Plasma plume density diagnosis system based on Wollaston prism

Abstract

The invention provides a plasma plume density diagnosis system based on a Wollaston prism. The plasma plume density diagnosis system comprises a laser ablation subsystem, a differential interference subsystem, an image acquisition subsystem and a general subsystem, the laser ablation subsystem is used for generating plasma plume; the differential interference subsystem is used for providing a beam of high-quality and collimated continuous laser as probe light for interference measurement, realizing detection of a density field of plasma plume, and converting phase change caused by plasma into a recordable interference fringe pattern; the image acquisition subsystem is used for capturing a transient interference fringe pattern in a target material ablation process under accurate time sequence control; and the general subsystem is used for providing a stable and controllable experimental environment for a target ablation experiment. The device is high in anti-interference capability, high in measurement precision and high in temporal-spatial resolution, can realize clear imaging of the evolution process of transient plasma plume generated by laser ablation, and quantitatively inverts the distribution of a two-dimensional electron density field.

Description

Technical Field

[0001] This invention relates to the fields of high-energy laser-matter interaction, plasma physics diagnostics, and optical precision measurement, specifically to a plasma plume density diagnostic system based on a Wollaston prism. Background Technology

[0002] Laser ablation technology, due to its ability to generate high-temperature, high-pressure, and high-speed plasma plumes, has wide applications in aerospace propulsion (such as laser ablation micro-thrusters), materials processing, and nanomaterial fabrication. The characteristics of the plasma plume, especially its spatiotemporal distribution of electron density, are key physical parameters for evaluating energy coupling efficiency, impulse characteristics, and propulsion performance.

[0003] However, the plasma plumes generated by laser ablation are characterized by their instantaneous nature (on the order of microseconds or even nanoseconds), high temperature and pressure (tens of thousands of Kelvin), spatial microscopicity (on the order of millimeters to centimeters), and strong spontaneous emission interference, making direct observation and quantitative measurement of their internal density field extremely difficult.

[0004] Currently, commonly used flow field visualization techniques mainly include: Shadowing method: Simple in structure, but sensitive to the second derivative of the density gradient, suitable only for qualitative observation of flow field structure. Schlieren method: Sensitive to the first derivative of density, capable of qualitative to semi-quantitative analysis, but difficult to achieve quantitative inversion of absolute density across the entire field. Mach-Zehnder interferometry: Can quantitatively measure optical path difference, and thus invert density. However, as a dual-path system, it is extremely sensitive to environmental vibrations and airflow disturbances, has complex optical path collimation and adjustment, poor anti-interference capability, and is difficult to operate stably in complex experimental environments.

[0005] To overcome the limitations of the aforementioned techniques, Nomarski proposed differential interferometry, also known as polarization shearing interferometry, in the 1960s. This technique, based on the birefringence effect of a Wollaston prism, shears a beam of light into two beams with a small angle between them and perpendicular polarization directions, causing them to interfere. Its core advantage lies in: Common optical path design: The object light and the reference light propagate in almost the same path, and are not sensitive to environmental disturbances such as mechanical vibration and temperature drift.

[0006] High sensitivity: It is sensitive to the refractive index gradient (i.e., density gradient), and the fringe displacement directly corresponds to the optical path difference derivative.

[0007] Compact structure: The optical path is relatively simple, making it easy to collimate and integrate.

[0008] Despite the obvious advantages of differential interferometry, its successful application to the diagnosis of electron density in transient, high-intensity, and strongly interfering laser plasma plumes still faces many challenges: how to design an optical path that can resist strong plasma light interference, how to accurately capture the microsecond-level evolution of the interferogram, and how to extract and invert the absolute electron density value from the interference fringes with high precision.

[0009] Therefore, developing a comprehensive diagnostic system that integrates high-performance optical components, precise timing control, high-speed image capture, and dedicated image processing algorithms is of significant innovative importance and practical value. Summary of the Invention

[0010] To address the technical problems existing in the background art, this invention proposes a plasma plume density diagnostic system based on a Wollaston prism. The system is reasonably designed, has strong anti-interference ability, high measurement accuracy, and high spatiotemporal resolution. It can clearly image the evolution process of transient plasma plumes generated by laser ablation and quantitatively invert the distribution of its two-dimensional electron density field.

[0011] To address the aforementioned technical problems, this invention provides a plasma plume density diagnostic system based on a Wollaston prism, comprising a laser ablation subsystem, a differential interferometry subsystem, an image acquisition subsystem, and a general subsystem. The laser ablation subsystem is used to generate high-power-density pulsed lasers, which are used to ablate the target material and generate a plasma plume. The differential interferometry subsystem is used to provide a high-quality, collimated continuous laser beam as a probe light for interferometry, enabling the detection of the density field of the plasma plume and converting the phase change caused by the plasma into a recordable interferometric fringe pattern. The image acquisition subsystem is used to capture transient interference fringe patterns during the target ablation process under precise timing control. The general subsystem is used to provide a stable and controllable experimental environment for target ablation experiments.

[0012] The plasma plume density diagnostic system based on the Wollaston prism, wherein the differential interferometry subsystem includes an optical probe module and a Wollaston prism interferometry module; The optical probe module employs a 532nm continuous laser, with a beam expander and a precision adjustment frame sequentially matched along its probe light output path. The beam expander consists of a concave lens, a first convex lens located on the beam output path of the concave lens and on the light-inlet side of the general subsystem, and a second convex lens located on the light-outlet side of the general subsystem, arranged sequentially along the probe light output path of the optical probe module, thereby ensuring that the probe light covers the density field of the plume. The precision adjustment frame is fitted onto the concave lens and the first convex lens and is used to adjust the distance between the concave lens and the first convex lens according to their focal lengths, so that the probe light forms parallel light. The Wollaston prism interference module is used to generate interference fringes over a large range. It includes a Wollaston prism, a polarizer, and a polarizer. The polarizer is disposed in the beam output path of the second convex lens to convert the probe laser into linearly polarized light. The Wollaston prism is disposed in the beam output path of the polarizer. The polarizer is disposed in the beam output path of the Wollaston prism to cause interference of the sheared light split by the Wollaston prism, forming an interference fringe pattern that can be acquired by the image acquisition subsystem.

[0013] The plasma plume density diagnostic system based on the Wollaston prism, wherein: the Wollaston prism has a beam splitting angle of 1°, which shears and separates the linearly polarized light output from the incident polarizer into two sheared beams with a small angle between their propagation directions and perpendicular polarization directions.

[0014] The plasma plume density diagnostic system based on the Wollaston prism, wherein: the general subsystem includes a vacuum chamber module and a timing control module; The vacuum chamber module is used to provide a set environmental pressure for the ablation of the target material. It includes a vacuum chamber body, optical glass windows, a mechanical pump and molecular pump assembly, a pressure sensor, and a target material platform. The optical glass windows are symmetrically arranged on the light-inlet and light-outlet sides of the vacuum chamber body. The target material platform is located inside the vacuum chamber body and mounted on a three-dimensional combined translation stage with three-dimensional translation function. The mechanical pump and molecular pump assembly are mounted on the vacuum chamber body to create a vacuum environment inside the vacuum chamber body. The pressure sensor is located inside the vacuum chamber body to detect the vacuum level inside the vacuum chamber body. The timing control module is used to precisely trigger the image acquisition subsystem to perform exposure at a preset delay time point after the laser ablation subsystem is triggered. It includes a digital delay generator and an oscilloscope. The digital delay generator is connected to the oscilloscope, the laser ablation subsystem, and the image acquisition subsystem respectively via signal transmission lines. The oscilloscope is connected to the laser ablation subsystem and the image acquisition subsystem respectively via signal transmission lines.

[0015] The plasma plume density diagnostic system based on the Wollaston prism includes: an image acquisition subsystem comprising an ICCD camera, a HiCATT25 image intensifier, a QM1 long working distance microscope, and a data processing computer; the HiCATT25 image intensifier is installed at the front end of the ICCD camera and achieves image enhancement in low-light environments through photoelectric conversion, electron multiplication, and image processing; the QM1 long working distance microscope is installed at the front end of the HiCATT25 image intensifier and is used to obtain high-resolution, high-definition images outside the vacuum chamber. The ICCD camera is matched and set in the beam output optical path of the differential interferometer subsystem. It is used to acquire the interference fringe pattern output by the differential interferometer subsystem and is connected to the data processing computer, the digital delay generator and the oscilloscope respectively through signal transmission lines. The data processing computer is used to receive and process the interference fringe patterns acquired by the differential interferometer subsystem and the ICCD camera, and to invert the two-dimensional electron density field of the plasma plume by calculating the displacement of the interference fringe.

[0016] The plasma plume density diagnostic system based on the Wollaston prism comprises: a laser ablation subsystem that ablates a target material by focusing to generate a high-power-density pulsed laser, producing a plasma plume; the subsystem includes a nanosecond pulsed laser, a planar beam splitter, a power meter, and a third convex lens; the nanosecond pulsed laser provides adjustable laser energy density and is connected to the digital delay generator and the oscilloscope via signal transmission lines; the planar beam splitter is disposed in the laser output path of the nanosecond pulsed laser to split the received pulsed laser into a reflected beam and a transmitted beam output; the power meter is disposed in the transmitted beam output path of the planar beam splitter to measure the energy density of the output beam of the nanosecond pulsed laser; and the third convex lens is disposed in the reflected beam output path of the planar beam splitter to focus the beam, thereby increasing the energy density of the pulsed laser and allowing for a higher adjustable upper limit for the beam's energy density.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects: The plasma plume density diagnostic system based on the Wollaston prism of this invention is well-conceived and can be used for quantitative and visual diagnosis of the electron density field of transient plasma plumes generated by laser ablation of energetic materials. This invention integrates Nomarski differential interferometry, high-speed imaging technology and image processing algorithms to achieve high spatiotemporal resolution and non-contact measurement of plasma plume density field, which will provide a powerful tool for understanding the dynamics of transient plasma plumes caused by pulsed laser ablation.

[0018] The core of this invention lies in constructing a common-path differential interferometry optical path using a Wollaston prism. By measuring the interference fringe displacement caused by the transient plasma plume generated during laser ablation of the target, and combining this with a dedicated image processing algorithm and inverse Abel transform, the two-dimensional electron density field distribution of the plasma plume is quantitatively derived. This effectively overcomes the technical bottlenecks of traditional interferometry's poor anti-interference capability and the difficulty in quantitative measurement using shadowing and schlieren methods. It boasts advantages such as high sensitivity, high stability, and high spatiotemporal resolution. This invention is particularly suitable for studying the plasma plume characteristics of energetic materials during laser ablation, providing crucial diagnostic tools and data support for aerospace propulsion performance evaluation, energetic material combustion mechanism analysis, and laser processing process monitoring.

[0019] The features and advantages of this invention are mainly reflected in the following aspects: High anti-interference capability: Thanks to the common optical path design of the Nomarski interferometer, the system has natural immunity to environmental vibration, airflow and temperature drift. Its stability is far superior to dual optical path systems such as the MZ interferometer, making it more suitable for complex laser ablation experimental environments.

[0020] High spatiotemporal resolution: Employing a nanosecond-gated ICCD camera, the high-speed motion of plasma can be effectively "frozen" and strong plasma self-luminescence interference can be suppressed to obtain clear interference images. The temporal resolution can reach the nanosecond level, while the spatial resolution is determined by the camera pixels and magnification.

[0021] Quantification and visualization: This invention not only provides morphological images of plasma plumes, but more importantly, it uses a complete set of physical models and algorithms to quantitatively inverse the absolute electron density value from the interference fringes and finally generate a two-dimensional electron density field cloud map.

[0022] Wide applicability: This system can be used to study the plasma characteristics of various targets, such as metals, polymers, and composite materials, under laser ablation. By adjusting the vacuum chamber pressure, it can simulate different working conditions from atmospheric environments to space environments.

[0023] Integration and Automation: The system integrates triggering, acquisition, processing and analysis processes, and realizes batch and automation of image processing and data inversion through programming, which greatly improves the efficiency and reliability of data processing. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the overall structure of the plasma plume density diagnostic system based on the Wollaston prism of the present invention. Figure 2 This is a detailed diagram of the shearing, beam splitting, and interference principle of the Wollaston prism involved in the plasma plume density diagnostic system based on the Wollaston prism of this invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention will be further explained below with reference to specific embodiments.

[0028] like Figure 1-2 As shown, this embodiment provides a plasma plume density diagnostic system based on a Wollaston prism, including a laser ablation subsystem 1, a differential interferometry subsystem 2, an image acquisition subsystem 3, and a general subsystem 4.

[0029] The laser ablation subsystem 1 is used to generate high-power-density pulsed laser light to ablate the target material and generate a plasma plume. The laser ablation subsystem 1 includes a nanosecond pulsed laser, a planar beam splitter, a power meter, and a third convex lens f4. It focuses the laser to generate a high-power-density pulsed laser light to ablate the target material and generate a plasma plume. The nanosecond pulsed laser has a wavelength of 532 nm; it is equipped with a power meter and a third convex lens f4 (to focus the beam to approximately 1 mm). The nanosecond pulsed laser provides adjustable laser energy density to ensure that the adjustable range of laser energy density covers various ablation mechanisms such as the ablation threshold of the material and phase explosion. The planar beam splitter is located in the laser output path of the nanosecond pulsed laser to split the received pulsed laser light into a reflected beam and a transmitted beam output. The power meter is located in the transmitted beam output path of the planar beam splitter to measure the energy density of the output beam of the nanosecond pulsed laser. The third convex lens f4 is located in the reflected beam output path of the planar beam splitter to focus the beam and increase the energy density of the pulsed laser, thus allowing for a higher adjustable upper limit of the beam energy density.

[0030] The differential interferometer subsystem 2 is used to provide a high-quality, collimated continuous laser beam as a probe light for interferometry, enabling the detection of the plume density field and converting the phase change caused by the plasma into a recordable interferometric fringe pattern. It includes an optical probe module and a Wollaston prism interferometer module.

[0031] The optical probe module uses a 532 nm continuous laser. A beam expander (used to enlarge the beam diameter and improve collimation) and a precision adjustment frame are sequentially matched on its probe light output path. The beam expander consists of a concave lens f1, a first convex lens f2 located on the beam output path of the concave lens f1 and on the light-inlet side of the general subsystem 4, and a second convex lens f3 located on the light-outlet side of the general subsystem 4, which are sequentially arranged on the probe light output path of the optical probe module, so that the probe light covers the density field of the plume. The precision adjustment frame is set on the concave lens f1 and the first convex lens f2 and is used to adjust the distance between the optical lenses according to the focal length of the optical lenses so that the probe light forms parallel light.

[0032] The Wollaston prism interferometer module (such as...) Figure 2 The system is used to generate interference fringes over a large area. It includes a Wollaston prism with a beam splitting angle of 1°, polarizer P1, and polarizer P2. Polarizer P1 is positioned in the beam output path of the second convex lens f3 to convert the probe laser into linearly polarized light. The Wollaston prism is positioned in the beam output path of polarizer P1, which shears and separates the incident linearly polarized light into two beams, o-ray and e-ray, with a small angle between their propagation directions and perpendicular polarization directions. Polarizer P2 is positioned in the beam output path of the Wollaston prism, causing the sheared beams split by the Wollaston prism to interfere, forming an interference fringe pattern that can be acquired by the image acquisition subsystem 3. Finally, the test area is clearly imaged onto the target surface of the ICCD camera of the image acquisition subsystem 3.

[0033] The general subsystem 4 is used to provide a stable and controllable experimental environment for target ablation experiments, including a vacuum chamber module and a timing control module.

[0034] This vacuum chamber module provides a set environmental pressure for the ablation of the target material. It includes a vacuum chamber body, optical glass windows, a mechanical pump and molecular pump assembly, a pressure sensor, and a target platform. Optical glass windows are symmetrically arranged on the light-inlet and light-outlet sides of the vacuum chamber body. The target platform is located inside the vacuum chamber body and mounted on a three-dimensional combined translation stage with three-dimensional translation capabilities to ensure the accuracy of the ablation position for each operation. The mechanical pump and molecular pump assembly are mounted on the vacuum chamber body to create a vacuum environment within the chamber. The pressure sensor is located inside the vacuum chamber body to detect the vacuum level within the chamber.

[0035] This timing control module is used to precisely trigger the image acquisition subsystem 3 for exposure at a preset delay time point after the laser ablation subsystem 1 is triggered. It precisely controls the triggering timing between the ablation laser, probe laser, and ICCD camera to ensure acquisition at specific moments in plasma evolution. It includes a digital delay generator and an oscilloscope. The digital delay generator is connected to the oscilloscope, laser ablation subsystem 1, and image acquisition subsystem 3 via signal transmission lines; the oscilloscope is also connected to both laser ablation subsystem 1 and image acquisition subsystem 3 via signal transmission lines. The nanosecond pulsed laser of laser ablation subsystem 1 is connected to the digital delay generator and oscilloscope of the timing control module via signal transmission lines.

[0036] The image acquisition subsystem 3 is used to capture transient interference images during the target ablation process under precise timing control. This subsystem includes an ICCD camera, a HiCATT25 image intensifier, a QM1 long working distance microscope, and a data processing computer. It possesses high sensitivity and nanosecond-level gated exposure capability, effectively freezing the instantaneous high-speed plasma movement and suppressing background interference from plasma self-luminescence. The HiCATT25 image intensifier is installed in front of the ICCD camera, achieving image enhancement in low-light environments through photoelectric conversion, electron multiplication, and image processing. The QM1 long working distance microscope is installed in front of the HiCATT25 image intensifier to obtain high-resolution, high-definition images outside the vacuum chamber of the general subsystem 4. The ICCD camera is matched and positioned in the beam output path of the differential interferometry subsystem 2, acquiring the interference fringe pattern output by the differential interferometry subsystem 2 and connected to the data processing computer, the digital delay generator of the general subsystem 4, and the oscilloscope via signal transmission lines. The data processing computer is used to receive and process the interference fringe patterns acquired by the differential interferometer subsystem 2 and the ICCD camera, and to invert the two-dimensional electron density field of the plasma plume by calculating the displacement of the interference fringe.

[0037] The diagnostic system of the present invention can simulate the evolution of plasma density field under different pressure environments through the vacuum chamber module, and obtain a two-dimensional electron density field by combining the analysis results of the differential interferometry subsystem and the image acquisition subsystem. This system will provide a powerful tool for understanding the dynamics of instantaneous plasma plumes caused by pulsed laser ablation.

[0038] The method for diagnosing plasma plume density based on the Wollaston prism plasma plume density diagnostic system of this invention is as follows: Step S1: Use the interference probe photonic system 1 to emit probe light, adjust the differential interference subsystem 2, and obtain clear background interference fringes on the image acquisition subsystem 3; Step S2: Place the target material on the target material platform of the vacuum chamber module and set the ambient pressure; Step S3: Set the delay time between the ablation laser pulse and image acquisition through the timing control module; Step S4: The digital delay generator triggers the laser ablation subsystem 2 to generate pulsed laser to ablate the target material. At the same time, the timing control module triggers the image acquisition subsystem 3 at the set delay time to acquire the interference image containing the plasma plume. Step S5: The acquired image is transmitted to the data processing computer, which calculates the displacement of the interference fringes and inversely determines the two-dimensional electron density field of the plasma plume.

[0039] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0040] Example: Measurement of electron density in plasma plume from laser-ablated Al@GAP target Sample preparation: Al@GAP composite powder was pressed into tablet-shaped targets with a diameter of 10 mm and a thickness of 2 mm using a tablet press at a pressure of 30 MPa.

[0041] System settings: Place the target material in the vacuum chamber and adjust the ambient pressure to 75 kPa. Set the ablation laser energy density to 15.6 J / cm². Set the probe wavelength to 532 nm. Set the ICCD camera gate width to 50 ns. Set the delay time between the ablation laser and ICCD acquisition to 10.5 μs using a delay generator.

[0042] Image acquisition: First, the background interference fringe pattern is acquired without triggering the ablation laser. Then, the ablation laser is triggered, and the deformed interference fringe pattern containing the plasma plume is acquired at a delay of 10.5 μs.

[0043] Data Processing: The acquired images are imported into a computer processing program. The program automatically performs image preprocessing, registration, binarization, and thinning. The fringe displacement ΔS is calculated. The Radon inverse transform and Abel inverse transform algorithm modules are called to inversely determine the electron density distribution of the plasma plume.

[0044] Output results: The program generates a curve of electron density as a function of radius and a two-dimensional false-color cloud map of electron density field.

[0045] This invention is well-conceived, has strong anti-interference capabilities, high measurement accuracy, and high spatiotemporal resolution. It can clearly image the evolution process of transient plasma plumes generated by laser ablation and quantitatively invert the distribution of their two-dimensional electron density field.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A plasma plume density diagnostic system based on a Wollaston prism, characterized in that: The diagnostic system includes a laser ablation subsystem (1), a differential interferometry subsystem (2), an image acquisition subsystem (3), and a general subsystem (4). The laser ablation subsystem (1) is used to generate a high power density pulsed laser to ablate the target material and generate a plasma plume. The differential interferometer subsystem (2) is used to provide a high-quality, collimated continuous laser beam as a probe light for interferometric measurement, to detect the density field of the plasma plume, and to convert the phase change caused by the plasma into a recordable interferometric fringe pattern. The image acquisition subsystem (3) is used to capture transient interference fringe patterns during the ablation of the target material under precise timing control. The general subsystem (4) is used to provide a stable and controllable experimental environment for target ablation experiments.

2. The plasma plume density diagnostic system based on a Wollaston prism according to claim 1, characterized in that: The differential interference subsystem (2) includes an optical probe module and a Wollaston prism interference module; The optical probe module uses a continuous laser with a wavelength of 532nm. A beam expander and a precision adjustment frame are sequentially matched on the probe light output path. The beam expander consists of a concave lens (f1) on the probe light output path of the optical probe module, a first convex lens (f2) located on the beam output path of the concave lens (f1) and on the light-inlet side of the general subsystem (4), and a second convex lens (f3) located on the light-outlet side of the general subsystem (4), so that the probe light covers the density field of the plume. The precision adjustment frame is fitted on the concave lens (f1) and the first convex lens (f2) and is used to adjust the distance between the concave lens (f1) and the first convex lens (f2) according to the focal length of the concave lens (f1) and the first convex lens (f2) so that the probe light forms parallel light. The Wollaston prism interference module is used to generate interference fringes with a large range. It includes a Wollaston prism, a polarizer (P1), and a polarizer (P2). The polarizer (P1) is set in the beam output path of the second convex lens (f3) to convert the probe laser into linearly polarized light. The Wollaston prism is set in the beam output path of the polarizer (P1). The polarizer (P2) is set in the beam output path of the Wollaston prism to cause interference of the sheared light split by the Wollaston prism, forming an interference fringe pattern that can be acquired by the image acquisition subsystem (3).

3. The plasma plume density diagnostic system based on a Wollaston prism according to claim 2, characterized in that: The Wollaston prism has a beam splitting angle of 1°, which shears and separates the linearly polarized light output from the incident polarizer (P1) into two beams of sheared light with a small angle between their propagation directions and perpendicular polarization directions.

4. The plasma plume density diagnostic system based on a Wollaston prism according to claim 1, characterized in that: The general subsystem (4) includes a vacuum chamber module and a timing control module; The vacuum chamber module is used to provide a set environmental pressure for the ablation of the target material. It includes a vacuum chamber body, optical glass windows, a mechanical pump and molecular pump assembly, a pressure sensor, and a target material platform. The optical glass windows are symmetrically arranged on the light-inlet and light-outlet sides of the vacuum chamber body. The target material platform is located inside the vacuum chamber body and mounted on a three-dimensional combined translation stage with three-dimensional translation function. The mechanical pump and molecular pump assembly are mounted on the vacuum chamber body to create a vacuum environment inside the vacuum chamber body. The pressure sensor is located inside the vacuum chamber body to detect the vacuum level inside the vacuum chamber body. The timing control module is used to precisely trigger the image acquisition subsystem (3) to perform exposure at a preset delay time point after the laser ablation subsystem (1) is triggered. It includes a digital delay generator and an oscilloscope. The digital delay generator is connected to the oscilloscope, the laser ablation subsystem (1) and the image acquisition subsystem (3) respectively through signal transmission lines. The oscilloscope is connected to the laser ablation subsystem (1) and the image acquisition subsystem (3) respectively through signal transmission lines.

5. The plasma plume density diagnostic system based on a Wollaston prism according to claim 4, characterized in that: The image acquisition subsystem (3) includes an ICCD camera, a HiCATT25 image intensifier, a QM1 long working distance microscope, and a data processing computer. The HiCATT25 image intensifier is installed at the front end of the ICCD camera and achieves image enhancement in low-light environments through photoelectric conversion, electron multiplication, and image processing. The QM1 long working distance microscope is installed at the front end of the HiCATT25 image intensifier and is used to obtain high-resolution, high-definition images outside the vacuum chamber. The ICCD camera is matched and set in the beam output optical path of the differential interferometer subsystem (2). It is used to collect the interference fringe pattern output by the differential interferometer subsystem (2) and is connected to the data processing computer, the digital delay generator and the oscilloscope respectively through signal transmission lines. The data processing computer is used to receive and process the interference fringe patterns acquired by the differential interferometer subsystem (2) and the ICCD camera, and to invert the two-dimensional electron density field of the plasma plume by calculating the displacement of the interference fringe.

6. The plasma plume density diagnostic system based on a Wollaston prism according to claim 4, characterized in that: The laser ablation subsystem (1) ablates the target material by focusing to generate a high-power-density pulsed laser, producing a plasma plume. It includes a nanosecond pulsed laser, a planar beam splitter, a power meter, and a third convex lens (f4). The nanosecond pulsed laser is used to provide adjustable laser energy density, and it is connected to the digital delay generator and the oscilloscope respectively via signal transmission lines; The planar beam splitter is disposed in the laser output optical path of the nanosecond pulse laser and is used to split the received pulse laser into a reflected beam and a transmission tube beam for output. The power meter is disposed in the output optical path of the transmitted beam of the planar beam splitter and is used to measure the energy density of the output beam of the nanosecond pulse laser. The third convex lens (f4) is disposed in the output optical path of the reflected beam of the flat beam splitter. It is used to focus the beam to improve the energy density of the pulsed laser and make the upper limit of the adjustable energy density of the beam higher.

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