Electron multiplier and photoelectron multiplier containing the same

Abstract

This embodiment relates to an electron multiplier or the like having a structure for achieving faster response characteristics than conventional technologies. The electron multiplier comprises at least a dynode unit, a tube socket, a coaxial cable, a conductive member, and a capacitor. The dynode unit includes a multistage dynode, an anode, and a pair of insulating support members. The exposed portion of the inner conductor, which forms part of one end of the coaxial cable, is introduced into the dynode unit together with the end of the outer conductor. This structure allows the capacitor to be positioned in the space between the dynode unit and the tube socket, and the exposed portion of the inner conductor to be fixed to the portion of the anode held between the pair of insulating support members.

Description

Technical Field

[0001] The present invention relates to an electron multiplier and a photomultiplier. Background Art

[0002] Electron multipliers with multi-stage dynodes that cascade multiply secondary electrons in response to electron input are widely used as key components of various detectors operating under vacuum (reduced pressure), such as charged particle detectors used in photoelectron multipliers and mass analyzers. As a technique for achieving high-speed response in electron multipliers applicable to such a wide range of applications, for example, the following is known: a capacitor is arranged between the final dynode opposite the anode and the other dynodes adjacent to it, thereby suppressing reflection of high-frequency components and, as a result, reducing ringing in the output signal waveform. Furthermore, the ringing reduction effect is more effective when capacitors are connected directly to each dynode or by wiring shorter than a wire. Therefore, in the photoelectron multipliers disclosed in Patent Documents 1 and 2, the multi-stage dynodes and anode are housed within a sealed container, along with the capacitors.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 55-046203

[0006] [Patent Document 2] U.S. Patent No. 3,450,921

[0007] [Patent Document 3] Japanese Patent No. 4573407 (Japanese Patent Application Laid-Open No. 2002-042719) Summary of the Invention

[0008] [Problems to be Solved by the Invention]

[0009] The inventors have reviewed the above-mentioned prior art and have discovered the following problems. For example, in the photomultiplier of Patent Document 1, a capacitor is directly formed using the back surface of the final dynode (the final dynode functions as one electrode of the capacitor). On the other hand, the connection of the capacitor to the dynode adjacent to the final dynode (the adjacent dynode) is achieved through a wire. Specifically, one end of the wire is connected to the other electrode of the capacitor formed by the back surface of the final dynode, and the other end of the wire is connected to the protrusion of the adjacent dynode protruding from the insulating plate that holds the adjacent dynode. As a result, when the capacitor and the dynode are connected by a wire, it may not be possible to obtain a sufficient ringing reduction effect. Moreover, the inner conductor (signal line) of the coaxial cable is also connected to the protrusion of the anode protruding from the insulating plate via a wire (having a smaller cross-sectional area than the signal line), making it difficult to obtain a sharper output signal waveform (high-speed response characteristics).

[0010] The photomultiplier disclosed in Patent Document 2 includes a shield electrode surrounding a grid-shaped collector and final dynode. The inner conductor (signal line) of the coaxial cable is connected to the final dynode rather than the collector, and a capacitor is used to decouple the collector from ground potential. The photomultiplier disclosed in Patent Document 2 uses the collector as an anode during normal operation. However, when high-speed signals (instantaneous high currents) are used, the collector voltage fluctuates (due to instability). Therefore, as shown in the figure, the final dynode is used as the anode, and this final dynode is set to a potential lower than the set potential of the collector. Thus, the invention disclosed in Patent Document 2 is intended to provide a stable voltage supply to the collector and does not disclose a structure for achieving high-speed response characteristics. That is, in the above-mentioned patent document 2, although the connection relationship between each part is disclosed, the physical wiring structure (the configuration of each part, the use of wires as connecting components, etc.) is not disclosed at all, and it is impossible to know whether high-speed response characteristics can be achieved only in this wiring state.

[0011] For reference, in the photoelectron multiplier disclosed in Patent Document 3, a metal light shield (conductive member) is housed within a sealed container. However, the potential of the light shield is supplied via a wire drawn from outside the container, and the light shield does not contribute to high-speed response characteristics.

[0012] The present invention has been developed to solve the above-mentioned problems, and its purpose is to provide an electron multiplier having a structure useful for achieving faster response characteristics than the conventional technology, a photoelectron multiplier to which the electron multiplier can be applied, and a charged particle detector to which the electron multiplier can be applied.

[0013] [Methods for solving the problem]

[0014] The electron multiplier of this embodiment constitutes a key component of various detectors, such as charged particle detectors used in photoelectron multipliers and mass spectrometers. It primarily comprises a dynode unit, a stem, a coaxial cable, a conductive member, and a capacitor. The dynode unit is structured to cascade multiply incoming electrons and extract them as electrical signals. Specifically, it includes a multistage dynode, an anode, and a pair of insulating support members. The multistage dynode performs cascade multiplication of electrons. The anode is an electrode "set to a higher potential than the set potential of the final dynode in the multistage dynode and captures electrons emitted from the final dynode." The pair of insulating support members integrally hold at least the multistage dynode and the anode. The stem has a first surface and a second surface opposite the first surface, and holds the dynode unit while allowing multiple lead pins to pass through. The stem also holds the dynode unit in a space on the first surface side, located opposite the second surface relative to the first surface. A coaxial cable comprises an inner conductor; an insulating material disposed on the outer circumference of the inner conductor; and an outer conductor disposed on the outer circumference of the insulating material. Alternatively, the entire coaxial cable may be disposed in the first-surface space, or at least one end portion may be disposed in the first-surface space by passing a tube socket through the space. A conductive member is disposed in the first-surface space and is set to the same potential as the final dynode, which directly supplies multiplied electrons to the anode. A capacitor is disposed in the first-surface space and is arranged on the wiring between the conductive member and the outer conductor of the coaxial cable.

[0015] In particular, in an electron multiplier having the above-described structure, the exposed portion of the inner conductor located in the first surface side space is directly or indirectly secured to a portion of the anode sandwiched between a pair of insulating support members, with a portion of the inner conductor forming one end of the coaxial cable exposed from both the insulating material and the outer conductor. This configuration allows both securing the coaxial cable and the anode with sufficient mechanical strength and housing the capacitor within a sealed container.

[0016] In addition, each embodiment of the present invention can be more fully understood through the following detailed description and the accompanying drawings. These embodiments are only illustrative and should not be considered to limit the present invention.

[0017] The scope of further application of the present invention will become clear from the following detailed description. However, although the detailed description and specific examples represent preferred embodiments of the invention, they are merely illustrative, and it is obvious that various modifications and improvements within the scope of the invention can be made by those skilled in the art based on the detailed description.

[0018] [Effects of the Invention]

[0019] According to the electron multiplier of this embodiment, one end of the coaxial cable (including the exposed portion of the inner conductor, the end of the insulating material, and the end of the outer conductor) is introduced into the dynode unit, enabling the exposed portion of the inner conductor of the coaxial cable to be fixed to the anode. This improves response characteristics compared to conventional techniques. Furthermore, by introducing the end of the outer conductor of the coaxial cable into the dynode unit, a structural modification is achieved that is effective in suppressing ringing in the output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [ Figure 1 ] Figure 1 This is a partially broken view schematically showing an example of the internal structure of a photoelectron multiplier (an example of the photoelectron multiplier of this embodiment) as an example of a detector including the electron multiplier of this embodiment as a main part.

[0021] [ Figure 2 ] Figure 2 An example of a photoelectron multiplier according to this embodiment is shown along Figure 1 FIG. 1 is a diagram showing a cross-sectional structure of line II shown in FIG.

[0022] [ Figure 3 ] Figure 3 It is a diagram for explaining the schematic configuration and response characteristics of a power supply circuit for operating an example of the photoelectron multiplier according to the present embodiment.

[0023] [ Figure 4 ] Figure 4 This is a diagram showing the assembly process of the main parts of an example of the photoelectron multiplier according to this embodiment.

[0024] [ Figure 5 ] Figure 5 A diagram schematically illustrating the connection between the inner conductor of a coaxial cable and the anode in a sealed container.

[0025] [ Figure 6 ] Figure 6 A diagram schematically illustrating the positional relationship between a shield electrode and a coaxial cable in a sealed container.

[0026] [ Figure 7 ] Figure 7 A diagram for schematically illustrating the structural features of a conductive member.

[0027] [ Figure 8 ] Figure 8 Graphs for explaining the difference in response characteristics between Sample 1 and Comparative Example 1, which partially employ the structural features of the photoelectron multiplier according to this embodiment.

[0028] [ Figure 9 ] Figure 9 Graphs for explaining the difference in ringing suppression effect between Sample 2 and Comparative Example 2, both of which employ the structural features of the photoelectron multiplier according to the present embodiment. DETAILED DESCRIPTION

[0029] [Description of the embodiment of the present invention]

[0030] First, the contents of the embodiments of the present invention will be individually listed and described.

[0031] (1) The electron multiplier of this embodiment constitutes the main part of various detectors such as charged particle detectors used in photoelectron multipliers and mass spectrometers. As one form, it mainly includes a dynode unit, a tube seat, a coaxial cable, a conductive member, and a capacitor. The dynode unit has a structure for cascading multiplication of the electrons that have arrived and extracting them as electrical signals. Specifically, it includes a multistage dynode, an anode, and a pair of insulating support members. The multistage dynode cascade multiplies the electrons. The anode is an electrode that is "set to a potential higher than the set potential of the final dynode in the multistage dynode and captures the electrons emitted from the final dynode." The pair of insulating support members at least integrally holds the multistage dynode and the anode. The tube seat has a first surface and a second surface opposite to the first surface, and holds the dynode unit in a state where a plurality of lead pins pass through. In addition, the tube seat holds the dynode unit in a space on the first surface side located on the opposite side of the second surface relative to the first surface. A coaxial cable comprises an inner conductor; an insulating material disposed on the outer circumference of the inner conductor; and an outer conductor disposed on the outer circumference of the insulating material. Alternatively, the coaxial cable may be disposed entirely in the first surface side space, or at least one end portion may be disposed in the first surface side space by passing a tube holder through the space. A conductive member is disposed in the first surface side space and is set to the same potential as the final dynode that directly supplies multiplied electrons to the anode. A capacitor is disposed in the first surface side space and is arranged on the wiring between the conductive member and the outer conductor of the coaxial cable. Alternatively, the conductive member may be composed of one or more conductive elements.

[0032] In particular, in an electron multiplier having the above-described structure, the exposed portion of the inner conductor, which constitutes a portion of one end of the coaxial cable—that is, the exposed portion of the inner conductor located in the space on the first surface side while exposed from the ends of the insulating material and the outer conductor—is directly or indirectly fixed to a portion of the anode sandwiched between a pair of insulating support members. Thus, one end of the coaxial cable (including the exposed portion of the inner conductor, the end of the insulating material, and the end of the outer conductor) is introduced into the dynode unit (the space sandwiched between the pair of insulating support members). By achieving a structure that allows the exposed portion of the inner conductor of the coaxial cable to be fixed to the anode, the response characteristics are improved compared to conventional techniques. Furthermore, by introducing the outer conductor of the coaxial cable into the dynode unit, a capacitor (decoupling capacitor) for suppressing reflection of high-frequency components can be positioned near the final dynode. This structure allows for a structural modification that is effective in suppressing ringing in the output signal.

[0033] Moreover, the photoelectron multiplier and charged particle detector of the present embodiment both contain an electron multiplier (electron multiplier of the present embodiment) having the structure as described above as a main part. In particular, the photoelectron multiplier, in addition to the electron multiplier having the structure as described above, further comprises a cathode and a sealed container. The cathode emits photoelectrons toward the dynode unit in response to light input. The sealed container comprises: a main body (envelope) extending along the central axis and having an opening end that is predetermined to intersect with the central axis; and a tube seat that functions as the above-mentioned tube seat. The main body accommodates at least the cathode and the dynode unit. The tube seat is in close contact with the opening end in a state where the opening end is blocked. In addition, the coaxial cable is held in the tube seat in a state where the other end of the coaxial cable passes through the tube seat from the first surface to the second surface. On the other hand, since the charged particle detector supplies electrons to an electron multiplier having the above-described structure, it includes a conversion dynode that emits electrons toward the electron multiplier in response to input of charged particles. In particular, in this charged particle detector, a stem is disposed within a vacuum container, and the entire coaxial cable is disposed in the space between the anode and the stem (the first surface side space).

[0034] (2) As one aspect of this embodiment, since the exposed portion of the inner conductor constituting a portion of the end of one side of the coaxial cable is fixed to the anode, it is preferred that the exposed portion of the inner conductor, together with the end of the outer conductor, is located in a space clamped by a pair of insulating support members (inside the dynode unit). In this case, the anode and the inner conductor of the coaxial cable can be firmly fixed without passing through other wiring components. In addition, as one aspect of this embodiment, when the tube seat side is viewed from the dynode unit side along the direction from the first surface toward the second surface, the dynode unit is preferably configured so that the portion of the anode clamped by the pair of insulating support members (the portion of the coaxial cable to which the exposed portion of the inner conductor is fixed) overlaps with the portion of the first surface (tube seat) where the coaxial cable is arranged. With this configuration, the inner conductor of the coaxial cable can reach the anode by the shortest distance.

[0035] (3) As one aspect of this embodiment, the conductive member, which is composed of one or more conductive elements, preferably has a cross-sectional area larger than the cross-sectional area of ​​each of the plurality of lead pins. Furthermore, by fixing a portion (the first portion) of the conductive member to the final dynode (the conductive member is set to the same potential as the final dynode), ringing of the output signal can be effectively suppressed.

[0036] (4) In one aspect of this embodiment, the capacitor has one external electrode fixed to a portion (the second portion) of the conductive member, and the other external electrode electrically connected to the outer conductor of the coaxial cable (the portion located between the stem and the dynode unit). Specifically, by placing the capacitor closer to the conductive member, which is set to the same potential as the final dynode, the occurrence of ringing in the output signal can be more effectively suppressed.

[0037] (5) As one aspect of this embodiment, the conductive member preferably includes a shielding electrode mounted on a pair of insulating support members. In addition, in order to bring one end of the coaxial cable closer to the anode, the shielding electrode preferably has an opening for allowing the exposed portion of the inner conductor and the end of the outer conductor to pass through from the stem side toward the anode. Generally, the shielding electrode is provided to limit the movement of light or ions generated when electrons collide with the dynodes toward the dynode unit, but in this embodiment, the shielding electrode is utilized as a conductive member set to the same potential as the final dynode. In this case, as one aspect of this embodiment, the capacitor is located in the space between the shielding electrode and the stem. Furthermore, as one aspect of this embodiment, in a configuration in which the electron multiplier is housed in a sealed container or in a configuration in which the stem of the electron multiplier itself functions as part of the sealed container (in this case, the internal space of the sealed container corresponds to the first surface side space), the capacitor housed in the sealed container preferably includes a ceramic capacitor because it can operate in a vacuum state (decompressed state) and can be easily joined to the conductive member.

[0038] Each aspect listed above in the column “Description of the embodiment of the present invention” can be applied to each of all other aspects or to all combinations of these other aspects.

[0039] [Details of the embodiment of the present invention]

[0040] The specific structures of the electron multiplier, photoelectron multiplier, and charged particle detector of this embodiment are described in detail below with reference to the accompanying drawings. The present invention is not limited to the examples shown in the claims and is intended to encompass all modifications within the meaning and scope equivalent to those in the claims. In the description of the drawings, identical elements are denoted by identical reference numerals, and repeated descriptions are omitted.

[0041] In addition, the following disclosure describes an example of a photoelectron multiplier that includes the electron multiplier of this embodiment as its main component. Similar to the photoelectron multiplier, a charged particle detector also includes the electron multiplier of this embodiment as its main component. The charged particle detector has a structure similar to that of a photoelectron multiplier, except that it lacks a vacuum container (sealed container), the structure of the tube base is not limited to a structure with through-lead pins, a conversion unit that converts charged particles from the conversion dynode or Faraday cup into electrons instead of a cathode, and the entire coaxial cable is arranged in the space between the dynode unit and the tube base. The following description of the example of the photoelectron multiplier also applies to the charged particle detector.

[0042] Figure 1 This is a partially broken diagram schematically showing an example of the internal structure of a photoelectron multiplier (an example of the photoelectron multiplier of this embodiment) as an example of a detector including the electron multiplier of this embodiment as a main part. Figure 2 An example of a photoelectron multiplier according to this embodiment is shown. Figure 1 FIG. 1 is a diagram showing a cross-sectional structure of line II shown in FIG.

[0043] like Figure 1 As shown, the photoelectron multiplier 100 includes a sealed container 110 , and includes a cathode 120 and an electron multiplying unit disposed in the sealed container 110 . The sealed container 110 has a pipe 130 at the bottom thereof for evacuating the interior (which is sealed after evacuation).

[0044] The sealed container 110 is composed of a cylindrical main body 110a and a tube base 110b. The main body 110a has a face plate with a cathode 120 formed inside. The tube base 110b holds the coaxial cable 600 and a plurality of lead pins 140 while each of these is passed through. The main body 110a extends along a central axis (tube axis) AX and has an open end that defines an opening intersecting with the central axis AX. The tube base 110b is tightly attached to the open end of the main body 110a while blocking the open end. After the residual gas is discharged through the pipe 130, the internal space of the sealed container 110 is sealed, thereby maintaining a predetermined decompression state. Within the sealed container 110, the electron multiplying unit is held at a predetermined position within the sealed container 110 by the lead pins 140 extending from the tube base 110b into the sealed container 110.

[0045] The electron multiplying unit is composed of a focusing electrode 200, an accelerating electrode 300, and a dynode unit 400 with an anode 500 disposed therein. The focusing electrode 200 is used to correct the trajectory of photoelectrons emitted from the cathode 120 so that they are focused toward the dynode unit 400. It is positioned between the cathode 120 and the dynode unit 400 and has a through-hole for allowing photoelectrons from the cathode 120 to pass through. Furthermore, the accelerating electrode 300 accelerates photoelectrons emitted from the cathode 120 toward the dynode unit 400. It is positioned between the focusing electrode 200 and the dynode unit 400 and has a through-hole for allowing photoelectrons that have passed through the through-hole of the focusing electrode 200 to pass further toward the dynode unit 400. The accelerating electrode 300 reduces the variation in the travel time of photoelectrons from the cathode 120 to the dynode unit 400 caused by the photoelectron emission site of the cathode 120. The dynode unit 400 includes: a multi-stage dynode DY1 to DY4 for sequentially cascading and multiplying secondary electrons emitted in response to photoelectrons arriving from the cathode 120 via the focusing electrode 200 and the accelerating electrode 300; an anode 500 for capturing the secondary electrons cascade-multiplied by the multi-stage dynodes DY1 to DY4 as electrical signals; and a pair of insulating support members 410a and 410b for integrally holding the multi-stage dynodes DY1 to DY4 and the anode 500 (see FIG. 1 ). Figure 4 ).

[0046] The coaxial cable 600 includes an inner conductor 610 extending along the central axis AX, similar to the plurality of lead pins 140; a glass material 620 serving as an insulating material disposed on the outer circumference of the inner conductor 610; and an outer conductor 630 disposed on the outer circumference of the glass material 620. The tip (exposed portion) of the inner conductor 610, which is to be fixed to the anode 500, is exposed from the ends of the glass material 620 and the outer conductor 630. The exposed portion of the inner conductor 610, the end of the glass material 620, and the end of the outer conductor 630 constitute one end of the coaxial cable 600. The inner conductor 610 (particularly the exposed portion), along with the ends of the glass material 620 and the outer conductor 630, are also introduced into the sealed container 110. The coaxial cable 600 is secured to the stem 110b, which is maintained at a reduced pressure, via a hermetic seal 640. Furthermore, one end of the coaxial cable 600, which is formed by the exposed portion of the inner conductor 610, the end of the glass material 620, and the end of the outer conductor 630, is located in the space sandwiched between the pair of insulating support members 410a and 410b. The exposed portion of the inner conductor 610 is directly or indirectly fixed to the portion of the anode 500 sandwiched between the pair of insulating support members 410a and 410b. The inner conductor 610 (particularly the exposed portion) is fixed to the anode 500 by resistance welding.

[0047] The conductive member 800 and the capacitor (decoupling capacitor) 700 are housed in the sealed container 110. Figure 1 In the example shown in FIG. 1 , the conductive member 800 includes a shield electrode 450 mounted on a pair of insulating support members 410a and 410b. A portion of the shield electrode 450 is resistance-welded to the fourth-stage dynode (final-stage dynode) DY4. Furthermore, the cross-sectional area of ​​the shield electrode 450 (the area of ​​the region sandwiched between the surface facing the multi-stage dynodes DY1 to DY4 and the surface facing the inner wall of the sealed container 110) is larger than the cross-sectional area of ​​the lead pin 140. Furthermore, as Figure 4 and Figure 6 As shown, one external electrode of capacitor 700 is bonded and fixed to metal plate 660 via silver paste 900, while the other external electrode of capacitor 700 is bonded and fixed to one end of metal plate 650 via silver paste 900. Both metal plates 650 and 660 have a cross-sectional area larger than that of lead pin 140. Metal plates 650 and 660, fixed to both ends of capacitor 700, are resistance-welded to shield electrode 450 and outer conductor 630 of coaxial cable 600, respectively. Furthermore, metal plate 650, like metal plate 660, may have a strip shape to facilitate resistance welding of metal plate 650 and shield electrode 450.

[0048] The electron multiplying unit housed in the sealed container 110 is as follows: Figure 2 As shown, the focusing electrode 200, the accelerating electrode 300 and the dynode unit 400 are connected together by a pair of insulating support members 410a and 410b (see FIG. Figure 4 In particular, the positional relationship of the focusing electrode 200, the accelerating electrode 300, the first-stage dynode DY1 to the fourth-stage dynode (final-stage dynode) DY4, and the anode 500 is fixed by the pair of insulating support members 410a and 410b.

[0049] Thus, the photoelectron multiplier 100 has a structure in which at least the first-stage dynode DY1 and the second-stage dynode DY2 included in the dynode unit 400 are directly opposed to the accelerating electrode 300 without a conductive member interposed therebetween, and at least the accelerating electrode 300 and the dynode unit 400 are integrally held. In the photoelectron multiplier 100 of this embodiment, the accelerating electrode 300 accelerates the photoelectrons traveling from the cathode 120 toward the first-stage dynode DY1. Therefore, the variation in the photoelectron travel time from the cathode 120 to the first-stage dynode DY1 is significantly reduced.

[0050] exist Figure 2 The internal structure of the coaxial cable 600 and the positional relationship between the coaxial cable 600 and the anode 500 are clearly shown. Specifically, the coaxial cable 600, which is fixed to the stem 110b via the seal 640, has its end extending from the stem 110b toward the anode 500 (the end extending to within the dynode unit 400 defined by the space between the pair of insulating support members 410a and 410b). At one end of the coaxial cable 600, a portion of the inner conductor 610 is exposed from the glass material 620 and the outer conductor 630. This exposed portion of the inner conductor 610 is fixed to the anode 500 by resistance welding. Furthermore, since the exposed portion of the inner conductor 610 of the coaxial cable 600 is fixed to the anode 500 at the shortest distance, as will be described later, when viewing the stem 110b from the cathode 120 along the central axis AX of the sealed container 110, the portion of the anode 500 where the exposed portion of the inner conductor 610 is fixed overlaps the portion of the stem 110b where the coaxial cable 600 passes through. In this case, the portion of the anode 500 where the inner conductor 610 is fixed naturally becomes the portion sandwiched between the pair of insulating support members 410a and 410b. Therefore, the anode 500 and the exposed portion of the inner conductor 610 of the coaxial cable 600 can be directly connected, without requiring a connection through other wiring components, such as wiring having a cross-sectional area comparable to that of the lead pin 140, which has a smaller cross-sectional area than that of the inner conductor 610.

[0051] Figure 3(a) is a diagram for explaining a schematic configuration of a power supply circuit for operating an example of the photoelectron multiplier of this embodiment having the above-described structure. Figure 3 (b) is a diagram for explaining the response characteristics of an example of the photoelectron multiplier according to this embodiment.

[0052] like Figure 3 As schematically shown in (a), within the sealed container 110 of the photoelectron multiplier 100, a cathode 120, a focusing electrode 200, an accelerating electrode 300, multi-stage dynodes DY1 to DY4, and an anode 500 are arranged on the inner wall surface of the panel of the main body 110a toward the tube base 110b. The arrangement of the first-stage dynode DY1, the second-stage dynode DY2, the third-stage dynode DY3, and the fourth-stage dynode (final dynode) DY4 is shown in the order in which photoelectrons or secondary electrons pass through. In addition, the potentials of the cathode 120, the focusing electrode 200, the multi-stage dynodes DY1 to DY4, and the anode 500 are as shown in FIG. Figure 3 As shown in (a), the voltage divider circuit is set to divide the voltage provided by the power supply V by a series circuit of multiple R and capacitor C. Figure 3 In the example of (a), the accelerating electrode 300 is set to the potential of the fourth-stage dynode DY4.

[0053] One end of the coaxial cable 600 is guided into the space on the stem 110b side within the sealed container 110, and the exposed portion of the inner conductor 610 is directly fixed to the anode 500. Furthermore, a capacitor (ceramic capacitor) 700 is also housed within the sealed container 110. One of its external electrodes is resistance-welded to a conductive member 800 via a predetermined conductive member. This conductive member 800 is set to the same potential as the fourth-stage dynode DY4. Furthermore, the other external electrode of the capacitor 700 is electrically connected to the outer conductor 630 within the sealed container 110 via a predetermined conductive member.

[0054] As the response characteristic of the photoelectron multiplier 100 having the above-mentioned structure, the anode output (electron signal) becomes as follows Figure 3 (b) The shape as shown in the figure. Figure 3The waveform shown in (b) is the anode-side output waveform assuming light from a delta function light source reaches cathode 120. Typically, when photoelectrons are emitted from cathode 120 in response to light from the light source, secondary electrons multiplied by the multistage dynodes DY1 to DY4 reach anode 500 and are output as electrical signals to the outside of sealed container 110. The time from the output of photoelectrons from cathode 120 to the peak of the anode output is called the "electron transfer time." The period from when the signal level reaches 10% of the peak value to when it reaches 90% of the peak value is called the "rise time," and conversely, the period from when the signal level reaches 90% of the peak value to when it reaches 10% of the peak value is called the "fall time."

[0055] Secondly, Figure 4 FIG1 is an assembly process diagram of the main parts of an example of the photoelectron multiplier of this embodiment. Figure 4 As shown in the example, the electron multiplying unit is composed of a focusing electrode 200, an accelerating electrode 300, and a dynode unit 400 including an anode 500. The focusing electrode 200 and the accelerating electrode 300 are each provided with a through hole for allowing photoelectrons from the cathode 120 to pass toward the first-stage dynode DY1.

[0056] exist Figure 4 In the illustrated example, the focusing electrode 200 is composed of a body portion 210 (essentially the focusing electrode body; in this specification, the body portion 210 is simply referred to as the "focusing electrode") and reinforcement members 250a and 250b for inhibiting rotation of the body portion 210. The body portion 210 has a cylindrical shape and includes a flange portion extending inward from one open end of the body portion 210 and defining a through-hole. The flange portion is gripped by a slit groove provided in the protrusions of the first and second insulating support members 410a and 410b, which constitute the pair of insulating support members.

[0057] The accelerating electrode 300 has an opening for allowing photoelectrons from the cathode 120 to pass toward the first-stage dynode DY1, and also has a flange portion for securing the accelerating electrode 300 to the first and second insulating support members 410a and 410b. The accelerating electrode 300 is secured to the first and second insulating support members 410a and 410b by gripping protrusions provided on the first and second insulating support members 410a and 410b through slits provided in the flange portion.

[0058] The dynode unit 400 is composed of the first-stage dynodes DY1 through DY4 (the final dynode), and the anode 500, which are held by the first and second insulating support members 410a and 410b, respectively. Furthermore, each of the first-stage dynodes DY1 through DY4 (the final dynode) has a reflective secondary electron emission surface. These reflective secondary electron emission surfaces receive photoelectrons or secondary electrons and re-emit them in the direction of their incidence. Furthermore, fixing plates DY1a and DY1b are provided at both ends of the first-stage dynode DY1, held by the first and second insulating support members 410a and 410b. Specifically, the first-stage dynode DY1 is held by the first and second insulating support members 410a and 410b, with the fixing piece DY1a extending through the slit provided in the first insulating support member 410a and the fixing piece DY1b extending through the slit provided in the second insulating support member 410b. Similarly, the second-stage dynode DY2 has fixing pieces DY2a and DY2b at its ends, the third-stage dynode DY3 has fixing pieces DY3a and DY3b at its ends, and the fourth-stage dynode DY4 has fixing pieces DY4a and DY4b at its ends.

[0059] The anode 500 has an electron capture surface at a position where secondary electrons emitted from the fourth-stage dynode DY4 arrive, and has a fixed surface 510 (see Figure 5 (a) The fixing surface 510 is used to fix one end of the coaxial cable 600 inserted into the sealed container 110, particularly the front end of the inner conductor 610. Furthermore, a pair of fixing pieces 500a and a pair of fixing pieces 500b are provided at both ends of the anode 500 so as to be held by the first and second insulating support members 410a and 410b.

[0060] Furthermore, shield electrodes 450 are mounted on the first and second insulating support members 410a and 410b, covering the two gaps between the exposed side of the anode 500 and the side of the stem 110b. Furthermore, cathode electrodes 460 are mounted on the first and second insulating support members 410a and 410b on the opposite sides of the shield electrodes 450. Cathode electrodes 460 also have fixing plates 460a and 460b, which fit into recesses provided in the first and second insulating support members 410a and 410b, respectively. Furthermore, a metal plate 460c is resistance-welded to the back surface of the cathode electrode 460. This metal plate 460c contacts the metal film extending from the cathode 120 along the inner wall of the main body 110a of the sealed container 110.

[0061] Shielding electrode 450 is equivalent to Figure 3The conductive member 800 shown in (a) is composed of a first conductive plate 450a and a second conductive plate 450b, each having a cross-sectional area larger than that of the lead pin 140 (the first and second conductive plates 450a and 450b are resistance-welded). Here, a notch 451a is provided in the first conductive plate 450a. Similarly, a notch 451b is also provided in the second conductive plate 450b. By resistance-welding the second conductive plate 450b to the first conductive plate 450a, a through-hole is formed through which one end of the coaxial cable 600 passes. Therefore, one end of the coaxial cable 600 can directly reach the space sandwiched between the first and second insulating support members 410a and 410b through the through-hole provided in the shielding electrode 450.

[0062] In addition, fixing pieces 453a and 453b are provided on the first conductive plate 450a, and the fixing pieces 453a and 453b are respectively resistance-welded to the fixing pieces DY4a and DY4b of the fourth-stage dynode DY4. With this structure, the shielding electrode 450 is set to the same potential as the fourth-stage dynode DY4. In addition, the end of the first conductive plate 450a provided with the notch 451a extends further toward the stem 110b side than the second conductive plate 450b is fixed. The external electrode of one side of the capacitor (ceramic capacitor) 700 is electrically connected to the portion extending to the stem 110b side. Specifically, the metal plate 660 is bonded and fixed to the external electrode of one side of the capacitor 700 via silver paste 900, and an area 452 (see FIG. 4 ) for fixing by resistance welding is ensured in the portion extending to the stem 110b side. Figure 4 and Figure 6 ).

[0063] The other external electrode of the capacitor 700 is electrically connected to the outer conductor 630 of the coaxial cable 600 introduced into the sealed container 110. This electrical connection is achieved through the metal plate 650. That is, one end of the metal plate 650 is resistance welded to the outer conductor 630 of the coaxial cable 600. On the other hand, the other external electrode of the capacitor 700 is bonded and fixed to the other end of the metal plate 650 via silver paste 900 (see Figure 4 and Figure 6 ). Through the above assembly steps, the electron multiplying unit of the photoelectron multiplier 100 of this embodiment can be obtained.

[0064] Figure 5 (a) and Figure 5 (b) is used to schematically illustrate the Figure 4 The arrow (observation direction) S1 shown in FIG is a diagram showing the structure of the electron multiplying unit constructed as described above, particularly the connection state between the exposed portion of the inner conductor 610 in the coaxial cable 600 and the anode 500 in the sealed container 110. Figure 5 (a) and Figure 5 In (b), in order to clarify the positional relationship between the coaxial cable 600 and the anode 500 , the shielding members such as the shield electrode 450 are omitted.

[0065] like Figure 5 As shown in (a), the anode 500 is inserted into the corresponding slit holes of the first insulating support member 410a through a pair of fixing pieces 500a, and on the other hand, a pair of fixing pieces 500b are inserted into the corresponding slit holes of the second insulating support member 410b, thereby being held by the first and second insulating support members 410a and 410b. In such a held state, the electron capture surface of the anode 500 faces the side of the fourth-stage multiplier DY4. In addition, the fixed surface 510 to which the exposed portion of the inner conductor 610 in the coaxial cable 600 is resistance-welded is in a positional relationship intersecting with the electron capture surface. In this way, by tilting the fixing surface 510 relative to the electron capture surface, when the exposed portion of the inner conductor 610 is resistance-welded to the fixing surface 510, the end of one side of the coaxial cable 600 can be introduced into the sealed container 110 without bending. On the other hand, in Figure 5 In the example shown in (b), the exposed portion of the inner conductor 610 is resistance-welded to the electrode member 520 having the fixing surface 510. The electrode member 520 is a metal member that constitutes a portion of the anode 500, and by resistance-welding the electrode member 520 to the side surface of the anode 500, the exposed portion of the inner conductor 610 is indirectly fixed to the anode 500.

[0066] In addition, even in Figure 5 (a) and Figure 5 In any of the examples (b), one end of the metal plate 650 is also resistance-welded to the outer peripheral surface of the outer conductor 630 at one end of the coaxial cable 600 introduced into the sealed container 110. A region 651 (see FIG. 1 ) where the other external electrode of the capacitor 700 is bonded and fixed to the other end of the metal plate 650 via the silver paste 900 is secured. Figure 6 ).

[0067] As described above, by introducing one end of the coaxial cable 600 (including the exposed portion of the inner conductor 610, the end of the glass material 620, and the end of the outer conductor 630) into the sealed container 110, a configuration is achieved in which the exposed portion of the inner conductor 610 of the coaxial cable 600 can be directly fixed to the fixing surface 510 of the anode 500. This improves the response characteristics compared to the conventional technology. Furthermore, by also introducing the end of the outer conductor 630 of the coaxial cable 600 into the sealed container 110, a capacitor (ceramic capacitor) 700 for suppressing reflection of high-frequency components can be placed within the sealed container 110. In this case, the occurrence of ringing in the signal waveform emitted from the anode 500 can be effectively suppressed.

[0068] Furthermore, to ensure a secure connection between the inner conductor 610 of the coaxial cable 600 and the anode 500, the length of the inner conductor 610 exposed from the glass material 620 and outer conductor 630 of the coaxial cable 600 (the length of the exposed portion) is preferably short. Therefore, one end of the coaxial cable 600, including at least the end of the outer conductor 630, is preferably introduced closer to the anode 500, that is, into the space between the first and second insulating support members 410a and 410b. In this configuration, when viewing the stem 110b from the cathode 120 side along the central axis AX of the sealed container 110, the dynode unit 400 is positioned such that the anode 500 having the fixing surface 510 overlaps the portion of the stem 110b through which the coaxial cable 600 passes.

[0069] Secondly, Figure 6 4 is a diagram for schematically illustrating the positional relationship between the shield electrode 450 and the coaxial cable 600 in the sealed container 110. Figure 6 The plan shown in the upper left is along Figure 4 The arrow S1 shown is a plan view when viewing the electron multiplying unit (particularly, the first conductive plate 450a of the shield electrode 450). Figure 6 The plan view shown in the lower left is along Figure 6 The arrow S2 shown is a plan view of the shield electrode 450 (the first conductive plate 450a and the second conductive plate 450b). Figure 6 The plan view shown in the upper right corner is along Figure 6 Arrow S3 shows a plan view of the shield electrode 450 (particularly the second conductive plate 450 b ), and particularly shows in detail the fixed state between the shield electrode 450 and the capacitor 700 , and the fixed state between the capacitor 700 and the metal plate 650 .

[0070] The photoelectron multiplier 100 can be obtained from Figure 6The various structural features described above are confirmed in the plan views shown in the various directions. Specifically, (a) the portion of the inner conductor 610 of the coaxial cable 600 that is exposed within the interior space of the sealed container 110 is fixed to the fixing surface 510 of the anode 500, which is held between the first and second insulating support members 410a and 410b. (b) Because the capacitor 700 can be housed within the sealed container 110, the outer conductor 630 of the coaxial cable 600 is also introduced into the sealed container 110. (c) In particular, to shorten the exposed portion of the inner conductor 610, the end of the outer conductor 630 is positioned within the space held between the first and second insulating support members 410a and 410b. (d) When viewed from the cathode 120 side along the central axis AX of the sealed container 110 toward the stem 110b, the anode 500 overlaps with the portion of the stem 110b through which the coaxial cable 600 passes. (e) The first and second conductive plates 450a and 450b constituting the shield electrode 450 both have a cross-sectional area larger than that of the lead pin 140. (f) The capacitor 700 can be located in the space between the shield electrode 450 and the stem 110b, and as a result, is housed within the sealed container 110. (g) To bring one end of the coaxial cable 600 closer to the anode 500, the shield electrode 450 has an opening that allows the exposed portion of the inner conductor 610, along with the ends of the glass material 620 and the outer conductor 630, to pass from the stem 110b side toward the anode 500.

[0071] In addition, the installation position of the capacitor 700 is not limited to Figure 6 The metal plates 650 and 660 are respectively bonded and fixed to the external electrodes at both ends of the capacitor 700 via silver paste. Therefore, by adjusting the shapes of the metal plates 650 and 660, the capacitor 700 can be set to a position that does not hinder the soldering operation, for example, Figure 6 The position shown in the upper right of FIG is closer to the position of the stem 110b (a configuration in which the capacitor 700 is sufficiently separated from the welding portion). In this case, sufficient space required for the welding operation can be ensured between the second conductive plate 450b and the capacitor 700.

[0072] Figure 7 For a brief description Figure 3 FIG 8 is a diagram showing the structural features of the conductive member 800 (including the shielding electrode 450). That is, in order to suppress the reflection of high frequency components, as shown in FIG. Figure 7 As shown in the upper left of FIG, the cross-sectional area Sa of the conductive member 800 having a length L1 is preferably larger than the cross-sectional area of ​​the lead pin 140. However, as Figure 7As shown in the upper right of [reference], even for conductive members having the same length L1, a conductive member 800a having a larger cross-sectional area Sb (> Sa) like the shielding electrode 450 described above is effective in suppressing reflection of high-frequency components. Additionally, as Figure 7 shown in the lower left of [reference], even for conductive members having the same cross-sectional area Sa, a conductive member 800b having a shorter length L2 (< L1) is effective in suppressing reflection of high-frequency components.

[0073] To confirm the above technical effects of the photomultiplier 100 of the present embodiment, [references] Figure 8 and Figure 9 are used to illustrate the case where "by comparing a sample including the structural features of the photomultiplier 100 of the present embodiment with a comparative example, the response characteristics are improved". Additionally, Figure 8 FIG. [reference] is a diagram for illustrating the difference in response characteristics between a sample 1 partially adopting the structural features of the photomultiplier of the present embodiment and a comparative example 1. Additionally, Figure 9 FIG. [reference] is a diagram for illustrating the difference in ringing suppression effects between a sample 2 adopting the structural features of the photomultiplier 100 of the present embodiment and a comparative example 2. Additionally, Figure 8 and Figure 9 The structures of the sample 1, sample 2, comparative example 1, and comparative example 2 shown in [reference] only show the main parts, and the structures not shown in any of the photomultipliers are the same as the above structures.

[0074] In Figure 8 FIG. [reference], the structure and response characteristics of the comparative example 1 and the structure and response characteristics of the sample 1 of the present embodiment are shown. In Figure 8 FIG. [reference], as the structures of both the comparative example 1 and the sample 1, the fourth-stage dynode DY4 and the anode 500 held by the first and second insulating support members 410a and 410b are shown. In the comparative example 1, although one end of the coaxial cable 600 is introduced into the sealed container 110 through the base 110b, the exposed part of the inner conductor 610 is directly resistance-welded to the fixing piece 500b of the anode 500 protruding from the outside of the insulating support member 410b. Therefore, the length of the exposed part of the inner conductor 610 is adjusted to 10 mm.

[0075] On the other hand, in the sample 1, one end of the coaxial cable 600 is introduced into the space clamped by the first and second insulating support members 410a and 410b through the base 110b, and the exposed part of the inner conductor 610, which is only 2 mm exposed from the ends of the glass material 620 and the outer conductor 630, is resistance-welded to the fixing surface 510 of the anode 500.

[0076] In the photoelectron multiplier of Comparative Example 1 having the above-described structure, the full width at half maximum (FWHM) of the waveform of the anode output obtained was 410 ps. On the other hand, in the photoelectron multiplier of Sample 1, the full width at half maximum (FWHM) of the waveform of the anode output obtained was 383 ps, confirming an improvement in the response characteristics (higher speed).

[0077] Secondly, in Figure 9 The structure and response characteristics of Comparative Example 2 and the structure and response characteristics of Sample 2 of this embodiment are shown. Figure 9 In the figure, the structures of Comparative Example 2 and Sample 2 both show the fourth-stage dynode DY4 and anode 500 held by the first and second insulating support members 410a and 410b. However, in the configuration of Comparative Example 2, while one end of the coaxial cable 600 is introduced into the sealed container 110 via the stem 110b, the exposed portion of the inner conductor 610 is located outside the space between the first and second insulating support members 410a and 410b. Therefore, the exposed portion of the inner conductor 610 has a length of 10 mm and is resistance-welded to the fixing piece 500b of the anode 500 (the portion protruding outside the insulating support member 410b). One of the external electrodes of the capacitor 700 housed in the sealed container 110 is adhesively fixed to one end of the metal plate 961 using silver paste, while the other end of the metal plate 961 is resistance-welded to the outer circumference of the outer conductor 630. One end of metal plate 962 is bonded and fixed to the other external electrode of capacitor 700 via silver paste. The other end of metal plate 962 is resistance welded to voltage supply lead pin 950, and one end of voltage supply lead pin 950 is resistance welded to fixing piece DY4a of fourth-stage dynode DY4.

[0078] On the other hand, the photoelectron multiplier of Sample 2 includes a shield electrode set to the same potential as the fourth-stage dynode DY4. In Sample 2, one end of the coaxial cable 600 is introduced into the space between the first and second insulating support members 410a and 410b via the stem 110b. A 2 mm portion of the inner conductor 610, exposed from the ends of the glass material 620 and outer conductor 630, is resistance welded to the fixing surface 510 of the anode 500. Furthermore, one external electrode of the capacitor 700 is bonded and fixed to one end of the metal plate 660 using silver paste. The other end of the metal plate 660 is resistance welded to the shield electrode 450. The other external electrode of the capacitor 700 is bonded and fixed to one end of the metal plate 650 using silver paste. The other end of the metal plate 650 is resistance welded to the outer circumference of the outer conductor 630.

[0079] Comparison of the waveforms of the anode outputs of the photoelectron multipliers of Comparative Example 2 and Sample 2 having the above-described structures reveals that the waveform of the anode output of Sample 2 exhibits a significant ringing suppression effect.

[0080] It is clear from the above description of the present invention that various modifications can be made to the present invention. Such modifications cannot be considered to depart from the spirit and scope of the present invention, and all improvements that are obvious to those skilled in the art are included in the scope of the following claims.

[0081] [Explanation of symbols]

[0082] 100…Photoelectron multiplier

[0083] 110…Sealed container

[0084] 110a…Main body

[0085] 110b…tube socket

[0086] 120…cathode

[0087] 140…lead pins

[0088] 200…focusing electrode

[0089] 300…accelerating electrode

[0090] 400...Dynode Unit

[0091] DY4…4th stage dynode (final stage dynode)

[0092] 410a…first insulating support member

[0093] 410b…Second insulating support member

[0094] 450...Shielding electrode (example of a conductive member)

[0095] 451a, 451b…notch (forming a through hole)

[0096] 500…Anode

[0097] 520…Electrode component

[0098] 600…coaxial cable

[0099] 610…Inner conductor

[0100] 620…Glass material (an example of insulating material)

[0101] 630…Outer conductor

[0102] 700…capacitor

[0103] 800, 800a, 800b…conductive components.

Claims

1. An electron multiplier, characterized in that have: a dynode unit that performs cascade multiplication of electrons and extracts them as electrical signals, and includes a multistage dynode, an anode, and a pair of insulating support members. The anode is set to a potential higher than the set potential of the final dynode in the multistage dynode and captures electrons emitted from the final dynode. The pair of insulating support members at least integrally hold the multistage dynode and the anode. a stem having a first surface and a second surface opposite to the first surface, wherein the dynode unit is held in a space on the first surface side located on the opposite side of the second surface relative to the first surface; a coaxial cable comprising an inner conductor, an insulating material, and an outer conductor, at least one end of which is disposed in the first surface side space, the insulating material being disposed on the outer circumference of the inner conductor, and the outer conductor being disposed on the outer circumference of the insulating material; a conductive member disposed in the first surface side space and set to the same potential as that of the final dynode that directly supplies the multiplied electrons to the anode; and a capacitor provided in the first surface side space and arranged on the wiring between the conductive member and the outer conductor of the coaxial cable; The exposed portion of the inner conductor, which constitutes a portion of the one end portion of the coaxial cable and is located in the first surface side space while being exposed from the ends of the insulating material and the outer conductor, is fixed to a portion of the anode sandwiched between the pair of insulating support members without intervening other wiring elements. The capacitor is physically separated from the conductive member and fixed to the conductive member in order to suppress the generation of ringing of the output signal. The one end portion of the coaxial cable is positioned in a space sandwiched between the pair of insulating support members in order to increase the speed of response characteristics.

2. The electron multiplier according to claim 1, wherein The exposed portion of the inner conductor and the end portion of the outer conductor are located together in a space sandwiched by the pair of insulating support members.

3. The electron multiplier according to claim 1, wherein When the stem side is viewed from the dynode unit side along the direction from the first surface toward the second surface, the dynode unit is arranged so that the portion of the anode clamped by the pair of insulating support members overlaps with the portion of the first surface where the coaxial cable is arranged.

4. The electron multiplier according to claim 2, wherein: When the stem side is viewed from the dynode unit side along the direction from the first surface toward the second surface, the dynode unit is arranged so that the portion of the anode clamped by the pair of insulating support members overlaps with the portion of the first surface where the coaxial cable is arranged.

5. The electron multiplier according to claim 1, wherein The tube holder holds a plurality of lead pins, The conductive member has a cross-sectional area larger than that of each of the plurality of lead pins, and is set to the same potential as that of the final dynode by fixing a first portion of the conductive member to the final dynode.

6. The electron multiplier according to claim 2, wherein: The tube holder holds a plurality of lead pins, The conductive member has a cross-sectional area larger than that of each of the plurality of lead pins, and is set to the same potential as that of the final dynode by fixing a first portion of the conductive member to the final dynode.

7. The electron multiplier according to claim 3, wherein: The tube holder holds a plurality of lead pins, The conductive member has a cross-sectional area larger than that of each of the plurality of lead pins, and is set to the same potential as that of the final dynode by fixing a first portion of the conductive member to the final dynode.

8. The electron multiplier according to claim 4, wherein The tube holder holds a plurality of lead pins, The conductive member has a cross-sectional area larger than that of each of the plurality of lead pins, and is set to the same potential as that of the final dynode by fixing a first portion of the conductive member to the final dynode.

9. The electron multiplier according to any one of claims 1 to 8, wherein The capacitor includes: one external electrode fixed to the second portion of the conductive member; and the other external electrode electrically connected to the outer conductor of the coaxial cable.

10. The electron multiplier according to any one of claims 1 to 8, wherein The conductive member includes a shield electrode mounted on the pair of insulating support members, the shield electrode having an opening for passing the exposed portion of the inner conductor together with the end portion of the outer conductor from the stem side toward the anode.

11. The electron multiplier according to claim 9, wherein: The conductive member includes a shield electrode mounted on the pair of insulating support members, the shield electrode having an opening for passing the exposed portion of the inner conductor together with the end portion of the outer conductor from the stem side toward the anode.

12. The electron multiplier according to claim 10, wherein: The capacitor is located in the space between the shielding electrode and the stem.

13. The electron multiplier according to claim 11, wherein The capacitor is located in the space between the shielding electrode and the stem.

14. The electron multiplier according to any one of claims 1 to 8, wherein The capacitor includes a ceramic capacitor.

15. The electron multiplier according to claim 9, wherein The capacitor includes a ceramic capacitor.

16. The electron multiplier according to claim 10, wherein: The capacitor includes a ceramic capacitor.

17. The electron multiplier of claim 11, wherein: The capacitor includes a ceramic capacitor.

18. The electron multiplier of claim 12, wherein: The capacitor includes a ceramic capacitor.

19. The electron multiplier of claim 13, wherein: The capacitor includes a ceramic capacitor.

20. A photoelectron multiplier, characterized in that: Include: The electron multiplier according to any one of claims 1 to 19; a cathode that emits photoelectrons toward the dynode unit in response to light input; and The sealed container comprises: a main body extending along a central axis and having an open end defining an opening intersecting the central axis, and accommodating at least the cathode and the dynode unit; and a tube holder functioning as the tube holder, being in close contact with the open end in a state where the open end is blocked. The coaxial cable is held by the stem in a state where the other end portion of the coaxial cable passes through the stem from the first surface toward the second surface.

Images