JPS6348143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When pulsed light with an extremely sharp rise is incident on a photomultiplier tube, a pulsating component occurs in the detected output signal, making it impossible to observe the accurate waveform of the incident light. This pulsating component is caused by the fact that the stray capacitance between the anode and the final stage dynode facing it and the inductance of their lead wires form a parallel resonant circuit, and this resonant circuit is activated by the electron flow incident on the anode. Occur. Therefore, the present invention attempts to reduce the above-mentioned pulsating component by reducing the inductance in the above-mentioned resonant circuit.

FIG. 1 is a longitudinal sectional view of a part of an embodiment of the present invention, and FIG. 2 is an enlarged view of the A-A cross section thereof, with one end 2 of a cylindrical glass vacuum-tight container 1 being an incident window for light rays L. A stem 7 having lead wires 3, 4, 5, 6, etc. sealed is provided at the other end. This airtight container 1
Two rectangular plate-shaped porcelain electrode holding plates 8, 8 are provided inside, and a lattice-shaped anode 9, a U-shaped final stage dynode 10, and each stage dynode 11, 12 curved in an approximately arc shape are provided. etc. are installed. Each of these electrodes has support wires spot-welded on the back and inserted into holes in the holding plates 8, 8, and the lead wires 3, 4, 5 are connected to the anode 9, respectively.
It is connected to the support wires of the final stage dynode 10 and the preceding stage dynode 11. In such a photomultiplier tube, a conductor plate 14 is attached to the back surface of the final stage dynode 10 via a heat-resistant insulating foil 13 such as mica, and the support wire 15 of the conductor plate is connected to the lead wire 5 of the adjacent dynode 11. A capacitor is connected between the dynodes 10 and 11 by connecting to
C ₁ is formed.

FIG. 3 is a diagram showing an example of the electrical configuration and the circuit used in the above embodiment, in which the dynode is used as a direct electrode between the final stage dynode 10 facing the anode 9 and another dynode 11 adjacent thereto. Alternatively, the capacitor _C1 is formed by electrodes connected by lead wires that are sufficiently short compared to the lead wires 4, 5, etc. Therefore, this capacitor is connected to the lead wires 4 and 5 inside the vacuum-tight container 1.
The base end of this lead wire is connected to a potentiometer P to apply an appropriate potential, and is also grounded via large capacity capacitors C ₂ and C ₃ . Furthermore, there is a stray capacitance C ₀ between the anode 9 and the final stage dynode 10 opposite thereto.
There is. The anode lead wire 3 is connected to the center conductor of a coaxial cable K, and a load resistor R having a characteristic impedance is connected to the terminal end of the cable, leading to an amplifier.

In the circuit shown in Fig. 3 above, since the capacitors C ₂ and C ₃ are sufficiently large, the inductances of the lead wires 3, 4, and 5 are set as L ₀ , L ₁ , and L _{2 ,} respectively, and the dynode 1
If the power source for the pulsating electron beam current entering the anode 9 from 0 is represented by E, the equivalent circuit shown in FIG. 4 is established. Moreover, if the capacitance of the capacitor C ₁ is made sufficiently large, the inductances L ₁ and L ₂ are equivalent to when they are directly connected in parallel. To give an example, when the inductances L ₀ , L ₁ , and L ₂ are all 23 mH, a capacitor C ₁ of 200 pF is formed. Further, since the parallel circuit of the inductances L ₁ and L ₂ and the inductance L ₀ are connected in series, if this is represented by one inductance L, the equivalent circuit shown in FIG. 5 is obtained. In other words, since an inductance L and a stray capacitance _C0 of, for example, about 5 pF form a parallel resonant circuit with respect to the power supply E, a large resonant current flows through the resistor R, and the output signal includes a pulsating component at the resonant frequency. , this frequency is given by 1/2π√ ₀ . Also, the amplitude increases as Q increases, but
Its Q is given by ωL/R. In this case, the photomultiplier tube of the invention as described above has a capacitor C ₁
Although L ₂ is further connected in parallel to the inductance L ₁ by forming the above-mentioned L ₀ and L ₁ ,
Since L ₂ is the inductance in the lead wires of approximately equal length connected to electrodes in the vicinity of each other, these are approximately equal values as described above.
Therefore, when L ₁ and L ₂ are connected in parallel, the inductance is obviously 0.5L ₀ , but since an inductance L ₀ is also connected in series, the total inductance L is 1.5L ₀ .
On the other hand, in a conventional photomultiplier tube without a capacitor _C1 , the inductance L shown in Fig. 5 is
Since it is formed by a series circuit of _L1 and Lo, its value is clearly 2Lo. Therefore, according to the invention, the inductance of a series resonant circuit as shown in FIG. 5 is reduced from 2L ₀ to 1.5L ₀ , or three quarters. Therefore, the Q of the output circuit is lowered, and vibration of the output signal due to a sudden change in incident light is suppressed, and the frequency of the resonant output can be increased.

Figure 6 shows the frequency characteristic curve of a photomultiplier tube using a lead wire with an inductance of 23 mH as mentioned above. Conventionally, the resonant frequency of the output circuit was 330 MHz as indicated by the broken line p, but when capacitor _C1 By forming it, it was raised to 360MHz. Additionally, as shown in Fig. 7, in the past, the output S produced a vibration component T as shown by the broken line, but with the present invention, the signal no longer has the energy to excite the resonant circuit. , the above-mentioned vibration component can be removed as shown by the solid line.

As described above, in the present invention, by simply forming a simple capacitor at the tip of the lead wire, it is possible to increase the frequency and reduce the amplitude of the pulsating component included in the output when the incident light changes suddenly. That is, since the frequency becomes higher, it is possible to prevent pulsation when the change in the incident light is relatively gradual, and the distortion of the signal waveform is reduced due to the decrease in amplitude, so that an accurate waveform can be observed.

[Brief explanation of drawings]

Fig. 1 is a longitudinal side view of a part of the embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view taken along line A-A in Fig. 1, and Fig. 3 is an example of the electrical configuration and circuit used in the embodiment of Fig. 1. FIGS. 4 and 5 are diagrams showing equivalent circuits of the circuit of FIG. 3, and FIGS. 6 and 7 are diagrams explaining the operation of the present invention. In the figure, 1 is a vacuum-tight container, 2 is a light beam entrance window, 3,
4, 5, 6 are lead wires, 7 is a stem, 8 is an electrode holding plate, 9 is an anode, 10 is a final stage dynode,
11 and 12 are dynodes, 13 is an insulating foil, 14
1 is a conductor plate, and 15 is a support wire.

Claims (1)

[Claims] 1 between the final stage dynode facing the anode and another dynode adjacent to the final stage dynode, connected to each of the dynodes directly or with a lead wire that is sufficiently short compared to the lead wires thereof, and A photomultiplier tube comprising a capacitor sealed in a vacuum-tight container together with an anode, a dynode, etc.