JPS60185349A - Fluorescent x-ray multiplier tube - Google Patents

Abstract

PURPOSE:To improve the photoelectric sensitivity thus to improve the brightness by arranging an intermediate layer composed of an oxide layer and a conductive layer between a phosphor substance layer and a photoelectric face composed of antimony, potassium and cesium. CONSTITUTION:An input phosphor face 2 and a photoelectric cathode 3 are arranged in close proximity in a vacuum container 1 at the input side to constitute a X-ray phosphor multiplier tube. Here, the input face is formed by providing a phosphor material layer 11 mainly composed of cesium iodide on the concave face of a substrate 10 made of aluminum then providing an aluminum layer 131 and a conductive layer 132 while controlling to be transparent against the light emitted from the phosphor substance layer 11 thereafter providing a photoelectric face 14 composed of antimony, potassium and cesium. Consequently, chemical isolation between the phosphor material layer 11 and the photoelectric face 14 is achieved sufficiently while the conductivity of the photoelectric face 14 in both directions is improved resulting in considerable improvement of the brightness and the service life.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to improvements in X-ray fluorescence multipliers.

[Technical background of the invention and its problems]

Among image tubes, X-ray fluorescence intensifier tubes are widely used for medical purposes, including industrial destructive inspections and other X-ray industrial televisions.

This type of X-ray fluorescence intensifier tube is constructed as shown in Fig. 1, and has an envelope (1
) has an input phosphor screen (2) and a photocathode (3) inside the input side.
) are placed close together.

On the other hand, an anode (4) is placed inside the output side of the envelope (1), and an output fluorescent screen (5) is formed along the inner side wall of the envelope (1). A focusing electrode (6) is formed. After the incident X-rays are converted into light at the input phosphor screen (2), the light causes the light cathode (3) to emit photoelectrons (8), and these photoelectrons (8) are transferred to the anode (
4) Accelerate and focus with the focusing electrode (6) and output the phosphor screen (
5), the fluorescent material is excited and emitted, and an optical image (9) with enhanced brightness is observed.

By the way, the above-mentioned X-ray fluorescence intensifier tube has conventionally been constructed as shown in FIG. 2 in terms of human power.

That is, on the concave side of a substrate (10) mainly made of aluminum and having a certain curvature, there is a phosphor layer (11) made of cesium iodide as a matrix and to which activators such as sulium, lyrium, etc. are added. is formed by a vacuum evaporation method, and a photocathode 12 made of antimony and cesium is formed on this phosphor layer (11) also by a vacuum evaporation method. ] Phosphor layer made of cesium iodide (
11) is not sufficiently stable with respect to cesium as a substrate for forming a photocathode, so the photocathode (12) made of antimony and cesium formed on the phosphor layer (11) has a photoelectric sensitivity of 10 microamperes at most. / lumen. Also, under normal usage conditions,
A phenomenon in which the photoelectric sensitivity gradually decreases due to the instability of the substrate is observed. As a result, the light emitted by the phosphor layer (11) is not sufficiently converted into photoelectrons (8) (see Figure 1), resulting in low brightness, and the brightness further decreases as the usage time increases. Right side. Another drawback is that a photocathode made of antimony and cesium cannot be formed unless a large amount of cesium is introduced into the tube and reacted with antimony. In other words, the phosphor (5) used on the output surface (see Figure 1) is exposed to some of the high-il 1 degree cesium vapor introduced during the formation of the photocathode, causing a decrease in brightness. As the process progresses further, the phosphor material on the output surface turns black and the output image product (
It is to make Q completely defective.

[Purpose of the invention]

This invention was made to improve the above-mentioned drawbacks, and it not only improves the photoelectric sensitivity, brightens the brightness, and further improves the life characteristics, but also reduces the quality of the output screen when forming the photocathode. The purpose of this invention is to provide an X-ray fluorescence intensifier tube with high image quality.

(Summary of the Invention) The present invention includes a substrate having a curvature, a phosphor layer formed on the concave surface of the substrate and having a matrix of cesium iodide, and a photocathode formed on the phosphor layer. An J, which is almost transparent to luminescence;
Furthermore, antimony, potassium, and [?] are formed in a controlled manner on this intermediate layer. 3- An X-ray fluorescence multiplier tube characterized in that it is equipped with a photocathode made of Si, and an intermediate layer made of an oxide layer and a conductive layer between the phosphor layer and the photocathode as the structure of the input surface. By sequentially forming the phosphor layer and the photocathode, the intermediate layer isolates the phosphor layer and the photocathode to prevent their reaction with each other, and the non-conductivity is covered by the >jl electric layer, which does not result in an improvement in photoelectric sensitivity.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

In other words, the input surface of the X-ray fluorescence multiplier according to the present invention has an oxide layer (13) between the phosphor layer (11) and the photocathode (14).
1> and a conductive layer (132), and the photocathode 14 is made of antimony, potassium, and cesium instead of the conventional antimony and cesium.

The intermediate layer consisting of the oxide layer (13+) and the conductive layer (13,,) prevents a chemical reaction between the phosphor layer (11) and the photocathode (14) mainly due to transfer of cesium, and This has the effect of increasing the conductivity in the plane direction.

4- That is, on the concave surface of a substrate (1) made of aluminum or the like and having a certain curvature, a phosphor layer (11) containing cesium iodide as a matrix and an activator added thereto (1-1) lium or thallium, etc. is formed. On this phosphor layer (11), an oxide layer (131), for example, aluminum oxide, is formed in a controlled state so that it is almost transparent to the light emitted from the phosphor layer (11), and furthermore, this oxide layer (11) is Material layer (13+
A conductive layer (132) such as aluminum is formed on the surface of the phosphor layer (132) in a controlled state so that it is almost transparent to light emitted from the phosphor layer (11). Furthermore, this conductive layer (1
32) A photocathode (14) made of antimony, potassium, and sium is formed on top.

Note that since the configuration other than the input surface is the same as that in FIG. 1, detailed explanation will be omitted.

A method of manufacturing such an input phosphor screen will be described below.

The first method is to vacuum deposit cesium iodide (11) with helium added as an activator onto a clean aluminum substrate 10 with a certain curvature to a thickness of 100 to 150 microns. 4 Lee. After that 200...
The activation treatment is carried out at a temperature of 400°C. At this point, the surface of the phosphor layer (11) grows vertically from the substrate 10.
Because of the grain boundaries between crystals with a diameter of approximately 20 μm [-1 μm], the shape is extremely uneven. Aluminum oxide is deposited on this layer by a known method to form a -C oxide layer (
131) is formed. Next, a conductive layer (13,,') is formed on this surface by a known method while controlling the transmittance of τ...for example, aluminum in vacuum.

At this time, the aluminum conductive layer (13□) is deposited until the thickness decreases to about 50%, and the thickness of the aluminum conductive layer (13□) is reduced to about 50%. The resistance value is felt by the tester 11, that is, it is C less than MΩ.This input surface is mounted inside the tube (), and then it is mounted on an exhaust stand and the prescribed baking is completed.Next, the antimony is measured by the light transmittance. Controlled drop to 80% of the initial level -
evaporate until After that, potassium and antimony are added alternately and reacted until the photoelectric sensitivity reaches its maximum. Next, when cesium and antimony are added alternately and reacted, the photoelectric sensitivity is further improved, and the reaction is continued until the maximum sensitivity is reached, and the reaction between antimony, potassium, and cesium photocathode (14) is completed.

The brightness of the X-ray fluorescence increased H'z tube formed by the above method is 40% brighter than the conventional one, and the low Vft degree was 0 to 5% in the prefectural test using the method described above. Met.

The image quality of the output phosphor screen (5) (see Figure 1) was clear and hardly covered with alkali metal.

By the way, an intermediate layer consisting of one layer, for example aluminum oxide,
When a photocathode (14) made of antimony, potassium, and cesium is formed in the same manner as above after forming a layer of oxide, silicon oxide, etc. to a thickness of several thousand angstroms, the resistance of the photocathode itself is It was found that the supply of charge was not smooth because of the large value.

The X-ray fluorescence multiplier of the present invention is constructed as described above and shown in the drawings, and includes a low-resistance intermediate layer, ie, an oxide layer (13+)', between the phosphor layer (11) and the photocathode 14. Since a conductive layer (132) and a conductive layer (132) are formed, it is possible to use a photocathode (14) made of antimony, potassium, and cesium. In other words, the resistance of the conventional photocathode made of antimony, potassium, and cesium is higher than that of the photocathode made of antimony and cesium, so it is used like the input surface of an X-ray fluorescence multiplier tube. When applied to a large area, the supply of charge becomes insufficient, resulting in a particularly bright image, i.e., when there are many incident X-rays and a large amount of photocurrent is required, only the peripheral area near the charge supply source can be imaged. Fluorescence multiplier tubes and other devices have fatal drawbacks, especially cesium iodide phosphors, which have extremely uneven surfaces.
The above-mentioned defects were noticeable in F.

On the other hand, the photocathode made of antimony, potassium, and cesium is well suited to the cesium iodide phosphor, and the peak wavelength of the emission spectrum of A is the most sensitive peak wavelength of the photocathode made of antimony, potassium, and cesium. are in good agreement, and at 400nllll, which is the peak wavelength of the emission spectrum, it has about twice the sensitivity compared to the conventional photocathode made of antimony and cesium, so in terms of spectral electric shock, the photocathode made of antimony and potassium and cesium is better. is optimal in combination with a phosphor layer.

Therefore, in the X-ray fluorescence multiplier made according to the structure of the present invention, chemical separation between the phosphor layer and the photocathode is achieved by the function of the intermediate layer consisting of the oxide layer and the conductive layer, and the photocathode The electrical conductivity in both directions has also been improved, resulting in a 60-100% improvement in brightness compared to the conventional one, and as a result of a forced test for one year under normal usage conditions, the brightness deterioration during use was approximately 20% lower than the conventional one. % decrease (), the one of the present invention clearly improved by 5% in terms of It life characteristics.

Furthermore, even when the incident x mm is large, an image with substantially uniform characteristics can be obtained over the entire screen.

Furthermore, another advantage of using a photocathode made of antimony, potassium, and cesium is that the amount of alkali metal introduced into the tube during the formation of the photocathode has been reduced to less than half of the conventional amount, so the output phosphor screen is not exposed to cesium, resulting in improved image quality ( )
, it became possible to obtain clear images.

〔Effect of the invention〕

According to the present invention, the luminance 1α and the lifetime characteristics are improved compared to the Δ:uniform described above, and an X-ray fluorescence multiplier tube of great practical value can be provided.

[Brief explanation of drawings]

, Fig. 1 is a schematic configuration diagram showing a conventional X-ray fluorescence multiplier used to explain an embodiment of the present invention, and Fig. 2 is an enlarged view of the input surface of the conventional X-ray fluorescence multiplier. FIG. 3 is a sectional view showing an enlarged input surface of an X-ray fluorescence intensifier tube according to an embodiment of the present invention. 10... Substrate, 11... Phosphor layer, 1
3. ......Intermediate layer, 13□...Conductor layer, 14...Photoelectric agent Patent attorney Noriyuki Chika 11- Figure 1

Claims (1)

[Claims] 1. In an X-ray fluorescence multiplier tube comprising a substrate having a curvature, a phosphor layer made of cesium iodide as a matrix formed on the concave surface of this substrate, and a photocathode formed on this phosphor layer. °C1 An intermediate layer consisting of an oxide layer formed on the phosphor layer and a conductive layer formed on the surface of this layer, and this intermediate layer is almost transparent to light emitted from the phosphor layer. An X-ray fluorescence multiplier tube formed in a controlled manner and further comprising a photocathode made of antimony, potassium, and cesium on the intermediate layer.