JPH083984B2 - Secondary electron multiplier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a channel type secondary electron multiplier tube in which generation of ion feedback is suppressed.

[Prior Art] Generally, a secondary electron multiplier has a structure in which dynodes, which are electrodes for multiplying secondary electrons, are separated into a plurality of parts, and a multiplying path for secondary electrons is provided. It is continuous and there is a continuous dynode secondary electron multiplier called a channel type secondary electron multiplier.

The continuous dynode secondary electron multiplier has a parallel plate-shaped channel substrate or a pipe shape, and has a high resistance secondary electron emission surface on the inner surface. An example of a conventional continuous dynode secondary electron multiplier of this type is shown in FIG.

The secondary electron multiplier 1 has a secondary electron emission surface 4 made of a high resistance secondary electron emission material on the opposing surfaces of flat plate-shaped channel substrates 2 and 3 made of glass or ceramics arranged in parallel with each other. , 5 are formed respectively.

The secondary electron emission surfaces 4 and 5 formed on the respective channel bases 2 and 3 have a high voltage DC power supply 9 at the input end 7 and the output end 8 of the channel 6 formed between the channel bases 2 and 3. Connected to. The high-voltage DC power supply 9 generates an electric field in the axial direction of the channel 6 for accelerating the secondary electrons emitted from the secondary electron emission surfaces 4 and 5 of the channel substrates 2 and 3. Also, facing the output end 8 of the channel 6,
A collector 11 is provided for collecting the secondary electrons multiplied in the channel 6. A power supply 12 is connected between the collector 11 and the output end 8 of the channel 6 to generate an electric field that guides secondary electrons that are multiplied and output from the output end 8.

When the primary electrons 13 are made to enter from the input end 7 side of the secondary electron multiplier 1, the primary electrons 13 are emitted from the secondary electron emission surface 4, 4 of each channel substrate 2, 3 as shown by the solid line in FIG. Collide with 5 and generate secondary electrons. This secondary electron is accelerated by the electric field for accelerating it, and while drawing a parabolic locus, it further collides with the secondary electron emission surface 4,5 of each channel substrate 2, 3, and from there, the secondary electron is further generated. Secondary electrons that emit electrons and are multiplied by an avalanche by repeating this process are collected in the collector 11.

In the channel 6 of the secondary electron multiplier 1 having the above structure, the equipotential surface is perpendicular to the axial direction of the secondary electron multiplier 1 as shown by the dotted line in FIG. .
Therefore, the orbits of the secondary electrons between the channel substrates 2 and 3 are parabolic, and the number of collisions of the secondary electrons with the secondary electron emission surfaces 4 and 5 depends on the distance between the channel substrates 2 and 3. Is proportional to the ratio of the axial distances of. Therefore, in order to obtain a high gain secondary electron multiplier, it is necessary to increase the value of the above ratio, and the equipotential surface is used as a channel substrate.
It must be evenly aligned perpendicular to the few axes and the axis length must be increased.

In order to solve such a problem of the conventional continuous dynode type secondary electron multiplier, for example, Japanese Patent Publications Nos. 50-16145, 50-25303 and 52-38378, U.S. Pat. No. 3,235,765, etc., a gradient electric field type secondary electron multiplier has been proposed which can obtain an effective gain at a low acceleration voltage by utilizing a gradient electric field of acceleration of secondary electrons.

For example, in Japanese Patent Publication No. 50-25303, as shown in FIGS. 5 and 6, a first flat plate 21 having an inner surface having a secondary electron emitting property and a second plate having a high resistance or conductivity. Slab of
There are described secondary electron multipliers 24 and 25 in which 22 and 22 are arranged so as to widen the distance toward the output end 23. The equipotential surface formed between the first flat plate 21 and the second flat plate 22 is, as shown by dotted lines in FIGS. 5 and 6,
An acute angle is formed with respect to the first flat plate 21 and an output end 23
It becomes a high potential as you go to. As a result, the secondary electrons collide with the secondary electron multiplication surface 26 of the first flat plate 21 along the locus shown by the solid line, are multiplied, and are captured by the collector 27.

[Problems to be Solved by the Invention] Generally, at the output end of a secondary electron multiplier, electrons collide with residual gas because the density of electrons is high, and this residual gas produces a charge having a polarity opposite to that of the electrons. So-called ion feedback occurs in which the ions are ionized and collide with the secondary electron multiplier to generate secondary electrons, which are sequentially multiplied.

However, in the above-mentioned conventional gradient electric field type secondary electron multipliers 1, 24 and 25, as can be seen from the above, the main point is in the structure that mainly forms the gradient electric field, and reduction of ion feedback etc. Little attention was paid to stabilizing the behavior of.

The object of the present invention is to suppress the generation of ion feedback, to have a large multiplication effect, to operate stably even in a low vacuum,
It is an object of the present invention to provide a secondary electron multiplier capable of obtaining a large output current.

[Means for Solving the Problem] The invention according to claim 1 is the flat plate-shaped first channel substrate for secondary electron multiplication, and the second for generating a gradient electric field, which is arranged so as to face it. A channel is formed between the first channel substrate and the second channel substrate, and secondary electrons generated by collision of charged particles incident on one end of the first channel substrate collide with the first channel substrate along the direction of the gradient electric field. A secondary electron multiplying tube, which is multiplied by an avalanche in the process of moving to obtain a multiplied secondary electron flow from the other end of the channel substrate, wherein the first channel substrate is The second channel substrate is made of a material having a large secondary electron emission coefficient while the surface facing the second channel substrate has a resistance, and the second channel substrate has a surface having a resistance facing the first channel substrate. From And is subjected to a surface treatment to reduce the secondary electron emission rate, and the second channel substrate is shifted from one end of the first channel substrate toward the other end of the first channel substrate. And a high voltage is applied between one end and the other end of the first channel base body and between one end and the other end of the second channel base body to form the gradient electric field. It is characterized by that.

According to a second aspect of the present invention, a channel is provided between a flat plate-shaped first channel substrate for secondary electron multiplication and a second channel substrate for generating a gradient electric field, which is arranged so as to face it. And secondary electrons generated by the collision of charged particles incident on one end of the first channel substrate move while colliding with the first channel substrate along the direction of the gradient electric field. A secondary electron multiplier tube, which is adapted to obtain a secondary electron flow that is multiplied from the other end of the channel substrate, wherein the first channel substrate faces the second channel substrate. The surface of the second channel substrate is resistive and the surface of the second channel substrate facing the first channel substrate is resistive, and the second channel substrate has a secondary electron emission coefficient. Electronic release The first and second channel substrates are arranged such that their one ends and their other ends are aligned with each other, while the first channel substrate and the second channel substrate are arranged such that their respective ends are aligned with each other. One end and the other end of the first channel base are respectively provided with gradient electric field forming electrodes extending between the first channel base and the second channel base, and one end and the other end of the first channel base are provided. A high voltage is applied between the gradient electric field forming electrode and the gradient electric field forming electrode at one end of the second channel substrate and the other end to form the gradient electric field.

[Function] In the vicinity of the other end of the first channel substrate, since the multiplied secondary electron flow is output, the electron density is high, the electrons collide with the residual gas, and the residual gas has a charge opposite to that of the secondary electrons. Are ionized into ions having. The ions travel into the channel between the first and second channel substrates and strike the second channel substrate. But the second
Since the surface of the channel substrate of the first channel substrate facing the first channel substrate is made of a material having resistance and is subjected to a surface treatment to reduce the secondary electron emission rate, the secondary channel substrate is also affected by the collision of the ions. There is no emission of electrons and ion feedback is suppressed.

Then, the first channel base body and the second channel base body continuously resistance-divide the high voltage in the axial direction. By this resistance division, the first channel base and the second channel base
An equipotential surface is formed that connects equal potentials generated in the channel substrate. Therefore, when the first channel base and the second channel base are axially shifted, or when the gradient electric field forming electrode that is inserted between the first channel base and the second channel base is formed. , The equipotential surface formed between the first channel substrate and the second channel substrate is inclined. The tilted electric field is formed by the tilt of the equipotential surface.

[Advantages of the Invention] According to the inventions of claim 1 and claim 2,
The surface of the channel substrate of the first channel substrate facing the first channel substrate is made of a material having resistance, and the surface treatment for reducing the secondary electron emission rate is performed, so that the output end having a high electron density is provided. Even if the ions generated by the electrons colliding with the residual gas collide with the second channel substrate, secondary electrons are not emitted, and the generation of ion feedback is suppressed,
Stable operation can be obtained even in a low vacuum, noise generation due to ion feedback can be suppressed, and a large output current can be obtained without a gain suppression effect due to space charge.

According to the first aspect of the present invention, it is possible to generate the gradient electric field with a simple configuration without using a special power source, only by arranging the first channel base body and the second channel base body in a shifted manner. You can

Further, according to the second aspect of the present invention, the gradient electric field can be easily generated without using a special power source simply by forming the electrodes for forming the gradient electrodes on the first channel substrate and the second channel substrate. Can occur.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

The structure of one embodiment of the secondary electron multiplier according to the present invention is first described.
Shown in the figure.

The secondary electron multiplier 30 has a flat plate-shaped first channel base body 31 for secondary electron multiplication and a flat plate-shaped second channel base body 32 for generating a gradient electric field which is arranged so as to face it.
Consists of The second channel base 32 is arranged so as to be shifted from one end 31a of the first channel base 31 toward the other end 31b of the first channel base 31.

The first channel substrate 31 has resistance and a large secondary electron emission coefficient, for example, ZnO-Ti.
It is made of O ₂ -based ceramic material.

The second channel base 32 is also made of the same material as the first channel base 31. However, the surface 32c of the second channel substrate 32, which faces the first channel substrate 31, is intentionally roughened by, for example, the impact of argon ions, so that the surface treatment for reducing the secondary electron emission rate is performed. There is.

A collector 33 is arranged to collect the multiplied secondary electrons that jump out from between the other end 31b of the first channel substrate 31 and the other end 32b of the second channel substrate 32.

Between the electrode 34a formed on one end 31a of the first channel base 31 and the electrode 34b formed on the other end 31b, the electrode 35a formed on one end 32a of the second channel base 32 and the other end formed From the high voltage DC power supply 36,
DC high voltage is applied. Further, the collector 33, the electrode 34b at the other end 31b of the first channel base 31, and the second electrode
A DC voltage is applied from a DC power supply 37 between the other end 32b of the channel base 32 and the electrode 35b.

With such a configuration, the first channel base 31 and the second channel base 32 are arranged so as to be shifted from each other as described above, and therefore, as shown by the dotted line in FIG. An equipotential surface is formed between the first channel substrate 31 and the second channel substrate 32, and therefore, a gradient electric field is formed perpendicularly to this equipotential surface. At this time, a special power source for forming such a gradient electric field is unnecessary. The primary electrons 13 are incident from one end side of the channel 39 between the first channel base body 31 and the second channel base body 32, in which such a gradient electric field is formed, into the first channel base body 31.
When secondary electrons are generated by colliding with 31, in the gradient electric field, the secondary electrons make a motion close to a cycloidal motion and repeatedly collide with the secondary electron multiplication surface 38 of the first channel substrate 31, The multiplication of the secondary electrons is performed, and the secondary electron flow is extracted from the collector 33.

By the way, in the vicinity of the other end 31b of the first channel substrate 31, since the multiplied secondary electron flow is output, the electron density is high, the electrons collide with the residual gas, and the residual gas is opposite to the secondary electrons. It is ionized into a charged ion M ⁺ . Therefore, as shown in FIG. 2, the ions M ⁺ are channeled between the first channel substrate 31 and the second channel substrate 32.
It goes into 39 and collides with the second channel substrate 32. However, the second channel substrate 32 has a surface 32C facing the first channel substrate 31 made of a material having resistance,
In addition, since the surface treatment is performed to reduce the secondary electron emission rate, secondary electrons are not emitted even by the collision of the ions M ⁺ , and ion feedback is suppressed. As a result, stable operation can be obtained even in a low vacuum, generation of noise due to ion feedback can be suppressed, and a large output current can be obtained without the effect of suppressing gain due to space charge.

 Next, another embodiment of the present invention is shown in FIG.

The secondary electron multiplier 40 shown in FIG. 3 is similar to the secondary electron multiplier 30 shown in FIG. 1 except that the first channel substrate 31 and the second channel substrate 32 are connected to each other at their one ends 31a, 32a. And the other ends 31b and 32b thereof are arranged so that they are aligned with each other, while the electrode 35a at the one end 32a of the second channel base 32 of the secondary electron multiplier 30 and the first channel base of FIG. Instead of the other end 34b of 31, the first channel base 3
The gradient electric field forming electrodes 42 and 43 extending between the first and second channel substrates 32 are provided respectively. In FIG. 3, the parts corresponding to those in FIG. 1 are designated by the corresponding reference numerals, and the duplicated description will be omitted.

Between the electrode 34a at one end 31a of the first channel substrate 31 and the gradient electric field forming electrode 43 at the other end 31b, the gradient electric field forming electrode 42 at the one end 32a of the second channel substrate 32 and the other end 3 are formed.
A high voltage is applied from the DC high voltage power supply 36 between the electrode 2b and the electrode 35b.

40 is a secondary electron multiplier having a structure as shown in FIG.
The first channel base 31 and the second channel base 32
The electric field in the channel 39 between the
42 and 43 form equipotential portions on the input end side of the channel 39 on one end side of the second channel base 32 and on the output side of the channel 39 on the other end side of the first channel base 31. To do. Therefore, in the channel 39, a gradient electric field is formed by an equipotential surface similar to that of the secondary electron multiplier 30 of FIG. 1 as indicated by a dotted line in FIG. At this time, a special power source for forming such a gradient electric field is unnecessary. In the secondary electron multiplier 40 of FIG. 3 as well, the surface 32C of the second channel substrate 32 facing the first channel substrate 31 is subjected to the surface treatment for reducing the secondary electron emission rate. Even when the ions collide with each other, secondary electrons are not emitted, and ion feedback is suppressed.

In the above embodiments, the first channel substrate
The 31 and the second channel substrate 32 may be made of a flat glass plate, and a secondary electron emitting surface made of a secondary electron emitting substance may be formed on the surface thereof.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the structure of one embodiment of a secondary electron multiplier according to the present invention, FIG. 2 is an explanatory view of suppression of ion feedback in the secondary electron multiplier of FIG. 1, and FIG. The drawings are explanatory views showing the structure of another embodiment of the secondary electron multiplier according to the present invention, and FIGS. 4, 5, and 6 are the explanatory views showing the structure of the conventional secondary electron multiplier. It is a figure. 30 …… Secondary electron multiplier, 31 …… First channel substrate, 32
...... Second channel substrate, 34a, 34b, 35a, 35b …… Electrode, 3
6 …… DC high voltage power supply, 38 …… Secondary electron multiplier, 39 …… Channel, 40 …… Secondary electron multiplier, 42, 43 …… Gradient electric field forming electrode.

Claims (2)

[Claims] 1. A channel is formed between a flat plate-shaped first channel substrate for secondary electron multiplication and a second channel substrate for generating a gradient electric field, which is arranged to face the flat plate-shaped first channel substrate. In the process in which secondary electrons generated by collision of charged particles incident on one end of the first channel substrate move while colliding with the first channel substrate along the direction of the gradient electric field, they are sequentially multiplied by an avalanche. A secondary electron multiplier tube adapted to obtain a multiplied secondary electron flow from the other end of the channel substrate, wherein the first channel substrate has a surface facing the second channel substrate having resistance. And having a large secondary electron emission coefficient, the second channel substrate is made of a material whose surface facing the first channel substrate has resistance, and has a small secondary electron emission rate. Table The surface treatment is performed, and the second channel substrate is arranged so as to be shifted toward one end of the first channel substrate toward the other end of the first channel substrate. A secondary electron multiplier, wherein a high voltage is applied between one end and the other end of the substrate and between one end and the other end of the second channel substrate to form the gradient electric field. 2. A channel is formed between a flat plate-shaped first channel substrate for secondary electron multiplication and a second channel substrate for generating a gradient electric field which is arranged so as to face the flat plate-shaped first channel substrate. In the process in which secondary electrons generated by collision of charged particles incident on one end of the first channel substrate move while colliding with the first channel substrate along the direction of the gradient electric field, they are sequentially multiplied by an avalanche. A secondary electron multiplier tube adapted to obtain a multiplied secondary electron flow from the other end of the channel substrate, wherein the first channel substrate has a surface facing the second channel substrate having resistance. And having a large secondary electron emission coefficient, the second channel substrate is made of a material whose surface facing the first channel substrate has resistance, and has a small secondary electron emission rate. Table The surface treatment is performed, and the first channel base body and the second channel base body are arranged such that one ends of the first channel base body and the other end of the second channel base body are aligned with each other, while one end of the second channel base body and the second channel base body are arranged. The other end of the first channel substrate is provided with a gradient electric field forming electrode extending between the first channel substrate and the second channel substrate, respectively.
A high voltage is applied between the gradient electric field forming electrode at one end and the other end of the first channel substrate and between the gradient electric field forming electrode at the one end of the second channel substrate and the other end, and the gradient is obtained. A secondary electron multiplier having an electric field formed therein.