A device and method for measuring Z-pinch plasma magnetic field based on absorption spectrum

Abstract

This invention discloses a Z-pinch plasma magnetic field measurement device and method based on absorption spectrum, belonging to the technical field of magnetic field measurement devices. It includes anode and cathode plates disposed within a vacuum working chamber, with a load positioned between the plates. A pulsed current induces Z-pinch plasma in the load. This invention obtains the magnetic induction intensity by measuring the splitting of the self-emitted absorption spectrum of the Z-pinch plasma in a magnetic field. No additional diagnostic equipment is required; the device itself generates the absorption lines produced when the continuous spectrum of the Z-pinch plasma passes through sodium plasma. The measurement accuracy depends primarily on the observation time and spectrometer resolution, while the measurement range depends on the diffusion range of the sodium plasma. Furthermore, because the tracer is directly coated on the cathode plate, the excitation position of the generated sodium plasma is close to the load, thus overcoming the problem of excessive self-emitting in ordinary Zeeman splitting optical diagnostics of Z-pinch plasma, and realizing the measurement of the magnetic field distribution inside the Z-pinch plasma.

Description

Technical Field

[0001] This invention belongs to the technical field of magnetic field measurement devices, and relates to a Z-pinch plasma magnetic field measurement device and method based on absorption spectrum. Background Technology

[0002] Magnetic field measurement technology is widely used to solve important scientific and physical problems, and has broad applications in military, astronomy, resource exploration, and scientific research fields. Currently, there are three main methods for magnetic field measurement:

[0003] First, magnetic field measurements in a vacuum are performed using magnetic induction coils. Magnetic induction coils are widely used for measuring time-varying magnetic fields due to their simple principle, low cost, and ease of operation. The main body of a magnetic induction coil consists of one or more small coils, typically with 3-5 turns. During use, it is placed in a specific area of ​​the induced plasma. Changes in the magnetic field in the surrounding space induce an electromotive force (EMF) in the coil circuit. Since the magnitude of the EMF is proportional to the rate of change of the magnetic field strength over time, the magnitude of the magnetic field at the location of the magnetic induction coil can be obtained by integrating the induced EMF over time. However, the direct insertion of the magnetic probe into the induced plasma has two main effects: first, it cools the induced plasma and disturbs its motion; second, the induced current it generates interferes with the magnetic field of the induced plasma. Furthermore, when the external temperature is too high, the coating on the magnetic probe will be ablated, and the measurement signal may suddenly exceed the measurable threshold, damaging the measuring instrument. This is one of the limitations of magnetic probes.

[0004] Second, Faraday rotation, as a non-contact magnetic field measurement method, is suitable for magnetic field measurements in the presence of plasma in a vacuum. Using plasma as the magneto-optical medium, when a beam of linearly polarized light passes through the plasma, it can be considered as the superposition of two beams of equally amplitude left-handed and right-handed circularly polarized light. Due to the magneto-optical effect, these two beams have different refractive indices and propagation speeds, thus exhibiting different phase lags after traveling the same distance. This causes the linearly polarized light passing through the plasma to deflect, and the formula for calculating the deflection angle is:

[0005]

[0006] In the formula, λ is the incident light wavelength, and n e Let B be the electron density, B be the component of the magnetic field vector in the experimental optical path, and dl be the element of the incident optical path. However, this method requires a symmetrical distribution of plasma in space and knowledge of the electron density at all positions in the optical path, placing high demands on the environment.

[0007] Third, Zeeman splitting is also a non-contact magnetic field measurement method. It is generally based on the splitting of emission spectral lines in a magnetic field. The specific splitting situation is related to the magnitude and direction of the magnetic field, so the magnetic field distribution in the space can be measured. However, the Zeeman splitting effect has only been used for low-density plasmas in the outer layer of Z-pinch plasmas so far. The strong self-emission emitted by high-density plasmas near the center will cover the splitting of emission spectral lines, making it impossible to measure the magnetic field inside the plasma.

[0008] Z-pinch refers to the process by which induced plasma, generated under the influence of a pulsed current, reaches a high-temperature, high-density state under the influence of a magnetic field, simultaneously producing intense X-ray radiation. It is primarily used in X-ray sources or inertial confinement fusion. However, regarding the magnetic field distribution, the high magnetic field strength, wide variation range (10T-104T), short duration (~100 ns), and rapid change rate of the induced plasma, coupled with its extreme environment of high voltage (~MV), high current (~MA), and strong radiation, make it impossible for existing magnetic field measurement methods to efficiently and reliably measure the magnetic field of high-density Z-pinch plasma. Summary of the Invention

[0009] The purpose of this invention is to solve the technical problem of the inability to efficiently and reliably measure the magnetic field of Z-pinch plasma in existing technologies, and to provide a Z-pinch plasma magnetic field measuring device based on absorption spectrum. This invention is simple in principle, easy to operate, has a wide range of applications, and is highly efficient and reliable.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] In a first aspect, the present 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 to a pulsed power supply; the cathode plate is coated with a tracer; a load is disposed between the anode plate and the cathode plate for generating Z-pinch plasma; the tracer generates a corresponding plasma after being energized; 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 splits in the magnetic field to generate a split absorption spectral line; the optical fiber is disposed opposite to the load for collecting the split absorption spectral lines generated by the Z-pinch plasma, and the magnetic field distribution inside the Z-pinch plasma is obtained from the split absorption spectral lines.

[0012] A further improvement of the present invention is that:

[0013] It also includes a vacuum working chamber; the cathode plate, anode plate and load are disposed inside the vacuum working chamber; the working chamber is provided with a split absorption spectral line outlet.

[0014] A glass element is installed at the outlet of the split absorption spectral line.

[0015] A plano-convex lens is disposed between the glass and the optical fiber to focus the split absorption spectral lines onto the optical fiber.

[0016] Several optical fibers are arranged radially to form an optical fiber array.

[0017] The load is a metal wire.

[0018] The cathode plate has a porous structure on its surface for coating tracers.

[0019] The tracer is a sodium chloride solution.

[0020] The glass is quartz glass.

[0021] A method for measuring the magnetic field of Z-pinch plasma based on absorption spectrum includes the following steps:

[0022] Step 1: Coat the surface of the cathode plate with a saturated sodium chloride solution;

[0023] Step 2: Allow the sodium chloride solution to air dry naturally or dry it with a heat source until all the water in the sodium chloride solution has evaporated, thereby forming a layer of sodium chloride crystals on the surface of the cathode plate.

[0024] Step 3: Install a metal load between the anode and cathode plates;

[0025] Step 4: Align the relative positions of the plano-convex lens and the fiber array so that the focal point of the plano-convex lens, the center point of the fiber array, and the center point of the glass are on the same line.

[0026] Step 5: After calibration, use a vacuum pump to evacuate the area to be tested to a vacuum level below 7 × 10⁻⁶. -2 Pa;

[0027] Step 6: Turn on the pulse power supply, and the load generates Z-pinch plasma in a vacuum environment; at the same time, the sodium chloride crystals on the cathode plate will also be ablated, generating sodium plasma.

[0028] Step 7: The continuous spectral lines generated by the Z-pinch plasma are affected by the opacity when passing through the sodium plasma, resulting in absorption lines.

[0029] Step 8: The absorption spectral lines split in the magnetic field, producing split absorption spectral lines. The magnetic field distribution inside the Z-pinch plasma is obtained based on the split absorption spectral lines.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention applies a pulsed current to the load, causing it to directly generate Z-pinch plasma. A tracer is coated on the cathode plate; when the pulsed current is applied, the tracer directly generates the corresponding plasma. This invention obtains the magnetic flux density by measuring the splitting of the self-emitted absorption spectrum of the Z-pinch plasma in a magnetic field, without introducing other interference. The device itself can generate a continuous spectrum of the Z-pinch plasma as the absorption line under backlight conditions. The measurement accuracy mainly depends on the observation time and spectrometer resolution, while the measurement range depends on the diffusion range of the plasma generated by the tracer. Because the excitation position of the tracer is close to the load, this invention overcomes the problem of excessive self-emitting of Z-pinch plasma in ordinary Zeeman splitting optical diagnostics, enabling the measurement of the magnetic field distribution inside the Z-pinch plasma. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of a Z-pinch plasma magnetic field measurement device based on absorption spectrum.

[0034] Figure 2 This is a schematic diagram of the anode and cathode plate structure;

[0035] Figure 3 This is another schematic diagram of the structure of a Z-pinch plasma magnetic field measurement device based on absorption spectrum.

[0036] Wherein: 1-working chamber; 2-glass; 3-split absorption spectral line; 4-sodium chloride crystal; 5-sodium plasma; 6-cathode plate; 7-anode plate; 8-load; 9-plano-convex lens; 10-optical fiber; 11-reflector. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0039] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0040] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0041] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0042] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0043] The present invention will now be described in further detail with reference to the accompanying drawings:

[0044] See Figure 1 This invention discloses a Z-pinch plasma magnetic field measurement device based on absorption spectrum, comprising a vacuum working chamber 1; a split absorption spectral line 3 outlet is provided on the vacuum working chamber 1; a glass 2 is provided at the outlet of the split absorption spectral line 3; an anode plate 7 and a cathode plate 6 are provided inside the vacuum working chamber 1; a metal wire load 8 is provided between the anode plate 7 and the cathode plate 6; and an optical fiber 10 is provided outside the vacuum working chamber 1 for collecting absorption spectral lines; Figure 2 As shown, the cathode plate 6 is coated with a sodium chloride solution, and a layer of sodium chloride crystals can be formed on the cathode plate 6 by natural air drying or heat source drying. The anode plate 7 is connected to a pulsed power supply. When the pulsed power supply is connected, the metal wire load 8 is ablated to generate Z-pinch plasma, and the sodium chloride crystal 4 is ablated to generate sodium plasma 5. The continuous spectral lines generated by the Z-pinch plasma will generate absorption spectral lines due to radiative transport effects as they pass through the sodium plasma 5. The absorption spectral lines split in the magnetic field to generate split absorption spectral lines 3. The split absorption spectral lines 3 pass through the quartz glass 2 and are then collected by the optical fiber 10 after passing through the plano-convex lens 9. In this embodiment, a spatial magnetic field is provided by using a pulsed current, with an aluminum wire with a diameter of 50 micrometers and a height of 20 mm as the load, and the electrode surface is coated with sodium chloride as a tracer. Sodium chloride crystals are ablated to generate sodium plasma. The continuous spectral lines generated by the Z-pinch plasma will produce absorption lines due to radiative transport effects as they pass through the sodium plasma. The absorption lines split in the magnetic field to produce split absorption lines, which are then 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 based on the Zeeman split absorption lines in the magnetic field.

[0045] See Figure 3 In another embodiment of the present invention, a vacuum working chamber 1 is provided with a quartz glass 2 on the surface of the chamber body. The chamber contains a cathode plate 6, an anode plate 7, and a metal load 8. The surface of the cathode plate 6 is coated with sodium chloride crystals 4. After a pulsed current is applied, the metal load 8 generates Z-pinch plasma. The axial self-luminescence is affected by the sodium plasma 5, generating an absorption spectrum, and Zeeman splitting occurs in the magnetic field to generate split absorption spectral lines 3. A reflector 11 is located directly below the copper rod and is used to reflect the split light rays 3 through the quartz glass 2 to the plano-convex lens 9, thereby imaging to the optical fiber 10. The vacuum working chamber 1 is sealed with a steel plate and evacuated to a vacuum using a vacuum pump. The metal load is a cylinder with a diameter of 50 micrometers and a length of 20 mm.

[0046] This embodiment discloses a method for measuring the magnetic field of Z-pinch plasma based on absorption spectrum, including the following steps:

[0047] Step 1: Coat the surface of cathode plate 6 with a saturated sodium chloride solution;

[0048] Step 2: Allow the sodium chloride solution to air dry naturally or dry it with a heat source until all the water in the solution evaporates, thus forming a layer of fine sodium chloride crystals on the surface of the solid object.

[0049] Step 3: Install a metal load 8 between the anode and cathode plates;

[0050] Step 4: Apply a pulsed current to the electrode to generate Z-pinch plasma in a vacuum environment;

[0051] Step 5: Sodium chloride crystal 4 will be ablated to generate sodium plasma 5;

[0052] Step 6: The axial Z-pinch plasma self-luminescence is affected by sodium plasma 5, generating an absorption spectrum;

[0053] Step 7: The absorption spectrum splits in the magnetic field, converting into split absorption spectral lines 3, which are collected by the plano-convex lens 9 and the optical fiber 10.

[0054] Step 8: Obtain the magnitude of the magnetic induction intensity in continuous space based on the splitting of the absorption spectrum.

[0055] The specific operation method of this invention is as follows:

[0056] When a pulsed current is applied, the metal load 8 generates a Z-pinch plasma magnetic field under the action of the current; the Z-pinch plasma emits light spontaneously and is affected by sodium plasma 5, generating split absorption spectral lines 3; the fiber array simultaneously collects the split spectral lines at different diffusion positions; the collected spectral lines are fitted to obtain the magnitude of the magnetic induction intensity.

[0057] The principle of this invention is as follows:

[0058] When atoms or ions absorb energy, they are excited to higher energy levels. Atoms or ions in higher energy levels then transition to lower energy levels, emitting photons and producing a spectrum. Similarly, when light in a certain wavelength band is absorbed by a low-temperature gas, dark spectral lines are formed in the spectrum, called an absorption spectrum. When subjected to an external magnetic or electric field, the coupling mode of the angular momentum within the atom is affected, causing spectral lines to split. The effect of the magnetic field on the spectrum or energy levels is called the Zeeman effect. Sodium is currently considered one of the elements whose Zeeman splitting spectrum is most easily observed. To accurately calculate the Zeeman effect, we consider the case where the external magnetic field and the internal magnetic field of the LS coupling are equivalent, and introduce the Hamiltonian of the atomic state. Taking the 2P state of the sodium atom as an example, its Hamiltonian can be written as:

[0059]

[0060] In the formula, ξ represents the 3P energy level of sodium at 11.5 cm⁻¹. -1 , where μ is the term representing the coupling strength. B It is 0.4669 cm -1 T -1 The theoretical energy levels can be obtained through standard calculations using the Hamiltonian in the formula, and the splitting of spectral lines can be determined based on the energy changes between the energy levels.

[0061] Meanwhile, theoretical and experimental results show that the observed split spectral lines are not independent geometric lines, but have a certain width and outline, and are generally represented by line shape functions.

[0062] In this experiment, the line shape function is represented by the energy distribution function g(λ) according to wavelength, which is the ratio of the energy distributed within a unit wavelength interval near λ to the total energy. It is quantitatively described by the spectral line intensity I0, the full width at half maximum (FWHM) Δλ, and the center wavelength λ0. The center wavelength has been obtained through the above calculations.

[0063] In induced plasma, the secondary Stark effect is the main factor leading to spectral line broadening, resulting in Lorentz lines. It is a function of electron density and temperature:

[0064]

[0065] In the formula, N e The electron density is represented by α, the ion broadening parameter is α, and the half-width at half-maximum (FWHM) of electron collisions is ω. These parameters are related to the electron temperature T. e related.

[0066] The spectral lines in the experiment are also affected by instrument broadening, which can be measured using a mercury lamp. However, this broadening is negligible compared to the Stark broadening.

[0067] When the center wavelength and broadening of a split spectral line are determined, the shape of the spectral line can also be determined accordingly. Therefore, by fitting the experimental spectral line, the center wavelength and broadening of the spectral line can be obtained. Based on the splitting pattern of the center wavelength, the magnitude of the magnetic flux density in the region to be measured can be obtained.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Z-pinch plasma magnetic field measuring device based on absorption spectrum, characterized in that, The system includes an anode plate, a cathode plate, an optical fiber (10), and a vacuum working chamber (1). The anode plate is connected to a pulse power supply. The cathode plate is coated with a sodium chloride solution. A load (8) is provided between the anode plate and the cathode plate to generate Z-pinch plasma. The sodium chloride solution generates corresponding plasma after being energized. The continuous spectral lines generated by the Z-pinch plasma generate absorption spectral lines when passing through the corresponding plasma. The absorption spectral lines split in the magnetic field to generate split absorption spectral lines (3). The optical fiber (10) is arranged opposite to the load (8) to collect the split absorption spectral lines (3) generated by the Z-pinch plasma. The magnetic field distribution inside the Z-pinch plasma is obtained based on the split absorption spectral lines (3). The cathode plate, anode plate, and load (8) are arranged inside the vacuum working chamber (1). The working chamber (1) has an outlet for the split absorption spectral lines (3).

2. The Z-pinch plasma magnetic field measuring device based on absorption spectrum according to claim 1, characterized in that, A glass (2) is provided at the exit of the split absorption spectral line (3).

3. The Z-pinch plasma magnetic field measuring device based on absorption spectrum according to claim 2, characterized in that, A plano-convex lens (9) is provided between the glass (2) and the optical fiber (10) to focus the split absorption spectral line (3) onto the optical fiber (10).

4. The Z-pinch plasma magnetic field measuring device based on absorption spectrum according to claim 3, characterized in that, Several optical fibers (10) are arranged radially to form an optical fiber array.

5. The Z-pinch plasma magnetic field measuring device based on absorption spectrum according to any one of claims 1-4, characterized in that, The load (8) is a metal wire.

6. The Z-pinch plasma magnetic field measuring device based on absorption spectrum according to claim 5, characterized in that, The cathode plate has a porous structure on its surface for coating with sodium chloride solution.

7. The Z-pinch plasma magnetic field measuring device based on absorption spectrum according to claim 6, characterized in that, The glass (2) is quartz glass.

8. A method for measuring the Z-pinch plasma magnetic field based on the absorption spectrum using the apparatus according to any one of claims 3-7, characterized in that, Includes the following steps: Step 1: Coat the surface of the cathode plate with a saturated sodium chloride solution; Step 2: Allow the sodium chloride solution to air dry naturally or dry it with a heat source until all the water in the sodium chloride solution has evaporated, thereby forming a layer of sodium chloride crystals on the surface of the cathode plate. Step 3: Install a metal load between the anode and cathode plates; Step 4: Align the relative positions of the plano-convex lens (9) and the fiber array so that the focal point of the plano-convex lens (9), the center point of the fiber array, and the center point of the glass (2) are on the same line. Step 5: After calibration, use a vacuum pump to evacuate the area to be tested to a vacuum level below 7 × 10⁻⁶. -2 Pa; Step 6: Turn on the pulse power supply. The load (8) generates Z-pinch plasma in the vacuum environment. At the same time, the sodium chloride crystals on the cathode plate will also be ablated to generate sodium plasma. Step 7: The continuous spectral lines generated by the Z-pinch plasma are affected by the opacity when passing through the sodium plasma, resulting in absorption lines. Step 8: The absorption spectral lines split in the magnetic field, producing split absorption spectral lines. The magnetic field distribution inside the Z-pinch plasma is obtained based on the split absorption spectral lines.

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