RU2802341C1 - Method for simultaneous generation of a magnetic field and thermal stabilization of a quantum rotation sensor and a device for its implementation - Google Patents

Abstract

FIELD: gyroscopes.

SUBSTANCE: invention is based on the phenomenon of nuclear magnetic resonance, namely to a means of simultaneous generation of a magnetic field and thermal stabilization of a quantum rotation sensor. The device contains a solenoid, gas cells (GC), a temperature sensor, transverse field receiving coils, a transverse field signal amplifier, a temperature sensor error signal amplifier, a controller for controlling temperature and Larmor precession frequency in transverse coils. Two DC sources are connected to the controller output, loaded on the windings of direct and reverse currents (i₁, i₂) of the solenoid to provide total and differential currents for stabilizing the temperature and magnetic field. As a result of processing input signals, controller 9 generates control signals at outputs 1 and 2 such that DC sources 10 and 11 generate currents i₁ and i₂, respectively, allowing in total (i₁+i₂) to heat cell 2 to temperature T₀ with retention it at the level of accuracy required for a quantum system, and the difference current (i₁-i₂) to create and maintain a constant magnetic field B_z at the required level of accuracy.

EFFECT: getting rid of parasitic magnetism created by the heater and uncontrolled heating created by magnetic coils.

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Description

The invention relates to gyroscopes based on the phenomenon of nuclear magnetic resonance (hereinafter referred to as NMR) and is intended to control and maintain the necessary constant magnetic field and a given temperature in the volume of a working gas cell (hereinafter referred to as HC).

A known method of maintaining a stable uniform magnetic field using a solenoid located coaxially with the sensitivity axis of the quantum rotation sensor (hereinafter referred to as QDV) of the NMR gyroscope [1, 2]. Also known is a method of temperature control of HH using a temperature controller using a separate non-magnetic heater [3]. The disadvantages of separate temperature control and stabilization of the magnetic field are the complication of the KDV construction scheme, uncontrolled heating caused by the current flowing through the solenoid of the magnetic system, uncontrolled parasitic magnetic field created by the heater of the temperature control system of the GY, the need to have a separate solenoid and heater. To suppress the parasitic magnetic field of the heater, heating with alternating current and bifilar winding with the possibility of interlacing conductors or anti-parallel wiring of the printed conductors of the HJ heater are used [3–6]. However, the use of alternating current in the heater leads to pickup at the frequency of the heating current and its harmonics. This pickup interacts with the precession signals of the magnetically sensitive atoms of the GY quantum system and creates crosstalk, which can contribute to the QDV error of the gyroscope.

As part of similar KDVs, the function of the gas cell heater is currently performed by a separate device containing a maximally non-magnetic heater, for example, proposed in the patent [3] and a temperature sensor controlled by a temperature controller that ensures high-precision maintenance of the set temperature.

The solenoid described in [7 - 11] was adopted as a prototype of the proposed device. Such a solenoid, consisting of one winding (coil), creates the most uniform magnetic field in the internal volume. Prototype solenoid does not support heater function. It is planned to heat the KDV gas cell with a separate heater [3], which is included in the temperature control system along with a temperature sensor and a controller.

Figure 1 shows options for constructing a solenoid that combines the functions of a heater and a magnetic field source with a single-layer winding made of a twisted pair of conductors for forward and reverse current:

a ) solenoid based on the prototype [7 - 11] with the most homogeneous internal field,

b ) solenoid based on the prototype [7 - 11] on a cylindrical frame with a variable winding pitch,

c ) Ampère solenoid [12],

d ) a solenoid based on a Barker coil [12].

In all cases, the dotted line represents the vertical central axis.

The solenoid producing the magnetic field may include a conductive coil whose radius around the central axis is determined by a compound expression at each point of the central axis (Fig. 1a ). Thus, the magnetic solenoid may be substantially symmetrical about a plane at the midpoint of the magnetic solenoid along the internal axis.

A solenoid can be used that has a cylindrical generatrix surface, but a variable winding density along the length (Fig. 1b ). The maximum value of the distance between the turns approximately corresponds to the center point. For example, the series spacing between turns may be symmetrical about a center point along the length of the magnetic solenoid. As a result of the uneven spacing between the turns, the magnetic solenoid can have a substantially uniform magnetic field within the inner volume of the generating surface. Both of these design options for the solenoid [7 - 11] can be considered as a prototype.

Also known are the Ampere solenoid, consisting of an extended cylindrical coil (Fig. 1c ), a sectioned solenoid in the form of a Barker coil (Fig. 1d ), and a number of others considered in [12].

Disadvantages of the prototype: the need for separate temperature control and stabilization of the magnetic field leads to a complication of the KDV construction scheme, uncontrolled heating caused by the current flowing through the solenoid of the magnetic system, uncontrolled parasitic magnetic induction created by the heater of the DH thermostating system, the need to have a separate solenoid and heater. In addition, to suppress the parasitic magnetic induction of the heater, alternating current heating is used, which leads to interference at the heating frequency and its harmonics, which can serve as a source of a systematic error in the KDV.

The technical problem being solved is the improvement of the conditions for the functioning of a quantum system of GY, accompanied by a simplification of the QDV scheme.

Technical result achieved: getting rid of parasitic magnetic pickups created by the heater and uncontrolled heating created by magnetic coils. It also eliminates the need for AC heating and the need for a separate heater.

The proposed method: a method for the simultaneous generation of a magnetic field and thermal stabilization of a quantum rotation sensor, which consists in the development by a solenoid under the control of a controller of the temperature of the gas mixture necessary for the functioning of the quantum system of the gas cell and the magnetic field that sets the axis of sensitivity, characterized in that the solenoid has two windings designed for transmission of two opposite currents, while the solenoid windings are fed with direct current, and the sum of these currents determines the heat release of the system and is used to heat the internal volume of the solenoid, including the gas cell.

Implementation of the proposed method and device is achieved by combining the functions of a source of a constant magnetic field, which sets the sensitivity axis of the KDV, and a heating element of the temperature control system of the HJ in one structural unit - a solenoid with a special arrangement of windings.

Figure 2 shows: a) - a schematic diagram of the solenoid, b) - the proposed design of the organization of the solenoid windings. The designations in Figs. 2:

M - magnetic connection between the windings;

i ₁ - direct current of the first winding;

i ₂ - direct current of the second winding.

It is proposed to wind the solenoid from two interconnected, back-to-back windings - Fig. 2 a . In this case, the solenoid windings are fed with direct current, which eliminates the creation of pickups at the frequency of the heating alternating current and its harmonics.

This inclusion of the solenoid windings allows you to simultaneously implement two functions:

- source of magnetic field, proportional to the difference of flowing currents ( i ₁ - i ₂ ).

- a heater, the heat release of which is proportional to the total current in the windings ( i ₁ +i ₂ ), the sum of these currents determines the heat release of the system and is used to heat the internal volume of the solenoid, including the gas cell;

In the proposed design of the organization of the solenoid windings (Fig. 2b), which creates the most uniform magnetic field, the number of winding layers of the windings should correspond to 2 ^N , where N is an integer, ≥ 0, which will reduce the parasitic interference of the heater.

In FIG. 3 shows a block diagram of the proposed device for the simultaneous generation of a magnetic field and thermal stabilization of the KDV, operating on the proposed method, where:

1 - solenoid, consisting of two windings with magnetic coupling;

2 - gas cell KDV (hereinafter referred to as the gas cell);

3 - temperature sensor;

4 - coil for receiving a signal of the transverse projection of the magnetic field vector on the x axis;

5 - coil for receiving a signal of the transverse projection of the magnetic field vector onto the y axis;

6 - signal amplifier of the transverse projection of the magnetic field vector on the x axis;

7 - signal amplifier of the transverse projection of the magnetic field vector on the y axis;

8 - temperature sensor error signal amplifier;

9 - controller;

10 - direct current source i ₁ (hereinafter - IPT1);

11 - DC source i ₂ (hereinafter - IPT2);

M - magnetic connection;

z - axis of QDV sensitivity, coinciding with the longitudinal axis of the proposed solenoid 1 and the quantization axis of the quantum system GYa 2;

x, y - transverse axes of the KDV magnetic system;

S _x , S _y - controller input signals required to stabilize the magnetic field;

T ₀ - preset value of the operating temperature HJ;

Δ T - temperature error signal.

The control of the magnetic field source and the heater is carried out by the controller, which is part of the electronic part of the KDV circuit. This controller controls two direct current sources (DCS), the total output current of which provides heating of the solenoid coils to the temperature required for the operation of the HV. The current difference is maintained at a value necessary to create a constant longitudinal magnetic field that creates the quantization axis of the NMR gyroscope. The controller maintains the control of heating and magnetic field in a closed state and provides the necessary level of stabilization of the corresponding parameters in accordance with the requirements of the quantum NMR gyroscope system.

As the proposed solenoid, which combines two functions (a source of a magnetic field and a heating element) at the same time, an extended coil or a group of coaxial narrow rings (Barker coil) can be used, having a winding of 2 ^N (where N is an integer, ≥ 0) the number of winding layers with the creation of a twisted pair or parallel lines in the case of a printed method of manufacturing from conductors for the forward and reverse directions of current ( i ₁ , i ₂ ). When winding or designing a winding using the printed wiring method (sputtering, etching, etc.), recommendations on the combination of conductors for the forward and reverse current directions should be taken into account [3]. With the complete coincidence of the forward and reverse current, there is no magnetic field in such a coil. However, with independent control of the indicated currents, such a coil generates a magnetic field proportional to the difference in the currents feeding it.

The proposed method is as follows:

1. The solenoid, built according to the scheme of Fig. 2 a , having two magnetically coupled windings, the design variants of which are shown in FIG. 1 (ad) , and 2 b , generates a constant uniform magnetic field proportional to the difference of the electric current windings feeding it ( i ₁ -i ₂ ).

2. The solenoid generates thermal radiation proportional to the sum of the electric current windings feeding it ( i ₁ + i ₂ ), which ensures the functioning of the GW at a given temperature, necessary for the organization of a quantum system inside the GW.

3. Heating and magnetic field are controlled by the controller. For high-precision maintenance of the required values of the magnetic field induction and temperature, the magnetic and thermal circuits are maintained in a closed state using the signals of the transverse projection of the magnetic field vector on the x and y axes of the KDV and the temperature sensor involved in the formation of the input signals of the controller S _x , S _y and Δ T .

4. The temperature sensor performs the function of measuring the temperature of the GY. It is located near the technological offshoot of the HH, which serves as a reservoir of alkali metal (AL), the temperature of which is structurally ensured to be minimal in relation to the rest of the HH. The temperature gradient does not exceed 0.1°C, but it must be so that when the cell cools in the inactive state, the KDV, SM contained in it condenses back into the technological process, thereby preventing unwanted metallization of the walls of the DH. The temperature stabilizer maintains the temperature of the offshoot, ensuring precisely adjusted evaporation of alkali metal atoms into the working volume of the HW. As a temperature sensor, various non-magnetic thermistors can be used, for example, platinum, semiconductor, or specially made wire temperature sensors wound in compliance with the rules for suppressing the magnetic field they create, proposed in [4, 5].

5. Transverse components of the precession signals of a quantum system of quantum wells. Macroscopic magnetic moments of the atoms that make up the working gas mixture - alkali metal vapors and inert gases - are created inside a working HJ. Each of them precesses at its own frequency in a magnetic field. Under the action of external rotation of the KDV body relative to the sensitivity axis z , the observed frequency of the precession of magnetic moments corresponding to inert gases is shifted, which is the basis for determining the rotation speed. However, the sum of the frequencies of this precession remains unchanged and is used to stabilize the longitudinal magnetic field B _z . Signals containing information about precessing magnetic moments are read by special coils oriented along the transverse x and y axes of the HJ and the solenoid.

For high-precision stabilization of the magnetic field at the required value, the magnetic system is maintained in a closed state using a controller using input signals S _x and S _{y .}

Implementing the method device (figure 3) contains: the proposed solenoid; a temperature sensor located near the coldest part of the GY - an offshoot for storing alkali metal; receiving coils of transverse ( x and y ) fields, signal amplifiers of the transverse components of the magnetic field; temperature sensor error signal amplifier; solenoid temperature and magnetic field control controller; two IPTs connected to the controller output and loaded on the windings of the direct and reverse currents of the solenoid to provide total and differential currents to stabilize the temperature and magnetic field.

The proposed device works as follows.

Solenoid 1 generates a magnetic field B _z in the z direction; on the perpendicular directions x and y , signals of projections of the precession of the magnetic moment of the atoms that make up the quantum system of the GY arise. The quantum system formed in the gaseous medium of HH 2, when the operating temperature of the cell corresponds to the required value, under the action of a magnetic field B _z , which sets the QDV sensitivity axis and the measured rotation around this axis, generates precession signals of quantum objects (atoms, nuclei of the gases contained in it), which are perceived by transverse coils 4 and 5. After the necessary amplification by amplifiers 6, 7, these signals S _x , S _y are fed to the corresponding inputs of the controller 9 to stabilize the magnetic field. The third input of the controller 9 receives the temperature error signal ΔT generated by the temperature error signal amplifier 8 based on the comparison of the temperature sensor signal 3 with the preset value of the operating temperature of the gas cell T ₀ . As a result of processing the input signals, the controller 9 generates control signals at outputs 1 and 2 such that the IPT 10 and 11 generate currents i ₁ and i ₂ , respectively, allowing in total ( i ₁ + i ₂ ) to heat cell 2 to a temperature T ₀ with retention it at the level of accuracy required for a quantum system, and the difference current ( i ₁ - i ₂ ) to create a constant magnetic field B _z and keep it at the required level of accuracy.

The possibility of achieving a technical result is provided by the design of the solenoid. Each of the two coils that make up the proposed solenoid creates a magnetic field directed in mutually opposite directions. The vector summation of these fields gives the resultant field vector Bz , directed in the direction corresponding to the direction of the greater modulus of the vectors B ₁ or B ₂ , corresponding to the currents i ₁ and i ₂ . The differential current ( i ₁ - i ₂ ) does not physically flow anywhere, does not create heating and magnetic field. Therefore, the uncontrolled heating created by the magnetic coils is completely eliminated. The tracking automatic control system controls the entire residual magnetic field Bz and can be built in such a way that, due to the use of an integrating link in the controller, the error is reduced to zero. Similarly, the entire heat dissipation of both coils that make up the solenoid, corresponding to the sum of currents i ₁ and i ₂ ( i ₁ + i ₂ ), is controlled by its tracking system in the controller structure, which includes an integrating link that reduces the temperature error to zero.

When constructing a KDV according to the usual scheme, which provides for the separate organization of a single-winding solenoid that creates a magnetic field and a heating element responsible for the HW heating function, uncontrolled heating and a parasitic magnetic field occur. The following are the possible numerical values of the parameters when organizing the sensor:

- longitudinal magnetic field B _z = 10 μT;

- working temperature HY T = 80°C;

- solenoid coil constant (coefficient of current to magnetic field conversion)

K _L = 2·10 ^-3 T/A;

- constant of the heating element (coefficient of conversion of current into a magnetic field) K _T = 5·10 ^-7 T/A;

- average solenoid current I _L = 5 mA;

- maximum current of the heating element I _T = 0.5 A;

- thermal power released by the solenoid coil P _L = 275 μW;

- magnetic field induction created by the heating element when powered by direct current B _T = 250 nT.

The parasitic parameters arising from the separate creation of a magnetic field and cell heating (thermal power and magnetic field induction) are not controlled by the temperature and magnetic field controllers, respectively, and cause an uncontrolled systematic error of the QDV. The magnetic field induction created by the heating element can be largely suppressed by using alternating current for heating, but in this case, cross beats of the heating current frequency, its harmonics and the precession frequencies of the quantum system inside the GW occur, also leading to a systematic error of the sensor. The use of the proposed solenoid, consisting of two interconnected windings, allows you to completely avoid these problems.

Thus, the claimed technical result is achieved.

Information sources:

1. Patent EP 2666037. Gyroscope System Magnetic Field Error Compensation

2. Patent US 8600691 B2. Gyroscope System Magnetic Field Error Compensation

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Claims (2)

1. A method for the simultaneous generation of a magnetic field and thermal stabilization of a quantum rotation sensor, which consists in the development by a solenoid under the control of the controller of the gas mixture temperature and the magnetic field necessary for the functioning of the quantum system of the gas cell, which sets the axis of sensitivity, characterized in that the solenoid has two windings designed to transmit two oppositely directed currents, while the solenoid windings are fed with direct current, and the sum of these currents determines the heat release of the system and is used to heat the internal volume of the solenoid, including the gas cell. 2. A device for implementing a method for the simultaneous generation of a magnetic field and thermal stabilization of a quantum rotation sensor, consisting of a solenoid, a heating element and a controller, characterized in that the solenoid contains two windings designed to pass two opposing direct currents, while the solenoid creates a magnetic field proportional to the difference between forward and reverse currents, the sum of these currents determines the heat dissipation of the device and is used to heat the internal volume of the solenoid, including the gas cell, and the controller controls the sum and difference of currents in the windings.