Circuit structure for reducing dark current influence of photomultiplier

Abstract

The utility model relates to the technical field of photoelectricity, in particular to a circuit structure capable of reducing influence of dark current of a photomultiplier, which comprises the photomultiplier and an integrating circuit, and the anode of the photomultiplier is connected with a common terminal of a single-pole double-throw analog switch. One output terminal of the single-pole double-throw analog switch is connected with the input end of the integrating circuit, and the other output terminal of the single-pole double-throw analog switch is grounded; and the single-pole double-throw analog switch is controlled by the photomultiplier. According to the utility model, the structure is simple, the operation is convenient, in practical application, the adjustable resistor R1 is adjusted to offset dark current to the greatest extent, and the dynode of the photomultiplier is utilized to control the single-pole double-throw analog switch, so that the dark current does not flow into the integrating circuit when the anode of the photomultiplier has no pulse output; the contribution rate of the dark current to an integral result is reduced, and the problem that the dark current has a great influence on a measurement result is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to photoelectricity technical field, concretely relates to a circuit structure of reducing the influence of photomultiplier dark current. BACKGROUND

[0002] The photomultiplier also has a tiny current when there is no light, and this current is called dark current. The dark current of the photomultiplier is generally several nA to tens of nA, but when measuring a low dose rate radiation field by using the integral method, the integral value of the pulse current per second is also in the order of nA, and the dark current will have a great influence on the measurement result. CONTENT

[0003] The utility model discloses a circuit structure of reducing the influence of photomultiplier dark current.

[0004] The utility model provides the following technical scheme:

[0005] The utility model discloses a circuit structure of reducing the influence of photomultiplier dark current, including photomultiplier and integral circuit, the anode of photomultiplier is connected one single pole double throw analog switch's public terminal, one output terminal of single pole double throw analog switch is connected the input of integral circuit, and another output terminal of single pole double throw analog switch is grounded, single pole double throw analog switch is controlled by photomultiplier.

[0006] Further, the anode of the photomultiplier is connected to one end of an adjustable resistor R1, and the other end of the adjustable resistor R1 is connected to a positive voltage source.

[0007] Further, the photomultiplier is controlled by the single pole double throw analog switch through the dynode, the blocking capacitor C1, the amplifying circuit and the comparator in sequence.

[0008] Further, a fixed resistor R2 is arranged on the circuit in which the single pole double throw analog switch is grounded.

[0009] Compared with the prior art, the utility model has the advantages of simple structure, convenient operation, and when actually applied, the adjustable resistor R1 is adjusted to offset the dark current to the maximum extent, the single pole double throw analog switch is controlled by the dynode of the photomultiplier, and then the dark current does not flow into the integral circuit when the anode of the photomultiplier has no pulse output, the contribution rate of the dark current to the integral result is reduced, and the problem that the dark current has a great influence on the measurement result is solved. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 The utility model circuit structure block diagram.

[0011] Figure 2For the amplifier circuit structure schematic diagram.

[0012] Figure 3 For the monostable circuit structure schematic diagram.

[0013] Figure 4 For the integrator circuit structure schematic diagram. DETAILED DESCRIPTION

[0014] The utility model will be further described below in combination with the drawings.

[0015] Reference Figures 1-4 .

[0016] In an embodiment of the utility model, a circuit structure for reducing the influence of dark current of a photomultiplier tube, comprising a photomultiplier tube and an integrator circuit, the anode of the photomultiplier tube is connected to the common terminal of a single-pole double-throw analog switch, one output terminal of the single-pole double-throw analog switch is connected to the input end of the integrator circuit, and the other output terminal of the single-pole double-throw analog switch is grounded; the single-pole double-throw analog switch is controlled by the photomultiplier tube; in actual application, when the anode of the photomultiplier tube has pulse output, the anode of the photomultiplier tube is connected to the input end of the integrator circuit (C is connected to S1); when the anode of the photomultiplier tube has no pulse output, the connection between the photomultiplier tube and the integrator circuit is disconnected, and the anode of the photomultiplier tube is grounded (C is connected to S2); the dark current of the anode of the photomultiplier tube does not flow into the integrator circuit when the anode of the photomultiplier tube has no pulse output, and the contribution rate of the dark current to the integration result is reduced.

[0017] In an embodiment of the utility model, the anode of the photomultiplier tube is connected to one end of an adjustable resistor R1, and the other end of the adjustable resistor R1 is connected to a positive voltage source; when the anode of the photomultiplier tube has pulse output, the dark current also exists, at this time, the dark current is usually negligible compared with the pulse current, but there will be some influence on a small part of pulse current signals with small amplitude, and the dark current is offset to the maximum extent by adjusting the adjustable resistor R1.

[0018] In an embodiment of the utility model, the photomultiplier tube is through the dynode in proper order through the direct current separation capacitor C1, the amplification circuit, the comparator, the monostable circuit control the single pole double throw analog switch, working principle: the pulse signal of the dynode output of the photomultiplier tube is input to the amplification circuit through the direct current separation capacitor C1, and then the pulse output by the amplification circuit is input to the comparator, after triggering the threshold value of the comparator, the comparator outputs high level to trigger the monostable circuit to output fixed width square wave signal, to control the single pole double throw analog switch disconnects and the connection (C and S1) of integrating circuit, turns to ground (C and S2), the single pole double throw analog switch is controlled by the dynode of photomultiplier tube, instead of using the anode of photomultiplier tube to control the single pole double throw analog switch, the purpose is not to produce additional shunt to the anode of photomultiplier tube, guarantees the circuit flow of photomultiplier tube to flow into integrating circuit, if the anode of photomultiplier tube controls the single pole double throw analog switch, then the current of the anode of photomultiplier tube will have a part to flow into the circuit for control, thereby causing the current flowing into integrating circuit to be less than the actual current output by the anode of photomultiplier tube, this can make the linearity of instrument to be poor, and the gain of photomultiplier tube is related to the total high voltage of voltage division circuit, and the current taken out from the dynode of photomultiplier tube does not cause the total voltage of voltage division circuit to change, so taking out current from the dynode of photomultiplier tube does not change the gain of photomultiplier tube, and the output current of the anode of photomultiplier tube is not influenced.

[0019] In an embodiment of the utility model, the single pole double throw analog switch ground circuit is further provided with a fixed resistance R2, to ensure that after the anode voltage of photomultiplier tube is disconnected from the integrating circuit, the anode voltage of photomultiplier tube is normal.

[0020] The photomultiplier tube produced by Binsheng is CR125, and the maximum dark current is 10nA, and after the circuit connection structure is improved, the current detected by the actual integrating circuit is about 0.3nA, which further proves that the circuit structure of the utility model reduces the influence of dark current to a negligible degree.

[0021] Working principle: when the anode of the photomultiplier tube has pulse output, the adjustable resistance R1 is adjusted to offset the dark current to the maximum extent, when the anode of the photomultiplier tube has no pulse output, the connection between the photomultiplier tube and the integrating circuit is disconnected, the anode of the photomultiplier tube is grounded, so that the dark current does not flow into the integrating circuit, thereby realizing the contribution rate of reducing dark current to the integration result.

[0022] The embodiments of the present application are given for the purpose of example and description, although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary, and cannot be understood as limiting the present application, and the ordinary skilled in the art can change, modify, replace and transform the above embodiments within the scope of the present application.

Claims

1. A circuit structure for reducing the influence of dark current in a photomultiplier tube, characterized in that: It comprises a photomultiplier and an integrating circuit, the anode of the photomultiplier is connected to the common terminal of a single-pole double-throw analog switch, one output terminal of the single-pole double-throw analog switch is connected to the input of the integrating circuit, and the other output terminal of the single-pole double-throw analog switch is grounded; the single-pole double-throw analog switch is controlled by the photomultiplier.

2. The circuit structure for reducing the influence of dark current of a photomultiplier tube according to claim 1, characterized in that: The anode of the photomultiplier is connected to one end of an adjustable resistor R1, and the other end of the adjustable resistor R1 is connected to a positive voltage source.

3. The circuit structure for reducing the influence of dark current of a photomultiplier tube according to claim 1, characterized in that: The photomultiplier is controlled over the single-pole double-throw analog switch by the dynode, in sequence via a blocking capacitor C1, an amplifying circuit, a comparator and a monostable circuit.

4. The circuit structure for reducing the influence of dark current of a photomultiplier tube according to claim 1, characterized in that: A fixed resistor R2 is further arranged on the circuit in which the single-pole double-throw analog switch is grounded.

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