JPH01276544A - X-ray fluorescence multiplier tube - Google Patents

Abstract

PURPOSE:To obtain a multiplier tube with sufficient space resolution, high contrast and low noise by providing a phosphor layer on an input substrate irregularly patterned on the surface of an input face and bored with many through holes and directly or indirectly forming a photoelectric face on the phosphor layer. CONSTITUTION:A phosphor layer 600, a protective film 620 and a photoelectric face 630 are formed in sequence on the input substrate 640 of an input face 60. The surface of the input substrate 640 is irregularly patterned, many through holes are bored on the whole substrate 640. Many needle-shaped bundle block crystals 601 are grown on the phosphor layer 600, a reflecting material 603 with a high light reflection coefficient is inserted from the back of the input substrate 640 before the photoelectric face 630 is formed. When X-rays are fed to the input face 60, they are reflected by the light reflecting material 603 filled in gaps 602, light is not leaked into adjacent phosphors and effectively guided to the surface. The deterioration of resolution due to the scattering of light is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray fluorescence multiplier tube, and particularly to an improvement in its input surface.

(Prior Art) Generally, an object observation system using an X-ray fluorescence intensifier is configured as shown in FIG.
A line fluorescence multiplier tube is placed, and the modulated X transmitted through the subject 3
The output image obtained by the X-ray fluorescence multiplier tube upon incidence of radiation can be observed with, for example, an imaging camera and reproduced on a monitor television.

That is, in the X-ray fluorescence multiplier tube Z, an input surface 4 is disposed at one end, and an output fluorescence screen 5 is disposed at the other end facing the input surface 4, and during operation, a modulated X-ray image is displayed. into an optical image on the input surface 4,
Furthermore, this optical image is converted into a photoelectron image, and this photoelectron image is focused and accelerated to obtain an output image with enhanced brightness on the output phosphor screen 5. This output image is then observed using, for example, an imaging camera.

By the way, the input surface 4 of the conventional X-ray fluorescence multiplier tube 2 is
As shown in the figure, a phosphor layer 8 made of columnar crystals 7 of sodium iodide-activated cesium iodide phosphor is formed on the concave surface of a spherical aluminum substrate 6, and on this phosphor layer 8 is formed an aluminum oxide phosphor layer 8. It has a structure in which a photocathode 10 is formed through an intermediate layer 9 made of a layer of 1000 mL and an indium oxide layer.

(Problem to be Solved by the Invention) Now, in order to reduce the X-ray exposure of the subject 3, it is required to input the subject-transmitted X-rays into the phosphor layer 8 without loss and increase the amount of absorption thereof. Ru.

Regarding the phosphor layer 8, in order to increase the amount of X-ray absorption, it is better to make the columnar crystals 7 of the phosphor longer, but as the columnar crystals 7 become longer, the number of refractions of light increases, and the light is refracted from the side of the columnar crystals 7. The amount of light propagating to other columnar crystals 7 increases, reducing resolution. Therefore, it is not possible to make the columnar crystals 7 too long,
The limit is about 400 μm.

Therefore, in order to prevent the light emitted from a columnar phosphor from propagating to other columnar phosphors, a gap is created between these columnar phosphors, and a phosphor screen in which a light-reflecting material is embedded in this gap is developed in the United States. Patent Specification Section 4,011,
No. 454. This is done by vaporizing phosphor on a patterned input substrate and heat-treating it at 450 to 500°C to widen the gap between adjacent columnar phosphors to the same extent as the four parts of the input substrate. This phosphor screen is characterized in that this gap is filled with a material containing a light-reflecting material or a light-absorbing material to the same height as the phosphor screen.

This is because, as disclosed in U.S. Pat. and is expensive. for example,
The time required to cool the substrate temperature from 500℃ to 50℃ is 40℃.
minutes, to make a 500 μm thick phosphor layer (
5+60+40) x 500/125-420 minutes.

Further, in US Pat. No. 4,011,454, since there is a gap from the front surface to the back surface of the phosphor, another type of phosphor or a light reflecting material is embedded in this gap. However, due to differences in thermal expansion, etc., a small gap is created, and although the surface of the gap is coated with a transparent material such as silicone resin, pinholes are created in this, and the sensitivity of the photocathode formed thereon is reduced. Changes in photocathode sensitivity over time become large.

Furthermore, a light reflecting substance forms a blue color on the surface of the phosphor, which is extremely difficult to completely remove, resulting in a significant decrease in sensitivity.

Further, scattered X-rays generated from the subject 3 and scattered X-rays generated from the vacuum envelope near the input surface 4 are absorbed by the columnar crystals 7 of the phosphor layer 8, which lowers the contrast.

In order to improve these, for example, Japanese Patent Application Laid-Open No. 55-2180
In the invention described in Publication No. 5, a honeycomb-like holding plate made of a heavy metal material and having a plurality of openings partitioned by partition walls, and an input fluorescent screen formed by filling the openings of this holding plate with a fluorescent substance are used. A fluorescence multiplier tube is disclosed.

However, the invention described in Japanese Unexamined Patent Publication No. 55-21805 discloses that holes are formed in the honeycomb-shaped holding plate using an electron beam or a laser beam. In order to make a honeycomb-shaped holding plate with an inch diameter and a rough input surface, approximately 1000 hours or more of processing time is required, which is unrealistic.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide an inexpensive and highly reliable X-ray fluorescence intensifier tube with high X-ray absorption rate and improved resolution (and contrast).

[Structure of the Invention (Means for Solving the Problems) This invention provides an input J! in which the input surface has a white surface patterned with concave and convex portions and is provided with a large number of through holes. temporary and
It consists of a phosphor layer formed on this input substrate and a photocathode formed directly or indirectly on this phosphor layer, and the phosphor layer is made of block-shaped crystals corresponding to the uneven pattern of the input substrate. and tapers along the through hole of the input substrate to form a substantially closed gap on the photocathode side, and further includes a material containing at least a light reflecting material or a light absorbing material within the gap. This is an X-ray fluorescence intensifier tube that is filled with fluorophores and achieves sufficient spatial resolution, extremely high contrast, and low noise.

(Function) According to the present invention, when used in a subject observation system, X-rays emitted from the X-ray tube pass through the subject and enter the input window of the X-ray fluorescence intensifier. After reaching the input surface and passing through the input substrate, they cause the phosphors surrounded by optically shielded partitions to emit light. Since this phosphor has a sufficient thickness, it can absorb approximately 10,096 incident X-rays. Light generated within this phosphor is separated by an optically reflective material between adjacent phosphors and effectively reaches its surface. Therefore, a high-resolution, high-contrast X-ray fluorescence intensifier Δ tube can be provided without causing crosstalk.

Further, since the phosphor maintains almost continuity on the surface, by providing an appropriate protective film, the continuity of the surface can be maintained, and a highly reliable photocathode can be obtained.

As described above, in the X-ray fluorescence intensifier tube of the present invention, the MTF in the intermediate spatial frequency band is significantly improved, and an extremely high contrast X-ray image can be obtained.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

That is, the X-ray fluorescence multiplier of the present invention is constructed as shown in FIG. It consists of a body part 30 made of a hollowed cylindrical metal, and an output end part 50 made of glass and hermetically sealed to the body part 30 via a cylindrical sealing tube member 40 made of Kovar.

An input surface 60 is provided inside the input window 20 of the vacuum envelope 10, and an output phosphor screen 70 and a positive t! i! i90 is installed. Further, a focusing electrode 80 is coaxially disposed inside the body 30 of the vacuum envelope.

During operation, the X-ray image incident on the input window 20 is transmitted to the input surface 6.
0, and this converted photoelectron image is accelerated and focused by the anode 90 and the focusing electrode 80 and reaches the output phosphor screen 70, where a high-intensity light image appears.

Here, the input surface 1, which constitutes the essential part of the present invention, will be explained in detail with reference to FIGS. 1, 2, and 3. Note that Figure 1 is an enlarged view of a portion of Figure 2 (for convenience,
Figures 1 and 2 are drawn with the top and bottom reversed.) Further, FIG. 2 is a schematic enlarged sectional view of the input surface 60 of FIG. 5, and the dimensions are not similar. Furthermore, FIGS. 3(a), (b), and (C) show the input board 64 in FIG.
FIG. 3B is a cross-sectional view of the input board 640, which is composed of a front board 641 and a reinforcing board 642. And, Fig. 3(a) is similar to Fig. 3(b).
) represents a cross section taken along line AA'. FIG. 3(C) is a cross-sectional view taken along line BB' in FIG. 3(b), in which the back surface of the front substrate 641 is visible.

That is, the input surface is configured as shown in FIG. 2, and includes a phosphor layer 600 formed on the input JJIR 640, and a protective film 620 mainly composed of indium oxide formed on the phosphor layer 600. and a photocathode 630 formed on the protective film 620.

First, the input board 640 will be explained.
40 is constructed as shown in FIGS. 3(a), (b), and (c), and includes a front substrate 641 and a reinforcing substrate 642 bonded to each other.

The front substrate 641 is a thin plate with a thickness of about 100 μm, and is made of stainless steel, aluminum, or the like. Aluminum is preferable in terms of improving xH transmittance, but stainless steel is preferable in terms of workability.

A surface like this, 2! The surface of the temporary 641 is patterned into irregularities. That is, the width is approximately 80 to 90 μm, and the thickness is t. There is a tile-like protrusion 643 with a diameter of approximately 30 μm, and a concave groove 644 with a depth of dl surrounds the tile-like protrusion 643 adjacent to the tile-like protrusion 643.
They are separated by a period of about 3 to about 100 μm. During manufacturing, the tile-like protrusions 643 are made by pressing, etching, or the like. In addition, the tile-like protrusion 64
The spacing between adjacent 3 is approximately 10-20 μm. The depth of the groove 644 produced at this time is d, as described above. Next, a recess 646 having a depth d2 is formed from the back surface by etching or the like. At this time, if the thickness of the front substrate 641 is t, then the relationship t<d, 10d2 is established. The center of the intersection of the grooves 644 on the front surface and the four parts 646 on the back surface
By aligning the centers of the grooves 644 and 64,
A large number of through holes 6 continuously penetrate through the front substrate 641. Moreover, the tile-like projections 643 on the surface
Since it is supported by the partition wall 645 on the back side, it will not fall off.

The front substrate 641 thus produced is deformed by pressing or the like so that it has a concave surface as shown in FIG. 2. At this time, it is preferable to fill the recess 646 with plastic or the like so that the mesh shape does not deform, and then remove it after pressing.

On the other hand, the reinforcing substrate 642 is a relatively thick plate, for example, 500 μm.
Made of rrl aluminum plate. Because it is relatively thick, it is difficult to drill small through holes using the current technology (1:), so large through holes 649 of about 300 μm are bored.The period (pitch) of the partition walls 647 is approximately 300 μm, and the period of the above tile-like protrusions 643 (
pitch). The above-mentioned through hole 649 is
Naturally, it communicates with a large number of through holes consisting of grooves 644 and recesses 646 of the front substrate 641, and as a result, the input substrate 641
This means that a large number of through holes are drilled even in the case of 40 units.

The reinforcing substrate 642 configured in this way is similar to the front substrate 64.
1, it is formed into a concave surface as shown in FIG. At this time, the radius of curvature thereof is larger than that of the outer surface of the front substrate 641, and by overlapping these, the structure of the input substrate 640 as shown in FIG. 2 can be obtained.

At this time, the partition wall 648 of the front substrate 641 and the reinforcing substrate 642
The partition walls 647 are attached so as to coincide with each other at a certain period. When these are attached, their outer edges (not shown) are joined mechanically by spot welding or the like.

In this case, since the reinforcing substrate 642 only mechanically reinforces the front substrate 641, there is no need for the partition walls 648 and 647 to be in close contact everywhere, and therefore the processing accuracy of these substrates is It was not necessary and could be manufactured industrially in a sufficient size. Next, the phosphor layer 600 formed on the input substrate 640 will be described in terms of its manufacturing method.

As shown in FIG. 1, for example, C
By depositing sI under the conditions of Q, Qltoor, and 250° C., a block-shaped crystal 601, which is a bundle of many needle-shaped crystals, grows. At this time, under the above conditions, the width of the groove 644 of the tile-shaped protrusion 643 is about 30 μrn, so the gap 64 between the block-shaped crystals 601 is
2 is approximately 30 μIII, and as the block crystal 601 grows, the gap 602 becomes narrower. and,
At a thickness of approximately 400 μm, the surface becomes continuous with no gaps.

That is, in this invention, the gaps 602 between the block-shaped articles 601 are tapered along the grooves 644, which are the through holes of the front substrate 641 constituting the input substrate 640, and are substantially tapered on the side of the charging surface 630. It is closed and the surface substrate 6
41 side is set to 20 μm or more, and the charging surface 630 side is set to 1 μm or less.

If the above conditions are different, a patterned gap may also occur on the surface of Csl, but in this case, the second layer 1] of Cs is thinly deposited on the surface under high vacuum. (See Other Example 2 below) This makes the surface continuous.

This is to prevent pinholes and the like from forming on the surface of the protective film 620, thereby preventing a decrease in sensitivity of the photocathode 630 formed on the upper layer.

Prior to forming this photocathode 630, the following process is performed. That is, a reflective material 603 having a high light reflectance is inserted from the back surface of the input board 640 (the side opposite to Csl). This reflective material 603 may be, for example, fine powder of TiO2, Al2O3, etc., and is press-fitted from the back surface of the input board 640. in this case,
Since the reinforcing substrate 642 has sufficient strength, the reflective material 603 can be easily inserted into the gap 602 of the block-shaped crystal 601 without causing any deformation or the like.

At this time, the gap 602 is the phosphor layer 600, that is, the CsI
Since it is essentially zero on the surface of the reflective material 60
3 does not appear on the surface of Csl and does not reduce the light transmittance of the surface of Cs1 to the same extent.

By performing high-temperature treatment at 450 to 500° C. in the above-described state, the transparency of Csl increases and the sensitivity of the input surface can be increased.

Furthermore, by filling the through holes 649 of the reinforcing substrate 642 with particles 651 of a material having similar X-ray transmittance, preferably the same material, the amount of X-ray absorption is made uniform, and the partition walls of the reinforcing substrate 642 are filled with particles 651 of the same material. 647 from being identified.

Further, in this step, the degree of filling of the reflective material 603 can be improved by inserting the particles 651.

Further, by providing a metal thin film (not shown) on the outer surface of the reinforcing substrate 640, these particles 651 are held so that they do not come out (see other embodiments described later). The pattern period of the front substrate 641 is as small as 100 μm, which is close to the limit resolution of an X-ray fluorescence intensifier tube, so that this pattern does not appear in the image.

Now, during operation, when X-rays are incident on the entrance surface 60,
The beam passes through the input substrate 640 and enters the block-shaped crystal 601 of the phosphor layer 600 to emit light. block crystal 6
Since 01 is a bundle of needle-shaped crystals, the transmittance of light is greater in the depth direction than in the lateral direction, but it is reflected by the light reflecting material 603 filled in the gap 602 and adjacent to it. Light does not leak into the phosphor and is effectively guided to the surface.

Near the surface, the phosphor is continuous in a very thin layer, so that the light scattering that occurs in this area is negligible. A protective film 620 made of a transparent conductive film on the upper layer
This prevents the movement of the alkali metal constituting the photocathode 630 formed above, thereby maintaining high reliability.

As described above, since the resolution does not deteriorate due to light scattering, the phosphor layer 600 can be made thick to about 1 mm, and the X-ray absorption efficiency can be increased.

(Other Embodiments) In the above embodiment, the input M and l1ilE 640 consist of a front substrate 641 and a reinforcing substrate 642, but if the front substrate 641 has sufficient strength, the reinforcing substrate 642 may be omitted. I can do it.

Moreover, there is no problem even if the tile-like protrusion 643 of the front substrate 641 has a shape other than a square.

Furthermore, the relative positional relationship between the tile-like projections 643 on the front surface of the front substrate 641 and the four parts 646 on the back surface is as follows.
They may be relatively shifted as long as they do not separate and a through hole is formed.

Further, as long as this condition is satisfied, the periods may be shifted.

Furthermore, as shown in FIG. 6, it goes without saying that a thin layer 605 of phosphor may be formed on the surface of the block-shaped crystal 601, that is, between the block-shaped crystal 601 and the protective film 620.

In this case, this thin layer of phosphor 605 is preferably a collection of needle-like crystals, since this does not reduce the resolution and contrast. In addition, 650 in FIG. 6 is a through hole 649.
This is a thin plate to prevent the particles 651 inside from falling off.

Further, in the above embodiment, a light reflecting material 6 is provided within the gap 602.
03, but the gap 602 may be filled with particles made of conductive particles and a light reflecting substance. In this case, the conductive particles are filled on the photocathode 630 side, and the light reflective material is filled on the input substrate 640 side. Of course,
The conductive particles and the light reflecting material are inserted from the rear of the input substrate 640.

Also, a light reflecting material 603 filled in the gap 602
may be densely packed on the input board 640 side. That is, near the position where the X-rays are incident, that is, the input board 6
The resolution reduction effect is greater for light generated near 40, and the light in this region
1 at nearby frequencies.
This is important for improving F. Therefore, it is effective to fill the light reflecting material 603 with high density on the input substrate 640 side as described above. In order to achieve this, it is effective to insert a light reflecting material 603 from the rear of the input board 640, and as a result, a high MTF X-ray fluorescence multiplier can be realized.

For this purpose, it was effective that the size of the through hole, that is, the groove 644 and the recess 646 that penetrated the front substrate 641 of the input substrate 640 was in the range of 10 to 200 μm.

Further, in the above embodiment, a light reflecting material 6 is provided within the gap 602.
03, the gap 602 may be filled with a light absorbing material or a mixed material containing at least a light absorbing material. In this case, the light absorbing material filled in the gap 602 prevents light from leaking to the adjacent phosphor, so that the resolution characteristics of the phosphor layer 600 can be improved in the same way as in the above embodiment.

Further, in the above embodiment, a case was described in which the gap 602 is filled with powder, but as a method for filling the gap 602 with a substance, after filling the substance in a liquid state,
It may be solidified.

[Effects of the Invention] According to this invention, the conventional MTF shown in curve A in FIG.
As shown in curve B, the spatial frequency is 10 to 401p.
It is possible to significantly improve the MTF at /am,
Clear X-ray images can be obtained.

Furthermore, since the light reflecting material or the light absorbing material is inserted from the rear (back side) of the input substrate, the surface of the phosphor is not contaminated (high sensitivity can be achieved).

Also, place a light-reflecting material or a light-absorbing material behind the input board (
Because it is inserted from the back side), mechanical pressure can be applied, increasing the filling rate of the phosphor gap.

In addition, each of the tile-like protrusions on the surface of the front substrate is separated from other protrusions over the entire circumference by a groove around it, so that the block-like crystals formed above are also separated from each other over the entire circumference. Formed into independent blocks.

Therefore, the light reflecting material or the light absorbing material inserted from the back surface of the front substrate is inserted so as to surround these block crystals all around.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a part of the input surface of an X-ray fluorescence intensifier tube according to an embodiment of the present invention, and FIG. 2 is an X! ! j! FIG. 3(b) is a sectional view showing the entire input surface of the fluorescence multiplier tube, and FIG. ) is a cross-sectional view taken along line A-A' in (b) and viewed in the direction of the arrow, and (c) is a cross-sectional view taken along line B-B' in (b) and viewed in the direction of the arrow. 4 is an enlarged sectional view of a part of the input surface of an X-ray fluorescence multiplier according to another embodiment of the present invention, and FIG. 5 is an X-ray fluorescence according to an embodiment of the present invention. FIG. 6 is a cross-sectional view showing the whole of the multiplier tube, FIG. 6 is a characteristic curve diagram showing the characteristics of the present invention and the conventional X-ray fluorescence multiplier tube, and FIG.
The figure is a cross-sectional view showing the entire conventional X-ray fluorescence multiplier, and FIG. 8 is a cross-sectional view showing the input surface of the conventional X-ray fluorescence multiplier. 60... Input surface, 600... Phosphor layer, 601...
・Block crystal, 602... Gap, 603...
・Light reflecting or absorbing substance, 620...protective film, 630
...Photocathode, 640...Input board. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] (1) In an X-ray fluorescence multiplier tube that converts an incident X-ray image into photoelectrons at the input surface and accelerates and focuses the photoelectrons to obtain an electronically multiplied optical image from the output fluorescent screen, The input surface includes an input substrate having an unevenly patterned surface and a large number of through holes, a phosphor layer formed on the input substrate, and a phosphor layer formed directly or indirectly on the phosphor layer. The phosphor layer is made of a block-shaped crystal corresponding to the uneven pattern of the input substrate, and is tapered along the through-hole of the input substrate, and substantially on the photocathode side. An X-ray fluorescence multiplier tube having a closed gap, and further comprising a material containing at least a light reflecting material or a light absorbing material in the gap.