JPH088085B2 - Radial secondary electron multiplier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radial secondary electron multiplier tube in which multiplication is performed in the process of secondary electrons moving radially outward from the center of a circle. .

[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. There is a continuous dynode secondary electron multiplier called a continuous channel type secondary electron multiplier.

As a continuous dynode secondary electron multiplier, one having a parallel plate shape or a pipe shape and a structure including a channel substrate having a high resistance secondary electron emission surface on the inner surface is generally well known from the past. In order to increase the magnification and output current, a radial secondary electron multiplier tube has been proposed in which multiplication is performed in the process of secondary electrons moving radially outward from the center of the circle. .

For example, U.S. Pat. No. 3,436,590 proposes a radial secondary electron multiplier 1 having a structure as shown in FIGS. 4 and 5.

The radial secondary electron multiplier 1 is composed of two discs 2 and 3. And, on one of the discs 2, one of its main surfaces,
The grooves 4 are continuously formed concentrically. Each groove 4 has a substantially arcuate cross-section so that the curvature gradually increases as the distance from the center of the one disk 2 increases.
On the inner surface of each groove 4, except for the outermost groove 4a, a secondary electron emission layer 5 made of a material having a high secondary electron emissivity is formed. A collector electrode 6 is formed in the outermost groove 4a.

The other disk 3 is provided with a recess 7 on the main surface thereof opposite to the main surface of the one disk 2, and in this recess 7 as well, a half-cycle position is formed for each groove 4. The grooves 8 are formed so as to be displaced from each other, and the secondary electron emission layer 9 made of a substance having a high secondary electron emissivity is formed on each inner surface thereof.

The two discs 2 and 3 are superposed from the surface where the grooves 4 and 8 are formed and fixed integrally with each other. One of the terminal 11 and the collector electrode 6 provided at the center of one disc 2 A DC high voltage power supply 13 applies a DC high voltage to the high voltage terminal 12 connected to the secondary electron emission layer 5 in the inner groove 4. Further, between the terminal 14 provided in the center of the other disk 3 and the high voltage terminal 15 connected to the secondary electron emission layer 9 in the outermost groove 8, a DC high voltage power source 16 supplies a DC high voltage. Is applied.
As a result, an accelerating electric field is formed from the center of each disk 2, 3 to the outside. A DC voltage is also applied from the DC power supply 18 between the high voltage terminal 15 and the collector terminal 17 connected to the collector electrode 6.

When charged particles enter through the entrance 19 provided at the center of the one disc 2 and collide with the secondary electron emission layer 9 of the disc 3, secondary electrons fly out from the secondary electron emission layer 9, The secondary electrons that have jumped out are secondary electron emission layers 5 in the grooves 4 and 8 of the disks 2 and 3 one after another due to the electric force acting from the accelerating electric field.
While colliding with 9, it is multiplied by an avalanche and taken out from the collector electrode 6 as a secondary electron flow.

[Problems to be Solved by the Invention] By the way, in the radiation type secondary electron multiplier 1, as the distance from each center of the two disks 2 and 3 increases, the curvature increases as described above. There is a problem in that it is difficult to form the grooves 4 and 8 having a special shape having such a cross-section and to accurately form the secondary electron multiplication layers 5 and 9 thereon. Therefore, this type of radiative secondary electron multiplier is
So far, it has not been put to practical use.

It is an object of the present invention to provide a radial secondary electron multiplier tube which has a simple structure, is easy to manufacture, has a high multiplication efficiency, and can obtain a large output current, and has stable operation.

[Means for Solving the Problems] Therefore, according to the invention of claim 1, the disk-shaped first channel base body for secondary electron multiplication and the first channel base body are coaxially arranged so as to face the first channel base body. A second channel substrate for generating a gradient electric field, the second channel substrate being disposed between the first channel substrate and the second channel substrate.
The input end is between the entrance edge of the charged particle provided at the center of the channel base body and the first channel base body facing it, and the peripheral edge of the first channel base body and the peripheral edge of the second channel base body. A radial channel for multiplying secondary electrons having an output terminal between them is provided, and secondary electrons generated by collision of charged particles entering from the entrance with the first channel substrate are generated in the gradient electric field. In the process of moving toward the output end while colliding with the first channel substrate along the direction, the secondary electron flow is sequentially multiplied by the avalanche type to obtain the multiplied secondary electron flow from the output end of the channel. In the secondary electron multiplier, the first channel substrate is made of a material having a large secondary electron emissivity while the surface facing the second channel substrate has resistance, and the second channel substrate has the second channel substrate. The channel substrate is made of a material having a resistance surface facing the first channel substrate, and has a center electrode provided at the center of the first channel substrate and an outer periphery extending from the outer peripheral surface into the channel. A high DC voltage is applied between the electrode and between the inner electrode on the inner surface of the entrance provided on the inner surface of the second entrance of the second channel substrate and the outer electrode on the outer surface to form the gradient electric field in the channel. It is characterized by being formed.

Another aspect of the invention according to claim 2 is that the surface of the second channel substrate facing the first channel substrate is surface-treated to reduce the secondary electron emission coefficient. .

According to a third aspect of the present invention, a disk-shaped first channel base body for secondary electron multiplication and a second gradient electric field generation coaxially arranged facing the first channel base body are provided.
And a channel base of the first channel base and a second channel base provided between the first and second channel bases at the center of the second channel base and the first channel facing the periphery of the entrance for charged particles. A radial channel for secondary electron multiplication is provided, which has an input end between it and the substrate and an output end between the peripheral edge of the first channel substrate and the peripheral edge of the second channel substrate. Secondary electrons generated by collision of charged particles entering from the mouth with the first channel substrate collide with the first channel substrate along the direction of the gradient electric field and sequentially move toward the output end in the process of avalanche. A secondary electron multiplier tube, which is multiplied by a formula to obtain a multiplied secondary electron flow from the output end of the channel, wherein the first channel substrate is the second channel substrate. Of the second channel substrate is made of a material having a resistance and a large secondary electron emissivity, and a surface of the second channel substrate facing the first channel substrate is made of a material having resistance. The distance from the first channel base becomes smaller from the input end to the output end, and the distance between the center electrode provided at the center of the first channel base and the outer peripheral electrode provided on the outer peripheral surface and Two
A high direct current voltage is applied between the inner electrode of the entrance opening provided on the inner surface of the entrance opening of the channel substrate and the outer peripheral electrode provided on the outer peripheral surface of the channel substrate to form the gradient electric field in the channel. I am trying.

Another aspect of the invention according to claim 4 is that the surface of the second channel substrate facing the first channel substrate is surface-treated to reduce the secondary electron emission coefficient. .

[Operation] The resistive material of the first channel substrate and the second channel substrate continuously resistance-divides the high voltage in the radial direction of the first channel substrate and the second channel substrate.

Therefore, when a part of the outer peripheral electrode is extended to the peripheral edge of the surface of the first channel substrate facing the second channel substrate, on the surface of the first channel substrate facing the second channel substrate. , The center has the lowest potential, and the extended end of the outer peripheral electrode has the highest potential. On the other hand, in the first channel substrate, the inner surface of the entrance has the lowest potential and the outer surface has the highest potential. Therefore, the position of the first channel substrate having a potential equal to that of each part of the second channel substrate is shifted to the center side thereof. As a result, the equipotential surface in the channel tilts from the vertical position toward the first channel substrate side, and the electric field perpendicular to this equipotential surface also tilts toward the first channel substrate side to generate a tilted electric field.

When the distance between the second channel substrate and the first channel substrate decreases from the input end to the output end, and the second channel substrate is inclined with respect to the first channel substrate, this inclination Correspondingly, the equipotential surface in the channel connecting the same electric potentials of the first channel substrate and the second channel substrate also inclines toward the first channel substrate side. As a result, similarly, a tilted electric field tilted toward the first channel substrate side is generated.

When the surface of the second channel substrate facing the first channel substrate is subjected to a surface treatment for reducing the secondary electron emission coefficient, ions return from the output end into the channel, Even if it collides with the channel substrate, the generation of secondary electrons due to the collision is suppressed.

EFFECT OF THE INVENTION According to the invention of claim 1, a part of the outer peripheral electrode is extended to the periphery of the surface of the first channel substrate facing the second channel substrate, and Since the center has the lowest potential and the extended end of the outer peripheral electrode has the highest potential on the surface facing the second channel substrate, the first electrode having a potential equal to the potential of each part of the second channel substrate is formed.
The position of the channel substrate is shifted to the center side thereof, and a gradient electric field necessary for accelerating and multiplying secondary electrons generated by charged particles incident from the entrance of the second channel substrate is formed. As a result, the multiplication surface of the secondary electrons is circular and has a large area, the multiplication efficiency is high, and a large output current can be obtained, and a special power source for forming the gradient electric field is not required.

According to the invention of claim 3, the distance between the second channel base body and the first channel base body becomes smaller from the input end to the output end, and the second channel base body is closer to the first channel base body. Because it is inclined
Corresponding to this inclination, the equipotential surface in the channel connecting the same electric potentials of the first channel substrate and the second channel substrate also inclines toward the first channel substrate side, so that from the entrance of the second channel substrate. The gradient electric field required to accelerate and multiply the secondary electrons generated by the incident charged particles is formed, and the multiplication surface of the secondary electrons is circular and has a large area, resulting in high multiplication efficiency and high output current. It can be obtained, and no special power source for forming the gradient electric field is required.

According to the first and third aspects of the present invention, the entrance of charged particles can be provided in the central portion of the second channel substrate. Therefore, the opening area of the entrance can be increased to make the entrance particles effective. Can be detected.

According to the second and fourth aspects of the present invention, by making the surface of the second channel substrate facing the first channel substrate a surface having a property of suppressing the emission of secondary electrons with respect to the ions, from the output end side. The feedback of the ions can be suppressed, and a radial secondary electron multiplier with stable operation can be obtained.

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

The longitudinal section and the plane of the radial secondary electron multiplier according to the present invention are shown in FIGS. 1 and 2, respectively.

The radial secondary electron multiplier 21 has a disk-shaped first channel substrate 22 for secondary electron multiplication, a second channel substrate 23 for generating a gradient electric field, and these first channel substrates.
22 and an annular collector 24 arranged on the outer periphery of the second channel substrate 23.

The first channel substrate 22 is made of a substance having a large secondary electron emissivity, for example, ZnO—TiO ₂ -based ceramic semiconductor. The second channel substrate 23 is also made of the same ceramic semiconductor as the first channel substrate 22.

The first channel substrate 22 and the second channel substrate
23 are arranged coaxially and in parallel with each other, and a secondary electron multiplication channel 25 is formed between the first channel substrate 22 and the second channel substrate 23. This channel
The first channel substrate 22 has an input end between the first channel substrate 22 and the periphery of the charged particle entrance 26 provided at the center of the second channel substrate 23 and the first channel substrate 22 facing the inlet. It has as an output end between the peripheral edge and the peripheral edge of the second channel substrate 23.

The first channel substrate 22 has a center electrode 27 at the center thereof, and also has an outer peripheral electrode 28 extending from the outer peripheral surface into the channel 25. Further, the second channel substrate 23 has an entrance 26 through which charged particles are incident at the center thereof, and an inner surface electrode 29 of the entrance is provided on the inner surface of the entrance 26.
However, outer peripheral electrodes 31 are formed on the outer peripheral surfaces, respectively.

First channel base of the second channel base 23
The surface opposite to 22 is subjected to a surface treatment such as intentionally roughening by irradiating an argon ion beam to reduce the secondary electron emission coefficient. This is because the secondary electrons collide with the residual gas at the output end side of the channel 25 where the electron density is high due to the multiplication of the secondary electrons, and the residual gas has an opposite charge to the electrons. This is an effective means for preventing so-called ion feedback in which the ions return to the inside of the channel 25 and collide with the channel substrate to generate secondary electrons.

Center electrode 27 and outer peripheral electrode of the first channel substrate 22
A direct current high voltage is applied from a direct current high voltage power supply 32 to the signal line 28. In addition, the entrance 26 of the second channel substrate 23
A high DC voltage is applied from another DC high voltage power supply 33 between the inner surface electrode 29 and the outer peripheral electrode 31.

A channel 25 is provided between the collector 24 arranged on the outer periphery of the first channel base 22 and the second channel base 23 and the outer peripheral electrode 28 of the first channel base 22.
A DC power supply 34 for applying a voltage for trapping secondary electrons output from the output end of the collector 24 to the collector 24 is connected.

With such a configuration, the materials having resistance of the first channel base 22 and the second channel base 23 are
The direct current high voltage is continuously resistance-divided in the radial direction of the first channel base 22 and the second channel base 23.

Therefore, when a part of the outer peripheral electrode 28 extends into the channel 25 from the peripheral edge of the surface of the first channel substrate 22 facing the second channel substrate 23, the first channel substrate
On the surface of 22 facing the second channel substrate 23, the center has the lowest potential and the extended end of the outer peripheral electrode 28 has the highest potential. On the other hand, in the second channel substrate 23, the inner surface of the entrance 26 has the lowest potential and the outer surface has the highest potential. Therefore, the position of the first channel substrate 22 having a potential equal to that of each part of the second channel substrate 23 shifts to the center side thereof, and the equipotential surface in the channel 25 becomes
As shown by the dotted line in FIG. 1, it is inclined. As a result, a gradient electric field necessary for accelerating and multiplying secondary electrons generated by charged particles incident from the entrance 26 of the second channel substrate 23 is formed without using a special power source. As a result, the multiplication surface of the secondary electron is changed to the first channel substrate 22.
As a whole, the multiplication surface becomes large, the multiplication efficiency becomes high, and a large output current can be obtained.

Next, FIG. 3 shows a longitudinal section of another embodiment of the radial secondary electron multiplier according to the present invention.

The radial secondary electron multiplier 41 is the same as the radial secondary electron multiplier 21 described in FIGS. 1 and 2 except that the distance between the first channel substrate 22 and the second channel substrate 23 is the above. It is designed such that it becomes smaller from the input end to the output end, and the parts corresponding to those in FIG.

In the radial secondary electron multiplier 41 of FIG. 3, the second channel base body 23 'is inclined with respect to the first channel base body 22, and therefore the first channel base body 22 is corresponding to this inclination. The equipotential surface in the channel substrate 25 'connecting the same potentials of the second channel substrate 23' and the second channel substrate 23 'also inclines toward the first channel substrate 22 side as shown by the dotted line in FIG. As a result, the gradient electric field necessary for accelerating and multiplying the secondary electrons generated by the charged particles incident from the entrance of the second channel substrate 23 'is formed without using a special power source. In this case, since the distance between the central portions of the first channel base 22 and the second channel base 23 'is large, the secondary electrons generated between them are effectively multiplied.

In the embodiment shown in FIG. 3, although not specifically shown, a small hole is provided in the collector 24, and the laser beam is emitted from the small hole to the first channel substrate 22 and the second channel substrate.
While introducing into the channel 25 'between the 23' and the entrance
By introducing various molecules and atoms in place of electrons from 26 and causing various reactions in the vicinity of the input end of the channel 25 ', the generated electrons or ions are introduced into the channel and these molecules and atoms are introduced. Can be effectively detected.

In this case, a hole is made in the center of the first channel substrate 22 so that unreacted particles escape to the outside of the multiplier tube.

In the above embodiments, the first channel substrate
It is not necessary that the outer diameter of 22 and the outer diameter of the second channel substrates 23, 23 'be equal. If necessary, the outer peripheral electrodes 2 of the first channel substrate 22 and the second channel substrates 23, 23 '
The area of 8,31 parts can be set, the area of the secondary electron multiplication part can be adjusted, and the shape and size can be determined.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a radial secondary electron multiplier according to the present invention, FIG. 2 is a plan view of the radial secondary electron multiplier of FIG. 1, and FIG. A longitudinal sectional view of another embodiment of such a radial secondary electron multiplier, FIG. 4 is a partially cutaway plan view of a conventional radial secondary electron multiplier, and FIG. 5 is IV-IV of FIG. It is sectional drawing which follows the line. 21 …… Secondary electron multiplier, 22 …… First channel substrate, 2
3,23 '…… Second channel substrate, 24 …… Collector, 25,2
5 '... Channel, 26 ... Inlet, 27 ... Center electrode, 28 ...
… Peripheral electrode, 29 …… Inner entrance inner surface electrode, 31 …… Outer peripheral electrode, 32,
33 …… DC high voltage power supply, 34 …… DC power supply, 41 …… Radial secondary electron multiplier.

Claims (4)

[Claims] 1. A disk-shaped first channel substrate for secondary electron multiplication, and a second channel substrate for coaxially facing the first channel substrate for generating a gradient electric field. And a first channel substrate facing each other and a charged particle entrance opening provided in the central portion of the second channel substrate between the first channel substrate and the second channel substrate. And a radial channel for secondary electron multiplication having an input end between them and an output end between the peripheral edge of the first channel substrate and the peripheral edge of the second channel substrate. Secondary electrons generated by the charged particles colliding with the first channel substrate move toward the output end while colliding with the first channel substrate along the direction of the gradient electric field, and sequentially increase in an avalanche manner. Doubled A secondary electron multiplying tube adapted to obtain a multiplied secondary electron flow from the output end, wherein the first channel substrate has a resistance surface on a surface facing the second channel substrate. In addition, the second channel base body is made of a material having a resistance at the surface facing the first channel base body, and is provided at the center of the first channel base body. Between the center electrode and the outer peripheral electrode extending from the outer peripheral surface into the channel, and between the inner surface electrode of the second channel substrate on the inner surface of the incident opening and the outer peripheral electrode provided on the outer peripheral surface. A radial secondary electron multiplier is characterized in that a high DC voltage is applied between the two and the gradient electric field is formed in the channel. 2. The surface of the second channel substrate facing the first channel substrate is surface-treated to reduce the secondary electron emission coefficient.
Radial secondary electron multiplier described. 3. A disk-shaped first channel base body for secondary electron multiplication, and a second channel base body coaxially arranged facing the first channel base body for generating a gradient electric field. And a first channel substrate facing each other and a charged particle entrance opening provided in the central portion of the second channel substrate between the first channel substrate and the second channel substrate. And a radial channel for secondary electron multiplication having an input end between them and an output end between the peripheral edge of the first channel substrate and the peripheral edge of the second channel substrate. Secondary electrons generated by the charged particles colliding with the first channel substrate move toward the output end while colliding with the first channel substrate along the direction of the gradient electric field, and sequentially increase in an avalanche manner. Doubled A secondary electron multiplier tube adapted to obtain a multiplied secondary electron flow from the output end of the channel, wherein the first channel substrate has a resistance surface at a surface facing the second channel substrate. And having a large secondary electron emissivity, the second channel substrate is made of a material whose surface facing the first channel substrate has resistance, and the second channel substrate has the first channel substrate. Becomes smaller from the input end to the output end, and the distance between the center electrode provided at the center of the first channel base body and the outer peripheral electrode provided on the outer peripheral surface and the incidence on the second channel base body. Radial secondary characterized in that a high direct current voltage is applied between the entrance inner surface electrode provided on the inner surface of the mouth and the outer peripheral electrode provided on the outer surface to form the gradient electric field in the channel. Child photomultiplier tube. 4. The surface of the second channel substrate facing the first channel substrate is surface-treated to reduce the secondary electron emission coefficient.
Radial secondary electron multiplier described.