JPS6273548A - Electron multiplier tube - Google Patents

Abstract

PURPOSE:To reduce a leakage current by providing a conduction shielding layer surrounding a connection line implanted in a vacuum container, to which an electron focusing electrode is connected, while connecting said conduction shielding layer to the connection line to be connected to a reference potential point similarly implanted in the vacuum container. CONSTITUTION:The center of the stem part 10b of a vacuum container 10 has a trace 10a of a sealed and cut tube for exhaust and while surrounding this, a focusing electrode connection line 14, a connection line 15 to be connected to a reference potential point and the connection lines 16a-16n of diodes 12a-12n are implanted into the stem part 10b. A silver-pasted conduction shielding layer 13a is provided on the inner surface of the stem surface 10b so as to surround the focusing electrode connection line 14. And said connection shielding layer 13a is connected to a connection line 15 to be connected to a reference potential point. Similarly, the outer surface of the stem surface 10b is provided with a conduction shielding layer 13b so as to surround the focusing electrode connection line 14 while the silver-pasted conduction shielding layer 13b is connected to the connection line 15 to be connected to the reference potential point.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electron multiplier that multiplies electrons by utilizing the secondary electron multiplication effect of a dynode.

(Prior Art) An electron multiplier tube has an electron source such as a photocathode, a plurality of dynodes, and an electron collection electrode arranged in a vacuum-tight glass container.

It is widely used to multiply the number of electrons emitted by an electron source. In particular, when the electron source is a photocathode, it is used as a weak light detector.

An electron source, a plurality of dynodes, an electron collecting electrode, etc. are usually electrically connected to a plurality of lead-in wires implanted in a state that penetrates one bottom surface (stem) of the vacuum vessel, and are connected via the lead-in wires. connected to an external circuit.

FIG. 5 is a circuit diagram of a conventional photomultiplier tube.

Photocathode (electron source) 11, each dynode 123 to 12n
-1,! Approximately 1 is connected between the final stage dynodes 12n by power supply E.
oov voltages are applied sequentially.

The electron collecting electrode 17 is connected to the positive terminal (reference potential point) of the power source via a load resistor RL.

(Problems to be Solved by the Invention) When the electron multiplier tube is in use, the photocathode 11 and the dynodes 12a to 12 are connected to the stem portion.
A voltage is applied between the lead-in wires 16a to 16n of n and the lead-in wire of the collecting electrode 17.

The glass surface between the connecting wires has an electrolyte formed by moisture in the air (i.e. humidity) on the outer surface of the container and by alkali metals forming the charging cathode or dynode on the inner surface. An undesirable current (leakage current) flows due to the potential difference.

Although the leakage current is direct current, it contains thermal noise (alternating current component) because it passes through a resistor.

Since this thermal noise (AC component) cannot be separated from a signal current (AC component) component of the same level, the lower limit of the detectable signal level is regulated by this thermal noise.

An object of the present invention is to provide an electron multiplier tube that can minimize the influence of the aforementioned thermal noise.

(Means for Solving the Problem) In order to achieve the above object, the electron multiplier tube according to the present invention has a conductive shielding layer surrounding a connecting wire implanted in a vacuum container to which an electron collecting electrode is connected. , and this conductive shielding layer is connected to a connection line that is to be connected to a reference potential point that is also implanted in the vacuum container.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a perspective view showing an embodiment of an electron multiplier tube according to the present invention.

FIG. 2 is a diagram showing the stem portion of the electron multiplier tube. At the center of the stem portion 10b of the vacuum vessel 10, there is a part 10a after sealing off the exhaust pipe, and surrounding this there are the collecting electrode connection line 14 and the connection line 1 to be connected to the reference potential point.
5. Connection lines 16a to 16n of dynodes 12a to 12n
is implanted in the stem portion 10b.

On the inner surface of the stem surface 10b, a conductive shield [13
-a is provided. And this conductive shield ii 13
a is connected to a connection line 15 to be connected to a reference potential point.

Similarly, a conductive shielding layer 13b is provided on the outer surface of the stem surface 10b so as to surround the collecting electrode connection line 14.
The conductive shielding layer 13b of silver paste is connected to a connecting line 15 which is to be connected to a reference potential point (see FIG. 2).

FIG. 3 is a circuit diagram of the latter stage of the photomultiplier tube of the above embodiment.

The characteristics of a photomultiplier tube (hereinafter referred to as a conventional tube) having the same shape as the photomultiplier tube of the example described above but without the conductive shielding layers 13a and tab will be compared.

FIG. 4 shows the change in leakage current after the point in time when a DC voltage of 100 V was connected between the collecting electrode connection line 14 of each photomultiplier tube and the final stage dynode 16n. In the figure, curve A shows the change in leakage current of the conventional tube, and curve B shows the change in leakage current of the example photomultiplier tube.

In the example photomultiplier tube, the leakage current decreased to 0.1 pA or less after 100 seconds.

In conventional tubes, the leakage current after 100 seconds is 10-odd p.
However, the leakage current hardly decreases after that.

(Effects of the Invention) As explained in detail above, the electron multiplier according to the present invention is provided with a conductive shielding layer surrounding the connecting wire implanted in the vacuum container to which the electron collecting electrode is connected, and this conductive shielding layer is connected to a connection line that is to be connected to a reference potential point similarly installed in the vacuum container.

Therefore, leakage current observed in conventional photomultiplier tubes can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of an electron multiplier tube according to the present invention. FIG. 2 is a diagram showing the stem portion of the electron multiplier tube. FIG. 3 is a circuit diagram of the final stage of the electron multiplier tube. FIG. 4 is a graph showing a comparison of the leakage current characteristics of the conventional electron multiplier tube and the multiplier tube of the embodiment. FIG. 5 is a circuit diagram of a conventional electron multiplier tube. 1... Photomultiplier tube 10... Vacuum-tight container 10a of photomultiplier tube... Exhaust pipe trace 10b... Stem surface 11... Photocathode 12... Dynode group 13a... Inside the tube Shielding ring 13b...Extratubular shielding ring 14...Collecting electrode connection line 15...Connection line 16 to be connected to the base I$ potential point
a~16n...Dynode connection line 17...Collection 1 Patent applicant Hamamatsu Photonics Co., Ltd. Agent Patent attorney Inoro Hisao 1 Figure 2 Figure 3! 0 25 figures 4 figures AIMξ (Set)

Claims (2)

[Claims] (1) In an electron multiplier tube, a conductive shielding layer is provided surrounding a connecting wire implanted in a vacuum container to which an electron collecting electrode is connected, and this conductive shielding layer is connected to a reference potential also implanted in a vacuum container. An electron multiplier tube characterized in that it is connected to a connecting line that is to be connected to a point. (2) The electron multiplier tube according to claim 1, wherein the conductive shielding layer is formed on the inner or outer surface of the stem portion of the electron tube.