CN103901362B - The three axle magnetic detection modules based on multichannel SQUID Magnetic Sensors - Google Patents

Abstract

The present invention relates to a kind of three axle magnetic detection modules based on multichannel SQUID Magnetic Sensors, it is characterized in that described three-axle magnetic field detecting module, three directions are mutually orthogonal, the XYZ directions in space are corresponded to respectively, and the magnetic-field measurement to each direction is completed by multiple passage superconduction SQUID Magnetic Sensors devices；Multiple passage superconduction SQUID sensors constitute serial array or constitute parallel connected array by changing connection order.Serial array can improve the sensitivity of measurement, and parallel connected array can improve the signal to noise ratio and operating efficiency of measurement.Change the connection method of each component in module, the detecting module of different structure can be constructed, the difference of detecting module is required with meeting practical application, flexibility and the efficiency of detection system is improved.

Description

Three-axis magnetic detection module based on multi-channel SQUID magnetic sensor

technical field

The invention relates to the measurement of the earth's magnetic field by a superconducting SQUID magnetic sensor, more precisely the invention relates to a three-axis magnetic detection module based on a multi-channel SQUID magnetic sensor. It belongs to the technical field of magnetic field measurement.

Background technique

A superconducting quantum interference device (SQUID) is a superconducting quantum device composed of a superconducting Josephson junction and a superconducting ring. Its working principle is mainly based on the Josephson effect and magnetic field quantization, which can convert weak changes in the magnetic field into It is a measurable voltage, and its magnetic field sensitivity can reach the fT level. It is currently the most sensitive magnetic field sensor, so it has great development and application potential in the field of weak magnetic field detection, such as biological magnetic field detection, nondestructive testing, and earth magnetic field detection. . For example, both Magnetotelluric (MT) and Controlled Source Audio Magnetotelluric (CSAMT) applications in geophysical exploration require high-performance magnetic field sensors to measure the target magnetic field signal.

MT is to detect the naturally existing regional electromagnetic field. This type of natural electromagnetic field has a wide frequency band. Through the measurement and data analysis of these natural electromagnetic fields, we can understand the electrical structure of the earth's lithosphere. One of the basic exploration methods for oil and gas fields, MT has been greatly developed in recent years. Due to the weak signal of the MT natural field source, it is necessary to use a high-sensitivity magnetic sensor in the application.

Both CSAMT and MT belong to the category of frequency electromagnetic sounding. The difference between the two is that the excitation field source of CSAMT can be manually controlled. In view of the randomness of the MT field source and the weak signal, so that the observation is very difficult, the CSAMT adopts manual control of the emission current and The electric dipole or magnetic dipole of its frequency is used as the field source, and the apparent resistivity at different frequencies is calculated by measuring the electromagnetic field signals at different emission frequencies at locations far away from the field source to reflect the underground resistivity. distribution characteristics.

When conducting magnetotelluric surveys, both MT and CSAMT surveys are usually performed, and they all require sensitive magnetic sensors. In addition, the target signal of CSAMT is the magnetic field caused by different transmission frequencies, and the magnetic field of the earth's environment is regarded as noise. The influence of magnetic field noise therefore requires long-term measurements of fields at a single frequency.

However, when superconducting SQUID magnetic sensors are applied to MT and CSAMT, single-channel SQUID sensors are currently used for magnetic field measurement, and magnetic flux modulation locking circuits are used to read out magnetic signals induced by SQUID (DANTSKER, Eetc.HIGH-T- C3-AXIS DC SQUID MAGNETOMETER FOR GEOPHYSICAL APPLICATIONS), according to reports, the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences has only used superconducting SQUID magnetic sensor devices for MT and CSAMT application research. In the process of magnetic measurement, MT measurement has the characteristics of relatively wide frequency band, and in order to improve the signal-to-noise ratio of the system, CSAMT adopts the processing method of signal averaging, so it needs to perform long-term measurement at one measurement point, and the measurement time is longer than half an hour. Good for engineering applications.

The present invention intends to aim at the measurement characteristics of the above-mentioned superconducting SQUID magnetic sensor, and attempts to provide a three-axis detection module based on a multi-channel SQUID sensor, which can not only measure the magnetic fields in three orthogonal directions, but also meet the different requirements of MT and CSAMT , and flexibly change the module structure to suit its requirements, which in turn can improve work efficiency. In addition, this detection module is also expected to be applicable to other weak magnetic field detection fields.

Contents of the invention

The object of the present invention is to provide a three-axis magnetic detection module based on a multi-channel SQUID magnetic sensor. The present invention designs a three-axis magnetic field detection module, and the three directions are mutually orthogonal, respectively corresponding to XYZ directions in space. The magnetic field measurement in each direction is completed by multiple channel superconducting SQUID sensors. Multiple channel SQUIDs can form a series array or a parallel array by changing the connection order. The series array can improve the sensitivity of the measurement, and the parallel array can improve the measurement sensitivity. signal-to-noise ratio and work efficiency. Further characteristics are described as follows:

(1) Three-axis magnetic field detection module

The superconducting SQUID magnetic sensor is a vector sensor that can only measure the change of the magnetic field perpendicular to the plane of the device. When measuring the weak magnetic field signal, because the weak magnetic field signal is not completely perpendicular to the plane of the superconducting SQUID magnetic sensor device, the SQUID magnetic sensor senses the component of the magnetic field signal to be measured perpendicular to the SQUID plane, even in some cases , the uniaxial SQUID cannot measure the magnetic field signal, such as the magnetic field distribution generated by the current loop of the magnetic dipole as shown in Figure 1. It can be seen from the figure that at the points listed in A, B, C, D and E, If the uniaxial test is used, the magnetic field in the direction marked by the arrow cannot be measured, resulting in inaccurate measured magnetic field values. In addition, not only these special points, but also near these special points, sometimes the magnetic field signal is Very weak, the measured effect is not satisfactory. The above problems can be solved by using a three-axis magnetic detection module. The three-axis module is composed of magnetic sensors in three directions. As shown in Figure 2, these three directions are orthogonal to each other. In this way, the magnetic field signal to be measured can be carried out according to these three directions. Breaking it down, the magnetic sensor for each direction measures the magnetic field corresponding to its direction, and the magnetic field vector can be calculated from these three signals.

(2) Serial SQUID array

In the three-axis detection module, the magnetic detection component that detects each direction is composed of multiple SQUID magnetic sensors, and these superconducting SQUID magnetic sensor devices can be connected in series to form a series SQUID component, as shown in Figure 3, that is, the front The negative terminal of one superconducting SQUID magnetic sensor device is connected to the positive terminal of an adjacent superconducting SQUID magnetic sensor device. This series SQUID component has a large magnetic field-voltage conversion coefficient, assuming that the magnetic field change ΔB induced by each superconducting SQUID magnetic sensor device is ΔV, and its magnetic field-voltage conversion coefficient is ΔV/ΔB, when When n superconducting SQUID magnetic sensor devices form a series SQUID assembly, when the magnetic field changes to ΔB, the output voltage of the array is n*ΔV, and its magnetic field-voltage conversion coefficient is n*ΔV/ΔB, which is higher than that of a single superconducting SQUID magnetic sensor. The sensor device has improved by n times. The improvement of the magnetic field-voltage conversion coefficient allows the SQUID readout circuit to adopt a direct-reading circuit method. This circuit method is not only simple in structure and convenient to use, but also has a high slew rate and a large bandwidth, which can reach the order of MHz. These The advantages make it have a strong application potential when the magnetic field measurement with high slew rate and large bandwidth is required.

(3) Parallel SQUID array

In the three-axis detection module, the magnetic detection component that detects each direction can also be a parallel array composed of multiple SQUID magnetic sensors, as shown in Figure 4, that is, multiple SQUID sensors are not connected to each other, and each SQUID magnetic sensor The external magnetic field signals are sensed separately, and the sensitivity of the array is determined by the sensitivity of a single device in the array. However, since the environmental noise induced by each SQUID sensor is random and irrelevant, the uncorrelated magnetic field noise is superimposed together, and the magnetic field can be theoretically The noise is reduced by n ^1/2 , so paralleling SQUID arrays can increase the signal-to-noise ratio of the system by n ^1/2 .

In addition, since the parallel SQUIDs are installed on a plane, the distance between the devices is several centimeters, so two adjacent superconducting SQUID magnetic sensor devices can form a magnetic field gradiometer, as shown in Figure 4, the measured value of SQUID-1 is the magnetic field at position 1, and SQUID‐2 measures the magnetic field at position 2, then the magnetic field gradient can be calculated based on the magnetic fields at these two positions From the magnetic field measurements at positions 1 and 3, the magnetic field gradient can be calculated Similarly, through the SQUID array in the other two directions, the magnetic field gradient can be calculated These magnetic field gradient data enrich the magnetic field information, contribute to more accurate magnetic field inversion, and play an important role in geophysical exploration.

In the 3-axis magnetic detection module, the magnetic detection components that measure each direction can be connected in series or in parallel, and switches can be used to switch between different forms. In the measurement occasions that require high slew rate and large bandwidth, the series mode can be applied; in the occasions where the detection requires high signal-to-noise ratio, the parallel mode can be applied, which increases the flexibility of the three-axis magnetic field measurement module.

In addition to using series arrays or parallel arrays alone, in SQUID magnetic measurement applications, series arrays and parallel arrays can also be used in combination to form a measurement system with high slew rate, large bandwidth and high signal-to-noise ratio, such as each magnetic field In the measurement direction, a parallel array of 2 rows and 2 columns is used, and each unit is composed of 4 superconducting SQUID sensors connected in series. However, if it is designed in this way, the number of sensors will increase by 4 times, which will increase the cost of the system, which needs to be weighed in the application.

In a word, the present invention relates to a three-axis magnetic detection module based on a multi-channel SQUID magnetic sensor, which is characterized in that the three-axis magnetic field detection module has three directions orthogonal to each other, respectively corresponding to the XYZ directions of space, and for each direction The magnetic field measurement is completed by multiple channel superconducting SQUID magnetic sensor devices; multiple channel superconducting SQUID sensors form a series array or form a parallel array by changing the connection order. The series array can improve the sensitivity of the measurement, and the parallel array can improve the signal-to-noise ratio and work efficiency of the measurement. By changing the connection method of each component in the module, detection modules with different structures can be constructed to meet the different requirements of the detection module in practical applications and improve the flexibility and efficiency of the detection system.

Description of drawings

The schematic diagram of the magnetic field distribution produced by the magnetic dipole in Fig. 1;

Figure 2 is a schematic diagram of a three-axis magnetic field detection module;

Figure 3 Schematic diagram of serial SQUID connection;

Figure 4 is a schematic diagram of parallel SQUID connections, where (a) is a schematic diagram of a parallel array in one direction in a three-axis module, (b) is a schematic diagram of the entire three-axis module, and the superconducting SQUID magnetic sensor devices in (a) and (b) are mutually correspond;

Fig. 5 The manufacturing method of the three-axis detection module.

detailed description

According to the aforementioned design, the 3-axis detection module of the present invention is manufactured in a top-down manner, as shown in FIG. 5 .

The three-axis module is mainly divided into two parts, the carrier and the device, and the manufacturing of the carrier and the device can be completed separately and in parallel. Therefore, in the process of making the module, the carrier and the SQUID are firstly made separately, and then these two parts are integrated to form a 3 axis module. The specific production steps of 2×2 channel are:

First, determine the size parameters of the triaxial module. The size of the module is determined according to the size of the Dewar that provides the module with a low temperature environment. The size of this module is usually the same as the size of the carrier. Usually, the carrier of the module is designed as a cube structure with a side length of less than 10 cm. The carrier material is an epoxy material with stable performance in a low temperature environment, and the cube carrier is manufactured by machining technology, and some auxiliary mechanical structures are made on the carrier. Such as screw holes, etc. After the production is completed, measure the surface flatness of the cube and the angle between each plane, compare the design parameters, adjust and reduce the structural error of the carrier.

Second, while the carrier is being manufactured, the superconducting SQUID magnetic sensor device is prepared by micromachining technology. After the device is manufactured, the device is packaged according to the size of each direction of the three-axis module, because each side is arranged 2× 2-channel array, and a few centimeters of spacing between devices is required to prevent crosstalk issues between devices. After the device is packaged, before the superconducting SQUID sensor is installed in the module, perform performance testing and calibration for each device, including device noise, magnetic field voltage conversion parameters and other performance tests, and select devices with similar performance to manufacture the magnetic detection module. Ensure the uniformity of device performance.

Third, according to the design of the module, the superconducting SQUID magnetic sensor device is installed on the three-axis module, and the performance of the array in each direction is tested, and the three-axis module is continuously improved and perfected according to the measurement feedback results of the performance parameters.

Fourth, the quality of the magnetic detection module is guaranteed by testing each step of the device, component, and module preparation steps, so that the 3-axis detection module plays an important role in the application of weak magnetic field detection.

Claims (2)

1. a kind of preparation method of the three axle magnetic detection modules based on multichannel SQUID Magnetic Sensors, it is characterised in that using from Mode under above makes, and three described axle magnetic detection modules are divided into carrier and device two large divisions, and carrier and device system Make to separate and complete parallel；During module is made, carrier and superconduction SQUID Magnetic Sensor device systems are first respectively completed Make, then integrate this two parts, constitute 3 axle modules；The specific make step of 2 × 2 passages is：

First, the dimensional parameters of three axle modules are determined, according to the Dewar size determining module size that low temperature environment is provided by module, The size of module is identical with the size of carrier, and the carrier of usual module is designed as cube structure, the selection of carrier material be The stable epoxy material of performance under low temperature environment, and cube carrier is produced using mechanical manufacturing technology, made on carrier Go out the mechanical structure of screw auxiliary；After completing, the angle between cubical surface smoothness and each plane is measured, than To design parameter, the structural failure of carrier is adjusted and reduced；

Second, while carrier makes, superconduction SQUID Magnetic Sensor devices are prepared using micro fabrication, in device system After the completion of standby, according to the size in three each direction of axle module, device is packaged；2 × 2 passages battle array is arranged on each face Row, to prevent the cross-interference issue between device, it is necessary to leave several centimetres of spacing between device；After device encapsulation, Superconduction SQUID Magnetic Sensors are installed on before module, each device is carried out to include device noise, field voltage conversion ginseng The test performance test and demarcation of number performance, and select the close device of performance to manufacture magnetic detection module, it is ensured that device performance Homogeneity；

3rd, according to the design of module, superconduction SQUID Magnetic Sensor devices are installed on three axle modules, and to each side To array carry out performance test, according to the measurement feedback result of performance parameter, update and improve three axle modules；

4th, by the detection to each step in device, module making step, to ensure the quality of magnetic detection module.

2. the method as described in claim 1, it is characterised in that the length of side of the carrier of the module of cube structure is less than 10 centimetres.