JPH11102656A - Photo-detecting tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-detecting tube which selectively detects only the light of wavelength near 250 nm. SOLUTION: A photo-detecting tube 1 is provided with an incidence window 3 and a photocathode 5, the incidence window 3 is made of ozone free quartz glass, and the photocathode 5 is made of Cs-Te. The ozone free quartz glass selectively transmits the light of wavelength >= about 170 nm, and the Cs-Te selectively and photoelectrically converts the light of wavelength <= about 330 nm. Thus, in the photo-detecting tube, the peak of detecting sensitivity lies in wavelength 250 nm, and only the light of wavelength 250 nm ±about 80 nm can be selectively detected without an optical band-pass filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector tube such as a phototube or a photomultiplier tube.

[0002]

2. Description of the Related Art Conventionally, a photodiode using semiconductor Si has been known as a photodetector for measuring the light intensity of a light source. Further, a photodetector tube such as a photomultiplier tube is known as a photodetector that performs high-sensitivity photodetection.

[0003]

However, in the above-described photodetector tube, when monitoring the intensity of a light source that emits ultraviolet light having a wavelength of about 250 nm, an optical filter having a transmittance characteristic of transmitting only that specific wavelength is used. It was necessary to use together. That is, in the conventional photodetector tube, an optical filter having one or more specific wavelength light selective transmission characteristics is arranged in front of the photodetector tube, and the light transmitted through the optical filter is detected. Such an optical filter reduces the intensity of transmitted light and simultaneously increases the number of components. The present invention has been made to solve such a problem, and an object of the present invention is to provide a photodetector tube that selectively detects only light having a wavelength of about 250 nm.

[0004]

According to the present invention, there is provided a photodetecting tube comprising: an entrance window forming a part of an outer wall of a vacuum vessel; and a photocathode arranged in the vacuum vessel and photoelectrically converting light transmitted through the entrance window. In the light detection tube provided, the entrance window is made of ozone-free quartz glass, and the photocathode is made of Cs-Te. Ozone-free quartz glass has a wavelength of about 1
Light having a wavelength of 70 nm or more is selectively transmitted, and Cs-Te selectively photoelectrically converts light having a wavelength of about 330 nm or less. Therefore, in this photodetector tube, the wavelength is 250 nm ± about 8
Only 0 nm light can be selectively detected without using an optical bandpass filter.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A photodetecting tube according to an embodiment will be described below. The same reference numerals are used for the same elements or elements having the same functions, and overlapping descriptions are omitted.

FIG. 1 is a longitudinal sectional view of a light detecting tube 1 according to an embodiment. The light detection tube 1 is a photoelectric tube, and the upper end opening of the metal side tube 2 is sealed with a face plate 3 as an entrance window.
A vacuum container having a lower end opening sealed with a stem plate 4 is provided. The inside of the present vacuum vessel is reduced in pressure from the atmospheric pressure.
A photocathode 5 for photoelectrically converting the light λ transmitted through the entrance window 3 and a metal anode 6 for collecting electrons e emitted from the photocathode 5 are arranged in the vacuum vessel.

The photocathode 5 is formed on the inner surface of the entrance window 3. A predetermined potential is applied to the photocathode 5 via the side tube 2, and a higher potential is applied to the anode 6 than the cathode 5.
For example, when the photocathode 5 is grounded and a potential of 100 V is applied to the anode 6, an electric field is generated inside the vacuum vessel to pull the electrons e toward the anode 6 according to the voltage between them. Electrons e generated at the photocathode 5 in response to the incidence of the light λ are accelerated according to the internal electric field, then collide with the anode 6 and output as an output current through the lead pins 7 electrically connected to the anode 6. Is taken out. The lead pin 7 and the stem plate 4
Is hermetically sealed by a glass filling material 8.

FIG. 2 shows wavelength-incidence window transmittance (%) characteristics,
4 is a graph showing wavelength-photocathode radiation sensitivity (mA / W) characteristics and detection sensitivity (mA / W) characteristics of the phototube 1 itself obtained by synthesizing these. Of the light λ incident on the incident window 3, a component having a wavelength of λ ₁ or more passes through the incident window 3. Further, of the light lambda incident on the photocathode 5, component of the wavelength lambda ₂ or less it is photoelectrically converted by the photocathode 5. The wavelength λ ₂ is longer than the wavelength λ ₁ , and therefore, the phototube 1 itself has a detection sensitivity between the wavelengths λ _{1 and} λ ₂ .

The transmittance of the incident window 3 at the wavelength λ ₁ is about 1/100 of the transmittance at the wavelength λ ₁ +160 nm.
0, and the radiation sensitivity of the photocathode 5 at the wavelength λ ₂ is about 1/10 of the radiation sensitivity at the wavelength λ ₂ -160 nm.
00 or less.

The photoelectric tube 1 according to the present embodiment includes an incident window 3 forming a part of an outer wall of a vacuum vessel, and a photocathode 5 arranged in the vacuum vessel and photoelectrically converting light λ transmitted through the incident window 3. The entrance window 3 is made of ozone-free quartz glass, and the photocathode 5 is made of Cs-Te. Ozone-free quartz glass selectively transmits light having a wavelength of about 170 nm (= λ ₁ ) or more, and Cs-Te has a wavelength of about 330 nm (= λ ₁ ).
λ ₂ ) The following light is selectively photoelectrically converted. Therefore,
This phototube has a peak of the detection sensitivity near the wavelength of 250 nm, and can selectively detect only the light of the wavelength of 250 nm ± about 80 nm without using an optical bandpass filter. Further, each detection sensitivity at a wavelength of 250 nm ± about 80 nm which gives the peak value of the detection sensitivity of the present phototube is about 1/100 of the detection sensitivity of the peak value.
0 or less. The detection sensitivity of the phototube at a wavelength of 190 nm is about 1/1000 or less of the detection sensitivity of the peak value.
It can be detected separately from light of 5 nm and 365 nm. The ozone-free quartz glass used was ozone-free transparent quartz glass (model number T-1130) manufactured by Toshiba Ceramics Corporation. This ozone-free transparent quartz glass almost absorbs light of 210 nm or less.

FIG. 3 shows a photodetector tube 1 according to another embodiment.
FIG. The photodetector tube 1 is a photomultiplier tube, and includes a vacuum vessel in which an upper end opening of a glass bulb 12 is sealed with a face plate 13 as an entrance window, and a lower end opening is sealed with a stem plate 14. . The inside of the present vacuum vessel is reduced in pressure from the atmospheric pressure. In this vacuum container, a photocathode 15 for photoelectrically converting light λ transmitted through the entrance window 13 and a metal anode 16 for collecting electrons e emitted from the photocathode 15 are provided.
And are arranged. An electron multiplier composed of dynodes D _{1 to} D _{5 for} multiplying incident electrons is arranged between the cathode 15 and the anode 16 in order.

The photocathode 15 is formed on the inner surface of the entrance window 13, a predetermined potential is applied to the photocathode 15 via focusing electrodes 19 and 20, and the dynodes D _{1 to} D ₅ and the anode 16 have a cathode. A potential higher than 15 is provided. Thin film focusing electrode 19 is formed by metal such as aluminum on the glass bulb 12 an inner surface surrounding the space from the photocathode 15 to the dynode D ₁ of the first stage is deposited, the plate-shaped focusing electrode 20 a portion of the outer periphery Is made of a metal plate in contact with the thin film focusing electrode 19. The plate-shaped focusing electrode 20 has an opening at the center. These focusing electrodes 19 and 20 are connected to the photocathode 1
5 and the first dynode D
₁ together with the photocathode 1
An electric field for focusing the electrons generated in step 5 in the first-stage dynode D ₁ disposed immediately below the opening of the focusing electrode 20 is formed.

More specifically, the photocathode 15 and the focusing electrode 1
Reference potentials 9 and 20 are applied through a single lead pin 17, and higher potentials are applied to dynodes D _{1 to} D ₅ and the anode 16 through the remaining plurality of lead pins 17 in a later stage. For example, the photocathode 15 and the focusing electrode 1
9,20 to give the ground potential, given the potential of 100V to the anode 16, when applying a potential selected to dynodes D ₁ to D ₅ from the potential of 0～100V, photoelectric inside the vacuum chamber in accordance with the voltage between them The electrons e generated at the cathode 15 are transferred to the anode 1
An electric field pulling in six directions is generated.

The electrons e generated at the photocathode 15 in response to the incidence of the light λ are accelerated according to the internal electric field,
Collides with the dynodes D ₁ of the stage are multiplied, which further are multiplied while sequentially collides with the dynode D ₂ to D ₅ in the subsequent stage than eventually collide with the anode 16. The electrons e collected at the anode 16 are taken out as an output current via a lead pin 17 electrically connected to the anode 16.
The gap between the lead pin 17 and the stem plate 14 is hermetically sealed with a glass filling material 18.

This photomultiplier tube is a box-and-grid type photomultiplier tube. Each of the dynodes D _{1 to} D ₅ is a box type, and a grid is provided on the front surface thereof. A final dynode is arranged near the anode 16, but is not shown in the present embodiment.

The photomultiplier tube according to the present embodiment has an incident window 13 forming a part of the outer wall of the vacuum vessel and an incident window 13 disposed inside the vacuum vessel, similarly to the photoelectric tube according to the above embodiment.
And a photocathode 15 that performs photoelectric conversion of light λ transmitted therethrough,
The entrance window 13 is made of ozone-free quartz glass, and
The photocathode 15 is made of Cs-Te. As described above, the ozone-free quartz glass selectively transmits light having a wavelength of about 170 nm (= λ ₁ ) or more, and Cs-Te has a wavelength of about 330 nm.
Light of nm (= λ ₂ ) or less is selectively photoelectrically converted. Therefore, this photomultiplier tube has a peak of detection sensitivity at a wavelength of 250 nm, and a wavelength of 250 nm ± about 80 nm.
Can be selectively detected without using an optical bandpass filter.

Although the above-mentioned entrance window and photocathode are applied to a head-on type photodetector tube having a transmission type photocathode, these are side-on type photomultiplier tubes having a reflection type photocathode. Also, the present invention can be applied to a light detection tube such as an image intensifier.

FIG. 4 is a longitudinal sectional view of a photodetector tube module 100 having the photodetector tube 1 therein. The photodetector tube module includes an envelope 21 that houses the photodetector tube 1, a cap member 22 that seals an upper end opening of the envelope 21,
A sealing plate 23 for sealing the lower end opening of the surrounding cylinder 21. The cap member 22 has a through hole 24 formed along the longitudinal direction of the envelope 21, and can guide light λ from outside the module into the envelope 21 via the through hole 24.

A light diffusing plate 25 made of a material that transmits at least the light having the specific wavelength described above, such as ground glass, is disposed in the surrounding tube 21. The light diffusing plate 25 is formed between the entrance window of the photodetector tube 1 and the through hole 24. Is located between the light emitting ends. The light diffusion plate 25 seals the light emitting end of the through hole 24, diffuses the light λ introduced into the through hole 24, and irradiates the light λ toward the incident window of the light detection tube 1. In addition, an etching mesh may be arranged at the light emitting end of the through hole 24 in place of the light diffusing plate 25 to prevent deterioration of the photocathode. The above-mentioned light detection tube 1
An electric signal is output according to the incidence of light of a specific wavelength. This electric signal is supplied to a preamplifier 26 disposed inside the envelope 21.
And is output to the outside via a lead wire penetrating the sealing plate 23. This detection tube module can also be used as an ozone monitor for ozone sterilization and a water purifier monitor.

FIG. 5 shows a system configuration of a water purifier using the photodetection module 100. The water purifier has a water inlet 32 at a lower end of a water storage container 31 and a water outlet 33 at an upper end. The water introduced from the water inlet 32 into the water storage container 31 is exposed to light from the light source 34 in the water storage container 31 and sterilized. The light source 34 is disposed in a cylindrical wall 35 that penetrates the water reservoir 31 in the horizontal direction,
The light of the above specific wavelength equal to or less than ultraviolet light is emitted. The light source 34 is a KrF excimer lamp that emits light having a wavelength of 248 nm or a mercury lamp that emits light having a wavelength of 254 nm. The water storage container 31 and its cylindrical wall 35 are made of a material that transmits at least the light having the specific wavelength.

A concave portion 36 is formed on the outer surface of the water storage container 31.
Is arranged. Therefore, the light of the specific wavelength emitted from the light source 34 is detected by the photodetector tube module 100. The detection output of the photodetector tube module 100 is the amplifier 1
After being amplified by 01, it is output to the detection output meter 102. Therefore, the intensity of the specific wavelength light emitted from the light source 34 is displayed on the detection output meter 102.
Therefore, according to the present water purifier, since the light intensity from the light source 34 can be measured, it is accurately known whether the light source 34 is operating normally, that is, whether the water purification function is operating normally. be able to.

[0022]

As described above, according to the photodetector tube of the present invention, only light of a specific wavelength can be detected without using an optical bandpass filter, and photodetection can be performed with high sensitivity. be able to.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a photoelectric tube according to an embodiment.

FIG. 2 is a graph showing wavelength-incidence window transmittance (%) characteristics, wavelength-photocathode radiation sensitivity (mA / W) characteristics, and detection sensitivity characteristics of the phototube 1 itself obtained by combining these characteristics.

FIG. 3 is a longitudinal sectional view of the photomultiplier according to the embodiment.

FIG. 4 is a longitudinal sectional view of a photodetector tube module incorporating a photodetector tube.

FIG. 5 is a system configuration diagram of a water purifier using a photodetector tube module.

[Explanation of symbols]

 1: photodetector tube, 13: entrance window, 15: photocathode.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukihiro Isobe 1126 Nomachi, Hamamatsu City, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd.

Claims (1)

[Claims] 1. A photodetector tube comprising: an entrance window forming a part of an outer wall of a vacuum vessel; and a photocathode arranged in the vacuum vessel and photoelectrically converting light transmitted through the entrance window. A photodetector tube made of ozone-free quartz glass, wherein the photocathode is made of Cs-Te.