JPS63174255A - Photoelectron multiplier tube - Google Patents

Abstract

PURPOSE:To effectively shield the thermoelectrons emitted from a photoelectric face and improve the detection precision of photoelectrons by setting the position of a support pin nearest to the electrode support pin of a photoelectron emitting electrode plate and within a range that the incident light is not cut off by the shape of a metal plate. CONSTITUTION:A thermoelectron shielding metal plate 17 is provided between a photoelectron emitting electrode plate 6 and the first dynode 7 to block the effect of the thermoelectrons emitted from a photoelectric face and improve the detection precision of the light, i.e., S/N. The position of a support pin is on the line LN connecting the electrode support pin 23 of the second dynode 8 and the electrode support pin 21' of the photoelectron emitting electrode plate 6. The cross section shape of the metal plate 17 is formed nearly to follow the equipotential plane, thus the electrons emitted from the photoelectron emitting electrode plate 6 can pass the opening 33 of the metal plate 17 in the nearly vertical direction to the metal plate 17, and the probability that photoelectrons reach the dynode 7 can be improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a photomultiplier tube used in a fluorescence spectrometer, etc., and in particular to a photomultiplier tube used in a fluorescence spectrometer, etc. This paper relates to a photomultiplier tube that converts energy into a current corresponding to that energy.

[Conventional technology]

In order to accurately detect and measure the energy of weak light such as fluorescent light emitted from the excited state of atoms and molecules using a photomultiplier tube in a fluorescence spectrometer, etc., it is necessary to use a photomultiplier tube. It is necessary to effectively prevent the influence of thermionic emission from the surface.

As a photomultiplier tube having a structure that prevents the influence of thermionic emission, for example, one disclosed in Japanese Patent Publication No. 50-9628 is known.

In this photomultiplier tube, the cross-sectional area of light such as fluorescent light that enters the photocathode of the photoelectron emission electrode is generally small, and the area that is actually used within the entire surface of the photocathode is a small area (for example, 5 r. Focusing on the fact that the photocathode is limited to X 51III+), the i-structure of the photocathode is made different between a small area that is actually used and an area that is not actually used.

FIG. 10 is a sectional view of the photocathode of such a conventional photomultiplier tube. In FIG. 10, a multi-alkali photocathode 51 and a deposited layer 53 of silver or aluminum are sequentially deposited on a photocathode substrate 50. As shown in FIG. However, on the actually used area 54 of the multi-alkali photocathode 51, a silver or aluminum vapor deposited layer 5 is provided.
3 is not formed.

In a photocathode having such a structure, the work function of the photocathode material is small and the work function of silver or aluminum is large. evaporated layer 53 of
This prevents the emission of thermionic electrons from the area that is not actually used and is covered with
/N ratio can be improved.

However, in the above-mentioned photomultiplier tube, the silver or aluminum vapor deposition layer 53 is deposited after forming the multi-alkali photocathode 51, so when depositing silver or aluminum, these vapor deposition sources, etc. There is a problem in that the adsorbed cesium, potassium, and sodium simultaneously evaporate and excessive cesium, potassium, and sodium adhere to the multi-alkali photocathode 51, reducing the sensitivity of the multi-alkali photocathode in the long wavelength region. Ta.

In order to avoid such problems, a slit is formed in the path of photoelectrons and thermoelectrons emitted from the photocathode, that is, at a position facing the photocathode, without making any improvements to the structure of the photocathode of the photoelectron emission electrode. A photomultiplier tube has been proposed which is intended to improve the S/N ratio of photoelectron detection by providing a gate electrode with a fixed gate electrode. In addition, in order to improve the S/N ratio, a technique of providing a gate electrode with a slit facing the photocathode is proposed, for example, in the Japanese Patent Publication No. 5mm-5mm.
It has already been applied in streak tubes, as disclosed in No. 005.

FIG. 11 shows a
FIG. 2 is a partial schematic cross-sectional view of a photomultiplier tube to which a technique of providing a gate with a slit and a pole is applied.

In FIG. 11, a gate electrode 6 with a slit 62 is shown.
0 is provided facing the photocathode (not shown) of the photoelectron emission electrode plate 61. The slit 62 has approximately the same area as the area of the photocathode actually used (for example, 5 txm
x 5 nun), and the slit 6
2 is positioned at a position where the most photoelectrons emitted from the area of the photocathode actually used pass through, and the entire gate electrode 60 is positioned closer to the photoelectron emitting electrode plate 61 than the first dynode 63. is positioned.

Now, when photoelectrons are emitted by light incident on the photocathode from the direction of arrow F, these photoelectrons pass through gate T and slit 62 of pole 60 and proceed toward first dynode 63 in the direction shown by arrow FO. be able to.

Furthermore, thermoelectrons emitted from areas of the photocathode that are not actually used cannot pass through the slit 62, and the gate ring! ! 60. As a result, the photomultiplier tube shown in FIG. 11 prevents the influence of thermoelectrons.

[Problems to be Solved by the Invention] However, in the photomultiplier tube shown in FIG.
Since the photoelectron emitting electrode plate 61 is disposed near the gate electrode 1 facing the photoelectron emitting electrode plate 61, a part of the photoelectrons emitted from the area of the photocathode that is actually used cannot pass through the slit 62, and the gate electrode 60 It may be obscured by. FIG. 11 shows the trajectory of photoelectrons emitted in the direction of arrow Go by light incident on the photocathode in the direction of arrow G. Despite being emitted from the gate electrode 60
is shielded by

In this way, in the photomultiplier tube shown in FIG. 11, although it is possible to reduce the degree to which thermoelectrons reach the first dynode 63, it is possible to reduce the number of photoelectrons emitted from the area of the photocathode that is actually used. There was a problem in that the detection accuracy of photoelectrons, that is, the S/N ratio could not be significantly improved because the photoelectrons were blocked by the gate electrode 60 and could not reach the first dynode 63.

The present invention allows photoelectrons emitted from the photocathode to reach the first dynode without being blocked, while effectively blocking thermoelectrons emitted from the photocathode, thereby significantly improving the detection accuracy of photoelectrons. The purpose is to provide photomultiplier tubes.

[Means for solving problems]

The present invention provides a photoelectron emission electrode plate on which a photocathode is formed and a first
A metal plate having an opening of a predetermined size is provided between the metal plate and the dynode, and one edge of the metal plate is attached to the electrode support bin of the first dynode adjacent to the mesh electrode. , the other edge is a support bin disposed at a point on a line connecting the electrode support bin of the second dynode on the side adjacent to the first dynode and the electrode support bin of the photoelectron emission electrode on the side opposite to the mesh electrode. The positions of the support pins range from the position closest to the electrode support bin of the second dynode to the position closest to the electrode support bin of the photoelectron emission electrode plate, and the position of the support pin is such that the light incident on the photoemission electrode plate The photoelectron is set on the line in a range that is not interrupted by the shape of the metal plate, and the cross-sectional shape of the metal plate is determined by an equipotential surface passing through the set position of the support pin. The multiplier tube is used to improve the problems of the prior art described above.

[Effect]

Generally, when light is incident on a photoelectron emitting electrode plate, photoelectrons are emitted from the area of the photocathode that is actually used. Furthermore, thermoelectrons are emitted from the entire surface of the photocathode regardless of the incidence of light. In order to accurately detect photoelectrons emitted from the photocathode, it is necessary to prevent the influence of thermoelectrons emitted from the entire surface of the photocathode. In the present invention, a metal plate having an opening of a predetermined size is provided between the photoelectron emission electrode plate on which the photocathode is formed and the first dynode. One edge of this metal plate is attached to the electrode support pin of the first dynode, and the other edge is placed at a point on a line connecting the electrode support pin of the second dynode and the electrode support pin of the photoelectron emission electrode. The cross-sectional shape of the metal plate is determined by the equipotential plane passing through the set position of the support pin, so photoelectrons emitted from the area of the photocathode that is actually used are shielded by the metal plate. Thermionic electrons pass through an aperture of a predetermined size almost perpendicularly to the cross section of the metal plate without being used and reach the first dynode. It is blocked and does not reach the first dynode.

Thereby, only thermoelectrons can be blocked without preventing photoelectrons from reaching the first dynode.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic perspective view of a side-on type photomultiplier tube, and FIG. 2 is a schematic cross-sectional view taken along the line A--A in FIG.

In FIGS. 1 and 2, an upper substrate 3 and a lower substrate 4 made of an insulating material such as ceramic are arranged at a distance from each other in a glass hermetic bulb 2 of a photomultiplier tube 1. . The upper substrate 3 and the lower substrate 4 have exactly the same structure, and each is provided with a plurality of through holes for holding electrode support bottles.

Conductive electrode support pins 20.20' to 30.30' and electrode support pins 31 are inserted into corresponding through holes of the upper substrate 3 and lower substrate 4,
These electrode support pins are firmly locked to the upper substrate 3 and lower substrate 4. An electrode is fixed to each electrode support pin, thereby maintaining each electrode in a predetermined curved shape. That is, the mesh electrode 5. Photoelectron emission electrode plate 6. First dynode 7 to ninth dynode 15
, and the output electrode 16 are each connected to an electrode support pin 20 .
20', the pole support bin 21.21'.

Electrode support pin 22.22' to electrode support pin 30°30
', and is fixed to the electrode support pin 31.

One (e.g., electrode support pin 21) of a set of electrode support pins (e.g., electrode support pins 21, 21') supporting each electrode is connected by a lead wire passing through the stem 18.
Connected to pins for external circuit connection. For example, each electrode support pin 21, 22゜23.24.25, 26, 27,
28, 29°, 30.31 are pins K for external circuit connection.

DYI, DY2. DY3. DY4. DY5. DY6,D
Y7. DY8. DY9. Connected to P.

FIG. 3 shows the state of connection between such external circuit connection pins of the photomultiplier tube 1 and the external circuit.

In FIG. 3, the external circuit 19 is connected to the external circuit connection pins of the photomultiplier tube 1 through sockets S11. Sl to S9. Equipped with SIO. Socket 311 is connected to a power source (not shown) providing voltage -HV. In addition, sockets S1 to S9 are connected to bleeder resistors R1 to RIO and capacitors C1 to c3, respectively, from the power supply that provides voltage -HV.
It is divided and connected by. Note that the terminal of the bleeder resistor RIO on the opposite side from the side connected to the socket S9 is grounded. Also, bleeder resistors R8 to RIO
The capacitors C1 to C3 connected in parallel to the sockets S7 to S9 are used to maintain the voltages of the sockets S7 to S9 at a predetermined potential.

Furthermore, the socket SIO of the external circuit 19 is connected to the coaxial cable CBL. A coaxial cable CBL that accurately transmits a pulsed output signal is used in the socket SIO for taking out the output signal from the photomultiplier tube 1.

When the photomultiplier tube 1 is connected to the external circuit 19 having such a configuration, the photoelectron emission electrode plate 6 of the photomultiplier tube 1 is held at the lowest potential -HV via the pin K, and the first dynode 7 to The ninth dynode 15 has pins DYI to DY.
The potential increases one after another through 9.

FIG. 4 shows that when the photomultiplier tube 1 is connected to the external port i19 and a voltage is applied to each electrode of the photomultiplier tube 1 as described above, the photoelectron emission electrode plate 6, the first dynode 7, and The distribution of the equipotential surface EQV that occurs around the second dynode 8 is calculated and illustrated by computer simulation. In FIG. 4, the electrode arrangement of a conventional photomultiplier tube without the metal plate 17 of this embodiment, which will be described later, is used. Since the electric lines of force exist in a direction perpendicular to the equipotential surface EQV shown in FIG.
It goes toward the first dynode 7 along the line of electric force perpendicular to V, and is further multiplied sequentially from the first dynode 7 to the ninth dynode 15 along the same line of electric force. The photoelectrons multiplied to a predetermined magnification in this way are sent to the coaxial cable CB via the output electrode 31, pin P and socket SIO.
The signal is taken out as an output signal to the L output terminal OUT.

Nickel metal is used for the photoelectron emission electrode plate 6 of the photomultiplier tube 1, and cesium, an alkali metal with a small work function, is not adsorbed onto antimony metal so that photoelectrons can be easily emitted. A photocathode is provided. Further, nickel metal is also used for the first dynode 7 to the ninth dynode 15, and a material with a small work function similar to that of the photocathode is deposited on their surfaces.

When light enters a small area (for example, 5 rm is emitted toward the first dynode 7. Note that photoelectrons emitted in the direction of the light incident path are blocked by the mesh electrode 5. By the way, when the light incident on the photocathode is weak light with a very small number of photons, such as fluorescent light, the emission of thermoelectrons from the photocathode greatly affects the detection accuracy of the weak light.

In this example, in order to prevent the influence of thermoelectrons emitted from the photocathode and improve the light detection accuracy, that is, the S/N ratio, a photoelectron emitting electrode plate was used as shown in FIGS. 1 and 2. A metal plate 17 for thermionic shielding is provided between the first dynode 6 and the first dynode 7.

FIG. 5 is an enlarged view of such a metal plate 17 for shielding thermionic electrons, and FIG. 6 is a diagram showing the installation position and allowable range of shape of the metal plate 17.

The metal plate 17 is a photoelectron emitting electrode plate 6. First dynode 7
Like the ninth to ninth dynodes 15, they are made of nickel metal. The height H of the metal plate 17 is the same as that of the photoelectron emission electrode plate 6.
．． The height is approximately the same as the height of the first dynode 7 to the ninth dynode 15, which is approximately 24 cm.

The metal plate 17 receives photoelectrons emitted from the area where light actually enters on the photocathode of the photoelectron emission electrode plate 6, that is, the area where it is actually used (for example, a range of 5 m x 5 rm). An aperture 33 is provided for the passage of photoelectrons so that they are collected on the first dynode 7 without being blocked by the photoelectrons. The opening 33 is located at a distance Ll (for example, 8.5w>) from the lower edge 34 of the metal plate 17 and at a distance L2 (for example, 8.5w) from the upper edge 35 of the metal plate 17.
5) and the height L (for example, 7).
The right edge 36 of the metal plate 17 is attached to the electrode support pin 22 to which the first dynode 7 is fixed, and the left edge 37 of the metal plate 17 is attached to the support pin 38. . As a result, the maximum width of the opening 33 of the metal plate 17 becomes approximately the same as the distance between the electrode support pin 22 and the support pin 38 of the first dynode 7.

The position of the support pin 38 is on the line LN connecting the electrode support pin 23 of the second dynode 8 and the electrode support pin 21' of the photoelectron emission electrode plate 6, as shown in detail in FIG. The cross-sectional shape of the metal plate 17 is similar to that of the photoelectron emitting electrode plate 6 as shown in FIG. First dynode 7 and second dynode 8
is defined by the equipotential surface EQV around . That is, in FIG. 6, the support pin 38 is connected to the second dynode 8.
When the metal plate 1
The cross-sectional shape of the dynode 7 is such that it extends halfway along the equipotential plane EQVI passing through the position Psi to the electrode support pin 22 of the first dynode 7, as indicated by the symbol FGI in FIG. Further, in FIG. 6, the support pin 38 is located at a position PS on the line LN near the electrode support bin 21' of the photoelectron emission electrode plate 6.
2, the equipotential surface passing through the position W P S 2 is shown as EQV2 in FIG. It extends along the equipotential surface EQV2 passing through fPs2 to the electrode support pin 22 of the first dynode 7.

In this way, by making the cross-sectional shape of the metal plate 17 substantially along the equipotential plane, the electrons emitted from the photoelectron emission electrode plate 6 are directed through the opening of the metal plate 17 in a direction substantially perpendicular to the metal plate 17. 33, it is possible to increase the probability of the photoelectrons reaching the first dynode 7.

In addition, in FIG. 6, the support pin 38 is located at a position l on the line LN.
When the metal plate 17 is brought closer to the photoelectron emitting electrode plate 6 than P S 2 , the metal plate 17 will be placed in a part of the light incident path and will prevent the light from entering the photocathode. is the allowable limit position of the support pin 38 closest to the photoelectron emission electrode plate 6.

Since the metal plate 17 is made of the same nickel metal as the first dynode 7 and the like, it may be integrated with the first dynode 7 or may be a separate component from the first dynode 7 such as the electrode support pin 22. In any case, since the metal plate 17 is electrically connected to the first dynode 7, it has the same potential as the first dynode 7.

Further, the support pins 38 are inserted into through holes 39 and 40 provided in the upper substrate 3 and the lower substrate 4, respectively, and are firmly locked to the upper substrate 3 and the lower substrate 4 like the other electrode support pins.

The operation of the photomultiplier tube 1 having such a configuration will be explained using FIGS. 7 to 9.

FIG. 7 is a schematic diagram of a device that makes weak light enter the photomultiplier tube 41, and FIG. 8 is a conventional photomultiplier tube in which the photomultiplier tube 41 shown in FIG. 7 is not provided with the metal plate 17. (not shown), FIG. 9 shows the photomultiplier tube 1 of the present invention in the photomultiplier tube 41 shown in FIG. 7.
It is a figure which shows the output result when using.

In FIG. 7, a tungsten light bulb 42 is used as a light source. The tungsten bulb 42 is powered by a power supply 43 with adjustable voltage. The tungsten bulb 42 is lit at a color temperature of 2856°, and the tungsten bulb 42
The light emitted from the ND filter 44 adjusts the amount of light.
and an interference filter 45 with a center wavelength of 800 nm to reach the photomultiplier tube 41.

The light whose intensity is weakened by the voltage adjustment of the power source 43, the ND filter 44, and the interference filter 45 enters the photomultiplier tube 41 as discrete photons that can be separated as pulsed light.

The output results shown in Figures 8 and 9 are the maximum level that can be separated as pulsed light (that is, the photoelectrons emitted from the photocathode are observed separated one by one within the resolution time width of the measurement system). This is the wave height distribution measured when the voltage of the power source 43 was adjusted to a shape R) such that Fluorescence in actual fluorescence spectroscopy is extremely weak light with a smaller number of photons, and the probability that photoelectrons will be observed separately is even greater.

In the photomultiplier tube 41, photoelectrons are emitted by photons incident on the actually used area (for example, 5 rm x 5 rm) of the photocathode, and the photoelectrons are multiplied by the first to ninth dynodes and output. The pulse current IS is output from the electrode. The process in which photons incident on the photocathode are converted into photoelectrons is a Poisson process when the number of photons is small, and the multiplication process of the photomultiplier tube 41 is also a Poisson process, so the distribution of the pulse current IS, that is, the unit time The distribution of the number of photoelectrons emitted based on incident photons with a predetermined energy is a Poisson distribution.

Further, thermoelectrons are emitted from the entire surface of the photocathode, and these thermoelectrons are similarly multiplied and simultaneously output from the output electrode as dark current IN in a form superimposed on pulse current IS. Since the dark current IN is caused by thermoelectrons generated from the photocathode due to thermal fluctuation, its distribution follows a relaxation process and becomes an exponential distribution that attenuates with a relaxation constant τ.

The pulse current IS and dark current IN from the output electrode of the photomultiplier tube 41 are sent to a pulse height distribution analyzer (not shown) from the output terminal OUT of the coaxial cable CBL of the external circuit 19 as shown in FIG. .

The pulse height distribution analyzer measures pulse current IS and dark current IN.
It measures the frequency distribution of

The data DTI shown in FIG. 8 is obtained by multiplying photoelectrons and thermoelectrons using a conventional photomultiplier tube without the metal plate 17.
The frequency α of the pulse current IS including the dark current IN exceeding a certain level is measured.

All output below the above level is dark current. Data DT2 shown in FIG. 8 is obtained by measuring the frequency α of dark current IN by multiplying only thermoelectrons without making photons enter a conventional photomultiplier tube.

As described above, the pulse height distribution of the pulse current IS including the dark current IN is approximately a Poisson distribution, while the pulse height distribution of only the dark current IN is approximately an exponential distribution.

As can be seen by comparing data DTI and data DT2, when weak light that can be separated as pulsed light is incident, the influence of dark current IN on pulsed current IS becomes very large, and the detection of pulsed current IS accuracy,
That is, the S/N ratio decreases due to the dark current IN.

On the other hand, the data DT3 shown in FIG.
The data was measured under the same conditions as the data DTI in the figure. Further, data DT4 shown in FIG. 9 is obtained by multiplying only the thermoelectrons in the photomultiplier tube 1 of this embodiment, and the frequency α of the dark current IN is
was measured under the same conditions as data DT2 in FIG.

As can be seen by comparing data DT3 and data DT4 in FIG. 9, the frequency of dark current IN is significantly smaller than the frequency of pulse current IS. Furthermore, when comparing FIG. 8 and FIG. 9, it can be seen that the frequency of pulse current IS is the same in both cases, and the frequency of dark current IN is reduced to about 1/3 or less by providing the metal plate 17. .

From these measurement results, it is clear that the photomultiplier tube 1 of this embodiment in which the metal plate 17 is provided between the photoelectron emission electrode plate 6 and the first dynode 7 is different from the conventional photomultiplier tube in which the metal plate 17 is not provided. Compared to the tube, the frequency of the dark current IN is significantly reduced without any reduction in the frequency of the pulse current IS, so it can be seen that the detection accuracy of photoelectrons, that is, the S/N ratio can be significantly improved.

That is, in the photomultiplier tube 1 of this embodiment, the area of the photocathode actually used (for example, 5 yaa x 5 m+
A photoelectron is emitted by a photon incident on
These photoelectrons are not blocked by the metal plate 17 and are directed almost perpendicularly to the cross section of the metal plate 17.
can reach the first dynode 7 through the opening 33 of the dynode 7 . On the other hand, thermoelectrons emitted from areas of the photocathode that are not actually used cannot pass through the opening 33 of the metal plate 17 and are blocked by the metal plate 17 and cannot reach the first dynode 7. Therefore, what is multiplied by the photomultiplier tube 1 of this embodiment is only the photoelectrons and thermoelectrons emitted from the area of the photocathode that is actually used. Since the area is very small compared to the entire surface of the photocathode, the number of thermoelectrons that reach the first dynode 7 is very small compared to the number of thermoelectrons emitted at a uniform rate from the entire surface of the photocathode. As a result, the dark current IN is also reduced, and the photoelectron detection accuracy, that is, the S/N ratio can be improved.

In the examples shown in FIGS. 7 to 9, the number of photons incident on the photomultiplier tube 41 was set to the maximum level that can be separated into pulsed light. The number of fluorescence photons detected is even smaller;
Therefore, the frequency α of the pulse current IS is also the data DT3 in FIG.
Therefore, in order to ensure the detection accuracy of photoelectrons by fluorescence at a specified S/N ratio, the pulse current I
The photomultiplier tube 1 of this embodiment, which reduces only the dark current IN without reducing S, is extremely useful.

In addition, the photocathode of the photomultiplier tube 1 of this embodiment, like the conventional photomultiplier tube, adsorbs alkali metals cesium, potassium, and sodium onto antimony metal after degassing the photomultiplier tube 1. Since the multi-alkaline photocathode is made only by the above-described method and no other metal is deposited thereafter, the sensitivity in the long wavelength region can be maintained well in the multi-alkaline photocathode.

〔Effect of the invention〕

As explained above, according to the present invention, only the thermoelectrons are mainly shielded at a predetermined position between the photoelectron emission electrode plate and the first dynode without shielding the photoelectrons emitted from the photocathode. Since the metal plate has a predetermined cross-sectional shape with an aperture of a predetermined size required for can do well.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a photomultiplier tube of the present invention, FIG. 2 is a schematic cross-sectional view taken along line A-A in FIG. 1, and FIG. A diagram for explaining the connection state, Figure 4 is a diagram showing the equipotential surface around the electrode, Figure 5 is an enlarged view of the metal plate shown in Figures 1 and 2, and Figure 6 is the same as Figure 1. The mounting of the metal plate shown is a diagram to show the permissible range of position and shape. Figure 7 is a schematic diagram of a device that makes weak light enter a photomultiplier tube. Figure 8 is a photomultiplier shown in Figure 7. Figure 9 shows the output results when a conventional photomultiplier tube is used for the tube, and Figure 9 shows the output results when the photomultiplier tube shown in Figure 1 is used for the photomultiplier shown in Figure 7. Figure 10
The figure is a cross-sectional view of the photocathode of a conventional photomultiplier tube, and FIG. 11 is a partial schematic cross-sectional view of a conventional photomultiplier tube having a gate electrode with a slit. DESCRIPTION OF SYMBOLS 1... Photomultiplier tube, 5... Network electrode, 6... Photoelectron emission electrode plate, 7... First dynode, 8... Second dynode, 17... Metal plate, 21' , 22.2
3... Electrode support pin, 33... Opening, 34... Lower edge, 35... Upper edge, 36... Right edge, 37...
・Left edge, 38...Support pin, LN...Line, Psi
, PS2...Position of support pin, EQV, EQVl, E
QV2...Equipotential surface, FGI, FG2...Cross-sectional shape of metal plate Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent attorney Masaharu Uemoto 3 Figure 19 External circuit Figure 4 Figure 5 Figure 6 Figure 7 Figure 431 Tomihara Figure 8 Current Figure 10 Figure 11

Claims (1)

[Claims] 1) A metal plate having an opening of a predetermined size is provided between the photoelectron emission electrode plate on which the photocathode is formed and the first dynode, and one edge of the metal plate is provided. is attached to the electrode support pin of the first dynode on the side adjacent to the mesh electrode, and the other edge is attached to the electrode support pin of the second dynode on the side adjacent to the first dynode and the photoelectron on the side opposite to the mesh electrode. It is attached to a support pin placed at one point on a line connecting the electrode support pin of the emission electrode, and the position of the support pin is from the position closest to the electrode support pin of the second dynode to the electrode of the photoelectron emission electrode plate. The cross-sectional shape of the metal plate is set on the line in a range up to a position closest to the support pin and where light incident on the photoelectron emission electrode plate is not blocked by the cross-sectional shape of the metal plate, and the cross-sectional shape of the metal plate is set as above. A photomultiplier tube characterized in that it is defined by an equipotential surface passing through a set position of a support pin. 2) The metal plate has a height of about 24 mm, the opening is formed at a distance of about 8.5 mm from the upper and lower edges of the metal plate, and the opening has a height of about 24 mm. Claim 1, wherein the width of the opening is approximately 7 mm, and the maximum width of the opening is approximately the same as the distance between the electrode support pin of the first dynode and the electrode support pin of the second dynode. The photomultiplier tube described in .