CN116008875A - Z pinch plasma magnetic field measurement device and method based on absorption spectrum - Google Patents

Abstract

The invention discloses a Z pinch plasma magnetic field measuring device and method based on absorption spectrum, and belongs to the technical field of magnetic field measuring devices. The vacuum working chamber comprises a cathode plate and an anode plate which are arranged in the vacuum working chamber, wherein a load is arranged between the cathode plate and the anode plate, and pulse current can enable the load to generate Z pinch plasma. The invention obtains the magnetic induction intensity by measuring the splitting condition of the self-luminous absorption spectrum of the Z pinch plasma in a magnetic field, and can generate the absorption spectrum generated when the Z pinch plasma continuous spectrum passes through the sodium plasma without introducing other diagnostic devices, the measurement precision mainly depends on the observation duration and the resolution of a spectrometer, and the measurement range depends on the diffusion range of the sodium plasma. And the tracer is directly coated on the cathode plate, so that the excitation position of the generated sodium plasma is close to the load, the problem of over-strong self-luminescence of the Z pinch plasma in the common Zeeman splitting optical diagnosis can be overcome, and the measurement of the magnetic field distribution in the Z pinch plasma is realized.

Description

Z pinch plasma magnetic field measurement device and method based on absorption spectrum

Technical Field

The invention belongs to the technical field of magnetic field measuring devices, and relates to a Z-pinch plasma magnetic field measuring device and method based on an absorption spectrum.

Background

The magnetic field measurement technology is widely applied to the fields of military, astronomy, resource exploration, scientific research and the like. Currently, the magnetic field measurement methods mainly include the following three methods:

first, the magnetic field in vacuum is measured by the magnetic induction coil. Magnetic induction coils have the characteristics of simple principle, low cost and easy operation, and have been widely used for measuring time-varying magnetic fields. The main body of the magnetic induction coil is one or more small coils, the number of turns of the coils is generally 3-5, and the coils are placed in a certain region to be tested in the induction plasma in use, so that the change of a magnetic field in a space can generate induced electromotive force in a coil loop. Since the magnitude of the electromotive force is proportional to the rate of change of the magnetic field strength with time, the magnitude of the magnetic field at the position of the magnetic induction coil can be obtained after integrating the induced electromotive force with time. However, the influence on the induced plasma after the probe of the magnetic probe directly penetrates into the induced plasma is mainly as follows: firstly, the induced plasma is cooled and the movement process is disturbed; secondly, the induced current generated by itself will interfere with the magnetic field of the induced plasma. Meanwhile, when the external temperature is too high, the coating covered by the magnetic probe is ablated, and the measurement signal may be suddenly larger than a measurable threshold value, so that the measuring instrument is damaged, which is also one of the limitations of the magnetic probe.

Secondly, faraday rotation is used as a non-contact magnetic field measurement method, and is suitable for the magnetic field measurement condition when plasma exists in vacuum. When a beam of linearly polarized light passes through the plasma, the plasma is regarded as superposition of two beams of left-handed and right-handed circularly polarized light with equal amplitude. The two beams of light have different refractive indexes and propagation speeds due to magneto-optical effect, so that the two beams of light have different phase delays after passing through the same distance, and the linearly polarized light passing through the plasma deflects according to the calculation formula of the deflection angle:

wherein λ is the wavelength of incident light, n _e The electron density, B is the component of the magnetic field vector on the experimental optical path, dl is the element of the incident optical path. However, this method requires that the distribution of the plasma in space be symmetrical, and also requires a high environmental requirement given the electron density at all positions in the optical path.

Third, zeeman splitting also belongs to a non-contact magnetic field measurement method, and is generally based on the splitting of an emission line in a magnetic field, and the specific splitting condition is related to the size and the direction of the magnetic field, so that the magnetic field distribution in a space can be measured. However, the zeeman splitting effect is only used for the low-density plasma on the outer layer of the Z-pinch plasma, and the strong self-luminescence emitted by the high-density plasma near the center position can cover the splitting of the emission line, so that the internal magnetic field of the plasma cannot be measured.

Z pinch refers to the process of inducing plasma to reach a high Wen Gaomi state under the action of a magnetic field and generating strong X-radiation under the action of pulse current, and is mainly applied to an X-ray source or inertial confinement fusion and the like. However, in terms of magnetic field distribution, the magnetic field intensity in the induced plasma is high, the variation range is large (10T-104T), the duration time is short (100 ns), the variation speed is high, and the magnetic field is in extreme environments of high voltage (MV), high current (MA) and strong radiation, so that the existing magnetic field measurement method cannot be used for efficiently and reliably measuring the magnetic field of the high-density Z pinch plasma.

Disclosure of Invention

The invention aims to solve the technical problem that a Z pinch plasma magnetic field cannot be measured efficiently and reliably in the prior art, and provides a Z pinch plasma magnetic field measuring device based on an absorption spectrum. The invention has simple principle, convenient operation, wide range, high efficiency and reliability.

In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:

in a first aspect, the invention provides a Z-pinch plasma magnetic field measurement device based on absorption spectrum, comprising an anode plate, a cathode plate and an optical fiber; the anode plate is connected with a pulse power supply; the negative plate is coated with a tracer; a load is arranged between the anode plate and the cathode plate and used for generating Z pinch plasma; the tracer agent generates corresponding plasmas after being electrified; the continuous spectral lines generated by the Z pinch plasmas generate absorption spectral lines when passing through the corresponding plasmas, and the absorption spectral lines are split in a magnetic field to generate split absorption spectral lines; the optical fiber is arranged opposite to the load and is used for collecting split absorption lines generated by the Z-pinch plasma and obtaining the magnetic field distribution in the Z-pinch plasma according to the split absorption lines.

The invention further improves that:

the vacuum working cavity is also included; the cathode plate, the anode plate and the load are arranged in the vacuum working cavity; and a split absorption spectrum line outlet is arranged on the cavity of the working cavity.

And glass is arranged at the outlet of the split absorption spectrum line.

And a plano-convex lens is arranged between the glass and the optical fiber and is used for focusing the split absorption spectrum line on the optical fiber.

And a plurality of optical fibers are arranged along the radial direction to form an optical fiber array.

The load is a wire.

The surface of the cathode plate is provided with a hole structure for coating the tracer.

The tracer is sodium chloride solution.

The glass is quartz glass.

A Z pinch plasma magnetic field measurement method based on absorption spectrum comprises the following steps:

step 1, coating saturated sodium chloride solution on the surface of a cathode plate;

step 2, naturally air-drying or drying the sodium chloride solution by using a heat source until the moisture in the sodium chloride solution is completely evaporated so as to form a layer of sodium chloride crystal on the surface of the cathode plate;

step 3, mounting a metal load in the middle of the cathode and anode plates;

step 4, calibrating the relative positions of the plano-convex lens and the optical fiber array, so that the focal point of the plano-convex lens, the central point of the optical fiber array and the central point of the glass are positioned on the same line;

step 5, after the calibration is finished, the region to be measured is vacuumized by a vacuum pump to ensure that the air pressure is lower than 7 multiplied by 10 ^-2 Pa；

Step 6, switching on a pulse power supply, and generating Z pinch plasma in a vacuum environment by a load; meanwhile, sodium chloride crystals on the cathode plate are ablated to generate sodium plasma;

step 7,Z pinches the continuous lines produced by the plasma to be affected by opacity as they pass through the sodium plasma, producing absorption lines;

and 8, splitting the absorption spectrum line in the magnetic field to generate a split absorption spectrum line, and obtaining the magnetic field distribution in the Z pinch plasma according to the split absorption spectrum line.

Compared with the prior art, the invention has the following beneficial effects:

the invention applies pulse current to the load to directly generate Z pinch plasma, and the negative plate is coated with the tracer agent, when the pulse current is connected, the tracer agent can directly generate corresponding plasma. The invention obtains the magnetic induction intensity by measuring the split condition of the self-luminous absorption spectrum of the Z pinch plasma in a magnetic field, and can generate the Z pinch plasma continuous spectrum as the absorption spectrum under the condition of backlight without introducing other interference, the measurement accuracy mainly depends on the observation duration and the resolution of a spectrometer, and the measurement range depends on the diffusion range of the plasma generated by the tracer. Because the excitation position of the tracer agent is closer to the load, the self-luminous over-intensity problem of the Z pinch plasma in the common Zeeman splitting optical diagnosis can be overcome, and the measurement of the magnetic field distribution in the Z pinch plasma is realized.

Drawings

For a clearer description of the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a Z-pinch plasma magnetic field measurement device structure based on absorption spectra;

FIG. 2 is a schematic diagram of a cathode and anode plate structure;

fig. 3 is another schematic diagram of a Z-pinch plasma magnetic field measurement device structure based on absorption spectroscopy.

Wherein: 1-a working chamber; 2-glass; 3-split absorption lines; 4-sodium chloride crystals; 5-sodium plasma; 6-a cathode plate; 7-anode plate; 8-loading; 9-plano-convex lenses; 10-optical fiber; 11-mirrors.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the embodiments of the present invention, it should be noted that, if the terms "upper," "lower," "horizontal," "inner," and the like indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, or the azimuth or the positional relationship in which the inventive product is conventionally put in use, it is merely for convenience of describing the present invention and simplifying the description, and does not indicate or imply that the apparatus or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

Furthermore, the term "horizontal" if present does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the embodiments of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" should be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

The invention is described in further detail below with reference to the attached drawing figures:

referring to fig. 1, the embodiment of the invention discloses a Z pinch plasma magnetic field measuring device based on absorption spectrum, which comprises a vacuum working cavity 1; the cavity body of the vacuum working cavity 1 is provided with a split absorption spectral line 3 outlet; the outlet of the split absorption spectrum line 3 is provided with glass 2; an anode plate 7 and a cathode plate 8 are arranged in the vacuum working cavity 1; a metal wire load 8 is arranged between the anode plate 7 and the cathode plate 8; an optical fiber array 10 is arranged outside the vacuum working cavity 1 and used for collecting absorption spectrum lines; as shown in fig. 2, the cathode plate 8 is coated with sodium chloride solution, and a layer of sodium chloride crystals can be formed on the cathode plate 8 by natural air drying or heat source drying. The anode plate 7 is connected with a pulse power supply, when the pulse power supply is connected, the metal wire load 8 is ablated to generate Z-pinch plasma, the sodium chloride crystal 4 is ablated to generate sodium plasma 5, the continuous spectral line generated by the Z-pinch plasma generates an absorption spectral line due to radiation transport effect in the process of passing through the sodium plasma 5, the absorption spectral line is split in a magnetic field to generate a split absorption spectral line 3, and the split absorption spectral line 3 passes through the quartz glass 2 to pass through the plano-convex lens 9 and then is collected by the optical fiber array 10. In this example, a space magnetic field is provided by using a pulse current, an aluminum wire with a diameter of 50 micrometers and a height of 20mm is used as a load, and the surface of the polar plate is coated with sodium chloride as a tracer. Sodium chloride crystals are ablated to generate sodium plasma, and continuous spectral lines generated by Z pinch plasma generate absorption spectral lines due to radiation transport effect in the process of passing through the sodium plasma, and the absorption spectral lines are split in a magnetic field to generate split absorption spectral lines, so that the split absorption spectral lines are collected by an optical fiber array after passing through a plano-convex lens; the magnetic induction intensity inside the Z pinch plasma can be measured according to the Zeeman split absorption spectrum of the absorption spectrum in the magnetic field.

Referring to fig. 3, another embodiment of the present invention comprises a vacuum working chamber 1, wherein a piece of quartz glass 2 is arranged on the surface of the vacuum working chamber 1, the inside of the vacuum working chamber comprises cathode and anode plates 6 and 7 and a metal load 8, and sodium chloride crystals 4 are coated on the surface of the cathode plate 6; after pulse current is applied, the metal load 8 generates Z pinch plasma, the axial self-luminescence is influenced by the sodium plasma 5, an absorption spectrum is generated, and a split absorption spectrum line 3 is generated by Zeeman splitting in a magnetic field; a mirror 11 is located directly below the copper rod for reflecting the split light rays 3 through the quartz glass 2 to the plano-convex lens 9 for imaging to the fiber array 10; the vacuum working chamber 1 is sealed by a steel plate, and is pumped to vacuum by a vacuum pump; the metal load is a cylinder of diameter 50 microns and length 20 mm.

The embodiment discloses a Z pinch plasma magnetic field measurement method based on absorption spectrum, which comprises the following steps:

step 1, coating saturated sodium chloride solution on the surface of a cathode plate 6;

step 2, naturally air-drying or drying the sodium chloride solution by using a heat source until the moisture in the solution is completely evaporated so as to form a layer of fine sodium chloride crystals 4 on the surface of the solid object;

step 3, installing a metal load 8 in the middle of the cathode and anode plates;

step 4, pulse current is applied to the polar plate, and Z pinch plasma is generated in a vacuum environment;

step 5, sodium chloride crystals 4 are ablated to generate sodium plasma 5;

step 6, the self-luminescence of the axial Z pinch plasma is influenced by the sodium plasma 5, and an absorption spectrum is generated;

step 7, the absorption spectrum is split in a magnetic field and converted into split absorption spectrum 3, and the split absorption spectrum is collected through a lens 9 and an optical fiber array 10;

and 8, obtaining the magnetic induction intensity of the continuous space according to the splitting condition of the absorption spectrum.

The specific operation method of the invention is as follows:

switching on pulse current, and generating a Z pinch plasma magnetic field by the metal load 8 under the action of the current; z pinch plasma self-luminescence is acted by sodium plasma 5 to generate split absorption spectrum 3; the optical fiber array collects the split spectral lines at different diffusion positions at the same time; fitting the collected spectral lines to obtain the magnitude of the magnetic induction intensity.

The principle of the invention is as follows:

when an atom or ion absorbs energy, the atom or ion is excited to a high energy level, and the atom or ion at the high energy level transitions to a low energy level and emits photons to generate a spectrum. Also, when light of a certain wavelength band is absorbed by a low-temperature gas, a dark line is formed in the spectrum, which is called an absorption spectrum. When an external magnetic field or an electric field is applied, the coupling mode of the internal angular momentum of atoms is affected, spectral lines are split, and the influence of the magnetic field on the spectrum or the energy level is called the Zeeman effect. So far sodium is considered to be one of the most readily observed elements of the zeeman split spectrum. In order to accurately calculate the effect of the zeeman effect, we consider the hamiltonian amount of the incoming atomic state when the external magnetic field and the magnetic field within the LS coupling are appropriate. Taking the 2P state of sodium atoms as an example, the hamiltonian amount can be written as:

H＝μ _B (L+gS)B+ξLS

wherein, the 3P energy level of xi relative to sodium is 11.5cm ^-1 Mu, an item representing the coupling strength _B Is 0.4669cm ^-1 T ^-1 . Theoretical energy levels can be obtained through standard calculation by using Hamiltonian quantity in the formula, and the splitting condition of spectral lines can be obtained according to energy changes between the energy levels.

It has also been shown from theory and experiments that the observed split lines are not independent geometric lines, but have a certain width and profile, generally expressed as a linear function.

In this experiment, the linear function is expressed as a distribution function g (lambda) of energy in terms of wavelength, i.e. the ratio of energy distributed in a unit wavelength interval around lambda to total energy is expressed by spectral line intensity I ₀ Full width at half maximum Δλ and center wavelength λ of spectral line ₀ To quantify the center wavelength, the center wavelength has been calculated as described above.

In inducing the plasma 10, the secondary stark effect is the primary factor responsible for line broadening, the lorentz line type,

is a function of electron density and temperature:

wherein N is _e Representing electron density, alpha is ion broadening parameter, omega represents electron collision half-width, and they are associated with electron temperature T _e Related to the following.

The spectral lines in the experiments are also affected by the broadening of the instrument, which can be measured by mercury lamps in the experiments. But is negligible because of the small spread compared to stark.

When both the center wavelength and the broadening of the split line are determined, the shape of the line can be determined accordingly. Therefore, by fitting experimental spectral lines, the central wavelength and the size of the broadening of the spectral lines can be obtained. And obtaining the magnetic induction intensity in the region to be measured according to the splitting condition of the center wavelength.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The Z-pinch plasma magnetic field measuring device based on absorption spectrum is characterized by comprising an anode plate, a cathode plate and an optical fiber (10); the anode plate is connected with a pulse power supply; the negative plate is coated with a tracer; a load (8) is arranged between the anode plate and the cathode plate and is used for generating Z pinch plasma; the tracer agent generates corresponding plasmas after being electrified; the continuous spectral line generated by the Z pinch plasma generates an absorption spectral line when passing through the corresponding plasma, and the absorption spectral line is split in a magnetic field to generate a split absorption spectral line (3); the optical fiber (10) is arranged opposite to the load (8) and is used for collecting split absorption lines (3) generated by the Z-pinch plasma, and the magnetic field distribution inside the Z-pinch plasma is obtained according to the split absorption lines (3).

2. The Z-pinch plasma magnetic field measurement device based on absorption spectrum according to claim 1, further comprising a vacuum working chamber (1); the cathode plate, the anode plate and the load (8) are arranged in the cavity of the vacuum working cavity (1); the working cavity (1) is provided with a split absorption spectrum line (3) outlet.

3. The Z-pinch plasma magnetic field measurement device based on absorption spectrum according to claim 2, characterized in that a glass (2) is arranged at the exit of the split absorption spectrum (3).

4. A Z pinch plasma magnetic field measurement device based on absorption spectrum according to claim 3, characterized in that a plano-convex lens (9) is arranged between the glass (2) and the optical fiber (10) for focusing the split absorption spectrum (3) on the optical fiber (10).

5. The Z-pinch plasma magnetic field measurement device based on absorption spectrum according to claim 4, wherein several of the optical fibers (10) are arranged radially to form an optical fiber array.

6. The Z-pinch plasma magnetic field measurement device based on absorption spectrum according to any of claims 1-5, wherein the load (8) is a wire.

7. The absorption spectrum based Z-pinch plasma magnetic field measurement device according to claim 6, wherein the surface of the cathode plate is provided with a hole structure for coating a tracer.

8. The absorbance spectrum based Z-pinch plasma magnetic field measurement device of claim 7 wherein the tracer is sodium chloride solution.

9. The Z-pinch plasma magnetic field measurement device based on absorption spectrum according to claim 8, characterized in that the glass (2) is quartz glass.

10. A Z-pinch plasma magnetic field measurement method based on absorption spectrum using the device according to any one of claims 5-9, characterized by comprising the steps of:

step 1, coating saturated sodium chloride solution on the surface of a cathode plate;

step 2, naturally air-drying or drying the sodium chloride solution by using a heat source until the moisture in the sodium chloride solution is completely evaporated so as to form a layer of sodium chloride crystal on the surface of the cathode plate;

step 3, mounting a metal load in the middle of the cathode and anode plates;

step 4, calibrating the relative positions of the plano-convex lens (9) and the optical fiber array, so that the focal point of the plano-convex lens (9), the center point of the optical fiber array and the center point of the glass (2) are positioned on the same line;

step 5, after the calibration is finished, the region to be measured is vacuumized by a vacuum pump to ensure that the air pressure is lower than 7 multiplied by 10 ^-2 Pa；

Step 6, switching on a pulse power supply, and generating Z pinch plasma in a vacuum environment by a load (8); meanwhile, sodium chloride crystals on the cathode plate are ablated to generate sodium plasma;

step 7,Z pinches the continuous lines produced by the plasma to be affected by opacity as they pass through the sodium plasma, producing absorption lines;

and 8, splitting the absorption spectrum line in the magnetic field to generate a split absorption spectrum line, and obtaining the magnetic field distribution in the Z pinch plasma according to the split absorption spectrum line.

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