RU2793615C1 - Method for determining the magnetic field distribution - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: invention can be used to determine the distribution of the magnetic field in a given area of space (in particular, the working chambers of high-energy installations). Essence: to determine the distribution of the magnetic field in a given region of space, a target made of a magnetic material is placed. The surface of said target is heated to a temperature at which at least partial melting of said material occurs. The impact effect is carried out on the heated surface of said target, as a result of which particles of said material fly out and settle on the surface of said target. The distribution pattern of particles of said material on the surface of said target is fixed, corresponding to the distribution pattern of the magnetic field in a given region of space.

EFFECT: providing the possibility of determining the distribution of the magnetic field in any given area of space, including the working chambers of high-energy installations, including those in which an aggressive environment is created and/or there are increased requirements for the operating modes of such installations without the need to make significant changes to their design solutions.

10 cl, 15 dwg

Description

The claimed invention relates to the field of measuring technology and can be used to determine the distribution of the magnetic field in a given area of space (in particular, the working chambers of high-energy installations).

There is a known method for determining the distribution of the magnetic field in the working space of a planar magnetron (see "Analysis of the magnetic system of a planar magnetron source using a magnetic scanner", Proceedings of the XXVIII International Symposium "Thin Films in Electronics", "Nanoengineering", 2016, pp. 163- 166 [1]). In the known method, a Hall sensor is used, which is moved along the surface of the magnetron at a certain distance from it. First, the sensor captures the component of the magnetic field induction, perpendicular to the plane of the magnetron. Then the sensor is rotated to two other positions to fix the planar components of the magnetic field induction.

The main disadvantage of the known method is that the Hall sensor exhibits low reliability under extreme conditions (high temperature, high energy density). So, for example, exposure to such a sensor of high-temperature plasma can lead to its failure, both due to physical destruction, and as a result of changes in characteristics (see the article by Glazyrin I.V. et al. power fluxes ~1 TW/cm ² ”, VANT, series “Thermonuclear synthesis”, 2009, issue 2, p. 70 [2]).

In addition, with a single movable sensor, only time-invariant magnetic fields can be investigated. Rapidly changing magnetic fields (from nanoseconds to microseconds) cannot be studied with a single movable sensor.

There is a known method for determining the distribution of the magnetic field in the vacuum chamber of the KTM tokamak, including fixing the pattern of the distribution of the magnetic field (see the article Skakov M.K. "Thermonuclear Fusion", 2015, v.38, issue 4, pp. 41-50 [3]). In the known method, a matrix of 36 Hall sensors is used.

The disadvantages of the known method lie in the low reliability of Hall sensors under extreme conditions already described above, as well as in the rather complicated installation of a matrix of such sensors in the working space of the experimental setup (in particular, if the experiment takes place inside a vacuum chamber, a vacuum input will need to be made for each sensor for signal wires, which will greatly complicate the experiment). In addition, the destruction of Hall sensors as a result of exposure to an aggressive environment, for example, powerful plasma flows, leading to the need to dismantle and replace them, causes additional difficulties when using them in chambers with a constant operating pressure, in particular, the need to create a special lock element (see the article by Mitrofanova K.N. et al. “Investigation of the fine structure of PCS and magnetic fields in the axial region of the PF-1000 setup”, Plasma Physics, 2014, v.40, No. 8, pp. 721-737 [ 4]).

It should be noted that in [4] it is proposed to use other sensors instead of Hall sensors (representing miniature coils with several turns), which, nevertheless, does not solve the problem of their failure.

Known from [3] method is adopted as the closest analogue of the claimed method.

The technical problem solved by the claimed invention is to create a method for determining the distribution of the magnetic field in a given area of space, which has a wide range of applications with relative ease of use.

At the same time, a technical result is achieved, which consists in ensuring the possibility of determining the distribution of the magnetic field in any given area of space, including the working chambers of high-energy installations, including those in which an aggressive environment is created and/or there are increased requirements for the operating modes of such installations, without the need to make significant changes to their design solutions.

The technical problem is solved, and the specified technical result is achieved as a result of creating a method for determining the distribution of the magnetic field in a given area of space, in which:

- a target made of magnetic material is placed in a given area of space,

- heating the surface of said target to a temperature at which at least partial melting of said material occurs,

- impact is applied to the heated surface of said target, as a result of which particles of said material fly out and settle on the surface of said target, and

- fixing the distribution pattern of particles of said material on the surface of said target, corresponding to the distribution pattern of the magnetic field in a given region of space.

The source of said heating and/or the source of said shock can be both initially placed in a given area of space (for example, be part of a high-energy installation), and placed in it in connection with the need to provide heating and/or shock.

In one of the particular variants, a plasma focus installation is used as a source of said heating, as well as a source of said impact action, while said target is placed in the discharge chamber of said installation at a given distance from its anode and the surface of said target is affected by a single plasma pulse or a series such impulses.

In another particular variant, a laser installation is used as a source of said heating, as well as a source of said impact action, while said target is placed at a predetermined distance from the exit window of said installation and the surface of said target is affected by a single laser pulse or a series of such pulses.

In another particular embodiment, said heating of the surface of said target is carried out with the help of an inductor.

In another particular variant, said heating of the surface of said target is carried out using a current circuit located in close proximity to the surface of said target on the same side from which particles of said material are observed to settle.

In yet another particular embodiment, said heating of the surface of said target is carried out by passing an electric current through said target.

In another particular variant, said impact on the heated surface of said target is carried out by means of a mechanical shock to the center of said target from the side, the reverse side, from which particles of the said material are observed to settle.

In another particular embodiment, a mechanical impactor is used as a source of mechanical impact.

In another particular variant, a piezoelectric element is used as a source of mechanical shock, located on the surface of the said target from the side, the reverse side, from which particles of the said material are observed to settle.

In another particular embodiment, a bullet or projectile is used as a source of mechanical impact.

In another particular embodiment, a particle beam is used as a source of mechanical shock.

In another particular variant, said heating of the surface of said target and said impact on the heated surface of said target is carried out by a beam of charged particles.

Figure 1 shows a diagram of the implementation of the claimed method, according to one of the private options (in the installation of the plasma focus PF-5, FIAN).

Figure 2 shows a diagram of the implementation of the claimed method, according to another particular variant (in a laser machine).

On figa and 3b shows a diagram of the implementation of heating, according to another particular variant (induction heating).

Figure 4 shows a diagram of the implementation of the claimed method, according to another particular variant (heating by passing an electric current through the target and impact by means of a mechanical striker).

Figure 5 shows a diagram of the implementation of the claimed method, according to another particular variant (heating by means of a current circuit and impact by means of a piezoelectric element).

Figure 6 shows a diagram of the implementation of the impact, according to another particular variant (by means of a mechanical striker).

Figure 7 shows a diagram of the implementation of impact, according to another particular option (by means of a piezoelectric element).

Figure 8 shows a diagram of the impact, according to another particular option (using a bullet or projectile).

Figure 9 shows a diagram of the implementation of impact, according to another particular variant (using a particle beam).

Figure 10 shows a diagram of the implementation of the claimed method, according to another particular variant (heating and impact with a beam of charged particles).

Figure 11 shows the pattern of the distribution of particles of the molten material over the surface of the Fe target as a result of the action of nitrogen plasma pulses at a distance from the anode to the target, equal to 25 mm, when the capacitor bank is charged up to 18 kV at the PF-5 installation.

Figure 12 shows the pattern of the distribution of particles of the molten material over the surface of the Fe target as a result of the action of nitrogen plasma pulses at a distance from the anode to the target, equal to 50 mm, when the capacitor bank is charged up to 18 kV at the PF-5 installation.

Figure 13 shows the pattern of the distribution of particles of the molten material over the surface of the Al target as a result of the action of nitrogen plasma pulses at a distance from the anode to the target, equal to 25 mm, when the capacitor bank is charged up to 18 kV at the PF-5 installation.

Fig.14 and 15 demonstrate the possibility of simultaneous use of a beam of charged particles with a mechanical striker (Fig.14) and simultaneous use of a beam of charged particles with a piezoelectric element (Fig.15).

The plasma focus setup shown in Fig. 1 is one of the variants of the Z-pinch plasma device and consists of two coaxial copper electrodes (anode 1 and cathode 2), separated by a cylindrical ceramic insulator 3, and a capacitor bank 4. Anode 1 and cathode 2 are placed in the discharge chamber 5, which is filled with working gas to a pressure of several mm Hg. The energy stored in the capacitor bank 4 is supplied to the anode 1 through a controlled spark gap 6.

After applying voltage, an electrical breakdown occurs along the surface of insulator 3, leading to the formation of a current-plasma sheath (hereinafter referred to as CSP), which, under the action of ponderomotive forces, first breaks away from the surface of insulator 3, and then it moves in the interelectrode space in the direction of the ends of anode 1 and cathode 2.

After reaching the ends of the anode 1 and cathode 2, the TPO begins to move in the radial direction towards the vertical axis of the installation, while the TPO acquires the shape of a cone with the top directed towards the anode 1 (see pos.7 in figure 1). Due to the conical shape of the PCS, in the process of its compression on the vertical axis, a cumulative flow of dense high-temperature plasma is formed.

It is known that magnetic fields arise in plasma focus devices. For example, in the article by Krauz V.I. 3 using magnetic probes located at different distances from the setup axis and from the anode. The magnetic probes began to record the magnetic field generated by the PCS as it approached them.

To implement the claimed method, the target 8, mainly with a flat or hemispherical surface (which provides a clear picture of the distribution of the magnetic field), made of a magnetic material (an alloy based on iron or any other material that exhibits magnetic properties) is placed in the discharge chamber 5 at a given ( determined by the task of the experiment) distance from the anode 1.

As a result of exposure to the target surface 8 by a single plasma pulse or a series of such pulses (see item 9 in figure 1), the target surface 8 is heated to a temperature at which at least partial melting of the material from which the target is made occurs 8. In particular, in the PF-5 setup during the experiment, the surface of the target 8 can be heated to a temperature of more than 3000°C.

As a result, particles of the material from which the target 8 is made fly out and settle on the surface of the target 8. Next, the pattern of the distribution of material particles on the surface of the target 8 is recorded, corresponding to the pattern of the distribution of the magnetic field in the discharge chamber 5.

In the embodiment of the method shown in Fig. 2, the target 8 is placed at a predetermined (determined by the task of the experiment) distance from the output window 10 of the laser unit 11 and the surface of the target 8 is exposed to a single laser pulse or a series of such pulses (see pos. 12 in Fig. .2).

It is known that near a target irradiated with laser radiation, magnetic fields arise with a direction parallel to the target plane (see the article by Yu.S. Kas'yanov, G.S. Sarkisov "Spatial-temporal measurement of magnetic fields in laser-produced plasmas", Journal of Russian Laser Research, Vol.15, No. 3, 1994, pp.265-282, or review by J. A. Stamper "Review on spontaneous magnetic fields in laser-produced plasmas: Phenomena and measurements", Laser and Particle Beams, Vol.9, No. 4, pp.841-862).

As a result of exposure of the target surface 8 to a single laser pulse or a series of such pulses 12, the target surface 8 is heated to a temperature at which at least partial melting of the material from which the target 8 is made occurs.

As a result, particles of the material from which the target 8 is made fly out and settle on the surface of the target 8. Then, similarly, the pattern of the distribution of material particles on the surface of the target 8 is fixed, corresponding to the pattern of the distribution of the magnetic field in the region of space in front of the target 8.

In the embodiment of the method shown in FIG. 3, the target surface 8 is heated by induction heating. As shown in figa, the target 8 is placed inside the inductor 13 (coil with current coils), heated with alternating current, after which it is desirable to turn off the inductor 13 so that the magnetic fields created by it do not introduce errors into the studied magnetic fields of a given region of space, and also remove to the side so that the surface of the target 8 is not covered by the current coils of the inductor 13 (see Fig. 3b). After that, it is necessary to carry out a shock effect on the target 8, for example, by means of a mechanical striker (described in more detail with reference to Fig.6).

In the embodiment of the method shown in figure 4, the heating of the target surface 8 is carried out by passing an electric current through the target 8 using conductors (for example, industrial wires) 14. After heating, it is necessary to impact the target 8, for example, using a mechanical impactor described in more detail with reference to Fig.6).

In the embodiment of the method shown in Fig.5, the heating of the target surface 8 is carried out using a current circuit 15 located on the same side from which the particles of the target material 8 are observed. Power is supplied to the current circuit 15 through conductors 16. in particular, it can be made of tungsten filament (melting point 3422°C). The melting temperature of the circuit material 15 must be higher than the melting temperature of the target material 8. It is also possible to use as current circuits 15 electric heaters similar to those used in electric resistance furnaces, for example, from molybdenum disilicide (melting temperature 1300-1500 ° C), carborundum or silicate (melting point up to 1300°C). The choice of a suitable material for the current loop 15 will depend on the chosen material of the target 8 (namely, its melting point). In the general case, the current circuit 15, located on the same side from which the particles of the target material 8 are deposited, does not introduce significant distortion into the pattern of the distribution of the studied magnetic field. However, in the case when it is necessary to obtain the most reliable picture of the distribution, it is possible to remove the current circuit 15 away from the target 8 after the moment when its surface begins to melt. After heating, it is necessary to carry out an impact on the target 8, for example, by means of a piezoelectric element (described in more detail with reference to Fig.7).

In the embodiments of the impact action shown in Figs. 4-9, the impact on the heated surface of the target 8 is carried out by mechanical impact on the center of the target 8 from the side, the reverse side, from which the particles of the target 8 material are deposited. In particular, as shown in 6, a mechanical striker 16 can be used as a source of mechanical shock. The motor 17, powered, for example, from an industrial network using conductors 18, moves the piston 19, which, through the air gap 20, in turn, moves the striker 16, which strikes along the metal conductor (hub) 21 of the shock wave. The metal conductor (hub) 21 of the shock wave is fixed in the housing 22 using the holder 23 of the conductor (hub) 21 of the shock wave. The shock wave is transmitted through the concentrator 21 to the center of the target 8 and then propagates from the center to the periphery of the target 8 (the principle of operation, as in a jackhammer). It is possible to synchronize the moment of the beginning of melting of the target surface 8 with the moment of impact (one), but it is also possible to create constantly periodic impacts (as in a jackhammer).

As a source of mechanical shock, you can also use the piezoelectric element 24, installed on the surface of the target 8 from the side, the reverse side, from which the particles of the target material 8 are observed (see Fig.7). When voltage is applied to the piezoelectric element 24 through the conductors 25, it bends, thereby creating a shock wave in the target 8, which propagates from the center to the periphery.

As a source of mechanical shock, you can also use a bullet or projectile 26 that hits the center of the target 8 from the side, the reverse side, from which the particles of the target material 8 are deposited (see Fig.8). The mechanism for accelerating the bullet or projectile 26 is not shown; any of the known mechanisms (eg, a pistol mechanism) may be used. The arrow (pos. 27) shows the direction of movement of the bullet or projectile 26. The bullet or projectile 26, when it hits the target 8, creates a shock wave in it, propagating from the center to the periphery.

As a source of mechanical shock, it is also possible to use a beam of particles 28 (in particular, shots) falling into the center of the target 8 from the side, the reverse side, from which the particles of the target material 8 are deposited (see Fig. 9). The mechanism for accelerating the particle beam 28 is not shown, any of the known mechanisms can be used (for example, a pistol mechanism). The arrow (pos. 29) shows the direction of movement of the particle beam 28. The particle beam 28, when it hits the target 8, creates a shock wave in it, propagating from the center to the periphery.

Along with the above methods of heating the surface of the target 8, figure 10 shows another one, namely, using a beam of charged particles 30. The arrow (pos.31) shows the direction of movement of the beam of charged particles 30. The beam of charged particles 30, when hit on target 8, heats its surface. The advantage of this heating method is the possibility of directing the beam of charged particles 30 at an angle (i.e., not only perpendicular) to the target surface 8.

When charged particle beam 30 is perpendicularly incident on the target surface 8, it can be used to carry out both heating and impact on the heated target surface 8. In this case, the charged particle beam 30 must be located on the side from which the settling of particles of the target material 8 is observed.

The feasibility of the proposed method is confirmed by the experimental results obtained at the PF-5 installation. An analysis was made of the experimental data obtained as a result of irradiation of flat targets 8 made of Fe, Cu, and Al at various distances (~25 and ~50 mm) from the anode 1 PF-5 with plasma pulses. Nitrogen was used as the working gas. The capacitor bank 4 was charged up to 18 kV.

On the surface of the target 8 of Fe (ferromagnet) there was an orientation of small particles (drops) of molten metal along the lines of the magnetic field, which is associated with current filaments that form TPO when it converges over the anode 1 PF-5 (see figure 1). At a close (-25 mm) location of the Fe target 8, the magnetic field lines from the current filaments penetrate the metal and orient the metal drops.

As a result, for Fe, a pattern of curvature of conditional expansion lines of molten metal drops near the edge of the plasma impact zone is observed (see Fig. 11). When the target is removed from Fe at a greater distance (~50 mm), the observed pattern disappears (see Fig. 12), which is due to the weakening of the magnetic field from the current filaments at such a distance and, as a result, the insufficiency of the magnetic induction to rotate the molten metal drops on the surface of the target 8.

For Al (paramagnet) over the entire zone of plasma impact on the surface of the target 8, the pattern of a rectilinear distribution of molten metal drops is preserved (see Fig. 13). For Cu (diamagnet), a pattern similar to Al (not shown) takes place.

It should be noted that the discharge process in PF-5 has a periodic nature of a sinusoidal shape with a change in the sign of the potential at the anode 1 from "+" to "-". Figure 1 shows the direction of the currents and magnetic fields from them in the time period when the anode "+". It is the periodic change in the direction of the current and, accordingly, the changing direction of the magnetic field that contributes to the fact that we observe the rotation of the drops of molten metal (in the case of Fe) in Fig.11 both clockwise and counterclockwise.

Theoretically and experimentally, it was previously proven that a liquid metal is capable of responding to the effects of an external magnetic field (see, in particular, Michael Conrath's work "Dynamics of Liquid Metal Drops Influenced by Electromagnetic Fields", 2007, pp. 32-56 [6]) . In the mentioned work, it is shown that a disk of molten metal can take various fixed geometric shapes depending on the parameters of the magnetic field acting on it. In particular, the change in the shape of the molten metal disk depending on the magnitude of the current in the inductor that creates the external magnetic field and the frequency of the external magnetic field was studied, and it was shown that the initially round molten metal disk with an increase in the inductor current and the frequency of the external magnetic field changes its shape first to single-leaf, then to two-, three- and four-leaf, and with a further increase in the parameters, the drop breaks up into two or more separate drops, also having a shape of a different number of petals.

In the absence of a magnetic field component parallel to the plane of the target 8, or an insufficient value of this component (as in the case of the distance of the target 8 at a great distance from the TPO shown in Fig. 12), the distribution pattern of particles (droplets) of the molten magnetic material will not be observed turning drops (as in Fig.11). The pattern of distribution of drops of molten magnetic material will show a rectilinear distribution of drops from the center of the target 8 to its periphery (as in Fig.13).

In such a case, to implement the claimed method, it is necessary to use a target 8 with a curvilinear surface, in particular, a hemispherical surface, or change the location of the target 8 in a given area of space.

The proposed method is simple to use and allows, having a reference picture of the distribution of particles of molten magnetic material on the target surface in the presence of a magnetic field with known parameters in a given area of space, to compare it with patterns obtained under predetermined conditions. Thus, the proposed method allows to determine with a high degree of certainty the presence or absence of magnetic field components in a given region of space. In addition, the proposed method makes it possible to determine the parameters of the magnetic field with sufficient accuracy without the need to use complex (and often inapplicable under extreme experimental conditions) electronic means for measuring and recording magnetic field components.

Claims (10)

1. A method for determining the distribution of a magnetic field in a given region of space, including fixing the pattern of the distribution of the magnetic field, characterized in that a target made of a magnetic material is placed in a given region of space, the surface of said target is heated to a temperature at which at least partial melting of said material, an impact is made on the heated surface of said target, as a result of which particles of said material fly out and settle on the surface of said target, and a pattern of distribution of particles of said material on the surface of said target is recorded, corresponding to the pattern of distribution of the magnetic field in a given area space. 2. The method according to claim 1, characterized in that a source of said heating and/or a source of said impact is placed in a given area of space. 3. The method according to claim 1 or 2, characterized in that a plasma focus installation is used as a source of said heating, as well as a source of said impact action, while said target is placed in the discharge chamber of said installation at a predetermined distance from its anode and act on the surface of said target by a single plasma pulse or a series of such pulses. 4. The method according to claim 1 or 2, characterized in that a laser installation is used as a source of said heating, as well as a source of said impact action, while said target is placed at a predetermined distance from the exit window of said installation and the surface of said target is affected by a single laser pulse or a series of such pulses. 5. The method according to claim 1, characterized in that said heating of the surface of said target is carried out by means of induction heating. 6. The method according to claim 1, characterized in that said heating of the surface of said target is carried out by passing an electric current through said target. 7. The method according to claim 1, characterized in that said heating of the surface of said target is carried out using a current circuit located in close proximity to the surface of said target on the same side from which particles of said material are observed to settle. 8. The method according to any one of paragraphs. 5-7, characterized in that said impact on the heated surface of said target is carried out by means of a mechanical shock to the center of said target from the side, the reverse side, from which particles of said material are observed to settle. 9. The method according to claim 8, characterized in that a mechanical impactor or a piezoelectric element is used as a source of mechanical shock, located on the surface of the said target from the side, the reverse side, from which particles of the said material are observed to settle, or a bullet or projectile, or a beam of particles . 10. The method according to claim 1 or 2, characterized in that said heating of the surface of said target and/or said impact on the heated surface of said target is carried out using a beam of charged particles.

Images