JP2010262812A - Photomultiplier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve detection sensitivity by efficiently making photoelectron emitted from a photoelectric surface incident on dynodes. <P>SOLUTION: The photomultiplier 1 is equipped with: an upper frame 2 and a lower frame 4 disposed oppositely to each other, respective opposite surfaces 20a and 40a of which are formed of an insulating material; a side wall frame 4 constituting a casing with the frames 2 and 4; a plurality of stages of photomultiplication parts 33 aligned separately to each other in order from one end side on the opposite surface 40a of the lower frame 4 toward the other end side thereof; a photoelectric surface 41 provided on the one end side separately from the multiplier parts 33 to convert external incident light into photoelectron; a positive electrode part 34 provided on the other end side separately from the multiplier parts 33 to extract the electron multiplied by the multiplier parts 33 as signal; and a wall-like electrode 32 disposed to surround the photoelectric surface 41 as viewed from a direction normally facing the opposite surface 401 and having a cutout 35 formed at a portion facing the multiplier parts 33 on the other end side. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a photomultiplier tube that detects incident light from the outside.

  Conventionally, development of a small photomultiplier tube using a microfabrication technique has been advanced. For example, a thin photomultiplier tube in which a photocathode, a dynode, an anode, and the like are arranged on a substrate constituting a housing is known (see Patent Document 1 below). By adopting such a structure, fine processing of the apparatus is realized by a two-stage manufacturing process.

US Pat. No. 5,568,013

  However, in the conventional photomultiplier tubes as described above, the photoelectrons emitted from the photocathode are not partially incident on the electron multiplier portion depending on the potential of the housing, and the side tubes constituting the housing It may enter the substrate or the like. As described above, if the photoelectrons are incident outside the electron multiplying portion, the detection sensitivity is lowered.

  Therefore, the present invention has been made in view of such problems, and photoelectron multiplication capable of improving detection sensitivity by efficiently causing photoelectrons emitted from the photocathode to enter the electron multiplication section. The purpose is to provide a tube.

  In order to solve the above-mentioned problems, the photomultiplier tube of the present invention is arranged so as to face each other, and each facing surface is made of an insulating material, together with the first and second substrates. A side wall portion constituting the body, a plurality of electron multiplying portions arranged in order and spaced from one end side to the other end side on the opposing surface of the first substrate, and an electron multiplying portion on one end side A photocathode that converts the incident light from the outside into photoelectrons and emits photoelectrons, and is provided apart from the electron multiplier on the other end side and multiplied by the electron multiplier. An anode portion for taking out electrons as a signal, and a wall-like electrode which is disposed so as to surround the photocathode as viewed from the direction facing the opposite surface and has a notch formed at a portion facing the electron multiplier portion on the other end side .

  According to such a photomultiplier tube, incident light is converted into photoelectrons by being incident on the photocathode, and this photoelectron is incident on a plurality of stages of electron multipliers on the opposing surface of the first substrate. The multiplied electrons are taken out from the anode part as an electric signal. Here, the photocathode is surrounded by a wall electrode as viewed from the direction facing the opposite surface of the substrate, and a notch is formed on the other end side of the wall electrode. As a result of efficiently guiding the photoelectrons toward the electron multiplier, the detection sensitivity of light incident on the photocathode can be improved.

  It is preferable that the photocathode and the wall electrode are electrically connected. In this case, since an electric field suitable for guiding photoelectrons from the photocathode to the electron multiplier is formed, the photoelectrons can be guided more efficiently toward the electron multiplier, and the detection sensitivity of incident light can be improved. Further improve.

  It is also preferable that the notch is formed at a site corresponding to the region of the electron multiplication channel of the electron multiplication unit. By adopting such a configuration, photoelectrons can be more efficiently guided toward the electron multiplication region in the electron multiplication section, and the detection sensitivity of incident light is further improved.

  Furthermore, it is also preferable that a focusing electrode for focusing the photoelectrons emitted from the photocathode and guiding them to the electron multiplier is provided inside the notch. In this case, the photoelectrons can be guided more efficiently toward the electron multiplier section, and further improvement in detection sensitivity of incident light is realized.

  According to the present invention, it is possible to improve the detection sensitivity by causing the photoelectrons emitted from the photocathode to efficiently enter the electron multiplier.

1 is a perspective view of a photomultiplier tube according to a preferred embodiment of the present invention. It is a disassembled perspective view of the photomultiplier tube of FIG. It is a top view of the side wall frame of FIG. (A) is the bottom view which looked at the upper side frame of FIG. 1 from the back surface side, (b) is the top view of the side wall frame of FIG. It is a perspective view which shows the connection state of the upper side frame of FIG. 4, and a side wall frame. It is a disassembled perspective view of the photomultiplier tube which concerns on the modification of this invention. It is a disassembled perspective view of the photomultiplier tube which concerns on another modification of this invention. It is a disassembled perspective view of the photomultiplier tube which concerns on another modification of this invention. It is a disassembled perspective view of the photomultiplier tube which concerns on another modification of this invention. It is a top view of the side wall frame which removed the wall electrode from the side wall frame of FIG.

  Hereinafter, preferred embodiments of a photomultiplier according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

    1 is a perspective view of a photomultiplier tube 1 according to a preferred embodiment of the present invention, FIG. 2 is an exploded perspective view of the photomultiplier tube 1 of FIG. 1, and FIG. 3 is a side wall frame 3 of FIG. FIG.

  A photomultiplier tube 1 shown in FIG. 1 is a photomultiplier tube having a transmissive photocathode. The photomultiplier tube 1 has an upper frame (second substrate) 2, a side wall frame (side wall part) 3, and an upper frame 2. On the other hand, a housing constituted by a lower frame (first substrate) 4 facing the side wall frame 3 across the side wall frame 3 is provided. In this photomultiplier tube 1, the light incident direction on the photocathode intersects the electron multiplying direction in the electron multiplying portion, that is, light is incident from the direction indicated by arrow A in FIG. 1. The photoelectrons emitted from the photocathode are incident on the electron multiplier, cascade-amplify secondary electrons in the direction indicated by arrow B, and take out a signal from the anode.

  In the following description, along the electron multiplication direction, the upstream side (photocathode side) of the electron multiplication path (electron multiplication channel) is referred to as “one end side”, and the downstream side (anode side) as “ The other end side. Subsequently, each component of the photomultiplier tube 1 will be described in detail.

  As shown in FIG. 2, the upper frame 2 is configured with a wiring board 20 whose main material is a rectangular flat plate-like insulating ceramic as a base material. As such a wiring board, a multilayer wiring board such as LTCC (Low Temperature Co-fired Ceramics) capable of designing a fine wiring and freely designing the front and back wiring patterns is used. On the main surface 20b, the wiring substrate 20 is electrically connected to the side wall frame 3, a photocathode 41 (to be described later), a focusing electrode 31, a wall electrode 32, an electron multiplying portion 33, and an anode portion 34 to be externally connected. A plurality of conductive terminals 201 </ b> A to 201 </ b> D for supplying power from and extracting signals are provided. The conductive terminal 201A is used for supplying power to the side wall frame 3, the conductive terminal 201B is used for supplying power to the photocathode 41, the focusing electrode 31, and the wall electrode 32. The conductive terminal 201C is supplied to the electron multiplier 33. For this purpose, the conductive terminal 201D is provided for feeding power and extracting signals from the anode section 34, respectively. These conductive terminals 201 </ b> A to 201 </ b> D are mutually connected to a conductive film and conductive terminals (details will be described later) on the insulating facing surface 20 a facing the main surface 20 b inside the wiring board 20. These conductive films, conductive terminals and side wall frame 3, photocathode 41, focusing electrode 31, wall electrode 32, electron multiplier 33, and anode 34 are connected. The upper frame 2 is not limited to the multilayer wiring board provided with the conductive terminals 201, and is made of an insulating material such as a glass substrate through which conductive terminals for supplying power from outside and taking out signals are provided. A plate-like member may be used.

  The side wall frame 3 is configured by using a rectangular flat silicon substrate 30 as a base material. A penetrating portion 301 surrounded by a frame-like side wall portion 302 is formed from the main surface 30a of the silicon substrate 30 toward the surface 30b facing the main surface 30a. The through portion 301 has a rectangular opening, and the outer periphery thereof is formed along the outer periphery of the silicon substrate 30.

  In this penetration part 301, the wall-shaped electrode 32, the focusing electrode 31, the electron multiplication part 33, and the anode part 34 are arrange | positioned toward the other end side from one end side. The wall electrode 32, the focusing electrode 31, the electron multiplying portion 33, and the anode portion 34 are formed by processing the silicon substrate 30 by RIE (Reactive Ion Etching) processing or the like, and uses silicon as a main material.

  The wall-like electrode 32 will be described later when viewed from a direction facing a facing surface 40a of the glass substrate 40 described later (a direction substantially perpendicular to the facing surface 40a, a direction opposite to the direction indicated by the arrow A in FIG. 1). This is a frame-like electrode formed so as to surround the photocathode 41. The focusing electrode 31 is an electrode for converging photoelectrons emitted from the photocathode 41 and guiding the photoelectrons to the electron multiplier 33, and is provided between the photocathode 41 and the electron multiplier 33. .

  The electron multiplier 33 is composed of N stages (N is an integer of 2 or more) of dynodes (electron multipliers) set at different potentials along the electron multiplication direction from the photocathode 41 toward the anode 34. It has a plurality of electron multiplication paths (electron multiplication channels) across each stage. Further, the anode part 34 is arranged at a position sandwiching the electron multiplying part 33 together with the photocathode 41.

  The wall electrode 32, the focusing electrode 31, the electron multiplying portion 33, and the anode portion 34 are respectively provided with an anodic bonding, a diffusion bonding, and a sealing material such as a low melting point metal (for example, indium) on the lower frame 4. It is fixed by the joining etc. which were used, and is arrange | positioned two-dimensionally on this lower frame 4 by this.

  The lower frame 4 is configured with a rectangular flat glass substrate 40 as a base material. The glass substrate 40 is formed with a facing surface 40a that faces the facing surface 20a of the wiring substrate 20 with glass that is an insulating material. On the facing surface 40a, a portion facing the penetrating portion 301 of the side wall frame 3 (a portion other than the joining region with the side wall portion 302) is located at the end opposite to the anode portion 34 side at the transmission type photocathode. The photocathode 41 is formed. In addition, a rectangular recess 42 for preventing the multiplication electrons from entering the facing surface 40a is formed at a portion where the electron multiplying portion 33 and the anode portion 34 are mounted on the facing surface 40a. .

  The internal structure of the photomultiplier tube 1 will be described in more detail with reference to FIG. The electron multiplying portions 33 in the penetrating portion 301 are arrayed separately in order from one end side to the other end side on the facing surface 40a (in the direction indicated by the arrow B which is the electron multiplying direction). It consists of multiple dynodes. These multi-stage dynodes are provided so as to continue from the first stage dynode 33a on one end side to the final stage (N-th stage) dynode 33b on the other end side in the direction indicated by arrow B. A plurality of electron multiplying channels C composed of N electron multiplying holes are provided in parallel.

  The photocathode 41 is spaced from the first dynode 33a on the one end side on one end side on the facing surface 40a with the focusing electrode 31 in between. The photocathode 41 is formed as a rectangular transmissive photocathode on the facing surface 40 a of the glass substrate 40. When incident light transmitted through the glass substrate 40 which is the lower frame 4 from the outside reaches the photocathode 41, photoelectrons corresponding to the incident light are emitted, and the photoelectrons are first-staged by the wall electrode 32 and the focusing electrode 31. Guided to eye dynode 33a.

  Further, the anode part 34 is provided to be separated from the final stage dynode 33b on the other end side on the other end side on the facing surface 40a. The anode part 34 is an electrode for taking out electrons that have been multiplied in the direction indicated by the arrow B in the electron multiplication channel C of the electron multiplication part 33 to the outside as an electric signal.

  Furthermore, the wall-shaped electrode 32 is a rectangular frame-shaped electrode composed of a plurality of plate-shaped portions extending substantially perpendicularly along the inner wall of the side wall portion 302 from the facing surface 40 a toward the upper frame 2 in the through portion 301. It is erected on the facing surface 40a so as to surround the region where the photocathode 41 is formed along its edge. A cutout portion 35 having a substantially rectangular shape cut out at a portion of the other end side wall portion of the wall electrode 32 facing the region where the electron multiplication channel C is formed in the first stage dynode 33a. Is formed. A focusing electrode 31 is formed so as to extend substantially perpendicularly to the upper frame 2 side from a thin plate member 35a provided so as to connect both end portions on the facing surface 40a of the notch 35. In the present embodiment, the wall electrode 32, the thin plate member 35a, and the focusing electrode 31 are integrally formed, but may be formed separately.

  Next, the wiring structure of the photomultiplier tube 1 will be described with reference to FIGS. 4A is a bottom view of the upper frame 2 viewed from the back surface 20a side, FIG. 4B is a plan view of the side wall frame 3, and FIG. 5 is a connection between the upper frame 2 and the side wall frame 3. It is a perspective view which shows a state.

  As shown in FIG. 4A, the back surface 20a of the upper frame 2 has a plurality of conductive films 202 electrically connected to the conductive terminals 201B, 201C, and 201D inside the upper frame 2, and conductive A conductive terminal 203 electrically connected inside the upper frame 2 is provided to the conductive terminal 201A. Further, as shown in FIG. 4B, power supply portions 36 and 37 for connection to the conductive film 202 are respectively provided at the end portions of the electron multiplying portion 33 and the anode portion 34 so as to form a wall shape. At the corner of the electrode 32, a power feeding unit 38 for connection with the conductive film 202 is provided upright. The focusing electrode 31 is electrically connected to the wall electrode 32 by being formed integrally with the wall electrode 32 and the lower frame 4 together with the thin plate member 35a. Further, the wall-shaped electrode 32 is integrally formed with a connecting portion 39 having a rectangular flat plate on the facing surface 40a side of the lower frame 4, and the connecting surface 39 and the photocathode 41 on the facing surface 40a. The wall electrode 32 and the photocathode 41 are electrically connected to each other by bonding a conductive film (not shown) formed in electrical contact.

  When the upper frame 2 and the side wall frame 3 configured as described above are joined, the conductive terminal 203 is electrically connected to the side wall portion 302 of the side wall frame 3. In addition, the power supply unit 36 of the electron multiplying unit 33, the power supply unit 37 of the anode unit 34, and the power supply unit 38 of the wall electrode 32 are respectively corresponding conductive films via conductive members made of gold (Au) or the like. 202 is independently connected. With such a connection configuration, the side wall portion 302, the electron multiplying portion 33, and the anode portion 34 can be electrically connected to the conductive terminals 201A, 201C, and 201D, respectively, and the wall electrode 32 is focused. Together with the electrode 31 and the photocathode 41, it is electrically connected to the conductive terminal 201B (FIG. 5).

  According to the photomultiplier tube 1 described above, incident light is converted into photoelectrons by passing through the lower frame 4 and entering the photocathode 41, and the photoelectrons are converted into a plurality of photoelectrons on the opposing surface 40a of the lower frame 4. The electrons are multiplied by being incident on the electron multiplying section 33 of the stage, and the multiplied electrons are taken out from the anode section 34 as an electric signal. Here, the photocathode 41 is surrounded by the wall electrode 32 when viewed from the direction facing the facing surface 40a, and a notch 35 is formed on the other end side of the wall electrode 32. Photoelectrons from the photocathode 41 are prevented from entering a housing such as the side wall frame 3 and the photoelectrons are efficiently guided toward the electron multiplier section 33. As a result, the detection sensitivity of incident light on the photocathode 41 is detected. Can be improved.

Here, the effects of the present embodiment will be specifically described with reference to FIGS. 3 and 10. FIG. 10 is a plan view of the side wall frame 903 when the wall electrode 32 is removed from the side wall frame 3 of FIG. When the side wall frame 903 is used, most of the photoelectrons generated from the photocathode 41 due to incident light are incident on the first-stage dynode 33a, but a part of the photoelectrons is directed toward the side wall 302 (FIG. 10). In the direction of arrows E ₁ and E ₂ ), it may not contribute to the detection signal. This becomes more conspicuous when the potential of the side wall portion 302 is unstable. Further, the photoelectron generated from the region near the side wall 302 in the photocathode 41 has a larger influence on the side wall 302. That is, in the photocathode 41, it can be said that a region that is not easily affected by the side wall portion 302 is a substantial effective region, and therefore, the substantial effective area of the photocathode 41 is reduced. In order to cope with such a problem, it is conceivable to apply the same potential as that of the photocathode 41 to the side wall portion 302. There is a risk that a withstand voltage failure may occur. This problem is particularly noticeable in the anode part 34, and the electron multiplying part 33 becomes more conspicuous in the subsequent stage. In order to prevent the occurrence of such a withstand voltage failure, it is necessary to secure a sufficient space. As a result, the material area required for one chip may be increased, resulting in an increase in cost. In addition, light emission may occur due to collision of the multiplied secondary electrons with the insulator or the like on the other end side in the penetrating portion 301 or the like. Proceeds so that the light of the arrow E _3, the reach to the photocathode 41, the incident light is performed unrelated photoemission, Contact it also reduce the SN ratio will by generating noise detection signal is there.

On the other hand, in the present embodiment, the photoelectrons generated from the photocathode 41 are efficiently in the first stage regardless of the potential of the side wall portion 302 due to the presence of the wall-like electrode 32 in which the potential is stably set. towards dynode 33a can be incident (the direction of arrow E ₄ in FIG. 3). Moreover, even the light generated in the other end or the like of the through portion 301 has progressed toward the photocathode 41 (the direction of arrow E ₅ in FIG. 3), wall-shaped shielded by the electrode 32 photocathode 41 Can be prevented from entering. Thereby, even if the electric potential of the side wall part 302 is freely set, the detection sensitivity can be maintained, and the noise characteristic can be improved and the SN ratio can be improved. For example, the electrical noise characteristics of the photomultiplier tube 1 can be improved by setting the side wall portion 302 to a ground potential as a desired potential. In particular, by setting the ground potential, the noise reduction effect can be maximized, and the risk of electric shock to the human body can be reduced. Further, since it can be said that the region surrounded by the wall electrode 32 is a substantially effective photocathode region, it is possible to easily identify an appropriate light incident region when the photomultiplier tube 1 is viewed from the outside. it can.

  In addition, since the photocathode 41 and the wall electrode 32 are electrically connected and set to the same potential, photoelectrons from the photocathode 41 do not enter the wall electrode 32 and enter the electron multiplier 33. Since an electric field suitable for being guided is formed, the detection sensitivity is further improved.

  Further, the cutout portion 35 of the wall electrode 32 is formed at a portion facing the region of the electron multiplying channel C of the electron multiplying portion 33, so that the photoelectrons guided to the electron multiplying portion 33 are efficiently generated. The detection sensitivity of incident light can be further improved.

  In addition, this invention is not limited to embodiment mentioned above. For example, a photocathode 41A may be provided on the back surface (opposing surface 50a) side of the upper frame 2A as in a photomultiplier tube 1A that is a modification of the present invention shown in FIG. In this case, as the upper frame 2A, a glass substrate or other insulating substrate having light transmittance embedded in a power supply terminal can be used. As the lower frame 4A, various insulating substrates other than the glass substrate can be used. Can be used. The wall electrode 32 is disposed so as to surround the photocathode 41A when viewed from the direction facing the facing surface 50a of the upper frame 2A (substantially perpendicular to the facing surface 50a).

  Further, as a photomultiplier tube 1B which is a modification of the invention shown in FIG. 7, a reflective photocathode may be used as the photocathode. For example, a light-transmissive insulating substrate is used as the upper frame 2B, and an inclined surface that is inclined toward the other end side with respect to the opposing surface 40a is formed inside the wall electrode 32B of the side wall frame 3B. Then, the photocathode 41B is formed from the inclined surface to the facing surface 40a. As the shape of such an inclined surface, as long as the photoelectron generated from the photocathode 41B is directed to the electron multiplying unit 33 with the incident light transmitted through the upper frame 2B, it is curved even if it is a plane. It does not matter.

  Furthermore, various modifications can be made with respect to the wiring structure of the present embodiment. For example, as shown in FIG. 8, a conductive terminal 401 is formed so as to penetrate the lower frame 4C, and the photocathode 41, the wall electrode 32, the focusing electrode 31, the electron multiplier are passed through the conductive terminal 401. A configuration may be adopted in which power is supplied to the portion 33 and the anode portion 34. With such a configuration, the conductive film 202 (FIG. 4A) formed on the upper frame 2 and each electrode can be supplied with power independently.

  Moreover, as shown in FIG. 9, you may combine the lower frame 4C which provided the conductive terminal 401, and the upper frame 2C except the conductive terminals 201A-201D. In this case, an insulating substrate having a plurality of conductive films 202 formed on the back side is used as the upper frame 2C. By using the wiring structure described with reference to FIG. 4 in such a combination, from the conductive terminal 401 of the lower frame 4C, through the wall electrode 32, the electron multiplier section 33, and the anode section 34, Power can be supplied to the conductive film 202 of the upper frame 2C.

  In any of the embodiments and modifications, the wall-shaped electrode 32 does not necessarily surround the entire photocathode 41, and has a substantial effective region that can guide the emitted photoelectrons to the electron multiplier 33. If it surrounds, it is good also as arrangement | positioning which does not surround about an edge part.

  1, 1A, 1B ... Photomultiplier tubes, 2, 2A, 2B, 2C ... Upper frame (second substrate), 3 ... Side wall frame (side wall), 4, 4A, 4B, 4C ... Lower frame (first 1), 20a, 40a ... opposing surface, 31 ... focusing electrode, 32, 32B ... wall electrode, 33 ... electron multiplying part, 34 ... anode part, 35 ... notch part, 41, 41A, 41B ... photoelectric Surface, C ... Electron multiplication channel.

Claims (4)

A first substrate and a second substrate, which are arranged to face each other and each facing surface is made of an insulating material;
A side wall portion constituting a housing together with the first and second substrates;
A plurality of stages of electron multipliers arranged sequentially spaced from one end side to the other end side on the facing surface of the first substrate;
A photocathode that is provided on the one end side apart from the electron multiplier, converts incident light from the outside into photoelectrons, and emits the photoelectrons,
An anode section provided on the other end side apart from the electron multiplier section, and taking out the electrons multiplied by the electron multiplier section as a signal;
A wall-like electrode that is disposed so as to surround the photocathode when viewed from the direction facing the facing surface, and has a notch formed at a portion facing the electron multiplying portion on the other end side;
A photomultiplier tube comprising: The photocathode and the wall electrode are electrically connected,
The photomultiplier tube according to claim 1. The notch is formed at a site corresponding to an electron multiplication channel region of the electron multiplication unit,
The photomultiplier tube according to claim 1 or 2, wherein A focusing electrode for guiding the photoelectrons emitted from the photocathode to the electron multiplier is provided inside the notch,
The photomultiplier tube according to any one of claims 1 to 3.

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