the electrons emitted from the electron source 22 by the electrostatic electron lens (Weinert) 24 installed in the vicinity of the electron source 22. Can be formed into a focused electron beam, and the X-ray target 25 can be irradiated.

  Since the small high-voltage power supply 21 in this embodiment is installed inside the microfocus X-ray tube 2 on the X-ray target 25 side, the high-voltage power supply 21 and the X-ray target 25 can be connected by a short-distance internal high-voltage wiring 12. Further, since the high voltage portion is installed inside the X-ray tube, the high voltage portion does not exist outside the tube. In the present embodiment, the connection voltage between the primary power source 1 and the small high-voltage power source 21 inside the X-ray tube is, for example, 12-100 V direct current or alternating current.

  Next, an embodiment of a method for using the piezoelectric step-up transformer used in the small high-voltage power supply 21 according to the present invention will be described. The structure will be described with reference to cross-sectional views of the piezoelectric step-up transformer 30 shown in FIGS. The piezoelectric step-up transformer 30 is manufactured by laminating and firing a piezoelectric ceramic 31 such as barium titanate or lead zirconate titanate and a metal electrode 32. In this embodiment, the one based on lead zirconate titanate was used. The piezoelectric step-up transformer 30 is formed by printing a metal electrode 32 on the surface of a plate-shaped piezoelectric ceramic 31 and laminating and firing it, dividing it into an appropriate shape, forming external electrodes 33 and 34, and then applying a polarization treatment. It is a solid state device.

  The operation principle of the piezoelectric step-up transformer 30 used in the small high-voltage power supply 21 according to the present invention will be described with reference to FIG. The piezoelectric step-up transformer 30 usually has an AC power 41 close to a resonance frequency determined by the length in the longitudinal direction and the mechanical properties of the piezoelectric ceramic (10 to 200 kHz converted from a low-voltage DC or AC power supplied from the primary power supply 1 (preferably Is applied to the primary side (α), a strong mechanical vibration occurs in the longitudinal direction due to the electrostrictive effect on the secondary side (β). A voltage is generated by the piezoelectric effect of the mechanical vibration, and a voltage (V2) 42 boosted about 50 to 100 times is obtained at the output end. P indicates the polarization direction. Although there is no electromagnetic action at all in this operation principle, since it operates in the same way as a general electromagnetic transformer, it can be regarded as a step-up transformer. That is, the piezoelectric step-up transformer 30 boosts the voltage while suppressing heat generation and electromagnetic radiation noise. The step-up ratio is generally determined by the length from the operating principle, and the boostable power is approximately proportional to the volume of the piezoelectric element ((L + L ′) × W × T). The piezoelectric step-up transformer 30 of about 5-15 W can obtain a step-up ratio of about 50-100 times near the resonance frequency with respect to the input 41 of the high frequency AC power of 40-100 kHz.

  FIG. 5 shows a block diagram of the internal configuration of the small high-voltage power supply 21 using the piezoelectric step-up transformer having such an operation principle. In order to take out a high voltage of 30-100 kV for a microfocus X-ray tube, a Cockcroft half-wave rectification / multiplication circuit (voltage booster) in which the output side of the piezoelectric step-up transformer 30 (30a, 30b, 30c) is composed of a diode and a capacitor is used. Rectifier circuit) 50 for direct current conversion. The general power consumption of the microfocus X-ray tube is 10-50 W, and in this embodiment, a small high-voltage power source 21 capable of configuring a maximum of 45 W was realized. If a general piezoelectric transformer can handle 45 W alone, the size of the piezoelectric transformer increases, leading to an increase in cost due to a decrease in manufacturing yield. In the present embodiment, as shown in FIG. 5, a method of using a plurality of (for example, three) 15 W piezoelectric transformers (30a, 30b, 30c) in parallel is employed.

  On the primary side (α) of each piezoelectric step-up transformer, as shown in FIGS. 5 and 6, a transmission circuit (drive) using, for example, four semiconductor elements (FETs) based on the output signal of a VCO (voltage control oscillator) 51 Circuit) (55a, 55b, 55c), high frequency power of 40-100 kHz was applied. The voltage of the primary power source 1 was set to, for example, 100 V DC, and a boost ratio of 75 times was obtained. High frequency power of 7.5 kV in peak voltage was obtained on the secondary side of the piezoelectric step-up transformer (30a, 30b, 30c). The three piezoelectric step-up transformers (30a, 30b, 30c) applied input power to the transmission circuit through phase control circuits (52a, 52b) for making a phase difference of 120 degrees. The voltage is controlled by the same VCO (voltage control oscillator) 51 for all three piezoelectric transformers, and the step-up ratio is changed by changing the frequency of the primary side (α) input. Control is performed by returning a voltage control signal from the output side of the cockcroft half-wave rectification / multiplication circuit (voltage boosting rectification circuit) 50 to the VCO (voltage control oscillator) 51 through the voltage detection circuit 53. On the other hand, the current of the microfocus X-ray tube (X-ray generator) 2 is controlled by returning a current control signal to the filament power supply 211 through the current detection circuit 54.

  The alternating high voltage boosted by the piezoelectric step-up transformer (30a, 30b, 30c) has a peak voltage of about 50 kV through the cockcroft half-wave rectifier circuit 50 multiplied by 7 as shown in FIG. In this embodiment, for example, a three-phase rectification multiplication is performed with a phase difference of 120 degrees, so that a sufficiently smooth DC output voltage can be obtained as shown in FIG. It is. Further increasing the output power is achieved by connecting more piezoelectric step-up transformers 30 and cockcroft rectifier circuits (voltage boost rectifier circuits) 50 in parallel in accordance with the phase difference on the primary side (α). be able to. Piezoelectric transformers are difficult to achieve with the same boosting characteristics due to their manufacturing method, and the boosting characteristics are made uniform by selection, but there is some characteristic error due to the time-division application of power by phase control on the primary side (α). Even if there is, it is possible to take out a smooth 30-100 kV high-voltage DC voltage.

  That is, the small high voltage power source 21 according to the present invention is configured to generate a boosted DC power by controlling and using the phase of the high frequency AC power obtained from each of the plurality of piezoelectric step-up transformers 30 (phase of the high frequency power source). did. Further, the small high voltage power source 21 according to the present invention is characterized in that the frequency of the high frequency AC power (high frequency power source) for performing the boost control of the plurality of piezoelectric step-up transformers is the same.

  Next, FIG. 8 shows an actual substrate configuration of the piezoelectric step-up transformer 30 and the cockcroft half-wave rectification / multiplication circuit (voltage boosting rectification circuit) 50 according to the present invention. As a circuit board 60, a ceramic chip 61 is used, and a diode chip 63 and a capacitor chip 62 constituting a cockcroft half-wave rectification / multiplication circuit (voltage boosting rectification circuit) 50 are mounted by surface mounting. As the capacitor chip 62, a film chip capacitor having excellent high frequency characteristics was used. A diode chip 63 and a chip capacitor 62 are connected to one side of the ceramic substrate 61 by soldering, and the piezoelectric step-up transformer 30 inserted in the insulating case 64 is mounted on the opposite side of the ceramic substrate 61. These substrates were molded and sealed with an epoxy composite material mixed with ceramic powder, enabling stable high-pressure operation.

  The VCO (voltage control oscillator) 51, the phase control circuit (52a, 52b), the voltage detection on the ceramic substrate 71 in the same manner as the three substrates for the same cockcroft half-wave rectification / multiplication circuit (voltage boosting rectification circuit) 50 The circuit 53, the current detection circuit 54, and the filament power supply 211 are mounted to constitute the control circuit 70 for the piezoelectric step-up transformer, and the small high-voltage power supply 21 is composed of a total of four pieces. That is, in the small high-voltage power supply 21 installed in the microfocus X-ray tube (X-ray generator) 2 according to the present invention, each of the plurality of piezoelectric step-up transformers 30 includes a piezoelectric step-up transformer 30 and a cockcroft half-wave rectification / multiplication circuit. (Voltage boosting rectifier circuit) Each of the voltage boosting rectifier circuits is characterized by having a structure that is integrally formed on a substrate 60 and modularized.

  As seen here, no electrical component device that requires magnetism is used on this substrate, and even if it is installed inside the microfocus X-ray tube (X-ray generator) 2, Since the trajectory is not affected, the microfocus X-ray tube (X-ray generator) 2 having excellent stability of the X-ray focal position can be realized.

  Next, an X-ray measuring apparatus (X-ray analyzer, X-ray transmission image measuring apparatus or X-ray) equipped with a microfocus X-ray tube (X-ray generator) 2 having a small high-voltage power supply 21 according to the present invention installed therein. An embodiment of a line interferometer or the like) will be described with reference to FIG. The wavelength of characteristic X-rays emitted from the X-ray target 25 of the microfocus X-ray tube (X-ray generator) 2 through the X-ray transmission window 26 is determined for each element of the metal target. An X-ray selection device 81 such as an X-ray discriminating crystal monochromator or an X-ray reflecting mirror formed with a multilayer film is used to suppress only X-rays having other wavelengths while using only characteristic X-rays having a specific wavelength. Thus, only characteristic X-rays are selected and irradiated on the sample 83 in the X-ray analyzer, X-ray transmission image measuring device, or X-ray interferometer 82. Then, the X-ray obtained from the sample 83 is detected by the X-ray detector 84, and the data detected by the X-ray detector 84 is analyzed in the data processor 85, thereby obtaining an analysis or measurement result. Further, as a method not using the X-ray selection device 81, X-ray detection in an X-ray analysis apparatus, an X-ray transmission image measurement apparatus, or an X-ray interferometer 82 using a microfocus X-ray tube (X-ray generation apparatus) 2 It is possible to obtain a desired analysis result by applying only the data derived from the characteristic X-rays in the data processing device 85 by applying a device having X-ray discrimination capability to the detector 84 It becomes.

The perspective view which shows Embodiment 1 of the micro focus X-ray tube (X-ray generator) which mounts the small high voltage power supply which concerns on this invention inside. The perspective view which shows Embodiment 2 of the micro focus X-ray tube (X-ray generator) which mounted the small high voltage power supply which concerns on this invention inside the X-ray target side. Sectional drawing which shows the structure of the piezoelectric step-up transformer in the small high voltage power supply which concerns on this invention. Schematic which shows the operation principle figure of the piezoelectric step-up transformer in the small high voltage power supply which concerns on this invention. The block diagram which shows the internal structure of the small high voltage power supply using the piezoelectric step-up transformer which concerns on this invention. The figure which shows the three-phase cockcroft half-wave rectification multiplier circuit (voltage boosting rectifier circuit) including the piezoelectric step-up transformer of the small high-voltage power source according to the present invention. The figure which shows the control circuit of the piezoelectric step-up transformer of the small high voltage power supply which concerns on this invention. The perspective view which shows the structure of the actual board | substrate of the piezoelectric step-up transformer and the cockcroft half-wave rectification multiplication circuit (voltage step-up rectification circuit) of the small high voltage power supply which concerns on this invention. An X-ray measuring apparatus (an X-ray analyzer, an X-ray transmission image measuring apparatus, an X-ray interferometer, etc.) provided with a microfocus X-ray tube (X-ray generator) in which a small high-voltage power source according to the present invention is installed. FIG. 1 is a schematic configuration diagram illustrating an embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Primary power supply, 2 ... Micro focus X-ray tube (X-ray generator), 11 ... Primary power supply connection cable, 12 ... Internal high voltage wiring, 21 ... Small high voltage power supply, 22 ... Electron source (filament), 24 ... Wehnelt 25 ... X-ray target, 26 ... X-ray transmission window, 27 ... X-ray, 28 ... cable, 29 ... convergent electron beam, 211 ... filament power supply, 212 ... high voltage insulation transformer, 30, 30a, 30b, 30c ... piezoelectric booster Transformer 31, plate-shaped piezoelectric ceramic, 32 ... metal electrode, 33 ... external electrode, 34 ... external electrode, 41 ... AC input, 42 ... boosted voltage, 50, 50a, 50b, 50c ... Cockcroft half-wave rectification Multiplier circuit (voltage boosting rectifier circuit), 51... VCO (voltage control oscillator), 52 a, 52 b... Phase control circuit, 53. 55a, 55b, 55c ... transmission circuit (drive circuit), 60 ... circuit board, 61 ... ceramic substrate, 62 ... capacitor chip, 63 ... diode chip, 64 ... insulating case, 70 ... piezoelectric step-up transformer control circuit, 71 ... Ceramic substrate, 81... X-ray selection device, 82... X-ray analyzer, X-ray transmission image measuring device or X-ray interferometer, 83... Sample, 84.

Claims (8)

  An X-ray generator comprising an X-ray tube for generating X-rays, comprising an electron source and an X-ray target irradiated with a focused electron beam obtained from the electron source, Drive circuit for converting AC or DC power to high frequency AC power of 10-200 kHz, a piezoelectric step-up transformer for boosting the high frequency AC power converted by the drive circuit while suppressing heat generation and electromagnetic radiation noise, and the piezoelectric A compact high-voltage power supply having a voltage boosting rectifier circuit that boosts and rectifies AC power boosted by a boosting transformer to obtain a high voltage of 30 to 100 kV and loads between the electron source and the X-ray target. An X-ray characterized in that a high-voltage cable that is installed inside the tube and connects between the high-voltage output of the voltage boosting rectifier circuit and the load is not provided outside the X-ray tube. Generation Place.   The X-ray generator according to claim 1, wherein a plurality of the piezoelectric step-up transformers in the small high-voltage power source are used in parallel.   3. The power generation unit according to claim 1, wherein each of the plurality of piezoelectric step-up transformers in the small high-voltage power source generates power by controlling and using a phase of the high-frequency power obtained from the drive circuit. X-ray generator.   4. The X-ray generator according to claim 2, wherein each of the voltage boosting rectifier circuits is connected to each of the plurality of piezoelectric step-up transformers in the compact high-voltage power supply.   5. The X-ray according to claim 2, wherein in the small high-voltage power source, the frequency of the high-frequency AC power for performing boost control in each of the plurality of piezoelectric step-up transformers is the same. Generator.   In the small high-voltage power supply, each of the plurality of piezoelectric step-up transformers has a modularized structure in which a piezoelectric transformer and a voltage step-up rectifier circuit are integrally formed on the substrate for each piezoelectric step-up transformer unit. The X-ray generator according to claim 2, wherein the X-ray generator is provided.   The power supply to be input from the primary power supply provided outside the X-ray tube to the small high-voltage power supply installed inside the X-ray tube is a low voltage of 12-100V. The X-ray generation device according to any one of 5.   An X-ray measurement apparatus comprising the X-ray generation apparatus according to claim 1.

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