RU2481591C1 - Magnetometer with superconducting quantum interferometric sensor - Google Patents

Abstract

FIELD: physics.SUBSTANCE: magnetometer with a superconducting quantum interferometric sensor has a superconducting quantum interferometric sensor (SQIS) with matching electric circuits, which is connected to the input of an amplifier, the output of which is connected to the first input of a synchronous detector; the output of the synchronous detector is connected to the input of an integrator with an integrating capacitor; outputs of the bias current generator, low frequency generator and the integrator are connected to the SQIS; between the output of the low frequency generator and the second input of the synchronous detector there is a phase changer; and a buffer stage is connected by its input to the output of the integrator, wherein said buffer stage includes a double-threshold generator comparator, a direct voltage source, a single pulse generator and an electronic switch, wherein the double-threshold generator comparator is connected by the first input to the output of the integrator, by the second input to the direct voltage source; the single pulse generator is connected by its input to the output of the double-threshold generator comparator, and by the output to the control input of the electronic switch which is connected by its first and second outputs to the integrator to the plates of the integrating capacitor.EFFECT: improved operating characteristics of a magnetometer with a superconducting quantum interferometric sensor, automation of the operation of nulling the integrator.3 dwg

Description

The invention relates to devices for measuring variable magnetic quantities and can be used for magnetic measurements in the following areas: physics of magnetic phenomena, geophysics, medicine, biomagnetism.

A magnetometer with a superconducting quantum interferometric sensor (SQUID) is a device for measuring magnetic fields and their gradients. Its action is based on the Josephson effect [Clark J. Principles of action and the application of SQUID. - TIIER, 1989, v.77, No. 8, p.118-137].

A known magnetometer design with SQUID, in which the reset of the integrator, which is part of the electrical circuit of the device, is carried out by closing the toggle switch connected in parallel to the integrating capacitor. [Wellstood, Hayden, Clark. High-speed integrated magnetometer based on direct current SKIP. - Instruments for scientific research, 1984, No. 6, p.132-138].

The disadvantage of this design is that upon reaching the saturation magnetometer output, the measurement process stops. To resume measurements, the operator must manually reset the integrator each time, closing the toggle switch briefly. In this case, the operator must constantly monitor the output level of the magnetometer. Such actions require constant attention from the operator and a significant investment of time.

The closest technical solution to the claimed device is the design of a magnetometer with SQUID, having an electrical circuit consisting of the following main components: SQUID, bias current generator, low-frequency generator, phase shifter, amplifier, synchronous detector, integrator, buffer cascade [Drobin V.M. , Lobotka P., Trofimov V.N. Block of registration of a superconducting quantum magnetometer. - PTE, 1987, No. 3, p. 158-161 (prototype)]. The device has several modes for the dynamic range of the flow reduced to SQUID. Zeroing the integrator is done by closing the button connected in parallel to the integrating capacitor.

This design has the following disadvantages. The magnetometer has the highest sensitivity for the input stream only when operating in the mode with a minimum dynamic range. When switching to a mode with a large dynamic range, the sensitivity of the device decreases in proportion to the value of the dynamic range. When the output signal reaches the saturation magnetometer, the measurement process stops. To resume measurements, the operator must always reset the integrator by manually closing the button. In this case, the operator must constantly monitor the output level of the magnetometer. Such actions require constant attention from the operator and a significant investment of time, which leads to a partial loss of useful information and suboptimal expenditure of cryogenic resources.

The technical result of the invention is to improve the technical and operational characteristics of a magnetometer with a superconducting quantum interferometric sensor by increasing the dynamic range of the magnetometer without reducing sensitivity, automating the operation of resetting the integrator, and eliminating manual actions.

The technical result is achieved in that in a magnetometer with a superconducting quantum interferometric sensor containing a superconducting quantum interferometric sensor (SQUID) with matching electric circuits, connected to the input of the amplifier, the output of which is connected to the first input of the synchronous detector, the output of the synchronous detector is connected to the input of the integrator with integrating capacitor, the outputs of the bias current generator, low frequency generator and integrator are connected to SQUID, between the output of the generator the low frequency and the second input of the synchronous detector, the phase shifter is turned on, and the buffer cascade is connected to the integrator output by its input, the new one is that a two-threshold regenerator comparator, a constant voltage source, a single pulse generator and an electronic switch are introduced, and a two-threshold regenerator comparator is connected to the first input to the integrator output, the second input to a constant voltage source, a single pulse generator is connected by its input to the output of a two-threshold regenerative comparator output and to the control input of the electronic key, which, with its first and second outputs connected to the integrator to the plates of the integrating capacitor.

Comparative analysis with the prototype shows that the inventive device is characterized by the presence of new units: a two-threshold regenerative comparator, a constant voltage source, a single pulse generator, an electronic switch and their connection with the rest of the circuit elements.

These signs allow us to conclude that the proposed technical solution meets the criterion of "novelty."

When studying other well-known technical solutions in this technical field, the features that distinguish the claimed invention from the prototype are not identified, and therefore they provide the claimed technical solution with the criterion of "inventive step".

The invention is illustrated using graphic materials.

Figure 1 presents the functional diagram of a magnetometer with SQUID. Figure 2 shows the plot of the voltages at the outputs of the elements of the device. Figure 3 presents an example of the implementation of new nodes of the claimed device.

A magnetometer with SQUID (Fig. 1) contains a superconducting quantum interferometric sensor (SQUID) 1 with matching electric circuits, a bias current generator 2, a low-frequency generator 3, a phase shifter 4, an amplifier 5, a synchronous detector 6, an integrator 7 with an integrating capacitor, a buffer cascade 8. SQUID 1 is connected to the input of amplifier 5, the output of which is connected to the first input of the synchronous detector 6. The output of the synchronous detector 6 is connected to the input of the integrator 7. The outputs of the bias current generator 2, low-frequency generator 3 and integr The actuator 7 is connected to SQUID 1. Between the output of the low-frequency generator 3 and the second input of the synchronous detector 6, the phase shifter 4 is turned on. The buffer stage 8 is connected by its input to the output of the integrator 7.

In addition to the above, a magnetometer with SQUID contains a number of new nodes, namely: a two-threshold regenerator comparator 9, a DC voltage source 10, a single pulse generator 11 and an electronic key 12. The comparator 9 is connected to the integrator 7 output by the first (signal) input and the second input ( reference voltage) - to the source 10. The generator 11 is connected by its input to the output of the comparator 9, and by the output to the control input of the electronic key 12, which, in turn, is connected to the integrator 7 by its first and second outputs m integrating capacitor.

A magnetometer with SQUID works as follows. The magneto-sensitive sensor of the magnetometer is SQUID 1, and a bias current determining the operating point of SQUID 1 is supplied to it from the bias current generator 2. The low-frequency generator 3 serves to modulate the magnetic flux in SQUID 1. The SQUID 1 signal is amplified by amplifier 5 and detected by a synchronous detector 6, which controlled by the reference signal from the generator 3. To adjust the phase of the reference signal, use the phase shifter 4. The signal from the output of the synchronous detector 6 is filtered by the integrator 7 and fed to SQUID 1, inducing a magnetic flow from feedback loop. The voltage U ₇ from the output of the integrator 7 also goes to the input of the buffer stage 8, from the output of which the output signal of the magnetometer is taken. The increment of the output voltage of the integrator 7 is directly proportional to the change in the input (measured) magnetic flux F applied to SQUID 1 (figure 2). The full quasistatic flow applied to the SQUID is the sum of the input stream Φ and the stream from the feedback circuit and remains unchanged.

Regenerative two-threshold comparator 9 compares the output voltage U of the integrator ₇ 7 with a voltage U ₁₀ 10 DC voltage source. If the voltage U ₇ lies between two predetermined threshold voltages -U ₁₀ and U ₁₀ , a low output voltage corresponding to a voltage of "0" logical zero is present at the output of the comparator. In this case, the first and second outputs of the electronic switch 12 are open, and the electronic switch 12 does not affect the operation of the integrator 7. As soon as the voltage U ₇ is outside the specified range, the comparator 9 switches to the state with a high output voltage corresponding to the voltage “1” logical units. In more detail, the principle of operation and the advantages of a two-threshold regenerative comparator were described by the author earlier [RU 2426222 C1, Н03К 3/22, 5/24, 08/10/2011].

A positive difference in the output voltage U _{9 of the} comparator 9 starts the generator 11, the output of which is formed by a voltage pulse U _{11 of a} given duration. For the duration of this pulse, the outputs of the electronic switch 12 are closed to each other, discharging the integrating capacitor, the voltage U ₇ at the output of the integrator 7 becomes equal to zero. In this case, the magnetic flux applied to SQUID 1 from the feedback circuit abruptly changes by an integer number of magnetic flux quanta, and the comparator 9 switches to a state with a low output voltage corresponding to a voltage of “0”.

Thus, the saturation of the voltage U ₇ at the output of the integrator 7 is prevented, and the measurement process continues. In fact, this is equivalent to increasing the dynamic range of the magnetometer. It is noteworthy that the sensitivity of the magnetometer remains unchanged, since, in comparison with the prototype, the modes are not switched over the dynamic range of the stream reduced to SQUID.

Due to the fact that the comparator is regenerative, the fronts of its output signal are always sharp, even with very slow changes in the input signal. This is important when using logic circuits in subsequent stages, since often the length of the front of the input signals required for the correct operation of digital circuits is regulated from above.

Example (figure 3)

The two-threshold regenerator comparator 9 is made on operational amplifiers (op amps) 13-15, resistors 16-26, two-sided zener diodes 27, 28 and diodes 29, 30. This node, in fact, consists of two circuit-identical regenerator comparators (the first - on the OS 13 , resistors 16-19, zener diode 27 and the second on op-amp 14, resistors 20-23, zener diode 28), a voltage inverter on op-amp 15, resistors 24, 25 and a logic element 2 OR on diodes 29, 30, resistor 26. Resistors 16, 17, 20, 21, 24, 25 are selected with the same resistance values. As the OS 13-15 used chips type KR140UD608A; as zener diodes 27, 28, two-sided zener diodes of the type KS210B were used; as diodes 29, 30 used diodes type KD522B; the device uses resistors of type C2-10-0.25. At the output of the comparator, voltages corresponding to the high and low logical levels of the CMOS chips are formed.

The DC voltage source 10 is assembled on the basis of a precision Zener diode of the D818E type and an op amp of the KR140UD608A type included in the voltage follower circuit. The output voltage U ₁₀ is adjusted using a trimming resistor. The generator of 11 single pulses is assembled on a D-trigger, which is part of the CMOS chip K561TM1. The pulse duration is set by the parameters of the elements of the RC circuit. As an electronic key 12 involved one of the channels of the CMOS chip KR590KN7.

So, compared with a device for a similar purpose (prototype), the inventive device has several advantages. In him:

- automated operation of resetting the integrator;

- increased dynamic range of the magnetometer without reducing sensitivity;

- excluded a number of manual actions by the operator;

- the loss of useful information is excluded;

- optimized consumption of cryogenic resources.

Claims (1)

A magnetometer with a superconducting quantum interferometric sensor, comprising a superconducting quantum interferometric sensor (SQUID) with matching electric circuits connected to the input of the amplifier, the output of which is connected to the first input of the synchronous detector, the output of the synchronous detector is connected to the input of the integrator with an integrating capacitor, the outputs of the bias current generator, the low-frequency generator and the integrator are connected to the SQUID, between the output of the low-frequency generator and the second input of the synchronous det The phase shifter is turned on, and the buffer stage is connected by its input to the output of the integrator, characterized in that a two-threshold regenerator comparator, a constant voltage source, a single pulse generator and an electronic key are introduced into it, and the two-threshold regenerator comparator is connected by the first input to the integrator output, and the second input to a constant voltage source, a single pulse generator is connected by its input to the output of the two-threshold regenerative comparator, and by the output to the control input ics key that their first and second outputs connected to the integrator to the plates of the integrating capacitor.

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