JP3216944B2 - Phototube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phototube which converts photons incident on a photocathode (photocathode) into photoelectrons and extracts the photoelectrons from an anode, and more particularly to a phototube having a reflection type photocathode.

[0002]

2. Description of the Related Art As a photoelectron emission layer of this type of phototube, a photoelectron emission layer capable of responding to a wide range of light wavelengths has been developed, and a phototube having high photodetection sensitivity and a large S / N ratio has been realized. Therefore, this photoelectric tube is widely used in a field that requires a light detection region that cannot be handled by other semiconductor optical sensors or the like.

As such a conventional reflection-type phototube, a phototube having a structure shown in FIG. 7 is generally used.
A photocathode (cathode) 2 on which a photoelectron emission layer is formed and an anode 3 are provided in a glass bulb 1, and a constant voltage higher than that of the photocathode 2 is applied to the anode 3 on the lead wire 2.
a, 3a. When photons enter the photocathode 2, photoelectrons are emitted from the photocathode 2 in accordance with the amount of incident light. The photoelectrons are collected by the cylindrical anode 3 covering the inner surface of the glass bulb 1, and incident light is detected as an electric signal.

[0004]

However, in the above-mentioned conventional phototube, the glass bulb 1 is used as an airtight container for keeping the photocathode 2 and the anode 3 in a vacuum atmosphere. For this reason, when a mechanical shock was applied to the glass bulb 1 due to a handling error of the bulb or the like, the glass bulb 1 was immediately broken. Therefore, the handling of the phototube required caution.

When the inside of the glass bulb 1 is vacuum-sealed, heat is applied to a stem (not shown) made of a glass material supporting the photocathode 2 and an end of the glass bulb 1 to melt the glass. Let it fuse. However, when heat is applied in this way, the glass material is cracked due to the heat distortion, and the glass bulb 1 and the stem may be broken. further,
This heat is transmitted to the photocathode 2 and the photocathode 2 may be oxidized to deteriorate the light detection characteristics. Therefore, conventionally, it has been necessary to set the entire length of the glass bulb 1 to be long, to increase the distance between the vacuum sealing portion and the photocathode 2, and to adopt a structure in which heat is not easily transmitted to the photocathode 2. For this reason, it was difficult to reduce the size of the conventional phototube.

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem, and there is provided a reflection-type photoelectric tube having a structure which is small in size, suitable for mass production, has sufficient sensitivity to incident light, and has a structure which is not easily damaged. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention provides a container having a glass light receiving face plate for closing one opening of a metal side tube constituting an anode and a stem for closing the other opening of the side tube. And a photocathode disposed at a position facing the light receiving face plate in the container, and a phototube comprising a cathode extraction line penetrating the stem and electrically connected to the photocathode, wherein the stem is Has a metal stem, is connected to the side tube, an insulating material is interposed between the stem and the cathode lead wire, and the cathode is supported by the plurality of electrode lead wires. It is characterized by. INDUSTRIAL APPLICABILITY The photoelectric tube of the present invention is a reflection-type photoelectric tube having a small size, suitable for mass production, and having a structure that is not easily damaged, and has sufficient sensitivity to incident light.

A metal exhaust pipe penetrates the above,
It is preferable that the side pipe, the stem, and the metal exhaust pipe are electrically connected.

It is preferable that the side pipe on the other opening side has a bent flange outside the side pipe, and the stem is attached to the flange. It is preferable that the side tube on the one opening side has a bent flange inside the side tube, and the light receiving face plate is attached to the flange. Further, a case made of an insulating material can be put on the container.

[0010]

The photoelectric surface is vacuum-sealed in a metal container also serving as an anode electrode.

[0011] Further, by forming a metal container by closing one opening surface of the side tube with a light receiving surface plate and the other opening surface with a metal stem, vacuum sealing of the metal container welds the side tube and the metal stem. Can be done by

When a conductive film electrically contacting the metal container is provided on the inner surface of the light receiving section, photoelectrons emitted from the photocathode in response to incident light are efficiently collected at the anode electrode.

[0013]

1 is a perspective view showing a phototube according to a first embodiment of the present invention, and FIGS. 2 (a), 2 (b) and 2 (c) are a plan view, a side sectional view, and a rear view of the phototube, respectively. FIG.

The metal valve 11 has a cylindrical shape with both ends opened, and constitutes a side tube of a metal container. An inward flange 11a protruding into the inside of the valve is formed on one opening surface of the metal valve 11, and a light receiving face plate (face plate) 12 is fused to the inward flange 11a. The light-receiving surface plate 12 is made of a translucent glass material, and the light-receiving surface plate 12 closes one opening surface of the side tube. An outward flange 11b protruding outside the valve is formed on the other opening surface of the metal valve 11, and a metal stem 13 is formed on the outward flange 11b.
Are resistance welded. The metal valve 11 and the metal stem 13 are made of an alloy (kovar) of iron, cobalt, and nickel, and have a property of being easily fused to a glass material. The other opening surface of the side tube is closed by the metal stem 13, and the inside of the metal container is evacuated from the metal exhaust pipe 14 provided at the center of the metal stem 13, so that the inside of the metal container is in a vacuum state. Is kept. The metal valve 11, the metal stem 13, and the metal exhaust pipe 14 are in electrical contact with each other and are set at the same potential.

A disk-shaped photoelectric surface 15 is provided at a position facing the light-receiving surface plate 12 inside the metal container. The surface of the photoelectric surface 15 facing the light receiving surface plate 12 is Cs-56Te ^.
Is formed, and the photocathode 15 is fixed in the metal container by four cathode extraction lines 16. This fixing is performed by welding the peripheral end of the photocathode 15 and the cathode lead wire 16. The cathode lead wire 16 is made of a conductive material such as a copper wire, and is fixed to the metal stem 13 by a tapered hermetic glass 17 having electrical insulation.

The vacuum sealing of the photoelectric tube 21 is specifically performed as follows.

First, a metal stem 13 provided with a cathode take-out line 16 by a hermetic glass 17 is prepared. Then, the photocathode 15 on which ⁵⁶ Te is deposited in advance is welded to each cathode lead wire 16. Thereafter, the outward flange 11b of the metal valve 11 and the metal stem 13 are resistance-welded using a resistance welding jig, and the vacuum tightness of the flange portion of the metal container is maintained.

Next, as shown in FIG. 3, a plurality of photoelectric tubes 22 in the manufacturing process through the above steps are connected to a branch tube (branch portion).
23. The respective internal spaces of the exhaust pipes 14 provided in the photoelectric tubes 22 and the branch pipes 23 communicate with each other, and the branch pipes 23 are connected to a vacuum pump 25 via a valve 24. In addition, a container 27 containing a cesium source 26 is connected to the branch pipe 23. In such a state, the temperature of each phototube 22 is set to 180 ° C., and the vacuum pump 25 is driven to evacuate the inside of the metal container of each phototube 22. Upon completion of the evacuation, the degree of vacuum inside the metal container is confirmed. If the degree of vacuum has reached a predetermined degree, the process proceeds to the alkali activation step. That is, the cesium source 26 is heated by the high-frequency induction heater, and cesium is introduced into each metal container. By this alkali activation step, each photocathode 15
Photoelectron emitting layer made of: ^Cs-56 Te in is formed. Finally, the metal exhaust pipe 14 serving as the lower part of the metal container is cut off with a certain length left, and separated into individual photoelectric tubes 21.

The phototube 21 thus obtained is used as follows. That is, a cathode potential, usually a ground potential, is applied to the cathode extraction line 16, and an anode potential higher than the cathode potential is applied to the metal container. That is, in the photoelectric tube 21 according to the present embodiment, the metal container functions as an anode electrode. Since the metal valve 11, the metal stem 13, and the metal exhaust pipe 14 are electrically connected to each other, the anode potential applied to the metal container may be applied to any of them. However, the metal exhaust pipe 14 in the chip-off portion is easily clipped. To easily give an anode potential. When light is incident on the photoelectric surface 15 via the light receiving surface plate 12 in a state where a voltage is applied between the electrodes, photoelectrons are emitted from the photoelectric surface 15. The emitted photoelectrons are collected on an anode electrode, that is, a metal container, and incident light is extracted as an electric signal.

Since the anode potential is given to the metal container as described above, when it is actually used, as shown in FIG.
The case 31 is covered on the metal container and shielded. The case 31 is formed of an insulating material such as a Duracon resin, and has a configuration in which the anode potential is not transmitted to the outside.
FIGS. 3A, 3B and 3C show case 3 respectively.
2 shows a plan view, a side sectional view, and a back view of the photoelectric tube 21 covered by 1, and the same parts as those in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted.

The photocathode 15 of the phototube 21 having the structure of this embodiment is vacuum-sealed in a metal container also serving as an anode electrode. For this reason, the hermetic container is formed of a metal material, and is much more robust than a mechanically fragile hermetic container made of a conventional glass material. Therefore, even if a small mechanical impact is applied, the possibility of breakage as in the conventional case is small, and it is not necessary to handle the photoelectric tube with care as in the conventional case. In addition, since the photocathode 15 is provided in a metal container also serving as an anode electrode, and there is no need to provide an anode in an airtight container as in the related art, the size of the phototube can be reduced and the constituent materials can be saved.

Further, a metal container is formed by closing one opening surface of the metal valve 11 with the light receiving surface plate 12 and the other opening surface with the metal stem 13, so that the metal container is vacuum-sealed with the metal valve 11 and the metal stem. 13 by resistance welding. For this reason, the hermetic container is formed of a metal material, and does not require a heating step for vacuum sealing, so that there is no problem that cracks occur in the hermetic glass due to thermal strain as in the related art. Further, since there is no need to heat the bulb as in the related art, there is no possibility that the photocathode made of the alkali metal is oxidized, and the photodetection characteristics of the phototube do not deteriorate. In addition, conventionally, in order to make it difficult for heat for vacuum sealing to be transmitted to the photoelectric surface, the entire length of the glass bulb was set to be long.However, in the photoelectric tube of the present embodiment, since the airtight container is vacuum-sealed by resistance welding, There is no need to lengthen the total length of the valve. Therefore, the photoelectric tube according to the present embodiment can be further reduced in size in combination with the necessity of providing an anode in an airtight container, and can be made approximately the same size as a semiconductor optical sensor.

The characteristics of the phototube 21 according to the present embodiment are not different from those of the conventional phototube, and it is confirmed by the following experiments that the phototube 21 has a high photodetection sensitivity even if it is small. Was done.

The following Table 1 shows a phototube according to the present embodiment and a conventional phototube (model name: R1) manufactured by Hamamatsu Photonics Co., Ltd.
228) is a table in which the radiation sensitivity characteristics are compared. This conventional type phototube has the same Cs as the phototube according to the present embodiment.
Although they have in common that they have a -Te photoelectric surface, they differ in that each electrode is provided in a glass bulb.

[0025]

[Table 1]

In the experiment, as shown in the above table, the conventional type photoelectric tube (R1228) has six samples (No. 1 to No. 1).
6), a new type of phototube according to the present embodiment was performed on five samples (No. 1 to No. 5). First, light from a mercury lamp was irradiated with a voltage _Ebb of 90 [V] applied between the photocathode of each photoelectric tube and the anode electrode. The light emitted from this mercury lamp is mainly ultraviolet light having a wavelength of 254 nm. At this time, the radiation sensitivity of each photoelectric tube [nA / μ
W] is shown in “Suv (1)” in the leftmost column of the table. That is, the conventional sample No. The radiation sensitivity of the photoelectric tube of Sample No. 1 was 19.47 [nA / μW], and It is shown that the radiation sensitivity of Photocell 2 is 11.61 [nA / μW],. Similarly, a new type of sample No. The radiation sensitivity of the photocell of Example 1 was 22.40 [nA / μW], and the sample N
o. The radiation sensitivity of Photocell 2 was 18.23 [nA / μ.
W],... Also, this Suv
Right next column labeled "Suv (2)" in the (1) in a state where the voltage E _bb was applied in 25 [V] between the photocathode and the anode electrode, irradiating mercury lamp light to each phototube The radiation sensitivity [nA / μW] is shown.

From the table, the radiation sensitivity of each photocell is almost the same regardless of the conventional type and the new type.
It was also confirmed that the photodetection sensitivity hardly changed even when the supply voltage _Ebb was reduced in the new type of phototube.

Next, while supplying a voltage of 90 [V] to each photoelectric tube, the light of a 100 [W] bulb was irradiated in addition to the mercury lamp light. “Suv (1) next to Suv (2)
The column labeled “+ W” indicates the radiation sensitivity [nA / μW] of each phototube at this time. Further, a column indicated as “visible portion W” on the right of this column is Suv (1).
Among the radiation sensitivities in the column indicated by + W, a radiation sensitivity corresponding to light irradiation of a 100 [W] bulb is shown. That is,
The radiation sensitivity value shown in the column of visible portion W is Suv
(1) From the radiation sensitivity values shown in the column of + W, Suv (1)
The values obtained by subtracting the radiation sensitivity values shown in the column of "." Further, the “visible fraction W /
In the column labeled “Suv (1)”, a value obtained by dividing the radiation sensitivity value shown in the column of visible light W by the radiation sensitivity value shown in the column of Suv (1) is shown. In other words, the value in this column is
The ratio of the radiation sensitivity of 100 [W] bulb light to mercury lamp light is shown in percentage.

As shown in the table, even in the new type of phototube according to the present embodiment, even if visible light is irradiated from a 100 [W] bulb, the detection sensitivity of 254 nm ultraviolet light has almost no effect. Was confirmed.

Next, the current-voltage (IV) characteristics of the new type phototube and the I-V characteristics of the above-mentioned conventional type phototube will be described.
The result of comparison with the V characteristic is shown in the graph of FIG.

The horizontal axis of the graph indicates the voltage [V] applied between the photoelectric surface and the anode electrode. The vertical axis indicates the percentage of the photocurrent actually flowing on the photocathode when each voltage is applied, and is obtained on the photocathode when the radiation sensitivity becomes 20 [nA / μW] under an applied voltage of 90 [V]. The current is set to 100. Further, the IV characteristic line indicated by a solid line indicates the characteristic of the new type phototube according to the present embodiment, and the IV characteristic line indicated by the dotted line indicates the characteristic of the conventional type phototube. As shown in the graph, the characteristic lines are almost the same, and it is understood that the IV characteristics of the new type and the conventional type hardly change.

As described above, it has been proved that the phototube according to the present embodiment has a light detection sensitivity comparable to that of a conventional phototube, while being small.

Next, a phototube according to a second embodiment of the present invention will be described with reference to FIG.

In the phototube according to the above embodiment, one opening surface of the metal valve 11 is closed by the light receiving surface plate 12 and the other opening surface is closed by the metal stem 13 as shown in a schematic side sectional view of FIG. Photoelectrons having a structure and emitted from the photocathode 15 were collected by the metal valve 11 and the metal stem 13 set at the anode potential. On the other hand, in the photoelectric tube according to the present embodiment, as shown in the schematic side sectional view of FIG. 2B, a conductive film 42 having good light transmittance is thinly deposited on the inner wall surface of the light receiving surface plate 41, 42 has a structure in which it is in electrical contact with the metal valve 43. Thus, even if the conductive film 42 is formed on the back surface of the light incident window, the incident light passes through the conductive film 42 and reaches the photoelectric surface 44, and emits photoelectrons from the photoelectric surface 44. The photoelectrons are collected not only in the metal valve 43 and the metal stem 45 but also in the conductive film 42. Therefore, in the phototube 51 according to the present embodiment, the photoelectrons emitted from the photocathode 44 are more efficiently collected by the anode electrode, so that the total length of the phototube 51 can be further reduced. For this reason, it is possible to further reduce the size of the photoelectric tube. Note that the conductive film 42 may be anything as long as it has conductivity and good light transmittance.

[0035]

As described above, according to the present invention, the photocathode is vacuum-sealed in the metal container also serving as the anode electrode. For this reason, the mechanical strength of the photoelectric tube is increased, and the possibility that the photoelectric tube is damaged as in the related art is extremely reduced, and the reliability of the photoelectric tube is improved. In addition, since there is no need to provide an anode in the container, the size of the phototube can be reduced, and a phototube having an easily handled structure suitable for mass production can be realized.

In addition, by forming a metal container by closing one opening surface of the side tube with a light receiving surface plate and the other opening surface with a metal stem, vacuum sealing of the metal container welds the side tube and the metal stem. Can be done by For this reason, it is not necessary to heat the container to vacuum seal the inside of the airtight container as in the related art, and the problem of cracking of the glass material does not occur. Further, the photocathode is not oxidized by heating, and the characteristics of the photocathode are not deteriorated. Also, in order to secure a distance between the heating unit and the photocathode, it is not necessary to increase the length of the airtight container, so that it is not necessary to provide an anode in the container, so that the photoelectric tube can be downsized. .

When a conductive film electrically contacting the metal container is provided on the inner surface of the light receiving portion, photoelectrons emitted from the photocathode in response to incident light are efficiently collected at the anode electrode. For this reason, the metal container can be made smaller, and the size of the photoelectric container can be further reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a phototube according to a first embodiment of the present invention.

FIG. 2 is a view showing three surfaces of a phototube according to the first embodiment.

FIG. 3 is a view showing a manufacturing apparatus used for manufacturing a phototube according to the first embodiment.

FIG. 4 is a diagram in which a case is put on the photoelectric tube according to the first embodiment.

FIG. 5 is a graph showing current-voltage characteristics of a new type phototube and a conventional type phototube according to the first embodiment.

FIG. 6 is a schematic side sectional view illustrating a phototube according to a second embodiment of the present invention.

FIG. 7 is a schematic side sectional view showing the structure of a conventional phototube.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Metal bulb (side tube), 12 ... Light receiving surface plate, 13 ... Metal stem, 14 ... Metal exhaust pipe, 15 ... Photocathode (photocathode), 16 ... Cathode extraction line, 17 ... Tapered hermetic glass, 21 ... No. Phototube according to one embodiment, 42
... Conductive film, 51. Phototube according to the second embodiment.

Continuing from the front page (72) Inventor Katsumi Inaba 1126, Nomachi, Ichinomachi, Hamamatsu-shi, Shizuoka Prefecture Inside (72) Inventor Nobuo Nozuo 1126, Nomachi, Ichinomachi, Hamamatsu-shi, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. (72 ) Inventor Kazuyoshi Okano 1126 Nomachi, Hamamatsu-shi, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. (72) Inventor Hiroyuki Hisashima 1126 Nono-cho, Hamamatsu City, Shizuoka Prefecture 1 Inside Hamamatsu Photonics Co., Ltd. (56) References JP Hei 5-225933 (JP, A) JP-A-52-30152 (JP, A) JP-A-54-16171 (JP, A) JP-A-47-17555 (JP, U) JP-B-30-5518 (JP, A) , B1) Jikken 14-3004 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 40/00-40/20 H01J 43/28-43/30

Claims (5)

(57) [Claims] 1. A container having a light receiving face plate made of glass for closing one opening of a side tube made of metal constituting an anode, and a stem for closing the other opening of the side tube, and the light receiving portion in the container. In a phototube comprising a photocathode arranged at a position facing the face plate and a cathode lead-out line penetrating the stem and being electrically connected to the photocathode, the stem has a metal stem and the side tube A photocathode, wherein an insulating material is interposed between the stem and the cathode extraction line, and the cathode is supported by a plurality of the electrode extraction lines. 2. The photoelectric tube according to claim 1, wherein a metal exhaust pipe penetrates through the stem, and the side pipe, the stem, and the metal exhaust pipe are electrically connected. 3. The side pipe according to claim 1, wherein the side pipe on the other opening side has a bent flange outside the side pipe, and the stem is attached to the flange. A phototube as described. 4. The side tube according to claim 1, wherein the side tube on the one opening side has a bent flange inside the side tube, and the light receiving face plate is attached to the flange. Phototube. 5. The phototube according to claim 1, wherein a case made of an insulating material is covered on the container.