JP4402478B2 - Photomultiplier tube - Google Patents

Description

  The present invention relates to a photomultiplier tube incorporating a microchannel plate.

Conventionally, photoelectrons converted from incident light are detected by being multiplied by a microchannel plate (MCP). As an application of such a technique to a photomultiplier tube, there is an incident position detection device described in Patent Document 1 below. In this incident position detection device, photoelectrons emitted from the photocathode in the vacuum vessel are multiplied by the microchannel plate, and the multiplied electrons are anodes (anodes) that are a plurality of conductor groups arranged in rows and columns. ). And the incident position of light is detected from the electric current taken out from these anodes.
JP-A-1-201185

  However, in the above-described conventional so-called multi-anode type photomultiplier tube, a pseudo signal may be detected from one channel to an adjacent channel due to crosstalk between channels corresponding to each anode. As a result, there is a problem that a pseudo signal is superimposed on the output signal in the channel corresponding to the light incident position, and the time characteristic of the detected output signal is deteriorated. This deterioration of the time characteristic appears more prominently as the intensity of incident light increases, and affects the detection accuracy of incident light.

  Accordingly, the present invention has been made in view of such problems, and an object thereof is to provide a photomultiplier tube that improves the detection accuracy of incident light by suppressing crosstalk between channels.

In order to solve the above-mentioned problems, the photomultiplier tube of the present invention is fixed to one end face in a sealed container so as to oppose the photocathode and a photocathode that converts light incident from the outside into photoelectrons. A microchannel plate provided in a sealed container for multiplying photoelectrons emitted from the photocathode, and a film provided along the electron incident surface and the electron emission surface of the microchannel plate for supplying a voltage to the microchannel plate A plurality of electrodes arranged in parallel to face the microchannel plate on the other side in the sealed container, and an anode for taking out electrons emitted from the microchannel plate as an output signal. in opposing the electron emission surface, that is formed to be divided shape to correspond to the plurality of anodes And butterflies.

  In such a photomultiplier tube, light incident from one side of the sealed container is converted into photoelectrons by the photocathode, and the converted photoelectrons are multiplied by passing through the microchannel plate and then incident. It is taken out as an output signal from the anode of the channel corresponding to the position. At that time, an electrode corresponding to the anode is separately provided on the electron emission surface of the microchannel plate, and a voltage is independently supplied to the electrode, so that disturbance of the potential of the electron emission surface in the adjacent channel is reduced. Is done. Thereby, generation | occurrence | production of the pseudo signal in the output signal of each channel resulting from an induced current is suppressed.

  Moreover, it is preferable that the electrode is divided and provided on the electron incident surface and the electron emission surface so as to correspond to the plurality of anodes, respectively. In this case, the disturbance of the potential of the microchannel plate in each channel is reduced, and the pseudo signal superimposed on the output signal is further suppressed.

  Furthermore, the electrode is preferably formed so that the area on the electron emission surface is smaller than the area on the electron incident surface. Since the signal extracted from the peripheral portion of the electrode is likely to be mixed with noise due to dark current, the provision of such an electrode can prevent the noise generated in the peripheral portion of the electrode from affecting the output signal.

  Furthermore, a plurality of microchannel plates are stacked in the sealed container, and the electrode has an area on the electron emission surface on the other side that is larger than the area on the electron emission surface on one side between adjacent microchannel plates. It is also preferable that it is formed to be small. With such a configuration, the electron multiplication effect by the microchannel plate is increased, and the influence of noise generated in the periphery of each electrode on the output signal can be prevented.

  According to the photomultiplier tube of the present invention, detection accuracy of incident light can be improved by suppressing crosstalk between channels.

  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. Further, the dimensional ratios in the drawings do not necessarily match those described.

[First Embodiment]
FIG. 1 is a partially broken perspective view showing a first embodiment of a photomultiplier tube according to the present invention, and FIG. 2 is an exploded perspective view of the photomultiplier tube of FIG. This photomultiplier tube 1 is a device for emitting photoelectrons by light incident from the outside, multiplying the photoelectrons and outputting them as signals. As shown in FIG. 1, the photomultiplier tube 1 includes a sealed container 3, a photocathode 5 fixed on the light incident side (one side) in the sealed container 3, and a photocathode 5 in the sealed container 3. The microchannel plate 7 is provided to be opposed to the microchannel plate 7, and the anode 9 is provided to face the microchannel plate 7 on the other side of the sealed container 3.

  As shown in FIG. 2, the sealed container 3 includes a metal quadrangular columnar side tube 11, and an incident window 13 is fixed to one side opening end of the side tube 11. The incident window 13 is made of a glass material such as borosilicate glass, for example, and transmits incident light into the sealed container 3. On the inner surface of the incident window 13, a photocathode 5 for converting light incident from the incident window 13 into photoelectrons is formed. The photocathode 5 is formed so as to cover the entire inner surface of the incident window 13 in order to efficiently convert light incident from the incident window 13 into photoelectrons.

  On the other side of the sealed container 3 facing the photocathode 5, a rectangular plate-like microchannel plate 7 is disposed substantially parallel to the incident window 13. The microchannel plate has many extremely fine tubes (channel multipliers) whose inner walls are resistors and secondary electron emitters, multiplying photoelectrons incident on the channel multiplier from the electron incident surface, and It emits secondary electrons. The microchannel plate 7 multiplies photoelectrons incident on the electron incident surface 7i, which is a surface facing the photocathode 5, as secondary electrons inside, and then reverses these secondary electrons to the electron incident surface 7i. The light is emitted from the side electron emission surface 7o.

  On the other side inside the sealed container 3, four anodes 9 are juxtaposed in parallel and close to the electron emission surface 7 o of the microchannel plate 7. The shape of these anodes 9 is a rectangular shape obtained by dividing a surface corresponding to the electron emission surface 7 o into four parallel to the side tube 11. The anode 9 is for taking out secondary electrons emitted from the opposing part of the electron emission surface 7o as an output signal corresponding to each position. In other words, the light incident position of the incident window 13 can be detected by dividing the anode 9 in this way.

  Further, the other open end of the side tube 11 is sealed by a base plate 17 having a terminal 15 protruding outward. The terminal 15 is connected to an external power supply circuit, which will be described later. The power supply circuit supplies a voltage having a predetermined potential to the photocathode 5, the microchannel plate 7, and the anode 9, and outputs an output signal from each anode 9. Is taken out.

  Hereinafter, the configuration of the microchannel plate 7 will be described in more detail.

  FIG. 3 is a cross-sectional view along the arrangement direction of the anodes 9 of the microchannel plate 7. As shown in the figure, on the electron incident surface 7i of the microchannel plate 7, four flat electrodes 19i for supplying a voltage to the electron incident surface 7i of the microchannel plate 7 are formed. . On the electron emission surface 7o of the microchannel plate 7, four flat electrodes 19o for supplying a voltage to the electron emission surface 7o of the microchannel plate 7 are formed.

  The electrodes 19 o are divided and provided in substantially the same shape as the opposing anodes 9, and are arranged in parallel so that the arrangement direction thereof is the same as the arrangement direction of the anodes 9. On the other hand, the electrode 19i is formed in the same shape so as to be plane-symmetric with the electrode 19o formed on the opposite surface of the microchannel plate 7. Further, a contact electrode 21i and a contact electrode 21o are crimped to the electrode 19i and the electrode 19o, respectively, and the electrode 19i and the electrode 19o are connected via the contact electrodes 21i and 21o, a lead wire (not shown), and the like. The terminal 15 is connected independently.

  In order to appropriately detect incident light in the photomultiplier tube 1, predetermined voltages are applied so that the potential decreases in the order of the anode 9, the electrode 19 o, the electrode 19 i, and the photocathode 5. FIG. 4 is a diagram showing a connection relationship between the photomultiplier tube 1 and an external power supply circuit. As shown in the figure, the power supply circuit 23 is connected to the electrodes 19o and 19i and the photocathode 5 so that the potential decreases in the order of the anode 9, the electrode 19o, the electrode 19i, and the photocathode 5. The power supply circuit 23 is connected in parallel for each pair of electrodes 19i and 19o existing in a direction parallel to the side tube 11, and the potentials of these electrodes 19i and 19o can be controlled independently. .

  According to the photomultiplier tube 1 described above, light incident inside from the incident window 13 is converted into photoelectrons by the photocathode 5, and the converted photoelectrons pass through the microchannel plate 7 and are increased as secondary electrons. After being doubled, it is taken out from the anode 9 as an output signal.

  When electrodes are integrally formed on the microchannel plate as in the prior art, the output signal is taken out from the anode corresponding to the case where light is incident on a specific portion of the incident window. A pseudo signal appears. This phenomenon is called crosstalk, and when secondary electrons are emitted from the electron emission surface of the microchannel plate, the potential distribution of the electrode on the electron emission surface is temporarily disturbed, resulting in an adjacent anode having electric capacity. This is because an induced current is generated.

  On the other hand, the output signal detected in the photomultiplier tube 1 is sandwiched between a pair of electrodes 19i and 19o existing in a direction parallel to the side tube 11 from the light incident position in the incident window 13. It is taken out from the channel formed by the microchannel plate 7 and the anode 9 facing the electrode 19o. At that time, the electrode 19o corresponding to the shape of the anode 9 is divided and provided on the electron emission surface 7o of the microchannel plate 7, and the voltage is independently supplied by the electrode 19o. The disturbance of the potential of the surface 7o is reduced. As a result, the generation (crosstalk) of pseudo signals in the output signals of the respective channels due to the induced current due to the disturbance of the potential is suppressed.

  Furthermore, the gain of the microchannel plate 7 can be controlled independently for each channel, and a wider dynamic range of detectable light intensity is ensured.

  Further, since the electrode 19i is also provided separately on the electron incident surface 7i of the microchannel plate 7, voltage can be supplied independently also on the electron incident surface 7i, and the inside of the microchannel plate 7 in each channel can be supplied. The potential disturbance is reduced, and the pseudo signal superimposed on the output signal is further suppressed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is a partially broken perspective view of the photomultiplier tube according to the second embodiment, and FIG. 6 is a cross-sectional view taken along the arrangement direction of the anodes of the photomultiplier tube of FIG. The photomultiplier tube 101 according to the present embodiment is different from that of the first embodiment in that two microchannel plates are stacked and the shape of the electrodes on the microchannel plate is different.

  That is, as shown in FIG. 5, two rectangular plate-like microchannel plates 107 and 108 on the other side of the sealed container 3 facing the photocathode 5 are close to each other in parallel with the incident window 13. Arranged.

  As shown in FIG. 6, a plate-like electrode 119i for supplying a voltage to the electron incident surface 107i of the microchannel plate 107 is formed on the electron incident surface 107i facing the photocathode 5 of the microchannel plate 107. Has been. On the electron emission surface 108o facing the anode 9 of the microchannel plate 108, four flat electrodes 120o for supplying a voltage to the electron emission surface 108o of the microchannel plate 108 are formed.

  The electrodes 120o are divided and provided in substantially the same shape as the opposed anodes 9 and are arranged in parallel so that the arrangement direction thereof is the same as the arrangement direction of the anodes 9. On the other hand, the electrode 119i has a rectangular integral shape and is formed such that the distance between the edge and the side tube 11 is the same as the distance between the edge of the electrode 120o and the side tube 11. Has been.

  A contact electrode 121i and a contact electrode 121o are respectively crimped to the electrode 119i and the electrode 120o, and the electrode 119i and the electrode 120o are connected to the terminal 15 via the contact electrodes 121i and 121o and a lead wire (not shown). Connected independently.

  Further, on the electron emission surface 107o and the electron incident surface 108i facing each other of the microchannel plates 107 and 108, flat electrodes 119o and 120i having substantially the same shape as the electrode 119i are formed. The electrodes 119o and 120i are electrically connected to each other through contact with each other via a plate-like contact electrode.

  In order to appropriately detect incident light in the photomultiplier tube 101, predetermined voltages are applied so that the potential decreases in the order of the anode 9, the electrode 120o, the electrode 119i, and the photocathode 5.

  According to the photomultiplier tube 101 described above, the output signal taken out from the anode 9 is a set of electrodes 119i, 119o, 120i, which exist in a direction parallel to the side tube 11 from the light incident position in the incident window 13. It is taken out from a channel formed by 120o, microchannel plates 107 and 108 sandwiched between them, and anode 9 facing this electrode 120o. By arranging the two microchannel plates in this way, the detection sensitivity of incident light obtained by the entire photomultiplier tube 101 can be improved.

  In addition, since the electrode 120o corresponding to the shape of the anode 9 is divided and provided on the electron emission surface 108o of the microchannel plate 108, and the voltage is independently supplied by the electrode 120o, the electron emission surface in the adjacent channel. The disturbance of the potential at 108o is reduced. As a result, generation of pseudo signals (crosstalk) in the output signal of each channel due to the induced current due to the disturbance of the potential is suppressed.

  Furthermore, by changing the voltage supplied to each electrode 120o, the gains of the microchannel plates 107 and 108 can be independently controlled for each channel, and a wider dynamic range of detectable light intensity is secured.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 7 is a partially broken perspective view of the photomultiplier tube according to the third embodiment, and FIG. 8 is a cross-sectional view taken along the arrangement direction of the anodes of the photomultiplier tube of FIG. In the photomultiplier tube 201 according to the present embodiment, the electrode shape on the surface other than the surface facing the anode 9 of the microchannel plate is different from that of the second embodiment.

  That is, as shown in FIG. 8, the electrode 219i is on the electron incident surface 107i facing the photocathode 5 of the microchannel plate 107, and the electrode 219o is on the electron emission surface 107o on the opposite side of the electron incident surface 107i of the microchannel plate 107. However, the electrode 220i is formed on the electron incident surface 108i of the microchannel plate 108 facing the electron emission surface 107o. These electrodes 219 i, 219 o, 220 i are provided in substantially the same shape as the anode 9 and divided into four parts, and are arranged side by side so that the arrangement direction thereof is the same as the arrangement direction of the anode 9. The electrodes 219o and 220i are electrically connected to each other through contact with each other via a plate-like contact electrode.

  Contact electrodes 221i are respectively crimped to the electrodes 219i in the same manner as the electrodes 120o, and the electrodes 219i are independently connected to the terminals 15 through the contact electrodes 221i and lead wires (not shown).

  Also in the photomultiplier tube 201 described above, generation of a pseudo signal (crosstalk) in the output signal of each channel due to an induced current due to potential disturbance is suppressed, and also due to a decrease in electric field strength in the vicinity of the electron emission surface 108o. Saturation of the output signal is prevented.

  In addition, a voltage can be supplied independently to the electron incident surface 107i of the microchannel plate 107 for each channel, and the potential disturbance in the microchannel plates 107 and 108 in each channel is reduced, and a pseudo signal superimposed on the output signal. Is further suppressed.

  FIG. 9 shows the time change of the output signal detected in the adjacent channel in the photomultiplier tube 201. In this case, as the photomultiplier tube 201, electrodes 219i, 219o, 220i, and 120o having a thickness of 10 μm deposited thereon are used, so that the potential difference between the photocathode 5 and the anode 9 is 3000V. Voltage was supplied.

  In addition, FIG. 10 shows the time change of the output signal detected in the adjacent channel in the conventional photomultiplier tube. The photomultiplier tube in this case has the same configuration as the photomultiplier tube 201 except that the electrodes provided on both surfaces of the microchannel plates 107 and 108 are integrally formed. Using. In measuring the output signal, a voltage was supplied so that the potential difference between the photocathode 5 and the anode 9 was 2800V.

  9 and 10, the solid line represents the time change of the output signal taken out from the anode 9 of the channel corresponding to the light incident position of the photocathode 5, and the dotted line represents the channel corresponding to the light incident position of the photocathode 5. The time change of the output signal taken out from the anode 9 of the channel adjacent to is shown. These measurements were performed so that light was incident on only one channel.

  From these results, in both the conventional photomultiplier tube and the photomultiplier tube 201, the output signal detected in the adjacent channel corresponds to the time change of the output signal detected in the channel corresponding to the light incident position. Thus, a pseudo signal is superimposed. The relative output voltage of the pseudo signal with respect to the maximum value of the output signal is about 1/3 of that in the photomultiplier tube 201 compared to that in the conventional photomultiplier tube. Thereby, it can be seen that the generation of the pseudo signal in the photomultiplier tube 201 is effectively suppressed.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 11 is a partially broken perspective view of the photomultiplier tube according to the fourth embodiment, and FIG. 12 is a cross-sectional view along the arrangement direction of the anodes of the photomultiplier tube of FIG. In the photomultiplier tube 301 according to the present embodiment, the electrode shape on the surface other than the surface facing the photocathode 5 of the microchannel plate is different from that of the third embodiment.

  That is, as shown in FIG. 12, in the photomultiplier tube 301, the electrode 319 o is disposed on the electron emission surface 107 o of the microchannel plate 107, the electrode 320 i is disposed on the electron incident surface 108 i of the microchannel plate 108, and the microchannel plate 108. Electrode 320o is formed on each electron emission surface 108o in four parts. These electrodes 319o, 320i, and 320o are formed in a rectangular shape corresponding to the shape of the anode 9, and the arrangement direction thereof is the same as the arrangement direction of the anode 9.

  Further, along the channel corresponding to each anode 9, the area gradually decreases in the order of the electrode 219i, the electrode 319o, the electrode 320i, and the electrode 320o formed on the electron incident surface 107i of the microchannel plate 107. It is formed. More specifically, each of the electrodes 219i, 319o, 320i, and 320o has a shape in which the length of the side in the arrangement direction of the anode 9 is gradually reduced toward the other side in the sealed container 3. .

  In such a photomultiplier tube 301 as well, generation of a pseudo signal (crosstalk) in the output signal of each channel due to an induced current due to potential disturbance is suppressed, and also due to a decrease in electric field strength in the vicinity of the electron emission surface 108o. Saturation of the output signal is prevented.

  In addition, dark current tends to be generated due to scratches at the edge of the electrode formed on the microchannel plate. Therefore, the gain of the microchannel plates 107 and 108 at the edge portions of the 219i, 319o, and 320i can be reduced by reducing the electrodes stepwise toward the anode 9. As a result, generation of dark current in the output signal can be prevented.

  In addition, this invention is not limited to each embodiment mentioned above. For example, the shape of the anode in the photomultiplier tubes 1, 101, 201, 301 and the shape of the electrode formed on the microchannel plate are not limited to specific ones, and various shapes and division numbers can be used. . For example, as shown in FIGS. 13A to 13D, a rectangular shape having a different arrangement direction, a different number of divisions, a concentric shape, a triangular shape obtained by dividing a polygon, and the like can be given. .

  Further, the number of microchannel plates incorporated in the photomultiplier tubes 1, 101, 201, 301 is not limited to a specific number, and three or more microchannel plates may be incorporated.

It is a partially broken perspective view which shows 1st Embodiment of the photomultiplier tube by this invention. It is a disassembled perspective view of the photomultiplier tube of FIG. FIG. 2 is a cross-sectional view along the anode arrangement direction of the microchannel plate of FIG. 1. It is a figure which shows the connection relation of the photomultiplier tube of FIG. 1 and an external power supply circuit. It is a partially broken perspective view which shows 2nd Embodiment of the photomultiplier tube by this invention. FIG. 6 is a cross-sectional view along the anode arrangement direction of the photomultiplier tube of FIG. 5. It is a partially broken perspective view which shows 3rd Embodiment of the photomultiplier tube by this invention. It is sectional drawing along the anode arrangement direction of the photomultiplier tube of FIG. It is a time change of the output signal detected in the adjacent channel in the photomultiplier tube of FIG. It is a time change of the output signal detected in the adjacent channel in the conventional photomultiplier tube. It is a partially broken perspective view which shows 4th Embodiment of the photomultiplier tube by this invention. FIG. 12 is a cross-sectional view along the anode arrangement direction of the photomultiplier tube of FIG. 11. It is a figure which shows the modification of the shape of the electrode formed on an anode and a microchannel plate.

Explanation of symbols

  1, 101, 201, 301 ... Photomultiplier tube, 3 ... Sealed container, 5 ... Photocathode, 7, 107, 108 ... Microchannel plate, 7i107i, 108i ... Electron incident surface, 7o, 107o, 108o ... Electron emission surface , 9... Anode, 19i, 19o, 119i, 119o, 120i, 120o, 219i, 219o, 220i, 220o, 319o, 320i, 320o.

Claims (4)

A photocathode which is fixed to one end face in the sealed container and converts light incident from the outside into photoelectrons,
A microchannel plate that is provided in the sealed container so as to face the photocathode and multiplies photoelectrons emitted from the photocathode;
A film- like electrode provided along the electron incident surface and the electron emission surface of the microchannel plate, for supplying a voltage to the microchannel plate;
A plurality of parallel arrangements so as to face the microchannel plate on the other side in the sealed container, and an anode for taking out electrons emitted from the microchannel plate as an output signal,
The electrode is formed so as to have a shape divided so as to correspond to the plurality of anodes at least on an electron emission surface facing the anode.
A photomultiplier tube characterized by that.
The electrodes are provided separately on the electron incident surface and the electron emission surface so as to correspond to the plurality of anodes, respectively.
The photomultiplier tube according to claim 1. The electrode is formed such that the area on the electron emission surface is smaller than the area on the electron incident surface,
3. The photomultiplier tube according to claim 2, wherein A plurality of the microchannel plates are arranged in the sealed container,
The electrode is formed so that the area on the electron emission surface on the other side is smaller than the area on the electron emission surface on one side between the adjacent microchannel plates.
The photomultiplier tube according to any one of claims 1 to 3.

Images