CN-116359809-B - Method for measuring magnetic field of surface of first wall material in real time in-situ online contactless manner

Abstract

The invention provides a method for real-time in-situ online non-contact measurement of a first wall material surface magnetic field, which comprises the steps of ablating first wall materials in different magnetic field intensity areas by adopting high-energy nanosecond pulse laser of an endoscope structure and generating laser plasmas, radiating spectrum signals with wall element characteristic information by the laser plasmas in a cooling process, collecting and coupling laser plasma radiation light by utilizing an optical collecting system of the endoscope structure into a multi-core optical fiber, coupling the collected plasma radiation light into a spectrometer, transmitting spectrum data into a computer through the spectrometer for analysis, and screening out standard spectrums with highest correlation coefficients by extracting splitting and spatial distribution characteristics of spectrum characteristic peaks under different magnetic field intensities and comparing the standard spectrums with different directions and different magnetic field intensities in an established database, and finding and displaying the magnetic field intensity and the direction corresponding to the standard spectrums in the database so as to realize measurement of the magnetic field intensity and the direction.

Inventors

• WU DING
• WU HUACE
• HU XIAOHAN
• LIU JIAMIN
• DING HONGBIN
• HAI RAN
• LI CONG
• FENG CHUNLEI

Assignees

• 大连理工大学

Dates

Publication Date

20260508

Application Date

20230113

Claims (4)

1. 1. A method for real-time in-situ online contactless measurement of a magnetic field at a surface of a first wall material, comprising: The method comprises the steps of adopting high-energy nanosecond pulse laser of an endoscope structure to ablate first wall materials in different magnetic field intensity areas and generate laser plasmas, wherein the laser plasmas radiate spectrum signals with wall element characteristic information in the cooling process; Collecting and coupling laser plasma radiation light to a multi-core optical fiber using an optical collection system of an endoscope structure, coupling the collected plasma radiation light into a spectrometer, comprising: The high-energy nanosecond pulse laser (3) after receiving the trigger signal emits high-energy nanosecond pulse laser and reflects the high-energy nanosecond pulse laser through the first laser high-threshold reflecting mirror (4), the second laser high-threshold reflecting mirror (5) and the third laser high-threshold reflecting mirror (6) so as to adjust the laser direction and continue to propagate; The high-energy nanosecond pulse laser reflected by the third laser high-threshold reflecting mirror (6) passes through the first optical aperture (8) and the second optical aperture (9) respectively to realize beam collimation, and red indicating light emitted by the helium-neon laser indicator (7) is regulated to pass through the first optical aperture (8) and the second optical aperture (9) to realize coaxiality with laser beams; The collimated high-energy nanosecond pulse laser and red indicating light are subjected to beam expansion by a primary beam expander (10), reflected by a dichroic mirror (11) and continuously transmitted; The high-energy nanosecond pulse laser and the red indicating light continue to propagate forwards, and after being reflected by the aluminum film reflecting mirror (12), the high-energy nanosecond pulse laser and the red indicating light are re-expanded by a secondary beam expander consisting of a concave lens (13) and a convex lens (15), and meanwhile, the concave lens (13) is driven by a two-dimensional precise stepping motor (14) to move so as to realize a focusing function, so that detection of different areas of the first wall by the high-energy nanosecond pulse laser is ensured; The high-energy nanosecond pulse laser and red indicating light which are expanded again are reflected by an aluminum film reflecting mirror (16) and enter an endoscope barrel (25), and are focused by a laser focusing lens (17) and then reflected by an endoscope (18) to a first wall surface (20); The red indicating light is focused on the first wall surface (20) to determine the detection position, and the focusing system consisting of the concave lens (13) and the convex lens (15) is used for controlling the focusing size of the high-energy nanosecond pulse laser so as to realize the mm-level spatial resolution which is actually required; focusing high-energy nanosecond pulse laser onto the first wall surface (20), and performing ablation excitation to form transient laser plasma (21); the transient laser plasma (21) is reflected by the endoscope (18) and returns along the original path, and is focused into the multi-core linear array optical fiber (23) by the achromatic lens (22) after passing through the laser focusing lens (17), the aluminum film reflecting mirror (16), the convex lens (15), the concave lens (13), the aluminum film reflecting mirror (12) and the dichroic mirror (11) respectively; The spectrum data is transmitted to a computer for analysis through a spectrometer, through extracting splitting and spatial distribution characteristics of spectrum characteristic peaks under different magnetic field intensities and comparing the spectrum data with standard spectrums under different directions and different magnetic field intensities in an established database, the standard spectrum with the highest correlation coefficient is screened out, and the magnetic field intensity and direction corresponding to the screened standard spectrum are found in the database and displayed, so that the measurement of the magnetic field intensity and direction is realized.
2. 2. The method for real-time in-situ online contactless measurement of a magnetic field on a surface of a first wall material according to claim 1, wherein the high-energy nanosecond pulse laser with an endoscope structure ablates the first wall material in areas with different magnetic field intensities and generates a laser plasma, and the laser plasma radiates a spectrum signal with characteristic information of wall elements during cooling, comprising: The data acquisition and analysis computer (1) and the digital pulse delay generator (2) are in a normal state in communication with the two-dimensional precision stepper motor (14) and the antimagnetic rotating motor (19), and the high-energy nanosecond pulse laser (3) and the high-resolution spectrometer (24) are in an external triggering state; after the first wall detection position is determined, the data acquisition and analysis computer (1) respectively sends commands to the digital pulse delay generator (2), the two-dimensional precise stepping motor (14) and the antimagnetic rotating motor (19); The two-dimensional precise stepping motor (14) and the anti-magnetic rotating motor (19) respectively move to corresponding positions after receiving the command so that laser can be focused on the surface of a specific first wall material; After receiving the trigger signal, the digital pulse delay generator (2) respectively triggers the high-energy nanosecond pulse laser (3) to emit laser and the spectrometer to receive the laser plasma radiation optical signal according to the set time sequence.
3. 3. The method for real-time in-situ online contactless measurement of a magnetic field on a surface of a first wall material according to claim 1, wherein the spectral data is transmitted to a computer for analysis by a spectrometer, and the standard spectrum with the highest correlation coefficient is screened out by extracting splitting and spatial distribution characteristics of spectral characteristic peaks under different magnetic field intensities and comparing the extracted characteristics with standard spectrums under different directions and different magnetic field intensities in an established database, comprising: The multi-core linear array optical fiber (23) transmits the collected laser plasma radiation light to a spectrometer (24) equipped with an ICCD camera, so that spatial resolution and signal enhancement are realized; the spectrometer (24) synchronously transmits the collected laser plasma radiation spectrum signals to the data collection and analysis computer (1); The data acquisition and analysis computer (1) analyzes splitting and spatial distribution characteristics of the obtained plasma radiation spectrum under different magnetic field intensities in real time; by comparing splitting and spatial distribution characteristics of spectrum characteristic lines under different magnetic field intensities analyzed in real time by a data acquisition and analysis computer (1) with standard spectrums under different magnetic field intensities in an established database, screening out a standard spectrum with the highest correlation coefficient, and finding out the magnetic field intensity and direction corresponding to the standard spectrum in the database and displaying.
4. 4. The method for real-time in-situ online contactless measurement of a magnetic field of a surface of a first wall material according to claim 1, wherein the spectrometer is a high resolution spectrometer and the multicore fiber is a linear array fiber.

Description

Method for measuring magnetic field of surface of first wall material in real time in-situ online contactless manner Technical Field The invention relates to the technical field of magnetic field measurement, in particular to a method for measuring a magnetic field of a surface of a first wall material in real time in situ on line in a non-contact manner. Background When the magnetic confinement nuclear fusion device such as tokamak operates, an ohmic transformer is formed by a central solenoid and a heating field coil to heat fuel to generate plasma and form plasma current, and a circumferential magnetic field is generated by externally adding a longitudinal field coil distributed along the annular direction of the vacuum chamber. The polar magnetic field and the annular magnetic field generated by the plasma current form a superimposed magnetic field, thereby realizing the restraint of the plasma. In experimental study of plasma physics, measurement of various parameters of high-temperature plasma, such as plasma density, current, ion and electron temperature, magnetic field and the like, needs to be realized through various diagnostic systems. Among these parameters, measurement of the tokamak magnetic field distribution is critical for plasma control. Meanwhile, charged particles in the plasma do larmor rotary motion around magnetic lines, and the magnetic field direction has an important influence on the state of the plasma. Recent studies have found that the magnetic field direction has a large impact on the L-H switching power threshold, the internal and external asymmetry of the divertor, and the energy constraint level. The real-time knowledge of the strength and direction of the tokamak boundary magnetic field has important significance for the correction of the boundary particle transport model. Therefore, there is a need to develop a method that can acquire the magnetic field strength and direction of different areas of the first wall surface of a magneto-restrictive nuclear fusion device in real time. On the other hand, due to the imperfections of the magnetic field with respect to particle confinement, strong Plasma-Wall-interactions (PWI) can occur between the high heat flux and particle flux released by the high temperature Plasma from the core and the Plasma-Facing Components (PFCs). The dynamic information of the surface element composition of the first wall, particularly the divertor, is obtained in real time, and is important to understanding the physical process of PWI and optimizing the experimental conditions of the long-pulse high-parameter plasma. The Laser-induced breakdown spectroscopy (Laser-Induced Breakdown Spectroscopy, LIBS) technology is a non-contact in-situ on-line elemental analysis technology, and can realize real-time rapid detection of multiple elements. The LIBS technology has the working principle that a beam of high-energy pulse laser is focused on the first wall surface to ablate wall materials to generate transient high-temperature high-density plasmas, and then emission spectrums in the cooling process of the excited plasmas are acquired and analyzed through various optical detectors, so that qualitative and quantitative analysis of the elements of the sample to be detected is realized. However, the influence of the magnetic field intensity and the direction of the change of different areas on LIBS analysis is not negligible in the face of the Tokamak complex working condition. Therefore, the magnetic field intensity information of the wall surface can be calibrated by acquiring the LIBS signals synchronously, so that the accuracy of the LIBS analysis result is improved. The main methods for measuring the intensity and direction of the magnetic field of the first wall at present mainly comprise a magnetic probe method and a Hall probe method. The magnetic probe measurement method is used as a diagnosis method capable of measuring the intensity and the direction of the first wall magnetic field in real time, in situ and on line, is currently applied to all fusion devices in the world, but can inevitably generate interference on plasma as an invasive diagnosis method, and meanwhile, the method can only perform local measurement generally and cannot realize large-scale measurement. The hall probe measurement method has good accuracy for static magnetic fields, but is not suitable for being installed in a vacuum chamber. Experimental analysis results show that splitting and spatial distribution characteristics of element characteristic lines of LIBS spectrum have high correlation with the intensity and direction of the magnetic field on the surface of the first wall area to be measured. By establishing a database and a related model for element characteristic lines of the first wall material with different directions and different magnetic field strengths, the accurate measurement of the magnetic field strength and the direction of the surface of the first wall area