Magnetic field probe for a pulsed magnetic field probe in a radiation environment

Abstract

The application provides a magnetic field probe for a pulse magnetic field detector in a radiation environment, and solves the technical problem that a probe based on a magnetic resistance chip mainly applied to extremely low frequency magnetic field and current signal detection test scenes is easily interfered by power lines and signal lines exposed to the external environment in a radiation environment or a complex environment.The magnetic field probe comprises a magnetic resistance chip, a differential circuit, an amplification and filtering circuit, an electro-optical conversion circuit, an IPEX coaxial cable for connecting the circuit, and a coaxial optical fiber for signal output.The magnetic resistance chip senses an environmental magnetic field signal and outputs two opposite signals, the two opposite signals are sent to the differential circuit to eliminate common mode interference, the differential signal is conditioned through the amplification and filtering circuit, the amplified signal is sent to the electro-optical conversion circuit to be modulated into an optical signal, and the optical signal is output through the coaxial optical fiber, so that the measurement of electromagnetic pulses in a complex environment is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic signal detection, and in particular to a magnetic field probe for a pulsed magnetic field detector in a radiation environment. BACKGROUND

[0002] When a material is irradiated by pulsed x or gamma rays, photoelectrons are formed. When the rays irradiate a metal cavity, the movement of the photoelectrons and the charge rebalancing process of the cavity structure will excite electromagnetic pulses inside the cavity, which are referred to as "internal electromagnetic pulses" in the industry.

[0003] Generally, x or gamma ray accelerators can be used to carry out experimental research on internal electromagnetic pulses. However, due to the presence of photoelectrons and x or gamma rays penetrating into the cavity, the harsh radiation environment formed poses a challenge to the measurement of internal electromagnetic pulses. The traditional method uses a toroidal magnetic field antenna for measurement. However, due to the large volume of the toroidal antenna, it is difficult to avoid the interference caused by ray irradiation and electron deposition, which makes the output waveform superimposed with a large amount of interference, and even submerged in noise. Moreover, the output signal of the toroidal antenna is the differential signal of the measured waveform, which is difficult to process when integrating the signal to restore, and even the true waveform cannot be restored, which makes the relevant test data very scarce.

[0004] Magnetoresistive chips can directly measure external magnetic field signals based on the magnetoresistance effect of magnetic materials, in which the resistivity changes in a magnetic field. Currently, such sensors are mainly used in extremely low frequency magnetic field and current signal detection test scenarios, where the magnetic field signal amplitude of the test environment is large and the external interference is small, and there is no need to consider the design of anti-interference performance. In fact, as an active chip, the power line and signal line exposed to the external environment are easily disturbed if not handled properly. The existing magnetoresistive sensors cannot meet the measurement application in a radiation environment.

[0005] Therefore, based on the unique advantages of magnetoresistive chips, such as small size, high sensitivity and direct measurement, it is of great significance to develop a pulsed magnetic field detector that can be used in a radiation environment through common-mode interference suppression technology and electromagnetic shielding structure design.

[0006] Chinese Patent CN113702878A, entitled "Small-sized active differential magnetic field probe with high common-mode rejection ratio and high sensitivity", and Chinese Patent CN113702878A, entitled "Small-sized active differential magnetic field probe with high common-mode rejection ratio and high sensitivity", the magnetic field sensing units in the two magnetic field probes are two symmetrically placed toroidal antennas, and the output signal is still the differential of the measured magnetic field waveform. Moreover, the signal is transmitted to a receiving device such as a spectrum analyzer through a cable. The technical solutions of the two patents are still not suitable for the measurement of transient pulsed magnetic field signals in a radiation environment. SUMMARY

[0007] The magnetic field probe for the pulse magnetic field detector in a radiation environment aims to solve the technical problem that the probe based on the magnetic resistance chip mainly applied to the detection of extremely low frequency magnetic field and current signal and is easily interfered by the power line and signal line exposed to the external environment in a radiation environment or a complex environment.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] The magnetic field probe for the pulse magnetic field detector in a radiation environment comprises a metal shielding shell, a first magnetic resistance circuit board arranged outside the metal shielding shell, a second magnetic resistance circuit board arranged inside the metal shielding shell, a magnetic resistance chip welded on the upper surface of the first magnetic resistance circuit board, a differential circuit, an amplification and filtering circuit and an electro-optical conversion circuit connected in sequence and welded on the second magnetic resistance circuit board, and an IPEX coaxial cable for connecting the circuit and a coaxial optical fiber for signal output.

[0010] The output end of the magnetic resistance chip is connected with the input end of the differential circuit through the IPEX coaxial cable, and the electro-optical conversion circuit is connected with an external device through the coaxial optical fiber.

[0011] Further, the magnetic resistance chip is a differential output type, and is internally based on a Wheatstone bridge structure to output two opposite signals with the change of the external magnetic field.

[0012] Further, the magnetic sensitive axis of the magnetic resistance chip coincides with the direction of the measured magnetic field, and comprises four magnetic sensitive resistors with the same resistance, namely, resistors R1, R2, R3 and R4.

[0013] The two opposite signals output by the magnetic resistance chip are as follows:

[0014]

[0015] wherein, V out+ is the positive output signal of the magnetoresistance chip, V out- is the negative output signal of the magnetoresistance chip; V CC is the power supply voltage of the magnetoresistance chip; R is the resistance value of the magnetically sensitive resistor; ΔR is the change in resistance value of the magnetically sensitive resistor affected by the magnetic field.

[0016] Further, the differential circuit uses an instrument amplifier, the non-inverting input and inverting input of the instrument amplifier are connected with the positive output signal and negative output signal of the magnetoresistance chip through IPEX coaxial cable respectively, and a resistor R5 is connected between the non-inverting input and inverting input of the instrument amplifier, the instrument amplifier is used for subtracting and canceling the common-mode interference of the signal output by the differential circuit, and simultaneously outputting the amplified effective magnetic field output signal;

[0017] The effective magnetic field output signal V out is:

[0018]

[0019] wherein, G is the first amplification factor, and the value is related to the value of the resistor R5.

[0020] Further, the model of the instrument amplifier is INA849; the first amplification factor G = 1, and the instrument amplifier INA849 has a high common-mode rejection ratio of 90 dB and a frequency response bandwidth of 28 MHz under 1 times gain.

[0021] Further, the amplification filter circuit uses a high-frequency operational amplifier to construct a same-direction proportional amplification circuit to amplify the measurement signal.

[0022] The non-inverting input of the operational amplifier is connected with the effective magnetic field output signal, and simultaneously connected with one end of a resistor R6, the other end of the resistor R6 is grounded, and the resistor R6 determines the input impedance of the amplification filter circuit; the inverting input of the operational amplifier is grounded through a resistor R7, and a resistor R8 and a capacitor C1 in parallel are connected between the inverting input and the output; the second amplification factor of the amplification filter circuit is 1+R8 / R7; the output of the operational amplifier is connected with one end of an inductor L1 and one end of a capacitor C2, and the other end of the capacitor C2 is grounded; the inductor L1 and the capacitor C2 constitute an inverted L type low-pass filter, which filters out high-frequency interference and improves the signal-to-noise ratio of the output signal; the other end of the inductor L1 is connected with the input end of the electro-optical conversion circuit, and is used for outputting the conditioned measurement signal.

[0023] Further, the electro-optical conversion circuit uses a DFB laser to perform electro-optical conversion on the conditioned measurement signal.

[0024] Further, the first magnetic resistance circuit board is covered with copper on the upper and lower surfaces, and is installed at the opening of the metal shielding shell, so that the metal shielding shell forms a closed cavity.

[0025] Compared with the prior art, the application has the following beneficial technical effects:

[0026] 1. The magnetic field probe for the pulse magnetic field detector in a radiation environment provided by the application utilizes the advantages of small volume and high sensitivity of the magnetic resistance chip, adopts a common mode rejection, filtering and shielding structure design of the transmission signal, solves the common mode interference problem caused by external electric field, radiation environment and the like, can be used for measuring the electromagnetic pulse magnetic field signal in a system generated by an x, gamma radiation chamber, can also be used for measuring the magnetic field signal of high-altitude electromagnetic pulse, lightning electromagnetic pulse and the like, and has important application value in the field of electromagnetic compatibility and the like.

[0027] 2. The magnetic field probe for the pulse magnetic field detector in a radiation environment provided by the application is used for measuring the pulse magnetic field signal in a radiation environment based on the principle of small volume and direct measurement of the magnetic resistance chip, and the measured signal is what is seen. Through reasonable circuit design and shielding structure design and the like, the interference signal is effectively suppressed, and the measurement of the electromagnetic pulse in a system in a radiation environment is realized.

[0028] 3. The differential circuit provided by the application selects an instrument operational amplifier INA849 as the core, the instrument operational amplifier chip internally integrates three operational amplifiers, two operational amplifiers at the input end form a voltage follower to provide high input impedance and reduce the attenuation of the circuit to the weak input signal; the rear-stage operational amplifier is a full-differential amplifier to realize the subtraction operation of the two-way signal, and the INA849 has a high common mode rejection ratio of 90dB and a frequency response bandwidth of 28MHz under 1 times gain. The instrument amplifier simplifies the design of the differential circuit, and compared with the passive differential balun, has a high common mode interference signal rejection ratio.

[0029] 4. The electro-optical conversion circuit provided by the application is based on an electro-optical amplitude modulation mode, realizes the optical fiber transmission of the measurement signal, and has a simple circuit structure. Compared with a coaxial cable, the coaxial optical fiber has the advantages of low long-distance transmission loss, light weight, strong anti-electromagnetic interference and the like, and the coaxial optical fiber blocks the electrical connection of the signal transmission, and can effectively reduce the ground return loop interference of the electronic equipment and the common mode interference of the transmission signal. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a principle block diagram of the magnetic field probe for the pulse magnetic field detector in a radiation environment provided by the application;

[0031] Figure 2 It is a structural schematic diagram of the magnetic field probe for the pulse magnetic field detector in a radiation environment provided by the application;

[0032] Figure 3 Fig. 1 is a structural schematic diagram of a magnetic resistance chip in an embodiment of the present application;

[0033] Figure 4 Fig. 2 is a schematic diagram of a differential circuit in an embodiment of the present application;

[0034] Figure 5 Fig. 3 is a schematic diagram of an amplification filter circuit in an embodiment of the present application;

[0035] Figure 6 Fig. 4 is a schematic diagram of an electro-optical conversion circuit in an embodiment of the present application;

[0036] Figure 7 Fig. 5 is a waveform diagram of a pulsed magnetic field in a cylindrical cavity measured by an X-ray accelerator according to the present application;

[0037] Reference signs:

[0038] 1 - first magnetic resistance circuit board, 2 - magnetic resistance chip, 3 - metal shielding shell, 4 - second magnetic resistance circuit board, 5 - IPEX coaxial cable, 6 - coaxial optical fiber. DETAILED DESCRIPTION

[0039] In order to make the objects, advantages and features of the present application clearer, a magnetic field probe of a pulsed magnetic field detector in a radiation environment according to the present application is further described in detail below in combination with the drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0040] As shown in Figs. 1 to 5, Figure 1 and Figure 2 the magnetic field probe of the pulsed magnetic field detector in a radiation environment disclosed in the present embodiment comprises a metal shielding shell 3, a first magnetic resistance circuit board 1 arranged outside the metal shielding shell 3, a second magnetic resistance circuit board 4 arranged inside the metal shielding shell 3, a magnetic resistance chip 2 welded on the first magnetic resistance circuit board 1, a differential circuit, an amplification filter circuit and an electro-optical conversion circuit connected in sequence and welded on the second magnetic resistance circuit board 4, and an IPEX coaxial cable 5 for connecting the circuit and a coaxial optical fiber 6 for signal output.

[0041] The first magnetoresistive circuit board 1 has copper plating on both its upper and lower surfaces, and it is mounted at the opening of the metal shielding housing 3 to form a sealed cavity. The magnetoresistive chip 2 is soldered to the upper surface of the first magnetoresistive circuit board 1, and the signal is led to the lower surface of the circuit board through vias, minimizing the exposed traces of the magnetoresistive chip 2. The two output signals of the magnetoresistive chip 2 are connected to the two input terminals of the differential circuit via IPEX coaxial cables 5, avoiding secondary radiation generated inside the shielding housing during signal transmission. This minimizes the length of the exposed circuit board traces of the magnetoresistive chip and reduces interference from the external environment.

[0042] The output of magnetoresistive chip 2 is connected to the input of differential circuit via IPEX coaxial cable 5. The electro-optical conversion circuit is connected to external devices via coaxial fiber 6. After sensing the ambient magnetic field signal, magnetoresistive chip 2 outputs two opposite signals. These two opposite signals are sent to differential circuit to eliminate common-mode interference. Then, the differential signals are conditioned by amplification and filtering circuit. The amplified signals are sent to electro-optical conversion circuit to be modulated into optical signals, and finally output to external devices via coaxial fiber 6.

[0043] The magnetic sensing axis of the magnetoresistive chip 2 coincides with the direction of the magnetic field being measured. It is a differential output type, and its internal structure is based on a Wheatstone bridge. It can output two differential signals with equal amplitude and opposite direction as the external magnetic field changes.

[0044] like Figure 3 As shown, the magnetoresistive chip 2 used in this embodiment utilizes four sensitive resistors to form a push-pull Wheatstone bridge structure. Resistors R1 and R2 are connected in series, and resistors R3 and R4 are connected in series, then in parallel with resistors R1 and R2. The other ends of resistors R1 and R4 are connected to the positive terminal of the power supply, and the other ends of resistors R2 and R3 are connected to the negative terminal of the power supply. The resistance values ​​of each magnetoresistive chip are equal. The magnetic sensing directions of resistors R1 and R3 are the same and the same as the direction of the magnetic field being measured. The magnetic sensing directions of resistors R2 and R4 are the same, while the magnetic sensing directions of resistors R1 and R2 are opposite. As the external magnetic field changes, the resistance change ΔR is equal in magnitude but opposite in direction, thus achieving differential output of two signals. The connection point of resistors R1 and R2, and the connection point of resistors R3 and R4, respectively output two opposite signals, a positive output signal and a negative output signal, respectively.

[0045]

[0046] V out+ For the positive output signal of the magnetoresistive chip, V out- The negative output signal of the magnetoresistive chip, V CC The supply voltage for the magnetoresistive chip; R is the resistance value of the magnetoresistive sensor; ΔR is the change in resistance value of the magnetoresistive sensor due to the influence of the magnetic field.

[0047] The non-inverting input and the inverting input of the differential circuit are high-impedance inputs, and the differential output signal is followed or amplified, and has strong driving capability. The two input signals are subtracted, and when the same interference is superimposed on the two input signals, the interference can be theoretically completely offset, and the useful signal becomes twice the original.

[0048] As shown in Figure 4 , the differential circuit in the embodiment selects an instrument operational amplifier INA849 as the core, and the instrument operational amplifier chip internally integrates three operational amplifiers, which have the characteristics of high input impedance and high common-mode rejection ratio. The resistor R5 realizes amplification of the output signal, and the circuit subtracts the common-mode interference generated by external interference on the magnetic sensitive chip pin, and outputs the useful magnetic field signal:

[0049]

[0050] , wherein V out is the effective measured magnetic field signal output by the differential circuit; G is a first amplification factor, and the value is related to the value of the resistor R5, and finally realizes amplification of the output signal. INA849 has a high common-mode rejection ratio of 90dB and a frequency response bandwidth of 28MHz at 1 times gain.

[0051] As shown in Figure 5 , the amplification and filtering circuit in the embodiment uses a high-frequency operational amplifier to construct a same-direction proportional amplification circuit to amplify the measurement signal. The non-inverting input of the operational amplifier is connected with the resistor R6, which is used to determine the input impedance of the amplification circuit; the inverting input of the operational amplifier is connected with the resistor R7, and the inverting input and the output are connected with the parallel resistor R8 and the capacitor C1, and the amplification factor of the amplification circuit is 1+R8 / R7; the output of the operational amplifier is connected with the inductor L1 and the capacitor C2, and the inductor L1 and the capacitor C2 constitute an inverted L type low pass filter, which further filters the high frequency interference in the signal and improves the signal-to-noise ratio of the measurement signal.

[0052] As shown in Figure 6 , the electro-optical conversion circuit in the embodiment uses a DFB laser to convert the conditioned measurement signal into an optical signal, and finally outputs the measurement signal through a coaxial optical fiber 6 to avoid interference of the coaxial cable in the signal transmission process. The positive electrode of the DFB laser is connected with the power supply VCC through the bias resistor R10, and the signal output by the amplification and filtering circuit is connected with the positive electrode of the DFB laser through the load resistor R9 and the coupling capacitor C3. The bias resistor R10 is connected in series with the DFB laser to ensure that the DFB laser works at a suitable static current bias point, and the input signal is input to the positive input end of the DFB laser through the load resistor R9 and the coupling capacitor C3. The measurement signal is converted into an optical signal for transmission by amplitude modulation.

[0053] The implementation process is as follows:

[0054] The magnetic field probe pulse magnetic field detector is placed in the radiation field space to be measured, the magnetic sensitive axis of the magnetic resistance chip is coincided with the direction of the measured magnetic field, the measured signal is transmitted to the measurement shield room through the coaxial optical fiber 6, the optical signal is converted into an electric signal through the optical receiver, finally, the signal is recorded and stored by using the oscilloscope, and the pulse magnetic field detection is realized.

[0055] As shown in Figure 7 The measured pulse magnetic field waveform in the cylindrical cavity under the X-ray accelerator by using the above detector can be seen, the measurement result directly gives the signal waveform of the pulse magnetic field to be measured, the waveform characteristics and the peak magnetic field intensity are in good agreement with the theoretical calculation result, and the measurement result is ideal.

[0056] In summary, the magnetic field probe disclosed by the application reduces the coupling way of external interference to the maximum in the structural design, suppresses the common-mode interference caused by the external measurement environment through signal difference, and further improves the signal-to-noise ratio of the measurement signal through the signal conditioning of amplification and filtering, can be used for pulse magnetic field signal measurement in a radiation environment, and has the advantages of large dynamic range, high sensitivity, small structure, can directly measure the magnetic field signal and the like.

[0057] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A magnetic field probe for a pulsed magnetic field detector in a radiation environment, characterized in that: It includes a metal shielding housing (3), a first magnetoresistive circuit board (1) disposed outside the metal shielding housing (3), a second magnetoresistive circuit board (4) disposed inside the metal shielding housing (3), a magnetoresistive chip (2) soldered to the upper surface of the first magnetoresistive circuit board (1), a differential circuit, an amplification and filtering circuit and an electro-optical conversion circuit soldered to the second magnetoresistive circuit board (4) and connected in sequence, as well as an IPEX coaxial cable (5) for connecting the circuit and a coaxial optical fiber (6) for signal output; The output terminal of the magnetoresistive chip (2) is connected to the input terminal of the differential circuit via an IPEX coaxial cable (5), and the electro-optical conversion circuit is connected to an external device via a coaxial optical fiber (6). After sensing the ambient magnetic field signal, the magnetoresistive chip (2) outputs two opposite signals. The two opposite signals are sent to the differential circuit to eliminate common-mode interference. Then, the differential signal is conditioned by the amplification and filtering circuit. The amplified signal is sent to the electro-optic conversion circuit to be modulated into an optical signal. Finally, it is output to the external device through the coaxial optical fiber (6). The differential circuit uses an instrumentation amplifier. The non-inverting input and inverting input of the instrumentation amplifier are connected to the positive output signal and negative output signal of the magnetoresistive chip (2) through an IPEX coaxial cable (5), respectively. A resistor R5 is connected between the non-inverting input and inverting input of the instrumentation amplifier. The instrumentation amplifier is used to subtract and cancel the common-mode interference of the signal output by the differential circuit, and at the same time outputs an amplified effective magnetic field output signal. The amplification and filtering circuit uses a high-frequency operational amplifier to construct a non-inverting proportional amplifier circuit to amplify the measurement signal. The non-inverting input terminal of the operational amplifier is connected to the effective magnetic field output signal and also to one end of resistor R6, the other end of which is grounded. Resistor R6 determines the input impedance of the amplification and filtering circuit. The inverting input terminal of the operational amplifier is grounded through resistor R7. A resistor R8 and a capacitor C1 are connected in parallel between the inverting input terminal and the output terminal. The second-stage amplification factor of the amplification and filtering circuit is 1 + R8 / R7. The output terminal of the operational amplifier is connected to one end of inductor L1 and one end of capacitor C2, the other end of which is grounded. Inductor L1 and capacitor C2 form an inverted L-shaped low-pass filter to filter out high-frequency interference and improve the signal-to-noise ratio of the output signal. The other end of inductor L1 is connected to the input terminal of the electro-optic conversion circuit for outputting the conditioned measurement signal. The electro-optic conversion circuit uses a DFB laser to perform electro-optic conversion on the conditioned measurement signal.

2. The magnetic field probe for a pulsed magnetic field detector in a radiation environment according to claim 1, characterized in that: The magnetoresistive chip (2) is a differential output type, based on a Wheatstone bridge structure. It outputs two opposite signals as the external magnetic field changes. The two opposite signals are two differential signals with equal amplitude and opposite direction.

3. The magnetic field probe for a pulsed magnetic field detector in a radiation environment according to claim 2, characterized in that: The magnetic sensing axis of the magnetoresistive chip (2) coincides with the direction of the magnetic field being measured. It includes four magnetically sensitive resistors with the same resistance value, namely resistors R1, R2, R3 and R4. Resistor R1 is connected in series with resistor R2, and resistor R3 is connected in series with resistor R4. The other ends of resistors R1 and R4 are connected to the positive terminal of the power supply, and the other ends of resistors R2 and R3 are connected to the negative terminal of the power supply. The magnetic sensing directions of resistors R1 and R3 are the same and the same as the direction of the magnetic field being measured. The magnetic sensing directions of resistors R2 and R4 are the same, and the magnetic sensing directions of resistors R1 and R2 are opposite. The connection point of resistors R1 and R2, and the connection point of resistors R3 and R4 respectively output two opposite signals, namely a positive output signal and a negative output signal. The two opposite signals output by the magnetoresistive chip (2) are respectively: Among them, V out+ For the positive output signal of the magnetoresistive chip, V out- This is the negative output signal of the magnetoresistive chip; V CC The supply voltage for the magnetoresistive chip; R is the resistance value of the magnetoresistive sensor; ΔR is the change in resistance value of the magnetoresistive sensor due to the influence of the magnetic field.

4. The magnetic field probe for a pulsed magnetic field detector in a radiation environment according to claim 3, characterized in that: The effective magnetic field output signal V out for: Where G is the magnification factor of one level.

5. The magnetic field probe for a pulsed magnetic field detector in a radiation environment according to claim 4, characterized in that: The instrumentation amplifier is model INA849; the first-stage amplification factor G = 1.

6. The magnetic field probe for a pulsed magnetic field detector in a radiation environment according to claim 1, characterized in that: The first magnetoresistive circuit board (1) is covered with copper on both the upper and lower surfaces and is installed at the opening of the metal shielding shell (3), so that the metal shielding shell (3) forms a sealed cavity.

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