JPS58164136A - Phototube - Google Patents

Abstract

PURPOSE:To obtain a compact phototube that can be operated at a low saturation voltage by sealing and fixing one side of a cylindrical glass tube at the base sides of the first electrode whose top is rolled flatly and the second electrode so as to make the second electrode opposed to the first electrode in parallel, forming and discharging a photoelectric surface at the flat section of the electrodes, and sealing the other side of the glass tube airtightly. CONSTITUTION:The top of an electrode 1 made of alloy consisting of iron, cobalt, and nickel is pricessed in flat type. The second electrode 2 is opposed to the flat section of the first electrode 1 and is arranged in a glass tube 3 in parallel. After tellurium is deposited on the flat section of the first electrode, a stem section 31 is formed by inserting the electrode in the cylindrical glass tube 3 together with the second electrode 2 while the said relative positional relationship is being kept and fusing and depositing it on the glass tube 3. After the glass tube is discharged, a photoelectric surface made of cesium telluride is formed on the flat section of the first electrode. Then the top of the glass tube 3 is heated by means of a gas burner and is melted and then is sealed off.

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 applies a voltage between a photocathode and a photoelectric collecting electrode, and when light enters the charged cathode, the photoelectrons emitted from the photocathode are collected by the photoelectric collecting anode, and the photocurrent is sent out from the anode. It is an electron tube.

Since various photocathode systems have been developed that can handle a wide variety of wavelengths, they are 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, it is recommended to make the voltage sufficiently high and use it 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 photocell tubes had to be able to provide voltages of 25 volts or more.

The applied voltage required to form the 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-shaped portion is one of the causes of the repeated initiation of discharge due to the electric field.

Although there are many obstacles to miniaturizing phototubes, there is a strong trend in recent years to make phototubes smaller and use them in small portable devices that use batteries or the like as an electric sieve.

The present invention has been made in response to the above-mentioned gIH, and its purpose is to provide a phototube that is suitable for miniaturization and can be operated at a low saturation voltage.

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.

According to Mayuko Kai, the first electrode is formed by rolling the tip of a metal wire with a uniform diameter into a flat shape without welding, etc., and has a shape that promotes the initiation of electrical discharge. There is no pointed head. 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 11 electrodes forming the photocathode and the second electrode forming the collection electrode is short, photoelectrons can be collected well even at a low electrode tube voltage.

The phototube according to the present invention will be explained 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.

A photocathode is later formed to form a photocathode ll0)1
1 Pole 1 is formed by processing a metal wire with a diameter of 9.5 mm made of an alloy of iron, cobalt, and nickel. A portion 7 mm from the tip of the wire rod is rolled to form a flat plate.

The width of the flat plate portion is 1.4 mm.

In this embodiment, the second electrode 2 serving as a photoelectron collecting electrode is
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 charging cathode. The flat portion of the electrode 1 of II and the second electrode 2
The distance between Q and Q is 5 mm.

The outer diameter of the cylindrical glass tube 3 forming the vacuum tree container is 2.
．． 8 mm, and the inner diameter is 1.9 mm. After depositing tellurium on the flat plate-shaped portion of the first electrode, a second electrode 2 is formed.
At the same time, it is inserted into the cylindrical glass tube 3 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 is airtightly fixed to the base of the glass tube 3 in this manner, the other side of the glass tube 3', the upper side in the figure, is connected to a vacuum exhaust device and a cesium source.

When the vacuum evacuation device is operated and the degree of vacuum reaches lO to the minus 7th power Torr, cesium is introduced from the cesium cotton into the glass tube, and the 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.

The phototube according to the above embodiment manufactured in this way has an outer diameter of 2.13 mm and a total length of 27 mm, making it extremely small.

It is convenient if the first electrode 1 and the second electrode 2 are initially made integrally from one metal wire. One 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 with uneven weight to create a portion that will form a charging surface. Bend the abdomen of the cut metal wire so that the other end faces parallel to the flat rolled part °ζ
Make it U*cedar. In this state, the stem portion 31 is formed by supporting the glass tube 3 on one side with the abdomen facing outward and fixing the glass tube 3 by melting. After forming the stem portion 31, the abdomen may be cut to divide it into the If electrode and the 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 (1).

The smallest phototube currently known has an outer diameter of 9.5 m.
m, the total length is 25 mm. In order to use this phototube in a saturated state, it is necessary to apply a voltage of 25 volts or more to the electrode tube. The characteristics of this phototube are shown in FIG. 2 by the curve (■) for comparison.

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 the drawing]

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 for explaining the characteristics of the phototube. l...First electrode (charging cathode) 2...Pair 2 electrode (photoelectron collecting electrode) 3...Glass tube 31...Glass tube stem portion Patent applicant Hamamatsu Television Co., Ltd. Company agent Patent attorney Inoro Judo 1r “1 ・(, 2rji

Claims (1)

[Scope of Claims] +11 A second electrode made of a metal wire with a uniform diameter is attached to a first electrode made of a metal wire with a uniform diameter whose tip is rolled into a flat shape. The base side of each electrode is sealed and fixed to one side of a cylindrical glass tube so as to face parallel to the flattened part of the first electrode, and a photocathode is attached to at least the flattened part of the first electrode. A phototube constructed by forming and evacuating the glass tube, and sealing the other side of the glass tube with air. (2) The first electrode and the second electrode are formed by rolling one end of a piece of metal cotton into a flat shape, and bending the abdomen so that the other end faces parallel to the flattened part. 2. The phototube according to claim 1, wherein the phototube is made into a U-shape, which is fixed to one side of the glass tube with the abdomen facing outward, and then the abdomen is cut. (3) The phototube according to claim 1, wherein the photocathode is a cesium chillide photocathode.