CN116978769A - Multi-stage dynode multiplication structure with three-dimensional arrangement and electron multiplier comprising multi-stage dynode multiplication structure - Google Patents

Abstract

The invention belongs to the technical field of electron multipliers, and relates to a multi-stage dynode multiplication structure with three-dimensional arrangement, which adopts a planar and three-dimensional combined arrangement mode; the electron multiplier is of a three-dimensional structure, and the electron motion trail is in a three-dimensional space; the dynode is of a box grid type structure and comprises a cathode plate, an upper baffle, a lower baffle and a grid mesh, wherein the grid mesh is square in shape, and secondary electron emission films are covered on the surfaces of the cathode plate, the upper baffle and the lower baffle. Compared with the internal electric field of the dynode of the conventional structure, the internal electric field of the dynode electron multiplier with the separated three-dimensional structure is improved, secondary electrons generated by each dynode are more concentrated and reach the central position of a secondary electron emitter of the next dynode, so that the number of override electrons and trapped electrons of each dynode is reduced, and the secondary electron collection efficiency can be obviously improved. The overall gain of the electron multiplier is also improved.

Description

Multi-stage dynode multiplication structure with three-dimensional arrangement and electron multiplier comprising multi-stage dynode multiplication structure

Technical Field

The invention belongs to the technical field of electron multipliers, and relates to a multi-stage dynode multiplication structure in three-dimensional arrangement and an electron multiplier comprising the multi-stage dynode multiplication structure.

Background

The electron multiplier is a vacuum electronic device for signal amplification, and its gain can be up to 10 ⁷ ～10 ⁸ Currently, the method is widely applied to mass spectrometry technology, vacuum technology, space detection and cesium atomic frequency standard. Electron multipliers are mainly classified structurally into channel type and split dynode type. Among them, the split dynode type electron multiplier is most widely used with advantages of high gain, high reliability, wide dynamic range, long life, and the like. Today, dyndes of split dynode electron multipliers have developed a variety of structures including flat-plate, round cage, box-grid, shutter, etc. The working principle of the electron multiplier is as follows: the incident particles bombard the secondary electron emitter on the surface of the dynode through high-pressure acceleration, so that secondary electrons escape from the surface. In the process, the emergent angles of secondary electrons are distributed according to cosine between 0 and pi, but the energy of most secondary electrons is positioned near 10eV, so that most secondary electrons can bombard the next dynode under the action of an accelerating electric field between the dynodes at each stage. The electrons are continuously multiplied by such a process until finally collected by the collector, thereby achieving amplification of a weak incident signal. However, due to the wide distribution of the secondary electron emission angles, the accelerating electric field between the dynodes does not allow all secondary electrons to reach the next dynode. Wherein, part of secondary electrons can cross the next dynode and reach the subsequent dynode, so that the multiplication times of the secondary electrons are reduced, and the part of electrons are called as override electrons; some secondary electrons bombard the secondary electron emitter or other positions of the original dynode again, and the new secondary electrons cannot be excited again due to the lower energy of the secondary electrons, so that the number of the secondary electrons actually emitted by the dynode is reduced, and the part of electrons are called trapped electrons; finally, some secondary electrons are inevitably blocked by the grid or the back of the dynode during movement, and cannot reach the next dynode, and the part of electrons is called blocked electrons.

Today, the dynodes of all the split electron multipliers are arranged on the same plane, and the straight arrangement of the dynodes can maximize the secondary electron collection efficiency of each dynode. However, even in a straight line arrangement, the gain of the multiplier still cannot be close to the theoretical gain, and particularly when the number of stages of the electron multiplier reaches about 20 stages, the collection efficiency of each dynode directly determines the total gain.

The dynodes of the current separated electron multiplier are all arranged on the same plane, and under the design, the collection efficiency of each dynode can only reach about 95 percent due to the existence of override electrons, trapped electrons, blocked electrons and the like. When the number of electron multiplier stages reaches 20, the total collection efficiency is only 35.84%, which makes the planar electron multiplier achieve only 35.84% of the ideal gain.

Disclosure of Invention

The invention aims to provide a multi-stage dynode multiplication structure with three-dimensional arrangement and an electron multiplier comprising the multi-stage dynode multiplication structure, and solves the problem of low collection efficiency of dynodes.

The invention is realized by the following technical scheme:

the invention discloses a multi-stage dynode multiplication structure in three-dimensional arrangement, which adopts a planar and three-dimensional combined arrangement mode;

the electron multiplier is of a three-dimensional structure, and the electron motion trail is in a three-dimensional space;

the dynode is of a box grid type structure and comprises a cathode plate, an upper baffle, a lower baffle and a grid mesh, wherein the grid mesh is square in shape, and secondary electron emission films are covered on the surfaces of the cathode plate, the upper baffle and the lower baffle.

Further, the connection mode of two adjacent dynodes is divided into 3 structures, specifically named as vertical connection mode, same-direction connection mode and reverse connection mode; the two adjacent dynodes are named as an upper-level dynode and a lower-level dynode;

when the connection mode of two adjacent dynodes adopts vertical connection, the emergent direction of electrons passing through the lower-stage dynode is vertical to the incident direction of the upper-stage dynode;

when the connection mode of two adjacent dynodes adopts the same-direction connection mode, the emergent direction of electrons passing through the lower-stage dynode is unchanged from the incident direction of the upper-stage dynode;

when two adjacent dynodes are connected in a reverse connection mode, the emergent direction of electrons passing through the lower-stage dynode is opposite to the incident direction of the upper-stage dynode.

Further, the structure of the vertical connection is specifically:

the grid mesh of the incidence direction of the upper dynode and one baffle of the lower dynode are on the same plane, and the cathode plate of the upper dynode and the other baffle of the lower dynode are positioned at one side.

Further, the structure of the same-direction connection type is specifically as follows:

the baffle plates of the upper dynode and the lower dynode are on the same plane, and the grid mesh of the incidence direction of the upper dynode and the cathode plate of the lower dynode are on the same side.

Further, the structure of the reverse connection is specifically:

the baffle plates of the upper dynode and the lower dynode are on the same plane, the grid mesh of the incidence direction of the upper dynode and the outlet of the lower dynode are on the same plane, and the cathode plates of the upper dynode and the lower dynode are on the same side to form a semicircle.

Further, when the electron multiplier has seven stages of dynodes, the dynodes are named as a first stage dynode, a second stage dynode, a third stage dynode, a fourth stage dynode, a fifth stage dynode, a sixth stage dynode and a seventh stage dynode respectively, and the structure which most saves the space position of the multiplier is as follows:

the primary dynode and the secondary dynode are connected in the same direction, the secondary dynode and the tertiary dynode are connected vertically, the tertiary dynode and the quaternary dynode are connected vertically, the quaternary dynode and the fifth dynode are connected vertically, the fifth dynode and the sixth dynode are connected reversely, the sixth dynode and the seventh dynode are connected vertically, and the emergent end of the seventh dynode is provided with a collector.

Further, when the electron multiplier has seven stages of dynodes, the electron multiplier is named as a first stage dynode, a second stage dynode, a third stage dynode, a fourth stage dynode, a fifth stage dynode, a sixth stage dynode and a seventh stage dynode, respectively, and the highest gain structure is as follows:

the primary dynode and the secondary dynode are connected in the same direction, the secondary dynode and the tertiary dynode are connected in the vertical direction, the tertiary dynode and the quaternary dynode are connected in the same direction, the quaternary dynode and the fifth dynode are connected in the vertical direction, the fifth dynode and the sixth dynode are connected in the same direction, the sixth dynode and the seventh dynode are connected in the vertical direction, and the emergent end of the seventh dynode is provided with a collector.

Further, when the dynode of the electron multiplier has more, the highest gain structure is extended with the front three stages of dynodes of the seven stages of dynode electron multipliers as the base module.

The invention also discloses an electron multiplier comprising the multi-stage dynode multiplication structure in three-dimensional arrangement.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention aims to provide a multi-stage dynode multiplication structure with three-dimensional arrangement, wherein a dynode adopts a box grid type dynode, and the dynode comprises a cathode plate, an upper baffle plate, a lower baffle plate and a grid mesh, and secondary electron emission films are plated on the upper baffle plate and the lower baffle plate, so that the upper baffle plate and the lower baffle plate become secondary electron emitters. In the conventional structure, the electron track is limited to one plane, and the upper baffle plate and the lower baffle plate are used for limiting electrons from escaping from two sides to the outside of the structure. Furthermore, the grid mesh of the conventional dynode structure is rectangular, and the arc radius of the cathode plate is smaller than the height; the grid mesh of the dynode structure is square, and the arc radius and the height of the cathode plate are equal, because the traditional dynodes are only arranged on a plane, and only the size of each dynode is required to be the same. The dynodes are arranged in a three-dimensional way, and the dynodes can be ensured to be arranged in a three-dimensional way without electron leakage outside the structure only when the grid mesh is square and the arc radius of the cathode plate is equal to the height.

Simulation results show that: compared with the internal electric field of the dynode of the conventional structure, the internal electric field of the dynode electron multiplier with the separated three-dimensional structure is improved, secondary electrons generated by each dynode are more concentrated and reach the central position of a secondary electron emitter of the next dynode, so that the number of override electrons and trapped electrons of each dynode is reduced, and the secondary electron collection efficiency can be obviously improved. The overall gain of the electron multiplier is also improved.

Further, taking a seven-stage dynode as an example, one configuration that most saves the spatial position of the multiplier and the highest gain configuration are given. Space arrangement of dynodes is adopted, so that the space can be effectively utilized to reduce the volume of the electron multiplier; the space arrangement and the plane arrangement of the dynode are combined with each other, so that the average collection efficiency of the dynode is improved, and the gain of the multiplier can be obviously improved.

Drawings

FIG. 1 is a schematic diagram of two adjacent dynodes connected vertically;

FIG. 2 is a schematic diagram of two adjacent dynodes connected in the same direction;

FIG. 3 is a schematic illustration of another alternative two adjacent dynode reverse connection;

FIG. 4 is an electron bombardment plot of the dynode in the simulated optimal structure of three dynode planar arrangements;

FIG. 5 is an electron bombardment diagram of dynodes in an optimal structure of three dynode planar arrangements combined with a three-dimensional arrangement obtained by simulation;

fig. 6 is a planar arrangement of seven dynodes with the highest gain achieved as a control group for the present invention.

Fig. 7 is a graph of electron trajectories under a planar arrangement where seven dynodes achieve the highest gain.

FIG. 8 is a schematic view of the most space-saving structure of seven dynodes in combination with planar and spatial arrangements, which is embodiment 1 of the present invention;

FIG. 9 is a diagram of an electronic trace corresponding to the structure of FIG. 8;

FIG. 10 is another schematic view of the most space-saving structure of seven dynodes in combination with planar and spatial arrangements, which is embodiment 2 of the present invention;

FIG. 11 is a diagram of an electronic trace corresponding to the structure of FIG. 10;

FIG. 12 is a schematic view of the highest gain structure of seven dynodes in combination with a planar and spatial arrangement, and is embodiment 3 of the present invention;

FIG. 13 is a graph of electron trajectories for seven dynodes in a highest gain configuration with a combination of planar and spatial arrangements;

wherein, 100, cathode plate; 110. a grid mesh; 120. an upper baffle; 130. a lower baffle; 140. a secondary emitter; 150. an incident source; 170. a collector.

Detailed Description

The objects, technical solutions and advantages of the present invention will be more apparent from the following detailed description with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention, i.e., the embodiments described are merely some, but not all, of the embodiments of the invention.

The components illustrated in the figures and described and shown in the embodiments of the invention may be arranged and designed in a wide variety of different configurations, and thus the detailed description of the embodiments of the invention provided in the figures below is not intended to limit the scope of the invention as claimed, but is merely representative of selected ones of the embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention, based on the figures and embodiments of the present invention.

It should be noted that: the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements does not include only those elements. Furthermore, the terms "vertical," "same direction," and "opposite direction" are based on the orientation and positional relationship of the devices or components shown in the drawings, and are merely used to better describe the present invention, and do not require that the devices, components, or apparatus shown must have this particular orientation and therefore should not be construed as limiting the invention.

The features and properties of the present invention are described in further detail below with reference to examples.

Referring to fig. 1, there is shown the spatial arrangement of two adjacent dynodes, wherein the main structure of the dynode comprises four parts: cathode plate 100, grid 110, upper baffle 120, lower baffle 130, secondary emitter 140. The cathode plate 100 is formed in an arc-shaped sheet, and is made of stainless steel, and the secondary emitter 140 is made of a thin film material with a high secondary electron emission coefficient, and covers the surface of the cathode plate 100.

The grid 110 is also made of stainless steel and is square in shape to focus electrons.

The upper and lower baffles 120, 130 are also made of stainless steel, the surfaces of which are covered with a thin film of high secondary emission coefficient, on the one hand limiting the escape of secondary electron longitudinal motion out of the multiplier. On the other hand, the particles directly bombarded on the upper baffle plate and the lower baffle plate can be multiplied.

The first arrangement of two adjacent dynodes in the plane shown in fig. 1 is named vertical connection, in which electrons or ions are incident from the incident source 150, and after multiplication by two dynodes, the secondary electrons exit in a direction perpendicular to the incident direction.

Fig. 2 shows a second arrangement of two adjacent dynodes in a plane, named co-directional connection. The structure of the dynode is identical to that of the dynode in fig. 1, the two dynodes are positioned on the same plane, and the movement direction of electrons is not changed after the electrons pass through the two dynodes.

Fig. 3 shows a third planar arrangement of two adjacent dynodes, designated as reverse-connected. The efficient planar arrangement modes are only two as shown in fig. 2 and 3, and a large number of electrons can be exposed out of the multiplier structure in other planar arrangement modes, so that the collection efficiency of each dynode is obviously reduced, and the explanation is omitted here. The construction of the dynode of fig. 3 is identical to that of fig. 1, and the direction of motion is reversed after the electrons pass through both dynodes.

Comparative example 1

Fig. 4 is a preferred structure in which three dynodes are combined in a planar manner, wherein the electron distribution incident to the subordinate dynode (D2) is more dispersed. Meanwhile, since the secondary electrons have wider emission angle distribution, part of the secondary electrons are beaten on the secondary electron emitter again, and part of the secondary electrons are beaten on the surfaces of the upper baffle plate and the lower baffle plate, and since the energy of the secondary electrons is mainly concentrated near 10eV, even though the secondary electrons still beaten on the surface of the secondary electron emission material, electron multiplication cannot be realized, and the part of the secondary electrons can be finally trapped in D2 and cannot reach the next dynode.

Example 1

Fig. 5 shows an optimal three dynode structure in which a plane and a solid are combined, and due to the introduction of a solid combination mode between dynodes, the internal electric field of the dynode is changed, so that the electron distribution incident to the lower-stage dynode (D2) is significantly more concentrated, secondary electrons generated in D2 are easier to reach the lower-stage dynode (D3), the number of override electrons and trapped electrons of D2 can be significantly reduced, and the secondary electron collection efficiency of D3 can be significantly improved.

The electron bombards the dynode and is mainly determined by the electric field in the space of the dynode. In the case where the voltage difference U between two adjacent dynodes is the same, since the electric field e=u/d, the strength of the electric field E at the entrance of the dynode depends on the distance d between the position and the next-stage dynode. In the planar structure of fig. 4, this distance is simply the spacing on the plane, whereas the introduction of the three-dimensional structure of fig. 5 makes this distance a spatial distance, significantly greater. This results in less influence of the next dozen to the electric field at the entrance, less tendency for electrons to move to the next dynode, and more concentrated direction of movement.

Comparative example 2

Fig. 6 shows the highest gain structure with seven dynodes arranged in a plane, wherein seven dynodes are arranged in a straight line, the structure size is large, and the structure gain is still far from the ideal gain, which is used as the control group 2 of the present invention.

Fig. 7 is a graph of electron trajectories when the seven dynode planes shown in fig. 6 are arranged to obtain the highest gain structure.

Example 2

Fig. 8 is a schematic structural view showing a combination of seven dynode planes and spatial arrangement, which is embodiment 2 of the present invention. Compared with the control group in fig. 6, the space of the structure is fully occupied by the dynode, and the structure is the structure which saves the space position of the multiplier most. The structure shown in this example is only one of seven combinations that saves space. Because of the special dynode structure, the dynodes can be connected between planes or three-dimensional structures at will, the most space-saving structure of the seven continuous dynodes also has a combination mode as shown in figure 10 and the like, and various combination modes can be used as basic units, and when more dynodes are needed, the dynodes can be added in a similar mode after the seventh dynode;

fig. 9 and 11 correspond to the electronic track diagrams of the seven dynodes shown in fig. 8 and 10, respectively, which adopt the most space-saving structure of combining plane and space arrangement.

Example 3

Fig. 12 shows a high gain structure diagram combining seven dynode planes and spatial arrangement, wherein the planar arrangement shown in fig. 2, i.e. the homodromous connection, is arranged between the primary dynode and the secondary dynode, the three-dimensional arrangement shown in fig. 1, i.e. the vertical connection, is arranged between the secondary dynode and the tertiary dynode, then the planar arrangement shown in fig. 2 is arranged between the tertiary dynode and the quaternary dynode, and the three-dimensional arrangement shown in fig. 1 is arranged between the quaternary dynode and the fifth dynode. By repeating this, the highest gain structure can be realized.

The design concept is because the structure shown in fig. 5 is the highest gain three-stage dynode structure, and this example is formed by repeating fig. 5 as the smallest unit. Since the planar arrangement shown in fig. 2 and the stereoscopic arrangement shown in fig. 1 are merely positional relationships between two dynodes, the placement orientation thereof is still variable, so this example is also merely one of the high gain structures. For example, the dynode No. 5 and the dynode No. 4 in this case are arranged in a three-dimensional relationship, but the electron outlets of the dynodes are not necessarily downward, and upward.

With this structure, the electron override to electron blocking ratio in the dynode is reduced. Under the same simulation conditions, the simulation calculates that the average collection efficiency of each dynode in the structure of fig. 11 is 98.9%, and compared with the structure of the control group of fig. 6, the average collection efficiency of each dynode is improved by 3.37%. Likewise, when more dynodes are needed, the addition can continue in a similar manner after the seventh dynode;

fig. 13 shows a high gain structure electron trace diagram of a combination of seven dynode planes and spatial arrangements.

The electron multiplier provided by the invention has the following advantages:

(1) Space arrangement of dynodes is adopted, so that the space can be effectively utilized to reduce the volume of the electron multiplier.

(2) The space arrangement and the plane arrangement of the dynode are combined with each other, so that the average collection efficiency of the dynode is improved, and the gain of the multiplier can be obviously improved.

Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.

Claims (9)

1. The multi-stage dynode multiplication structure is characterized by adopting a planar and three-dimensional combined arrangement mode;

the electron multiplier is of a three-dimensional structure, and the electron motion trail is in a three-dimensional space;

the dynode is of a box grid type structure and comprises a cathode plate (100), an upper baffle plate (120), a lower baffle plate (130) and a grid mesh (110), wherein the grid mesh (110) is square in shape, and secondary electron emission films are covered on the surfaces of the cathode plate (100), the upper baffle plate (120) and the lower baffle plate (130).

2. The multi-stage dynode multiplication structure with three-dimensional arrangement according to claim 1, wherein the connection mode of two adjacent dynodes is divided into 3 structures, specifically named vertical connection type, homodromous connection type and reverse connection type; the two adjacent dynodes are named as an upper-level dynode and a lower-level dynode;

when the connection mode of two adjacent dynodes adopts vertical connection, the emergent direction of electrons passing through the lower-stage dynode is vertical to the incident direction of the upper-stage dynode;

when the connection mode of two adjacent dynodes adopts the same-direction connection mode, the emergent direction of electrons passing through the lower-stage dynode is unchanged from the incident direction of the upper-stage dynode;

when two adjacent dynodes are connected in a reverse connection mode, the emergent direction of electrons passing through the lower-stage dynode is opposite to the incident direction of the upper-stage dynode.

3. The multi-stage dynode multiplication structure of claim 2, wherein the structure of vertical connection is specifically:

the grid (110) of the incidence direction of the upper dynode and one baffle of the lower dynode are on the same plane, and the cathode plate (100) of the upper dynode and the other baffle of the lower dynode are positioned at one side.

4. The multi-stage dynode multiplication structure of claim 2, wherein the structure of the homodromous connection is specifically:

the baffle plates of the upper dynode and the lower dynode are on the same plane, and the grid (110) of the incidence direction of the upper dynode and the cathode plate (100) of the lower dynode are on the same side.

5. The multi-stage dynode multiplication structure of claim 2, wherein the structure of reverse connection is specifically:

the baffle plates of the upper dynode and the lower dynode are on the same plane, the grid (110) of the incidence direction of the upper dynode and the outlet of the lower dynode are on the same plane, and the cathode plates (100) of the upper dynode and the lower dynode are on the same side to form a semicircle.

6. The multi-stage dynode multiplication structure according to claim 2 wherein when the electron multiplier has seven stages of dynodes, the dynodes are respectively named as a first stage dynode, a second stage dynode, a third stage dynode, a fourth stage dynode, a fifth stage dynode, a sixth stage dynode and a seventh stage dynode, and the structure that most saves the space of the multiplier is:

the primary dynode and the secondary dynode are connected in the same direction, the secondary dynode and the tertiary dynode are connected vertically, the tertiary dynode and the quaternary dynode are connected vertically, the quaternary dynode and the fifth dynode are connected vertically, the fifth dynode and the sixth dynode are connected reversely, the sixth dynode and the seventh dynode are connected vertically, and the emergent end of the seventh dynode is provided with a collector (170).

7. The multi-stage dynode multiplication structure according to claim 2 wherein when the electron multiplier has seven stages of dynodes, the dynodes are respectively named primary dynode, secondary dynode, tertiary dynode, quaternary dynode, five-stage dynode, six-stage dynode, seven-stage dynode, and the highest gain structure is:

the primary dynode and the secondary dynode are connected in the same direction, the secondary dynode and the tertiary dynode are connected in the vertical direction, the tertiary dynode and the quaternary dynode are connected in the same direction, the quaternary dynode and the fifth dynode are connected in the vertical direction, the fifth dynode and the sixth dynode are connected in the same direction, the sixth dynode and the seventh dynode are connected in the vertical direction, and the emergent end of the seventh dynode is provided with a collector (170).

8. The multi-stage dynode multiplication structure according to claim 7 wherein when there are more dynodes of the electron multiplier, the highest gain structure is extended with the front three stages of dynodes of the seven stages of dynode electron multipliers as the base modules.

9. An electron multiplier comprising the stereoscopically arranged multi-stage dynode multiplication structure of any one of claims 1 to 8.