JPS593825B2 - photomultiplier tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In the present invention, photoelectrons emitted from a photocathode by light irradiation are sequentially collided with a plurality of dynos to which an appropriate positive voltage is applied, thereby multiplying the electrons, and finally multiplying the electrons. This relates to a photomultiplier tube that captures the collected electrons with a collecting electrode.

A bottomed cylinder called a box-and-grid type is divided into four equal parts by two orthogonal planes passing through the axis, a conductive mesh is formed on one of the divided planes to serve as an entrance for primary electrons, and the other side is divided into four equal parts. The dynode electrode of an electron multiplier tube has a dividing surface as a secondary electron exit and an inner wall of a curved surface as a secondary electron surface, as shown in dynode 4. in FIG.
The dynode array can be extended in the tube axis direction of the phototube 1 by setting the exit surfaces of the first stage dynode 4 and the third stage dynode 6 in opposite directions, as in the arrangement of 5.6°7.8 and 9. Because it can be stored efficiently and easily in a cylindrical container.

Therefore, most conventional photomultiplier tubes using box-and-grid type dynodes have used a dynode arrangement as shown in FIG.

In such a dynode arrangement, for example, the secondary electrons emitted from the dynode 5 and incident on the dynode 6 fly in trajectories shown by A, B, and C in FIG.
Since the secondary electrons emitted from the part of the secondary electron surface of the dynode 5 that is close to the dynode 6 enter the dynode T without colliding with the secondary electron surface of the dynode 6, the multiplication factor is significantly reduced. , when trying to detect a single photon, large variations occur in the output current.

This phenomenon similarly occurs with respect to electrons emitted from the dynode 1 and incident on the dynode 8.

On the other hand, the electrons emitted from the dynode 4 will surely collide with the secondary electron surface of the dynode 5 since the secondary electron surfaces of the dynode 4 and dynode 5 are substantially opposed to each other.

Therefore, like dynodes 14, 15, 16, and 1T in FIG. 2 showing the longitudinal cross-sectional structure of other photomultiplier tubes, the secondary electron surfaces of the front and rear dynodes are always opposite to each other, and as a result, every other photomultiplier In some cases, dynode arrays placed in the same direction were used.

However, according to this dynode arrangement, the dynode row extends at 45 degrees to the tube axis, so the airtight container
The number of dynode stages is limited by the single sidewall.

Except for the above-mentioned drawbacks, the present invention always arranges the secondary electron surfaces of the dynodes opposite to the secondary electron surfaces of the preceding and subsequent dynodes, and has four dynode rows arranged in parallel in the same airtight container. Four collection electrodes are installed corresponding to each dynode row, and four input lights can be detected simultaneously.

FIG. 5 is a view of a photomultiplier tube embodying the present invention viewed from the light incident side, where 22 is a side wall of a bottomed cylindrical container 21 having a square cross section, and 23, 2425 and 26 have the same structure. Four focusing electrodes are installed in the container 21 separated from the bottom surface of the substantially transparent bottomed cylindrical container and the photocathode formed on the inner wall of the bottom surface.

FIG. 6 is a longitudinal sectional view of the photomultiplier tube taken along the line A--A in FIG. 5, and 22 is the side wall of the container 21, which is the same part as FIG. 22.

Reference numeral 27 denotes a face plate constituting one bottom surface of the container 21, which is made of transparent glass, and has a photocathode 28 formed on its inner surface.

23 and 24 are focusing electrodes, one half of the bottom side of the container 21.
The container 2 has a cylindrical shape with a bottom at one end and has an open end facing the photocathode 28 together with other focusing electrodes 25 and 26 of the same shape not shown in FIG.
1 in parallel.

A rectangular through hole 29 is provided at the center of the bottom surface of the focusing electrode 23, and the electron incident surfaces of the first stage dynodes 31 of the dynode array 30 face each other.

The dynodes 31, 32, 33, 34, and 36 are the aforementioned box-and-grid type dynodes, and the secondary electron surfaces of each dynode are provided opposite to the secondary electron surfaces of the preceding and subsequent dynodes. , the odd-numbered dynodes and the even-numbered dynodes are installed in the same direction.

Therefore, the dynode array 5 is 45 mm with respect to the axis of the photomultiplier tube.
inclined at an angle and extending parallel to the adjacent side walls of the container.

Therefore, the collecting electrode 31 is provided on the extension of the axis of the adjacent focusing electrode 24 and facing the exit port of the final stage dynode 36 .

Similarly, dynode rows are provided corresponding to the through holes provided in the bottom surfaces of the focusing electrodes 24, 25, and 26, and reach the extensions of the axes of the focusing electrodes 26, 25, and 23, respectively.

As described above, the photomultiplier tube of the present invention consists of four box-and-grid type dynode arrays, and the secondary electron surface of each dynode is arranged so that the secondary electron surface of each dynode faces the secondary electron surface of the preceding and subsequent dynodes. By arranging them in this manner to form a dynode row, and each dynode row extending along the axis of the adjacent focusing electrode, the four dynode rows could be compactly housed as one in an airtight container. As a result, a photomultiplier tube with a high electron multiplication factor and no variation in electron multiplication factor can be obtained, and since the voltage applied to the photocathode, focusing electrode, and dynode can be common to all four dynode rows, it is airtight. This eliminates the need for a large number of lead wires that supply voltage through the walls of the container.

A photomultiplier tube having four dynode arrays is effectively used when simultaneously measuring the intensity of multiple spectra separated by a spectrometer, and is also commonly used as a gamma camera to detect cancer foci. A position detector is conveniently used because it has a large number of photomultiplier tubes arranged on one plane.

In the above-described embodiments, the focusing electrode has a cylindrical shape, but it may be any shape that can be efficiently and axially symmetrically arranged on the rectangular cross section of the airtight container, such as a rectangular cylindrical shape.

Furthermore, in order to efficiently collect electrons at the collecting electrode, one or more dynodes having a shape different from that of the box-and-grid dynode are installed between the final stage dynode and the collector electrode of the box-and-grid dynode array described above. It goes without saying that the present invention is also included in the present invention since the present invention is applied and produces effects even when the device is installed.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional views of a conventional photomultiplier tube. FIGS. 3 and 4 are diagrams showing the orbits of electrons within the dynode shown in FIGS. 1 and 2. FIG. FIG. 5 is a plan view showing the structure of the photomultiplier tube of the present invention;
FIG. 6 is a sectional view taken along the line AA in FIG. 5.

Claims (1)

[Claims] 1 A photocathode is formed on the inner wall of one transparent bottom of a bottomed cylindrical airtight container, and four cylindrical focusing electrodes each having a bottom at one end are placed symmetrically with respect to the axis of the airtight container, with the open end Arranged in parallel facing the photocathode, the bottomed cylinder is divided into four equal parts along the plane passing through the axis, a mesh 7 is formed on one divided surface to serve as an electron entrance, and the other divided surface is used as an electron exit. The desired number of dynodes as ports are sequentially arranged with the exit port and the entrance port facing each other,
and each of the four dynode rows arranged in the same direction every other row at the electron entrance of the first stage dynode,
Opposed to the through hole provided in the center of the bottom surface of the focusing electrode, making an angle of 45 degrees to the axis of the focusing electrode, and extending substantially parallel to the wall of the airtight container in the same rotational direction with respect to the axis of the airtight container. A photomultiplier tube characterized in that an electron focusing electrode is provided opposite to the electron exit aperture of the final stage dynode of each of the dynode rows.