JPH05217527A - Image tube - Google Patents

Abstract

PURPOSE:To judge the introducing quantity of alkaline metal from the reach state of the metal and the depth of coloring by arranging the substance which generates a coloring reaction with the alkaline metal at a proper position inside a bulb and allowing the vapor of the alkaline metal to contact with this substance, when the photoelectric surface of an image tube or a photomultiplier is prepared. CONSTITUTION:When a photoelectric surface is prepared, Cs is used as alkaline metal, and evaporated by the resistance heating, and gold and silver are used as the substance which coloring-reacts with Cs. Then, one between them, e.g. gold is welded on the side surface part A of the lower part, convergence electrode of an outer peripheral device 10 and the side surface part B of an input surface holding part 12r, and evaporation is repeated, diffusing the Cs vapor generated by a Cs dispenser 20. At first the gold installed at the A position is colored, and the generation starting period of Cs is judged, and when the gold installed at the B position is colored, judged that Cs reaches a photoelectric surface preparing position 12K. Accordingly, the introducing quantity can be estimated from the degree of coloring of the photoelectric surface 12K.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used in the field of image sensors. The present invention relates to an image tube in which the introduction amount of an alkali metal, which is one of the photocathode composition substances, can be easily recognized when the photocathode of the image tube is formed.

[0002]

2. Description of the Related Art In general, an image tube is one in which photoelectrons emitted from a photocathode of an input surface on which light is incident are accelerated by an electron lens and focused on an output fluorescent screen to output a visible light image. .. Further, for example, Cs-Sb is used as a material forming the photocathode.

When manufacturing such a photocathode, it is not possible to grasp the time when the alkali metal, which is one of the materials for forming the photocathode, and which is also used for the first layer of the photocathode, reaches the photocathode forming part and the amount of introduction. It is important in improving photoelectric conversion efficiency.

Conventionally, in order to know the arrival time and the amount of such alkali metal reaching the photocathode-forming site, a photosensor is built into the photomultiplier tube and used as a sensor, or an envelope. There are a method of observing the color adhered to a container and the like with the naked eye, a method of generating an alkali metal material by resistance heating evaporation, and using the applied voltage and current value as parameters.

[0005]

Among such conventional examples, the method using a photosensor such as a photodiode has a problem of high cost, and the mounting position in the tube is limited for exchanging electric signals. .. The second method of the conventional example has low accuracy because it cannot be visually recognized unless a large amount of alkali metal adheres to the inside of the envelope. In the third method, an evaporation source using a vapor deposition boat or a dispenser is used, but variations in the generated amount, voltage, and current occur due to individual shapes, which cannot be ignored, and can be guaranteed only for the time being.

An object of the present invention is to provide an image tube capable of easily recognizing the amount of alkali metal introduced or the time of generation of alkali metal vapor when forming a photocathode.

[0007]

The above-mentioned object can be achieved by arranging in the tube a substance that reacts with the alkali metal vapor at the time of forming the photocathode and is colored.

[0008]

A substance, such as gold, which causes a coloring reaction with an alkali metal at an appropriate position inside the image tube or the photomultiplier tube,
When silver or the like is placed, it is possible to judge whether or not the alkali metal has reached the photocathode because a coloring reaction occurs when the silver and the like come into contact with the vapor of the alkali metal. In addition, the introduction amount can be almost determined by the coloring density.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an X-ray image intensifier (II) as one example thereof, and is a schematic vertical cross-sectional view in the process of introducing an alkali metal into the first layer of the photocathode thereof.

In this figure, 10 is a glass envelope, 1
2w is an X-ray entrance window, and 12i is an input surface. Specifically, it is composed of a phosphor screen (not shown) that emits light upon stimulation of X-rays, a curved substrate (not shown) that supports the phosphor screen, and a photocathode 12k serving as an inner cathode. .. Note that 12r is a holding unit for the input surface 12i.

Further, 14 is an electron lens or a focusing electrode,
16 is an anode or an anode electrode, 18 is an output surface,
It comprises a fluorescent screen (not shown) and a glass substrate (not shown) that supports the fluorescent screen. In the drawing, a branch passage for degassing is shown on the lower left side and is connected to a pump.

This I.D. In this embodiment, Cs (cesium) is used as an alkali metal in the photocathode forming process of I. Further, Cs is generated by the resistance heating method. Further, Au is used as a substance that causes a color reaction with the alkali metal.
(Fri) is used.

Attach Au to the positions A and B in the figure. A
Indicates the side surface of the lower focusing electrode, and B indicates the side surface of the input surface holding portion 12r. Au is adhered or spot welded to each position or vapor-deposited. These positions are limited to the positions shown in the drawing, and it is sufficient that they do not interfere with the operation of the electrodes.

Alkali metal Cs is generated from the evaporation source Cs vapor deposition boat or dispenser 20. Occurred C
The vapor of s repeats re-evaporation while diffusing and mostly rises upward, but first, since the Au attached at the position of A is colored, the start timing of Cs generation can be determined. Next, A at the position of B
When u is colored, Cs almost reaches the photocathode forming place 12k.

Since the coloring concentration of Au changes depending on the reaction amount, if the color when Cs is an appropriate amount is found in advance, the appropriate amount of Cs can be controlled by the degree of coloring. In this way, a photocathode having good photoelectric conversion efficiency can be easily manufactured.

In the illustrated example, there are two Au-arranged locations, but only the location A may be provided. The amount of Cs introduced into the photocathode 12k is estimated as the degree of coloring changes from the hue due to the first arrival of Cs at that location. Further, although Au is attached to the electrode in the embodiment, it may be attached to another member.

[0017]

[Effects] According to the present invention, it is possible to determine the amount of alkali metal that reaches and is introduced into the photoelectric surface without using an expensive photo sensor. Further, compared to the photo sensor, the number of places where the substance that causes the color reaction is attached is limited because there is no exchange of electric signals, so that the substance can be easily attached at the optimum position. Therefore, more accurate determination is possible.

The above-mentioned conventional method depending on the adhesion state of the alkali metal to the wall of the envelope is easier than the present invention, but the degree of visual identification is considerably poor and its accuracy cannot be guaranteed.

[0019]

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an X-ray image intensifier showing an embodiment of the present invention.

[Explanation of symbols]

 10 Enclosure 12i Input Surface 12k Photoelectric Surface 12r Input Surface Holding Part 14 Focusing Electrode 16 Anode Electrode 18 Output Surface 20 Cs Dispenser A, B Au Placement

Claims (1)

[Claims] 1. An image tube, wherein a substance that reacts with an alkali metal vapor at the time of forming a photocathode and is colored is arranged in the tube.