JPS58184249A - Dynodes for secondary-electron multiplier - Google Patents

Abstract

PURPOSE:To cause secondary electrons produced on the surface of a thin plate to reach a dynode of the next stage efficiently. CONSTITUTION:In order to make dynodes 3 and 4, a plural number of thin plates 42 are positioned slanted to the main axis. When the pitch between the plates 42 which is in the direction perpendicular to the main axis is supposed to be (d) and the thickness of the dynodes 3 and 4 which is in the direction of the main axis is supposed to be (t), the dynodes 3 and 4 are constituted so that the relation of 1.5<=d/t<=1.75 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dynode of a secondary electron multiplier tube, and more specifically, to a dynode of a secondary electron multiplier tube in which the arrangement of thin plates constituting the dynode is improved.

Hereinafter, in this specification, the term "thin plate constituting a dynode" refers to a single thin plate whose at least one side has the ability to emit secondary electrons, and the basic unit of the dynode is formed by a plurality of these thin plates. . In addition, the secondary electron multiplier of the secondary electron multiplier is formed by one or more dynodes arranged perpendicularly to the main axis of the tube of the secondary electron multiplier. .

A secondary electron multiplier tube is generally placed in a vacuum tubular container.
It contains an electron source, followed by a secondary electron multiplier consisting of a series of dynodes, and finally an electron collecting electrode (collector).

These electrodes are arranged along the main axis of the tube in substantially the order described above. During operation of the secondary electron multiplier, appropriate voltages are applied to these electrodes in order to generate an electric field that accelerates electrons along the principal axis. At this time, the electrons emitted from the electron source collide with each diode in order along the tube axis, are multiplied each time, and collected by the collector.

(2) A type of secondary electron emission known as the Vanesian type is known. Each dynode of the spring-shaped secondary electron emitting electrode consists of a rectangular thin plate, the long sides of which are perpendicular to the main axis of the tube and the short sides inclined to the same axis. Two consecutive dynodes are arranged so as to be inclined in opposite directions with respect to the tube axis. Usually, a mesh electrode is provided on the side of each dynode on which electrons are incident, to which the same potential as that of the dynode is applied.

Hereinafter, a conventional springsian type secondary electron multiplier will be explained by giving an example.

FIG. 1 is an enlarged view of a part of a cross section of a conventional spring-shaped dynode. In the figure, reference numerals 11 and 12 are thin plates forming a dynode located at a relatively earlier stage.A cross section of the short side of the thin plate is shown in the paper. Each thin plate is inclined at 45 degrees to the main axis of the secondary electron multiplier. Further, in the figure, reference numerals 21 and 22 indicate thin plates forming a dynode located relatively at the rear. The thin plates 21, 22 of this dynode are inclined at 45 degrees in the opposite direction to the thin plates 11, 12 of the preceding dynode. Note that each thin plate has the same shape, and the length of the short side of the thin plate is 3.5 mm. In a conventional spring shan type dynode, the pitch d in the direction perpendicular to the main axis of the thin plate secondary electron multiplier tube forming the dynode and the thickness t of the dynode in the direction of the main axis of the secondary electron multiplier tube (the example above) Then t=3.5xO, 7=
2.45) was approximately 1.

1 between the front stage dynode 1 and the rear stage dynode 2
A voltage of 0.00 volts is applied, and this voltage gives the electrons collision energy to emit secondary electrons.

If electrons are incident on the above-mentioned dynode parallel to the main axis of the secondary electron multiplier tube, there is no gap at d/l-1, so all the electrons will definitely collide with one of the thin plates. The shape of such a dynode is referred to as optically opaque or simply opaque.

However, in the conventional Beneshkin-type dynode, the rate at which the secondary electrons emitted from the dynode reach the next stage and collide with each other is extremely low for the following reason. In other words, the electrons emitted from the part close to the previous stage dynode are moved by the electric field caused by the previous stage dynode in the direction indicated by the arrow al in Fig. 1.
It is returned to the dynode as shown in a'l. Because of the extremely weak electric field, some of the electrons emitted near the center of the dynode plate impinge on adjacent thin plates of the same dynode, as shown in FIGS. 1b and 1b. These electrons have substantially low energy and do not emit secondary electrons.

An object of the present invention is to provide a dynode for a secondary electron multiplier tube that can efficiently cause secondary electrons generated on the surface of a thin plate to reach the next stage dynode.

To achieve the above object, the dynode of the secondary electron multiplier according to the present invention is arranged perpendicularly to the main axis of the secondary electron multiplier, and the dynode of the secondary electron multiplier of the secondary electron multiplier is In the dynode of a secondary electron multiplier tube, d is the pitch in the direction perpendicular to the main axis between a plurality of thin plates arranged at an angle with respect to the main axis to form the dynode, and the front (5 ) (4) When the thickness of the dynode in the main axis direction is t, the dynode is configured such that the relationship of 1.5≦d/l≦1.75 holds between them.

According to the above structure, it is possible to improve the transfer efficiency of the secondary electrons generated in the dynode to the next stage dynode, and the object of the present invention can be completely achieved.

The dynode of the secondary electron multiplier according to the present invention will be explained in more detail below with reference to the drawings and the like.

FIG. 2 is an enlarged view of a part of the cross section of a spring shan-type dynode according to the present invention. Thin plates 31 and 32 at least on which the electrons are incident have the ability to emit secondary electrons.
is a thin plate that constitutes a part of the n-th stage dynode 3.

Similarly, the thin plate 4142 is a thin plate that constitutes the n+1-th stage dynode 4.

In the spring shan-type dynode according to the present invention, the pitch d of the thin plates constituting the dynode in a plane parallel to the main axis of the tube and the distance @1 in the tube axis direction of the thin plates are selected in the range of 1°5 to 1.75. be.

When viewed from the incident electrons, such a dynode (6) has a geometrically optically transparent part. In other words, it passes through the thin plate forming the dynode without touching it,
It appears that it may directly collide with a later stage dynode.

However, this is not a problem for the following reasons. Electrons emitted from the previous stage enter the dynode of the relevant stage with a certain degree of convergence so that they are difficult to escape.

The secondary electrons from the previous stage enter the stage with a distribution having the same pitch as the thin plates of the previous stage dynode, and the slopes of the thin plates of two consecutive dynodes are tilted in opposite directions with respect to the tube axis. Therefore, the following measures can be taken.

That is, by shifting the dynode by an appropriate distance from directly below the thin plate of the dynode in the preceding stage in the direction of the arrangement of the thin plates, most of the electrons incident on that stage can be made to collide with the thin plate of the dynode.

In addition, the dynode according to the present invention has a main part that emits electrons such that the emitted electrons are returned to the dynode by the electric field of the preceding dynode, and a part that emits electrons that collides with the adjacent thin plate. do not.

The reason for this will be explained qualitatively with reference to the drawings.

FIG. 3A is an explanatory diagram showing an electrode and an electric field, which is a partially enlarged cross-section of a conventional spring shan type dynode. The mesh electrode 10 is connected to the dynode 1, that is, the thin plate 1 of the dynode 1.
It has the same potential as 1.12.

The mesh electrode 20 is connected to the thin plate 1 at the same potential as the next dynode (not shown), i.e. 100 volts higher than the dynode 1.
Since the interval between 1 and 12 is narrow, the electric field generated by the mesh electrode 20 cannot penetrate into the interval. On the other hand, the electric field generated by the front dynode (not shown) creates an electric field that pushes the emitted electrons back through the gap between the mesh electrodes 10 to the surface area 13 of the thin plate 12 of the dynode near the front dynode.

Although this electric field is extremely weak, the initial velocity energy of the emitted electrons is also extremely small, so there is a possibility that they will be pushed back.

The vicinity of the center of the thin dynode plate 12 is not affected by the electric field caused by the front-stage dynode and the rear-stage dynode.

Furthermore, since the main component of the initial velocity of the emitted electrons is perpendicular to the surface of the dynode 12, there is a high possibility that the electrons emitted from this will collide with the adjacent dynode 11.

FIG. 3 is a partially enlarged view of the electrode and electric field of the spring shan-type dynode according to the present invention. The mesh electrode 30 is at the same potential as the thin plates 31, 32 of the dynode 3. Since the gap between the thin plates 31 and 32 of the mesh electrode 4o, which is 100 volts higher than the dynode 3, is wide, the electric field generated by the mesh electrode 40 enters the gap between the thin plates 31 and 32. Therefore, thin plate 3
The secondary electrons emitted from around the center of the dynode 2 pass through a trajectory as indicated by the arrow d and enter the next stage dynode (not shown). Furthermore, the electric field generated by the mesh electrode 40 affects the surface of the thin plate 32 near the front dynode (not shown), and the electric field from the front dynode (not shown) passes through the mesh electrode 20 to the front dynode of the thin plate of the dynode. It is not possible to create an electric field that pushes the secondary electrons back to the surface near the surface.

Next, a quantitative explanation will be given with reference to experimental results. The inventors of the present invention gradually increased only the pitch d of the thin plates in the direction parallel to the main axis of the conventional dynode (9) (8) as previously explained in FIG. The degree to which they reached the next stage was compared.

The horizontal axis is (d/l), and the vertical axis η is as follows.

Let η1 be the arrival at the next stage when (a/1) = 1 (point p in Figure 4), and let ηX be the degree of arrival when d = d, so η = ηX/η1. .

From Fig. 4, when d/l is from 1.0 (d/l = l is a conventional dynode) to 1.5, the above ratio η increases monotonically, and d
It can be seen that η>2 when /l is between 1.5 and 1.7. Among them, it was the highest at 1.64. d/l is 1.
When it becomes larger than 7, the η decreases. This is because the effect of the electric field mentioned above is saturated when d/l is between 1.5 and 1.75, but when d/l exceeds 1.5 to 1.75, the thin plate of the dynode is This is thought to be due to the fact that the transparent part becomes larger than the other part, and the number of electrons passing through the dynode increases without colliding with the dynode and being amplified.

As explained in detail above, the dynode of the secondary type (10) child multiplier according to the present invention has (d/l) of 1.5 to 1.
75, it was possible to reach the next stage more than twice as much as the conventional device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a dynode of a conventional secondary electron multiplier tube, and FIG. 2 is a schematic diagram showing an embodiment of a dynode of a secondary electron multiplier tube according to the present invention. FIG. 3 is a schematic diagram for explaining the change in electric field when the spacing between the thin plates is widened; FIG. 3 (A) shows a conventional dynode, and FIG. 3 (B) shows a dynode according to the present invention. be. FIG. 4 is a graph showing changes in the degree of arrival of secondary electrons to the next stage when the pitch d of the thin plate of the dynode in the direction parallel to the tube axis is changed. 1, 2. 3. 4... Dynode 11.12,2
1, 22, 31, 32, 41゜42...thin plate) Patent applicant Hamamatsu Television Co., Ltd. Agent Patent attorney Hisashi Inoro (11) S. 1 shi 1) ------+ 1. , , , , lQ A+ , , , , , =, , -, -2o
71w, --, cl---111010800. JM00. ．． 9180. ζ40 3l-4 (A'), (B)〆'A'4Figure 1. 1 Procedural amendment July 9, 1981 Patent Application No. 59853 2 Title of invention Dynode 3 of secondary electron multiplier tube Tall system with amended person case Patent applicant address name Name Hamamatsu Television Corporation 4, Agent 1 Description □ Contents of amendment (Japanese Patent Application No. 57-59853) (1) The scope of claims is amended as follows. "2. Claim +11 Arranged perpendicularly to the main axis of the secondary electron multiplier,
In the dynode forming the secondary electron multiplier of the secondary electron multiplier tube, the dynode is perpendicular to the main axis between a plurality of thin plates arranged at an angle with respect to the main axis to form the dynode. A dynode of a secondary electron multiplier tube, characterized in that the dynode of a secondary electron multiplier is constructed so that the following relationship holds true when the pitch in the direction is d and the thickness in the main axis direction of the dynode is t. 1, 5≦d/l≦1.75 (2) Claim 1, wherein the d/l is 1.64.
Secondary electron field W! :1. :, tube dynode. ”
(2) "Secondary electron multiplier" on page 2, line 13 of the specification is corrected to "secondary electron multiplier." (1) (3) "Secondary electron emission" in the first line of page 3 of the specification is corrected to "a type of dynode." (4) Delete "each of the secondary electron emitting electrodes" from the second line to the third line of page 3 of the specification. (5) “Dynote is rectangular.
..." is corrected to "The dynode is a plurality of rectangles...". (6) "Henneshan-type secondary electron multiplier" on page 3, line 11 of the specification is corrected to "Secondary electron multiplier formed by Hennesshan-type dynodes." (7) ra 1 a 2J on page 5, line 4 of the specification [
Correct to al, a2J. (8) rblb2J on page 5, line 7 of the specification is “bl,
Correct to b2J. (9) “Secondary electron multiplier” on page 5, line 17 of the specification
Delete. (10) Correct "Banesha type dynode" on page 6, line 9 of the specification to "Banesha type dynode". (11) In the 18th line of page 6 of the specification, "(2) Ground with distance t" is corrected to "ratio with distance t". (12) "Secondary electron" on page 7, line 8 of the specification is corrected to "electron". (13) Correct "Banesha-type dynode" in the third line of page 8 of the specification to "Banesha-type dynode." (14) "Gap" on page 8, line 9 of the specification is corrected to "gap". (15) "Interval" on page 8, line 10 of the specification is "gap"
Correct to. (16) “Dynode thin plate” on page 8, line 17 of the specification
(17) In the third line of page 9 of the specification, ``Figure 3 is a spring shan type dynode according to the present invention'' is changed to ``Figure 3 B is a spring shan type dynode according to the present invention''. ”. (18) In the 7th line of page 10 of the specification, "...and toto" is amended to "...tojito." Above (3)

Claims (2)

[Claims] (1) Arranged perpendicular to the main axis of the secondary electron multiplier,
Between a plurality of thin plates arranged at an angle with respect to the main axis to form the dynode, written on the dynode of the secondary electron multiplier that forms the secondary electron multiplier of the secondary electron multiplier. A secondary electron multiplier characterized in that the secondary electron multiplier is configured such that the pitch in the direction perpendicular to the principal axis of the dynode is d, and the thickness of the dynode in the principal axis direction is t, the following relationship holds between them: Double tube dynode. Note 1, 5≦d/l≦1.75 (2) Claim 1, wherein the d/l is 1.64.
The dynode of the secondary electron multiplier tube described in .