JPS6030063B2 - photomultiplier tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photomultiplier tube that multiplies photoelectrons generated by photoelectrically converting weak incident light on a photocathode using a secondary electron multiplier.

Photomultiplier tubes are widely used by being incorporated into spectrometers, radiation detectors, and the like.

Photomultiplier tubes are extremely large compared to other electrical components that have been miniaturized in recent years.

If photomultiplier tubes can be made smaller, especially if the length of the tube axis in all directions can be shortened, devices using photomultiplier tubes can be made smaller, so it is desirable to make photomultiplier tubes smaller. I have a strong request.

If the photocathode of a photomultiplier tube is made smaller, the photomultiplier tube can be made proportionally smaller, but this does not provide an essential solution. Below, we will first discuss the issue of miniaturization in connection with the configuration of conventional photomultiplier tubes.

FIG. 1 is a longitudinal sectional view of a typical conventional photomultiplier tube.

A typical conventional photomultiplier tube uses a box-and-grid type dynode as shown in FIG.

- A box-and-grid dynode is a shape in which silk M is stretched over one of the dividing surfaces of a quarter cylinder divided into four equal parts by a plane passing through the axis of a bottomed cylinder, as shown in Figure 2. say the dynodes.

The surface covered with silk M is the incident surface, and electrons enter from this surface, and 2
The secondary electron surface collides with the inner surface of the cylindrical side wall to emit secondary electrons. Secondary electrons are emitted from another splitting surface.

That is, a box-and-grid dynode can be said to change the direction of electron flow at right angles. When light L is incident on the photocathode 1, photoelectrons are emitted from the incident point.

These photoelectrons are incident on the box-and-grid first stage dynode 2, which is at a higher potential. Secondary electrons are emitted from the incident point of the first stage dynode 2, and these two
The secondary electrons enter the second stage terminode 3 which is at a higher potential. Similarly, the final stage, . The dynodes collide with each other in sequence up to the dynode 9, and the silk-like anode is collected in the tub.

The electron orbits are shown by arrows. Note that a higher potential is sequentially applied from the photocathode to the dynodes and anodes at each stage. Furthermore, each time the electrons collide with each dynode, the number of electrons is multiplied several times. In a photomultiplier tube, electrons emitted from the photocathode are transferred to the first stage, . all nodes must accept it.

Even if electrons emitted from the photocathode are skillfully concentrated and accepted, it is necessary to provide a correspondingly large incidence closure to the photocathode. In order to maintain a predetermined multiplication factor when the intensity of incident light is high, the current density on the secondary electron surface cannot be increased, so the secondary electron surface cannot be made small.

In addition, when the current density on the secondary electron surface is increased, the secondary electron surface tends to deteriorate. For this reason, the size of one dynode is limited, and the dynode cannot be made small.

In general, the dimension of the dynode in the electron travel direction and the diameter of the dynode are approximately equal. Since such dynodes are arranged in several stages to more than ten stages along the tube axis, the length of the photomultiplier tube inevitably becomes long.

An object of the present invention is to provide a photomultiplier tube whose length in the tube axis direction can be shortened by a new dynode structure and a dynode arrangement structure.

In order to achieve the above object, the photomultiplier tube according to the present invention multiplies photoelectrons emitted from a light haze surface into secondary electrons using a plurality of stages of tertiary nodes, in which the opening □ for accepting photoelectrons is located at the photoelectron The first box-and-grid type is parallel to the plane and the injection closing is perpendicular to the opening.
a stage dynode, and the first stage dynode, . a box-and-grid type second-stage dynode having an entrance opening □ for receiving secondary electrons from the first-stage dynode at an exit entrance of the dynode, and an exit opening □ in a direction perpendicular to the entrance opening □; At the injection close of the second stage dynode, the second stage dynode, . a box-and-grid-shaped third-stage dynode, which is provided with an entrance closure for receiving secondary electrons from the input entrance and has an exit closure in a direction perpendicular to the entrance entrance, and is arranged opposite to the exit surface of the third-stage dynode. A planar one formed by arranging small dynode elements in a plane perpendicular to the flow of electrons emitted from the exit surface of the third stage dynode.
It is configured by providing a rear-stage dynode including the above-mentioned surface dynode, and a collector electrode for collecting electrons multiplied by the latter-stage dynode.

According to the above configuration, the arrangement of the dynodes ends in the space up to the third stage of the subordinate photomultiplier tube, so that the length of the phototube in the tube axis direction can be shortened.

Hereinafter, the present invention will be explained in more detail with reference to the drawings and the like.

FIG. 3 is a longitudinal sectional view of an embodiment of a photomultiplier tube according to the present invention.

A photocathode 12 is formed on the bottom inner wall of one of the cylindrical glass airtight containers 11 .

The photoelectrons emitted by the photocathode 12 are concentrated by a collecting electrode 13 onto a box-and-grid first stage dynode 14 . The second stage dynode 15 is also the first stage dynode 1.
Like 4, it is a box-and-grid type dynode.

The outer cylindrical surface of the semi-cylindrical space formed by the second stage dynode 15 and the third stage dynode 16 is brought close to the glass airtight container 11, and the third stage dynode 1
Sufficient space is secured in the injection opening direction of No. 6.

Parallel to the output surface of the third stage dynode 16 is a first surface dynode 17 of the grating, a second surface dynode 18 of the grating, a third surface dynode 19 of the grating, a fourth surface dynode 20 of the grating, and a collector electrode 23. , and the final plate-shaped surface die/die 24 are arranged in this order.

The lattice surface dynodes 17, 18, 19, and 20 and the plate-shaped surface dynode 24 form a subsequent dynode.

FIG. 4 shows an enlarged view of a part of the lattice surface dynode, the collector electrode, and the final plate-like surface dynode.

The surface dynodes of the lattice have a pitch of 1, as shown in FIG.
It is based on multiple triangular prisms whose cross sections are isosceles triangles arranged parallel to each other in one plane. It is formed by

This isosceles triangle has a base of 0.5 ribs and a height of 0.25 ribs. The apex side sandwiched between two equal sides is the electron incident surface. Silk 21, 22, etc. are provided on the incident surface side of the surface dynode of the grating.

These silks are arranged to form equipotential surfaces perpendicular to the direction of electron incidence. The surface dynodes 17, 18 of the lattice (omitted in FIG. 4).

) and the spacing between adjacent surface dynodes 19 and 20 is 1.08 willow, and the lattice of the previous grid-like dynode (
The lattices of the surface dynode elements of the subsequent lattice are arranged to match the gaps between the triangular prisms. A net-like collector 23 is placed next to the surface dynode 22 of the final lattice.

Next to the net-like collector 23 is the flat final stage dynode 2.
4 is placed.

The surface dynodes 17, 18, 19, 20, the collector 23, and the plate-shaped dynode 24 are each fixed to a frame (not shown), and the frame is fixed to a support (not shown).

The grid surface dynodes 17 to 20, the collector 23, the plate surface dynode 24, and the silk fixed to the dynodes 17, 18, 19, and 2 are all made of stainless steel.

The triangular prisms of the lattice surface dynodes 17 to 20 and the surfaces of the plate surface dynodes 24 with which electrons collide are formed as secondary electron emitting surfaces made of antimony and alkali metals.

The diameter of the photocathode of the photomultiplier tube according to this embodiment is 51 sides, and the length of the tube is 77 sides.

When operating the photomultiplier tube according to the embodiment, the photocathode 12, the first stage dynode 14, and the second stage dynode 1 are
5. Apply increasing voltage to the third stage dynode 16, the final stage dynode, and the collector 23 in this order.

The voltage of the plane dynode of the grid of the final stage dynode becomes higher as the stage becomes later, and the voltage of the plate-shaped plane dynode is made higher than the voltage of the plane terminal of the final grid.

Since the photomultiplier tube according to the present invention is constructed as described above, it is different from the conventional photomultiplier tube (with a photocathode of the same area).
The length in the axial direction of the tube could be shortened by 23 Yanagi (23%) compared to the type of device shown in Figure 1).

Five photomultiplier tubes A, B, C, D and E of the above shape of the present invention are prepared, and their respective multiplication factors, maximum currents (pulse linearity deviation 3%), Co57 radiation are
The energy resolution, which is an index representing the dispersion of the current value obtained from the collector when it is incident on the photocathode through the l scintillator, was measured.

Table 1 below shows the ratio with conventional equivalent products.

The multiplication factor of the equivalent tube is 1.7 x 1 pi, and the maximum current is 5 A.
, the energy resolution is 9.05. This value was obtained by averaging the measured values of 10 equivalent tubes. Table 1 (
(Comparison with conventional equivalent product) [Multiplication factor] [Maximum current] [Energy resolution] A
I. 058 18 0.961B
O. 882 1.6 1
．． 005C O941 1.8
1.039D I. 058 20
1.027E I. 000
1.8 0994 As is clear from Table 1, the photomultiplier tube according to the present invention has characteristics equivalent to or better than those of the conventional equivalent product even if the length of the tube is shortened.

Although the embodiment has been described in detail above, various modifications can be made to this embodiment within the scope of the present invention.

For example, even if the latter stage dynode is configured using a Venetian-type dynode or a microchannel plate, the object of the present invention can be achieved in the same manner as in the embodiments described above.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of a conventional photomultiplier tube. FIG. 2 is a perspective view showing the shape of a box-and-grid dynode. FIG. 3 is a longitudinal sectional view of an embodiment of a photomultiplier tube according to the invention. FIG. 4 is an enlarged perspective view of a part of the lattice surface dynode, the collector electrode, and the final plate-like surface dynode. 11...
... Cylindrical glass airtight container, 12 ... Photocathode, 13 ... Collection east electrode, 14 ... First
Stage dynode, 15... Second stage dynode, 16...
...Third stage dynode, 17-20... Planar dynode of lattice, 21, 22... Network of plane dynodes of lattice, 23... Collector electrode, 24...・
240 plate-shaped surface dynodes, 3 figures, 2 ice figures, 4 figures

Claims (1)

[Scope of Claims] 1. A photomultiplier tube in which photoelectrons emitted from a photocathode are multiplied by secondary electrons using a plurality of stages of dynodes, wherein an aperture for receiving photoelectrons is parallel to the photocathode and an exit aperture is perpendicular to the aperture. The first box-and-grid shape that is the direction
a box-and-grid type second dynode, the exit aperture of the first stage dynode being provided with an entrance aperture for receiving secondary electrons from the first stage dynode, and having an exit opening in a direction perpendicular to the entrance aperture; a box-and-grid type third dynode, the exit aperture of the second stage dynode being provided with an entrance aperture for receiving secondary electrons from the second stage dynode, and having an exit opening in a direction perpendicular to the entrance aperture; a stage dynode, and one or more small dynode elements formed by arranging small dynode elements in a plane facing the exit surface of the third stage dynode and perpendicular to the flow of electrons emitted from the exit surface of the third stage dynode. 1. A photomultiplier tube comprising a rear-stage dynode including a planar dynode, and a collector electrode for collecting electrons multiplied by the rear-stage dynode. 2 One or more surface dynodes of the latter stage dynode are 2
The photomultiplier tube according to claim 1, which is a planar dynode of a lattice that emits secondary electrons. 3. The photomultiplier tube according to claim 2, wherein the one or more plane dynodes are provided in parallel and are formed by a lattice plane dynode. 4. The photomultiplier tube according to claim 3, wherein the second-stage dynode is formed of a plurality of parallel dynodes, a lattice-like surface dynode, and a plate-like surface dynode. 5. The photomultiplier tube according to claim 4, wherein the collector electrode is a net-like electrode inserted between the grid surface dynode and the plate-like surface dynode, which are provided in parallel.