JP5341019B2 - Capacitor and pulse shaping circuit - Google Patents

Description

  The present invention relates to a capacitor and a pulse shaping circuit constituting a pulse shaping circuit used for an accelerator, for example.

  Accelerators that accelerate electrons, protons, etc. and are used for research on nuclei, elementary particles, etc., require a very large output for the microwave source for acceleration, and are therefore pulsed depending on the required power, withstand voltage, and the like. Some of these pulse sources, which are microwave sources, have a peak power exceeding 200 MW (pulse width, several μs). In particular, the pulse rise time is fast, the top of the pulse is flat, and there is little fluctuation. However, it is very difficult to obtain a pulse power supply that satisfies such conditions with a large output.

  In general, a pulse power supply that sends out a high-power pulse includes an amplification-type pulse power supply that sequentially amplifies low-power pulses and outputs high-power pulses, and an appropriate pulse shaping circuit (PFN) that supplies electrical energy. There is a PFN-type pulse power source that stores and discharges with a large-capacity switch element to output a high-power pulse. Although it is easy to obtain an output with good pulse characteristics, the amplification method is large, complicated and very expensive in the case of a large output, so a small, simple and inexpensive PFN method is mainly used. . For example, as shown in FIG. 9, the PFN type pulse power supply includes a DC power supply 91, a charging circuit 92 connected to the DC power supply 91, a pulse shaping circuit 93 and a load 94 connected to the charging circuit 92 in series. , A pulse shaping circuit 93 and a switching element 95 connected in parallel to the load 94.

  The pulse shaping circuit 93 used for the PFN type pulse power supply includes a method using a transmission line such as a high-frequency coaxial cable having a characteristic impedance equal to a load, and a lumped constant circuit method using a coil and a capacitor.

  For example, as shown in FIG. 10, a transmission line 931 having a length L, such as a high-frequency coaxial cable, is used for the transmission line type pulse shaping circuit 93. In this transmission line system, the pulse width is determined by the time that electromagnetic waves travel back and forth through the transmission line 931. To obtain a pulse width of 5 μs, an RG / 8U coaxial cable (wavelength reduction rate 0.67) is used for the transmission line 931. A long cable of 500m is required. Further, the flatness and falling characteristics of the top of the pulse are degraded due to the loss and frequency characteristics of the cable used. Furthermore, practically, since there are restrictions on the withstand voltage of coaxial cables, the degree of freedom of impedance selection, volume, weight, price, etc., they are rarely used for large outputs.

For example, as shown in FIG. 11, the lumped constant circuit type pulse shaping circuit 93 has a configuration in which a coil 932 and a capacitor 933 are connected in a plurality of n stages as the pulse shaping circuit 93. This configuration is known as a delay circuit. When the value of n is infinite, a distributed constant circuit equivalent to a coaxial cable is obtained. The characteristic impedance of the pulse shaping circuit 93 in this method is Z ₀ = (L / C) ^1/2 , and the pulse width is τ = 2n (LC) ^1/2 (L: coil inductance, C: capacitor Capacity). The rising characteristics of the pulse are determined by the inductance of the first stage coil 932 of the pulse shaping circuit 93, the capacitance of the capacitor 933, and the value of the load 94. This lumped constant circuit type pulse shaping circuit 93 is widely used because of its high degree of design freedom. Patent Document 1 discloses a lumped constant circuit type pulse shaping circuit used for a pulse power source of an accelerator.

Japanese Patent Laid-Open No. 9-200002

  In recent years, in order to approach the fundamental problems of nuclear physics and particle physics, the High-Intensity Proton Accelerator Facility (J-PARC) in Japan, Fermi National Accelerator Laboratory (FNAL) in the US, and European collaboration in Switzerland At the Nuclear Research Organization (CERN), construction of large-scale accelerator facilities is underway, and research competition is being developed in Japan, the United States, and Europe. In these large-scale accelerators, there is a demand for generation of high-power high-speed pulses having advanced conditions that enable researchers to supply a stronger beam. For example, in J-PARC 50 GeV main ring synchrotron (MR), peak power 245 MW (35 kV / 7 kA), pulse width 4.3 μs, rise time 1 μs or less, pulse flatness 1% or less (flat part 4.3 μs or more) Generation of high-power high-speed pulses is demanded.

  Generating such a high-power, high-speed pulse with a lumped constant circuit type pulse shaping circuit is not only less flexible in the selection of usable coils and capacitors, but also due to parasitic inductance due to the capacitor structure, etc. It is very difficult because of the deterioration of the rise characteristic of the.

  The present invention has been proposed in view of the above problems, and an object of the present invention is to provide a capacitor and a pulse shaping circuit that can reduce a parasitic inductance and obtain a pulse having an excellent rising characteristic in the pulse shaping circuit.

Capacitor of the present invention is a capacitor comprising a capacitor body and the metal case, the capacitor body, the outer side is covered with an insulator, and one connection terminals provided projecting from one surface of the front Symbol capacitor body And the other connection terminal provided protruding from the other surface of the capacitor body, the metal case accommodates the capacitor body, has an opening around the one connection terminal, and the capacitor body. All the regions other than the opening are covered, and the other connection terminal is electrically connected to the metal case.
According to the above configuration, when a high-frequency current flows between the connection terminals, the magnetic flux induced by the high-frequency current is shielded by the metal case, and an eddy current is generated on the inner surface of the metal case. The space where magnetic energy is stored by being shielded with becomes narrow, and the intrinsic impedance can be reduced without increasing the energy. That is, it is possible to equivalently suppress the generation of parasitic inductance and reduce the parasitic inductance. When this capacitor is used in a pulse shaping circuit, it is possible to obtain a pulse having excellent rising characteristics in the pulse shaping circuit by suppressing parasitic inductance, for example, a pulse power source that generates a high-power high-speed pulse. be able to. In addition, the pulse flatness can be improved by reducing the parasitic inductance.

The capacitor according to the present invention is characterized in that the metal case and the capacitor body are provided close to each other. When provided in the vicinity, the metal case and the capacitor body insulator are provided in close contact, the metal case and the capacitor body insulator are partially separated, and the metal case and the capacitor body. The distance between the metal case and the capacitor body insulator in the case of partial or total separation includes the tolerance of the inner dimensions of the metal case and the capacitor body. This is the sum of the tolerances of the outer dimensions and means, for example, 4 mm or less.
According to the above configuration, when a gap is opened between the metal case and the capacitor body and the gap becomes large, there is a high possibility that electric charges are concentrated in the gap and discharge is generated between the metal case and the capacitor body. By providing the metal case and the capacitor body close to each other, it is possible to reliably prevent the occurrence of discharge.

The capacitor according to the present invention is characterized in that an insulating material is filled between the metal case and the capacitor body.
According to the above configuration, when a gap is opened between the metal case and the capacitor body and the gap becomes large, there is a high possibility that electric charges are concentrated in the gap and discharge is generated between the metal case and the capacitor body. By filling the insulating material between the metal case and the capacitor body, it is possible to reliably prevent the occurrence of discharge.

The capacitor of the present invention is characterized in that the periphery of the opening of the metal case is covered with corona ring.
According to the said structure, it can prevent that a discharge arises between one connection terminal and the end surface of the metal case which is the periphery of opening.

The pulse shaping circuit of the present invention is configured by connecting a plurality of capacitors of the present invention.
According to the above configuration, a lumped constant circuit type pulse shaping circuit that generates pulses having excellent rising characteristics can be obtained, and a pulse power source that generates high-power high-speed pulses can be configured easily and inexpensively.

In the pulse shaping circuit according to the present invention, the one connection terminal and the coil are connected to each other through a connection plate having a width as large as possible from the spatial distance and the circular distance at the installation position, for example, a connection plate having a width of 10 mm or more. It is characterized by.
According to the above configuration, it is possible to suppress the parasitic inductance generated in the connection plate even when the connection plate is long, to further improve the pulse rising characteristics of the pulse shaping circuit, and to reduce the resistance by reducing the resistance. Large current can flow smoothly.

The pulse shaping circuit of the present invention is characterized in that the metal cases of a plurality of the capacitors are electrically interconnected on the opening side.
According to the above configuration, a return circuit for high-frequency current flowing from one of the connection terminals is formed only on the inner surface of the metal case, and magnetic energy induced by the high-frequency current can be confined inside the capacitor. Further reduction and stray capacitance reduction can be achieved.

  The capacitor or the pulse shaping circuit of the present invention can reduce the parasitic inductance, and can obtain a pulse having excellent rising characteristics with the pulse shaping circuit. In addition, the pulse flatness can be improved by reducing the parasitic inductance.

(A) is a top view of the capacitor | condenser of embodiment by this invention, (b) is the partial cross section explanatory drawing, (c) is the bottom view. Explanatory drawing explaining the relationship between the high frequency current I, the magnetic flux (phi), and the eddy current E in the capacitor | condenser of embodiment. Explanatory drawing which shows a part of pulse shaping circuit which connects and comprises the capacitor | condenser of embodiment. FIG. 4 is a perspective explanatory view for explaining connection by a connecting plate of a capacitor in the pulse shaping circuit of FIG. 3. (A) is explanatory drawing of the return circuit of the pulse shaping circuit by the capacitor | condenser of embodiment, (b) is explanatory drawing of the return circuit of a comparative example. The figure which shows the rise characteristic of the pulse shaping circuit by this invention, and the rise characteristic of the pulse shaping circuit of a prior art example. Explanatory drawing which shows a part of pulse shaping circuit comprised by connecting the capacitor | condenser of a modification. (A) is an equivalent circuit diagram of the pulse shaping circuit of the modification by this invention, (b) is an equivalent circuit diagram of the pulse shaping circuit of a prior art example. The circuit explanatory drawing of the conventional pulse power supply of a PFN system. The circuit explanatory drawing of the transmission line system pulse power supply by the conventional PFN system. FIG. 6 is a circuit explanatory diagram of a pulse power supply of a conventional lumped constant circuit system using a PFN system.

[Capacitor and Pulse Shaping Circuit of Embodiment]
A capacitor and a pulse shaping circuit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram of the capacitor of the embodiment, FIG. 2 is an explanatory diagram for explaining the relationship among the high-frequency current I, the magnetic flux φ, and the eddy current E in the capacitor of the embodiment, and FIG. 3 is configured by connecting the capacitor of the embodiment. Explanatory drawing which shows a part of pulse shaping circuit. FIG. 4 is a perspective explanatory view for explaining the connection of the capacitor connecting plate in the pulse shaping circuit of FIG.

  As shown in FIG. 1, the capacitor 10 according to the present embodiment includes a capacitor main body 12 that is coated on the outside with an insulator, one connection terminal 13 that protrudes from one surface of the capacitor main body 12, and a capacitor main body. The other connection terminal 14 is provided so as to project from the other surface 12 and a conductive metal case 15 that houses the capacitor body 12.

  The capacitor body 12 has, for example, a substantially rectangular parallelepiped shape, and is entirely covered with an insulator such as plastic. One connection terminal 13 and the other connection terminal 14 of the capacitor body 12 are provided so as to protrude from one surface of the substantially rectangular parallelepiped shape and the other surface opposite to the one surface, respectively, and are provided on opposite surfaces. For example, a commercially available high-voltage capacitor (General Atomics Double End Plastic Case High-Voltage Capacitor) or the like can be used for the portion constituted by the capacitor body 12, one connection terminal 13, and the other connection terminal 14. .

  The metal case 15 has a substantially rectangular parallelepiped shape formed of, for example, a copper plate having a thickness of about 2 to 3 mm. In the metal case 15, an opening 151 for securing an insulation distance is formed around one connection terminal 13 of the capacitor body 12 to be accommodated. The metal case 15 covers the capacitor body 12 in a region other than the opening 151, and the other connection terminal 14 is fixed to the inner surface on the other surface side of the metal case 12 with a bolt 16. Is electrically connected.

  The metal case 15 and the insulator outside the capacitor body 12 are provided close to each other. In this case, the metal case 15 and the insulator of the capacitor body 12 are provided in close contact, the metal case 15 and the insulator of the capacitor body 12 are partially separated, and the metal case. 15 includes the case where the insulator of the capacitor body 12 is entirely separated, and the distance between the metal case and the insulator of the capacitor body when partially or completely separated is the inner dimension of the metal case. And the tolerance of the outer dimension of the capacitor body, for example, it means a case of 4 mm or less.

  When a high frequency current flows between the one connection terminal 13 and the other connection terminal 14 in the capacitor 10, the magnetic flux φ induced by the high frequency current I is shielded by the metal case 15, as shown in FIG. Eddy current E is generated in the surface of the metal case 15. Since the eddy current E shields the induced magnetic flux φ, the space in which the magnetic energy is stored becomes narrow, the rise in energy can be suppressed, and the inherent impedance can be reduced. And it is possible to suppress and reduce the occurrence of parasitic inductance equivalently.

  When the lumped constant circuit type pulse shaping circuit 20 is constituted by the capacitor 10, a plurality of capacitors 10 are connected as shown in FIGS. 3 and 4. For example, as shown in FIG. One connection terminal 13 and a coil 21 wound in a conductive spiral shape, such as a copper pipe, are connected in multiple stages via connection plates 221 and 222 and coil mounting members 231 and 232 to form a pulse shaping circuit 20. To do. For parts not particularly mentioned, it is possible to use the configuration of a normal lumped constant circuit type pulse shaping circuit.

  The coil attachment member 231 on the upper side in the figure is a plate having a hook part 2311 at the tip, and the hook part 2311 is hooked on the upper end of the coil 21 on the left side in the figure and attached to the coil 21 by soldering or the like. The connection plate 221 is substantially Z-shaped when viewed from the front, and the bent portion on the upper side in the drawing is fixed to the coil attachment member 231 by bolting or the like. The connecting plate 222 has a substantially inverted Ω shape when viewed from the front, and the bent portion at the left end in the figure is fixed to the bent portion at the lower side of the connecting plate 221 by bolting or the like, and the central part is fixed by bolting or the like. The connection terminal 13 is fixed and connected. The hook attachment member 232 has a plate shape having a hook portion 2321 at the tip. The hook portion 2321 is attached to the coil 21 by hooking the hook portion 2321 on the lower end of the coil 21 on the right side of the drawing and soldering or the like. It is fixed to the bent part on the right side by bolting or the like. In addition, the structure of the connection board in this invention is appropriate, the structure which connects between one connection terminal 13 * 13 with one connection board and the coil 21, or the connection board of the connection board 231 and 232 without providing. For example, an insertion engaging portion such as hook portions 2311 and 2321 that can insert the end portion of the coil 21 at the end portion may be provided and connected by a connection plate.

  One connection terminal 13 and the coil 21 are directly connected without using the connection plates 221 and 222, or the connection plates 221 and 222 that connect the one connection terminal 13 and the coil 21 are to reduce the parasitic inductance. For this reason, it is preferable to make the length as short as possible. However, when the length is increased due to the arrangement of the capacitor 10 and the coil 21, the plate widths of the connection plates 221 and 222 should be within the possible range with sufficient consideration for the space distance and creepage distance. It is preferable to increase the width so as to suppress parasitic inductance and reduce the resistance so that a large pulse current can flow smoothly. The connection plate for connecting the one connection terminal 13 such as the connection plates 221 and 222 and the coil 21 is preferably as wide as possible within the range where it can be installed in the pulse shaping circuit 20, for example, a connection plate having a width of 10 mm or more Good.

In the connection of the connection plates 221 and 222 having a wide plate width, it is possible to obtain an effect close to that of electrically connecting the one connection terminal 13 and the coil 21 directly, for example, shown by a two-dot chain line in FIG. The parasitic inductance generated in the portion can be eliminated as shown in FIG. 8A, and the parasitic inductance generated in the connection member when one connection terminal 13 and the coil 21 are connected by the connection members such as the connection plates 221 and 222 is eliminated. The rising characteristics of the pulse of the pulse shaping circuit 20 can be further improved.

  The metal cases 15 of the plurality of capacitors 10 in the pulse shaping circuit 20 are electrically connected to each other on the opening 151 side. In this example, the metal cases 15 are positioned on the peripheral surface of the opening 151 of the metal case 15 of one capacitor 10 and on the adjacent side. The conductive case 24 is placed on the peripheral surface of the opening 151 of the metal case 15 of the other capacitor 10 and installed, so that the metal case 15 of one capacitor 10 and the metal of the other capacitor 10 The case 15 is electrically interconnected. In addition, since a large pulse current flows, it is preferable that the connecting plate 24, the metal case 15, and the grounding location are securely fixed by a plurality of bolts or the like.

  With the configuration of the pulse shaping circuit 20, the connection plate 24 is at the ground potential regardless of the position of the metal case 15 of the capacitor 10, and a return circuit for the high-frequency current I flowing into the capacitor 10 from one connection terminal 13. As shown in FIG. 5 (a), the magnetic energy induced by the high-frequency current I flowing into the capacitor 10 from one connection terminal 13 is formed at the shortest distance only on the inner surface of the metal case 15 of the capacitor 10. 10 is confined inside.

  On the other hand, the one and the other capacitors 10 and 10 are placed at different locations from the above embodiment, for example, as shown in FIG. When connected, a return circuit for the high-frequency current I flowing into the capacitor 10 from one connection terminal 13 is formed not only on the inner surface of the metal case 15 of the capacitor 10 but also on the outer surface. In this case, the magnetic energy induced by the high-frequency current I flowing into the capacitor 10 from one connection terminal 13 is not confined only inside the capacitor 10 but spreads outside the capacitor 10 to increase parasitic inductance and stray capacitance. To do. As described above, it is preferable that the metal cases 15 of the plurality of capacitors 10 in the pulse shaping circuit 20 are electrically connected to each other on the opening 151 side of the metal case 15. The invention includes.

  The capacitor 10 and the pulse shaping circuit 20 according to the present embodiment, when the capacitor 10 is used for the pulse shaping circuit 20, reduce the parasitic inductance to suppress the current flowing through the parasitic inductance and obtain a pulse having excellent rising characteristics. For example, it can be used for a pulse power source that generates high-power high-speed pulses. Further, by reducing the parasitic inductance, it is possible to reduce the pulse pulsation and improve the pulse flatness, which is the degree of variation with respect to the peak power. Further, by providing the metal case 15 and the capacitor body 12 close to each other, the gap between the capacitor body 12 and the metal case 15 is eliminated, and it is ensured that discharge occurs between the capacitor body 12 and the metal case 15. Can be prevented. By electrically interconnecting the metal cases 15 of the plurality of capacitors 10 on the opening 151 side, magnetic energy can be confined inside the capacitor 10 to further reduce parasitic inductance and stray capacitance.

〔Example〕
A normal high-voltage capacitor composed of a pulse shaping circuit 20 (see A in the figure) by the capacitor 10 of the above embodiment and a capacitor main body and one and the other connection terminals without the metal case 15 and the like. FIG. 6 shows the results of a comparison experiment with a pulse shaping circuit (see B in the figure). Each pulse shaping circuit has a capacitor 20 pF, a coil 500 nH, and 30 stages. As can be seen from FIG. 6, the rise times are 0.7 μs for A and 0.8 μs for B, demonstrating the effects of the capacitor 10 and the pulse shaping circuit 20.

[Modifications of Embodiment, etc.]
In addition to the configurations of the inventions and embodiments, the invention disclosed in the present specification includes those specified by changing these partial configurations to other configurations disclosed in the present specification, or these configurations. Those specified by adding other configurations disclosed in the specification, or those obtained by deleting these partial configurations to the extent that partial effects can be obtained and specifying them, are included.

  For example, in the above-described embodiment, the metal case 15 and the capacitor body 12 are provided close to each other. Instead, the metal case 15 and the insulator of the capacitor body 12 are filled with an insulating material. A configuration is also possible. As the insulating material to be filled, it is preferable that the insulating material has a fluidity that can be easily filled by filling the gap, and further, an insulating material having a dielectric constant substantially equal to the material of the insulator outside the capacitor body 12 is used. It is preferable. More preferably, an insulating material having the same dielectric constant as the material of the insulator of the capacitor body 12 is filled. With this configuration, it is possible to eliminate the gap between the metal case 15 and the capacitor main body 12 and reliably prevent discharge from occurring in the gap.

  Further, as in the modification shown in FIG. 7, it is preferable that the periphery of the opening 151 of the metal case 15 is covered with the corona ring 17. In the example of FIG. 7, a corona ring 17 having a substantially L-shaped cross section is disposed on the upper side of the connecting plate 24, and the surface of the metal case 15 on the opening 151 side in the vicinity of the periphery of the opening 151 and the connecting plate laminated thereon. 24 covers the surface of the opening 151 side, covers the peripheral edge of the opening 151 and the one connecting terminal 13 side of the connecting plate 24 with the bent portion 172 at the tip, and surrounds the opening 151 of the metal case 15 by bolting or the like It is fixed to the surface. With this configuration, it is possible to prevent electric discharge from occurring between the one connection terminal 13 and the end face of the metal case 15 or the connecting plate 24 that is the periphery of the opening 151.

  In addition, a conductor may be provided in the pulse shaping circuit 20 so that it can be taken in and out of the coil 21 so that the inductance of the coil can be varied, and the flatness of the peak of the pulse can be adjusted to increase.

  In addition, the capacitor or pulse shaping circuit of the present invention can be used in a pulse power source such as a pulse modulator (modulator) or a kicker power source for an accelerator, and can also be used in a high power pulse radar device or the like.

  The present invention can be used, for example, as a pulse shaping circuit used for a pulse power source of an accelerator.

DESCRIPTION OF SYMBOLS 10 ... Capacitor 12 ... Capacitor main body 13 ... One connection terminal 14 ... The other connection terminal 15 ... Metal case 151 ... Opening 16 ... Bolt 17 ... Corona ring 171 ... Main body 172 ... Bending part 20 ... Pulse shaping circuit 21 ... Coil 221 , 222 ... connecting plates 231 and 232 ... coil mounting members 2311 and 2321 ... hook parts 24 ... connecting plates 91 ... DC power supply 92 ... charging circuit 93 ... pulse shaping circuit 931 ... transmission line 932 ... coil 933 ... capacitor 94 ... load 95 ... Switching element

Claims (7)

A capacitor comprising a capacitor body and a metal case,
The capacitor body, the outer side is covered with an insulator, and one connection terminals provided projecting from one surface of the front Symbol capacitor body, and the other connection terminals provided to protrude from the other surface of said capacitor body Have
The metal case houses the condenser body, which has an opening around the one connection terminal, and cover all areas other than the opening of said capacitor body, the other connection terminal to said metal case Capacitor characterized by electrical connection.   The capacitor according to claim 1, wherein the metal case and the capacitor body are provided close to each other.   The capacitor according to claim 1, wherein an insulator is filled between the metal case and the capacitor body.   The capacitor according to claim 1, wherein a peripheral edge of the opening of the metal case is covered with a corona ring.   A pulse shaping circuit comprising a plurality of capacitors according to claim 1 connected to each other.   6. The pulse shaping circuit according to claim 5, wherein the one connection terminal and the coil are connected to each other via a connection plate having a wide width as far as possible from the spatial distance and the circular distance at the installation position.   7. The pulse shaping circuit according to claim 5, wherein the metal cases of the plurality of capacitors are electrically interconnected on the opening side.

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