JPS5947425B2 - Phototube and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phototube that converts light into photocurrent, and more particularly to a phototube that is suitable for miniaturization and can be operated at a low saturation voltage.

A phototube is an electron tube that applies a voltage between a photocathode and a photoelectron collection electrode, collects photoelectrons emitted from the photocathode when light enters the photocathode, and sends out the photocurrent from the anode. It is.

Various photocathodes have been developed that can handle various wavelengths, and are therefore widely used to measure various amounts of incident light.

A phototube has the property that when the voltage between the photocathode and the photoelectron collecting electrode is below a certain value, the photocurrent changes as the voltage changes.

Therefore, in order to eliminate the voltage dependence, a method is recommended in which the voltage is set sufficiently high and the photocurrent is used in a region where the photocurrent does not change due to changes in voltage.

The region exhibiting saturation characteristics in which the photocurrent does not increase even when the voltage is increased is called the saturation region.

The saturation region of a typical phototube is the operating region where a voltage of 25 volts or more is applied between the photocathode and the photoelectron collection electrode.

Therefore, conventional phototube power supplies must be capable of providing voltages of 25 volts or more.

The applied voltage necessary to form a saturated region is considered to be closely related to the arrangement and shape of each electrode within the phototube.

When a high voltage is applied between the electrodes to form a saturated region, undesirable discharge due to the electric field is likely to occur between the photocathode and the collection electrode.

In order to prevent this discharge from occurring, it is necessary to increase the distance between the electrodes, which becomes an obstacle to miniaturization.

It is thought that the undesirable linkage, in which increasing the distance between the electrodes requires applying a corresponding voltage, is an impediment to miniaturization of phototubes.

Furthermore, in the manufacturing process of conventional phototubes, electric resistance welding is used when assembling electrodes.

During this welding, the melted electrode material may solidify in the form of needles in the radial direction due to rapid heating and pressure by the electrode of the welder.

It is thought that this needle-like portion is one of the causes of inducing the initiation of discharge due to the electric field.

Although there are many obstacles to miniaturizing phototubes, there has recently been a strong desire to miniaturize phototubes and use them in small portable devices powered by batteries or the like.

The present invention has been made to meet the above-mentioned needs, and an object thereof is to provide a phototube that is suitable for miniaturization and can be operated at a low saturation voltage, and a method for manufacturing the same.

In order to achieve the above object, the photocell according to the present invention has a first electrode made of a metal wire with a uniform diameter whose tip is rolled into a flat shape, and a second electrode made of a metal wire with a uniform diameter on the first electrode. The base side of each electrode is sealed and fixed to one side of a cylindrical glass tube so that the second electrode faces parallel to the flattened part of the first electrode, and at least the first electrode A photocathode is formed on the flat part of the electrode to exhaust air, and the other side of the glass tube is hermetically sealed.

The method for manufacturing the phototube includes an electrode material forming step of rolling one end of the metal wire flat and bending the other end into a U shape so as to face parallel to the flat rolled portion;
an electrode material fixing step of fixing the electrode material to the glass tube so that the bent portion of the electrode material is exposed to the outside of the glass; and forming a photocathode on at least the flattened portion of the electrode material within the glass tube. A photocathode forming step, an exhaust sealing step of exhausting the gas inside the glass tube and airtightly sealing the other end of the glass tube, and a cutting step of cutting the abdomen of the electrode material to make each electrode part independent. It is configured.

According to the above configuration, the first electrode is formed by rolling the tip of a metal wire having a uniform diameter into a flat shape without welding or the like, and has a smooth outer shape, and has a sharp point that promotes the initiation of electric discharge. There is no department.

Since the second electrode can be disposed close to and parallel to the flattened portion, the voltage between the electrodes for forming the saturated region can be extremely low.

Since the distance between the electrodes can be reduced, the diameter of the cylindrical glass tube can also be reduced, and the phototube can be made smaller.

Since the distance between the first electrode forming the photocathode and the second electrode forming the collection electrode is short, photoelectrons can be collected well even at a low interelectrode voltage.

Further, according to the method, the manufacturing process of the phototube is simplified, and the phototube can be provided at low cost.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The phototube according to the present invention and its manufacturing method will be described in more detail below with reference to the drawings and the like.

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

A portion of the glass tube is shown broken to make it easier to understand the internal structure.

The first electrode 1, on which a photocathode will later be formed, is made of an alloy of iron, cobalt, and nickel and has a diameter of 0.5 mm.
It is formed by processing a 5-van metal wire.

Seven portions from the tip of the wire are rolled to form a flat plate.

The width of the flat part is 1.4 inches.

In this embodiment, the second electrode 2 serving as a photoelectron collecting electrode is as follows:
An alloy wire having the same composition and the same thickness as the first electrode is cut and used as a round material.

The second electrode 2 is disposed in the glass tube 3 in parallel to and opposite to the flat portion of the first electrode 1 forming the photocathode.

The distance between the flat portion of the first electrode 1 and the second electrode 2 is 0.5y+on.

The outer diameter of the cylindrical glass tube 3 forming the vacuum-tight container is 2.
．． 8 rran, the inner diameter is 1.9 m.

After tellurium is vapor-deposited on the flat plate-shaped portion of the first electrode, it is inserted into the cylindrical glass tube 3 together with the second electrode 2 while maintaining the relative positional relationship.

A portion of the glass tube 3 corresponding to a position sufficiently distant from the tip of each electrode is locally heated and melted, and the first electrode 1 and the second electrode 2 are attached to the glass tube 3 while maintaining the above-mentioned positional relationship. The stem portion 31 is formed by welding.

After each electrode was airtightly fixed to the base of the glass tube 30 in this way, the other side of the glass tube 3, the upper side in the figure, was connected to a vacuum exhaust device and a cesium source.

When the vacuum evacuation device is operated and the degree of vacuum reaches 10 to the minus 7th power, cesium is introduced into the glass tube from the cesium source, and cesium chillide is introduced into the flat portion of the first electrode. A photocathode is formed.

Next, the top portion of the glass tube 3 is heated with a gas burner to melt and seal it.

The phototube according to the above embodiment manufactured in this way has an outer diameter of 2.8 rran and a total length of 27WtIrL, making it extremely small.

It is convenient to make the first electrode 1 and the second electrode 2 integrally from one metal wire.

A single metal wire is cut to a length longer than the required length of the first electrode 1 and the second electrode 2, and one end of the metal wire is rolled flat to form a portion that will form a photocathode.

The abdomen of the cut metal wire is bent so that the other end faces parallel to the flattened portion to form a U-shape.

In this state, the glass tube 3 is melted and fixed by supporting it on one side of the glass tube 3 so that the abdomen is on the outside.
form 1.

After forming the stem portion 31, the abdomen may be cut to divide it into a first electrode and a second electrode.

This allows the process to be significantly streamlined.

Next, the operating characteristics of the phototube will be explained with reference to FIG.

When the voltage of the electrode tube of the phototube was gradually increased while keeping the incident light flux constant, the photocurrent saturated from 3 volts.

That is, the saturation region of this phototube starts at 3 volts.

This characteristic is shown in FIG. 2 by the curve (I).

The smallest known phototube has an outer diameter of 9.5 mm.
．． , the total length is 251rrrrL.

In order to use this phototube in the saturation region, it is necessary to apply a voltage of 25 volts or more to the electrode tube.

For comparison, the characteristics of this phototube are shown in Figure 2 by the curve shown by the wholesaler.

As explained above, the phototube according to the present invention is extremely small and can operate in the saturation region at low voltage.

Therefore, it can be expected to have a wide range of applications in fields where it could not be used in the past.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of a phototube according to the present invention, with a part of the glass tube cut away to facilitate understanding of the internal structure. FIG. 2 is a graph illustrating the characteristics of the phototube. 1...First electrode (photocathode), 2...
- Pair 2 electrode (photoelectron collection electrode), 3...Glass tube, 31...Stem portion of the glass tube.

Claims (1)

[Claims] 1. A first metal wire having a uniform diameter whose tip is rolled into a flat shape.
A second electrode made of a metal wire having a uniform diameter is attached to one side of the cylindrical glass tube so that the second electrode faces parallel to the flattened portion of the first electrode. sealing and fixing the base side of each electrode on the side, forming a photocathode on at least the flat part of the first electrode and evacuation;
A phototube constructed by airtightly sealing the other side of the glass tube. 2. The phototube according to claim 1, wherein the photocathode is a cesium chillide photocathode. 3. An electrode material forming process in which one end of the metal wire is rolled flat and the other end is bent into a U-shape so as to face parallel to the flat-rolled part, and a bending part of the electrode material in which the electrode material is bent into the U-shape. a step of fixing an electrode material to a glass tube so as to expose it to the outside of the glass; a photocathode forming step of forming a photocathode on at least the flattened portion of the electrode material in the glass tube; A method for manufacturing a phototube comprising: an exhaust sealing step of evacuating internal gas and airtightly sealing the other end of the glass tube; and a cutting step of cutting the abdomen of the electrode material to make each electrode part independent.