Millimeter-wave coherent scattering diagnostic system for high-wavenumber turbulence monitoring in superconducting tokamaks

Abstract

The present invention provides a millimeter-wave coherent scattering diagnostic system for monitoring high-wavenumber turbulence in a superconducting tokamak. This system, belonging to the field of magnetic confinement fusion plasma diagnostics, comprises a millimeter-wave source, a first converging convex lens, a first high-density polyethylene (HDPE) vacuum window, a first concave mirror, a second concave mirror, a target plasma region, a third concave mirror, a fourth concave mirror, a second HDPE vacuum window, a second concave lens, and a millimeter-wave receiver, arranged sequentially along an optical path. The beam waist of the millimeter-wave coherent scattering diagnostic system is located at the center of the target plasma region. By arranging optical lens assemblies at the incident end and the signal receiving end within the vacuum of the tokamak device, the coherent scattering system can arrange the optical path in two different windows, increasing the scattering angle, enhancing the radial localization of the signal, and increasing the ability to scan different radial regions, thereby achieving long-term, stable, and effective measurement of high-wavenumber turbulence.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic confinement fusion plasma diagnosis, and in particular relates to a millimeter wave coherent scattering diagnostic system for superconducting tokamak high-wavenumber turbulence monitoring. Background Art

[0002] Magnetic confinement fusion is safe, clean, and readily available, making it a promising new energy source for humanity. The tokamak is currently the most promising device for achieving fusion energy. Future tokamak fusion power plants will require long-pulse operation to reduce power generation costs. Therefore, all tokamak fusion devices currently under construction and planning utilize an all-superconducting design. Turbulence-induced transport observed in all-superconducting tokamaks often far exceeds neoclassical transport levels (based on classical plasma transport theory after accounting for toroidal magnetic field effects), resulting in significant energy losses. Research into the mechanisms of turbulent transport is urgently needed. Furthermore, future fusion reactors rely on self-generated alpha particles as a heating source to sustain long-term plasma combustion. These particles primarily heat electrons, leading to a dominant electron thermal transport mechanism. High-wavenumber electron-mode turbulence is widely considered a key driver of electron thermal transport. Electron thermal transport is considered a key physics issue in magnetic confinement fusion research and requires urgent resolution. Therefore, it is imperative to conduct research on high-wavenumber turbulence and transport in all-superconducting tokamaks, with the ultimate goal of suppressing turbulent transport.

[0003] Electromagnetic coherent scattering diagnostics is a powerful tool for monitoring high-wavenumber density fluctuations and is widely recognized for its suitability for studying the physics of high-wavenumber turbulence and transport. This diagnostic approach requires a high-frequency, low-phase-noise electromagnetic wave beam to be incident on a plasma through a single window and scattered by free electrons within the plasma. The scattered electromagnetic wave, carrying information about the plasma turbulence fluctuations, is collected by a back-end receiving optical path through another window and projected onto a receiving detector. To achieve high-wavenumber turbulence diagnostics, the angle between the incident and scattered beams, known as the scattering angle, must be increased. This places higher demands on the transmission path of the diagnostic electromagnetic wave beam. Furthermore, the small scattering cross section makes it difficult to measure small-amplitude scattered signals, necessitating optimized back-end receiving optical path design to improve scattered signal reception efficiency. Given the large dewar chambers required for future superconducting fusion reactors, this significantly increases the distance between the diagnostic window and the burning plasma core. This poses challenges in achieving long-distance, collimated transmission of both the incident and scattered electromagnetic waves.

[0004] At present, due to the difficulty of optical path design, electromagnetic wave diagnostic equipment for millimeter wave high wave number turbulence measurement has not been established in the fully superconducting tokamak fusion device. In order to experimentally verify the turbulence physical model of fusion reactor plasma and promote the design and safe operation of fusion reactor, it is urgent to develop an electromagnetic wave scattering system for measuring high wave number turbulence behavior. This requires solving its core problem, namely the design of electromagnetic wave transmission optical path, including: (1) how to achieve long-distance electromagnetic wave collimated transmission in the vacuum dewar cavity; (2) how to optimize the optical path design to meet the adjustable scattering angle function, by increasing the angle between the incident optical path and the scattered beam, to increase the upper limit of the experimental measurement wave number; (3) how to increase the collection angle of the incident and scattered optical paths, and increase the amplitude of the scattered signal to ensure a high signal-to-noise ratio of the experimental results and the confidence of the physical results; (4) how to reduce the influence of device wall treatment such as lithiation and boronization on the reflectivity of the vacuum internal reflection concave mirror, which is helpful for long-term normal and stable operation of the diagnosis. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a millimeter-wave coherent scattering diagnostic system for superconducting tokamak high-wavenumber turbulence monitoring. By arranging an optical lens combination at the incident end and the signal receiving end in the vacuum of the tokamak device, the millimeter-wave coherent scattering system can arrange the optical path in two different windows, use millimeter waves to carry out scattering, enhance the pass rate of millimeter waves and signal electromagnetic waves, improve the stable measurement capability of the system, increase the scattering angle, enhance the radial localization of the signal, and increase the scanning capability of different radial areas, so as to achieve long-term stable and effective measurement of high-wavenumber turbulence.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A millimeter-wave coherent scattering diagnostic system for superconducting tokamak high-wavenumber turbulence monitoring includes a millimeter-wave source, a first converging convex lens, a first high-density polyethylene (HDPE) vacuum window, a first concave mirror, a second concave mirror, a target plasma region, a third concave mirror, a fourth concave mirror, a second HDPE vacuum window, a second concave lens, and a millimeter-wave receiver, which are sequentially arranged along an optical path. The first and second concave mirrors are arranged inside the neck of the tokamak device's incident beam emission window, and the third and fourth concave mirrors are arranged inside the neck of the tokamak device's receiving window.

[0008] The millimeter waves generated by the millimeter wave source are converged by a first converging convex lens and smoothly reach a first high-density polyethylene vacuum window; thereafter, the millimeter waves are converged by a first concave mirror and then reflected to a second concave mirror, converged and reflected to a target plasma region by the second concave mirror, and the target plasma region is a scattered signal generation region. The scattered signals are converged and reflected to a fourth concave mirror by a third concave mirror, and the fourth concave mirror reflects and converges the millimeter waves, so that the millimeter waves reach a second high-density polyethylene vacuum window. The scattered signals are converged by a second concave lens, optically amplified, and have a beam radius reduced, and enter a millimeter wave receiver. The millimeter wave receiver detects different frequencies and realizes electronic signal amplification through a millimeter wave antenna array and a secondary mixing method; the beam waist of the optical path of the millimeter wave coherent scattering diagnostic system is located at the center of the target plasma region.

[0009] Furthermore, the first converging convex lens and the second converging convex lens are made of HDPE material, and the first concave mirror, the second concave mirror, the third concave mirror and the fourth concave mirror are made of non-magnetic aviation aluminum, that is, the mirror positioning position is not affected by electromagnetic force.

[0010] Furthermore, the wavelength of the millimeter wave far exceeds that of the CO2 laser, which will greatly reduce the impact of device wall treatments such as lithiation and boronization on the reflectivity of the concave mirror in a vacuum.

[0011] Furthermore, the aperture of the first converging convex lens is larger than the aperture of the first high-density polyethylene vacuum window, and the aperture of the second converging convex lens is larger than the aperture of the second high-density polyethylene vacuum window.

[0012] Furthermore, the apertures of the first concave mirror and the second concave mirror are not less than the aperture of the first high-density polyethylene vacuum window, and the apertures of the third concave mirror and the fourth concave mirror are not less than the aperture of the second high-density polyethylene vacuum window.

[0013] Furthermore, the reflection angles of the second concave mirror and the third concave mirror do not exceed 90 degrees, and the reflection angles of the first concave mirror and the fourth concave mirror are not less than 45 degrees.

[0014] Furthermore, the first, second, third, and fourth concave mirrors are all mounted on the plasma side of the tube neck. The first concave mirror is located to the left of the second concave mirror, so that the second concave mirror cannot block the incident millimeter waves from the first concave mirror. The fourth concave mirror is located to the left of the third concave mirror, so that the fourth concave mirror cannot block the scattered electromagnetic wave signals from the third concave mirror.

[0015] Furthermore, the second concave mirror and the fourth concave mirror can adjust the overlapping area between the incident millimeter wave and the scattered electromagnetic wave (ie, the radial position of the scanning target plasma area) by rotating.

[0016] Furthermore, the millimeter wave receiver includes a millimeter wave antenna and a detection electronics system.

[0017] Furthermore, the millimeter wave receiver includes detecting scattered signals of different frequencies or different directions.

[0018] Furthermore, the first concave mirror is a fixed mirror, and the second concave mirror is a rotatable mirror. The second concave mirror adjusts the incident millimeter wave beam waist to different radial positions of the plasma according to experimental needs.

[0019] Furthermore, the third concave mirror is a rotatable mirror, and the fourth concave mirror is a fixed mirror. By adjusting the third concave mirror, an overlapping area exists between the incident millimeter wave and the scattered signal, namely the target plasma area.

[0020] Furthermore, the positions of the first converging convex lens and the second converging convex lens outside the vacuum of the tokamak device are movable along the direction of the optical path for optical path calibration.

[0021] Beneficial effects:

[0022] 1. The present invention provides a first converging convex lens to effectively control the divergence of the incident electromagnetic wave, ensuring that more than 99% of the energy passes through the first high-density polyethylene vacuum window, thereby solving the problem of the incident electromagnetic wavelength propagating in a collimated manner, improving energy transmission efficiency, and suppressing stray reflection signals;

[0023] 2. The present invention utilizes a first concave mirror and a second concave mirror to redirect the collimated electromagnetic wave after receiving it. This allows the wave to be incident on the plasma at an adjustable angle. By properly adjusting the angle of the fourth concave mirror, this not only helps ensure good spatial localization of the scattered signal but also enables radial scanning of the target plasma region, facilitating monitoring of turbulent evolution within different regions of the fusion reactor. Furthermore, the present invention optimizes the curvature radius of the dual concave mirrors. The curvature radius of one concave mirror (typically the first) is fixed, while the beam waist position is adjusted by adjusting the curvature radius of the other concave mirror. This ensures that the incident electromagnetic wave, propagating in quasi-Gaussian optics, converges to the Gaussian beam waist upon reaching the target plasma region. This design effectively improves the spatial resolution and energy density of the incident electromagnetic wave in the target plasma region, thereby enhancing the measurement signal-to-noise ratio.

[0024] 3. Based on the propagation characteristics of incident and scattered electromagnetic waves, this invention employs an asymmetric design. A large-aperture double concave mirror assembly (third and fourth concave mirrors) is used to maximize the reception of scattered electromagnetic wave signals and align them to quasi-parallel transmission signals. This design effectively solves the problem of long-distance transmission of scattered signals.

[0025] 4. In this invention, a second converging convex lens is installed in the receiving optical path as an optical gain lens to match the transmission direction of the scattered signal with the antenna direction of the electronic receiving module. This directly increases the optical gain of the receiving module and optimizes the signal-to-noise ratio of the measurement.

[0026] 5. The combination of the first and second concave mirrors at the incident end of the tokamak device in a vacuum, and the third and fourth concave mirrors at the signal receiving end, enables the millimeter-wave coherent scattering system to arrange the optical path in two different windows, improving the scattering angle and achieving effective measurement of high-wavenumber turbulence.

[0027] 6. The present invention uses millimeter waves for scattering. Because the wavelength of millimeter waves far exceeds that of CO2 lasers, they significantly reduce the impact of device wall treatments such as lithiation and boronization on the reflectivity of the concave mirror in a vacuum, facilitating long-term normal and stable operation of the diagnostic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the millimeter wave coherent scattering diagnostic system for high-wavenumber turbulence monitoring in a superconducting tokamak according to the present invention.

[0029] Among them, the figure markings are: millimeter wave source 1, first converging convex lens 2, first high-density polyethylene vacuum window 3, first concave mirror 4, second concave mirror 5, target plasma area 6, third concave mirror 7, fourth concave mirror 8, second high-density polyethylene vacuum window 9, second converging convex lens 10, millimeter wave receiver 11. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0031] like Figure 1 As shown, the millimeter wave coherent scattering diagnostic system for superconducting tokamak high-wavenumber turbulence monitoring of this embodiment includes a millimeter wave source 1, a first converging convex lens 2, a first high-density polyethylene vacuum window 3, a first concave mirror 4, a second concave mirror 5, a target plasma region 6, a third concave mirror 7, a fourth concave mirror 8, a second high-density polyethylene vacuum window 9, a second concave convex lens 10, and a millimeter wave receiver 11, which are arranged in sequence along the optical path.

[0032] The millimeter wave generated by the millimeter wave source 1 is converged by the first concave lens 2 and smoothly reaches the first high-density polyethylene vacuum window 3; thereafter, the millimeter wave is converged by the first concave mirror 4 and then reflected to the second concave mirror 5, and is converged and reflected to the target plasma region 6 by the second concave mirror 5. The target plasma region 6 is the scattered signal generation region. The scattered signal is converged and reflected to the fourth concave mirror 8 by the third concave mirror 7. The fourth concave mirror 8 reflects and converges the millimeter wave, so that it smoothly reaches the second high-density polyethylene vacuum window 9. The scattered signal is converged by the second concave lens 10 to be optically amplified, the beam radius is reduced, and it smoothly enters the millimeter wave receiver 11. The millimeter wave receiver 11 detects different frequencies and realizes compact, modular, and low-cost electronic signal amplification through the millimeter wave antenna array and secondary mixing.

[0033] The first concave mirror 4, the second concave mirror 5, the third concave mirror 6, and the fourth concave mirror 7 are all located on the plasma side of the tube neck. The first concave mirror 4 is located to the left of the second concave mirror 5, so that the second concave mirror 5 cannot block the incident millimeter waves of the first concave mirror 1. The fourth concave mirror 7 is located to the left of the third concave mirror 6, so that the fourth concave mirror 7 cannot block the scattered electromagnetic wave signals of the third concave mirror 3, ensuring that the incident millimeter waves and the scattered millimeter waves can be transmitted smoothly.

[0034] The second and fourth concave mirrors 5 and 7 rotate to adjust the radial overlap between the incident millimeter waves and the scattered electromagnetic waves (i.e., the radial position of the target plasma region), thereby facilitating monitoring of turbulent flow evolution within different regions of the fusion device. Preferably, the first and second high-density polyethylene vacuum windows 3 and 9 both seal the vacuum and provide high millimeter wave transmission.

[0035] The millimeter wave source 1, first and second converging convex lenses 2 and 10, and millimeter wave receiver 11 are located outside the tokamak's vacuum chamber. The first and second high-density polyethylene vacuum windows 3 and 9 serve as vacuum interfaces. The first and second concave mirrors 4 and 5 are located inside the neck of the tokamak's incident beam emission window, while the third and fourth concave mirrors 7 and 8 are located inside the neck of the tokamak's receiving window. The first and second concave mirrors 4, 5, 7, and 8 are typically mounted on a metal bracket inside the neck of the tokamak, primarily due to space limitations and the need to share the window with other diagnostic systems. For dedicated windows, the first, second, 5, 7, and fourth concave mirrors can be mounted directly on the inner wall of the neck.

[0036] The beam waist of the millimeter-wave coherent scattering diagnostic system optical path is located at the center of the target plasma region 6 . Figure 1 In the figure, light gray is the incident beam and dark gray is the scattered beam.

[0037] Preferably, the first converging convex lens 2 and the second converging convex lens 10 are made of HDPE. Preferably, the first concave mirror 4, the second concave mirror 5, the third concave mirror 7, and the fourth concave mirror 8 are made of non-magnetic aviation aluminum, that is, their positioning is not affected by electromagnetic force.

[0038] The wavelength of the millimeter wave is much longer than that of CO2 laser, which will greatly reduce the effect of device wall treatment such as lithiation and boronization on the reflectivity of the concave mirror in vacuum.

[0039] Preferably, the aperture of the first converging convex lens 2 should be larger than the aperture of the first high-density polyethylene vacuum window 3 , and the aperture of the second converging convex lens 10 should be larger than the aperture of the second high-density polyethylene vacuum window 9 .

[0040] Preferably, the apertures of the first concave mirror 4 and the second concave mirror 5 should not be smaller than the aperture of the first high-density polyethylene vacuum window 3 , and the apertures of the third concave mirror 7 and the fourth concave mirror 8 should not be smaller than the aperture of the second high-density polyethylene vacuum window 9 .

[0041] Preferably, the reflection angles of the first concave mirror 4, the second concave mirror 5, the third concave mirror 7 and the fourth concave mirror 8 do not exceed 90 degrees, and the reflection angles of the first concave mirror 4 and the fourth concave mirror 8 are not less than 45 degrees.

[0042] Preferably, the millimeter wave receiver 11 includes a millimeter wave antenna and a detection electronics system.

[0043] Preferably, the millimeter wave receiver 11 includes a device for detecting scattered signals of different frequencies or directions.

[0044] Preferably, the millimeter wave receiver 11 detects different frequencies and implements compact, modular, low-cost electronic signal amplification through a millimeter wave antenna array and secondary mixing.

[0045] Preferably, the positions of the first converging convex lens 2 and the second converging convex lens 10 outside the vacuum of the tokamak device are movable along the optical path direction for optical path calibration.

[0046] Preferably, the first concave mirror 4 is a fixed mirror, and the second concave mirror 5 is a rotatable mirror. The second concave mirror 5 can adjust the incident millimeter wave beam waist to different radial positions of the plasma according to experimental needs.

[0047] Preferably, the third concave mirror 7 is a rotatable mirror, and the fourth concave mirror 8 is a fixed mirror. By adjusting the third concave mirror 7 , an overlapping area such as the target plasma area 6 can be created between the incident millimeter wave and the scattered signal.

Claims

1. A millimeter wave coherent scattering diagnostic system for high-wavenumber turbulence monitoring in a superconducting tokamak, characterized in that: The invention comprises a millimeter wave source, a first converging convex lens, a first high-density polyethylene vacuum window, a first concave mirror, a second concave mirror, a target plasma region, a third concave mirror, a fourth concave mirror, a second high-density polyethylene vacuum window, a second concave lens, and a millimeter wave receiver, which are sequentially arranged along an optical path; the first concave mirror and the second concave mirror are arranged on the inner side of the tube neck of the incident beam emission window of the tokamak device, and the third concave mirror and the fourth concave mirror are arranged on the inner side of the tube neck of the receiving window of the tokamak device; The millimeter waves generated by the millimeter wave source are converged by a first converging convex lens and smoothly reach a first high-density polyethylene vacuum window; thereafter, the millimeter waves are converged by a first concave mirror and then reflected to a second concave mirror, converged and reflected to a target plasma region by the second concave mirror, and the target plasma region is a scattered signal generation region. The scattered signals are converged and reflected to a fourth concave mirror by a third concave mirror, and the fourth concave mirror reflects and converges the millimeter waves, so that the millimeter waves reach a second high-density polyethylene vacuum window. The scattered signals are converged by a second concave lens, optically amplified, and have a beam radius reduced, and enter a millimeter wave receiver. The millimeter wave receiver detects different frequencies and realizes electronic signal amplification through a millimeter wave antenna array and a secondary mixing method; the beam waist of the optical path of the millimeter wave coherent scattering diagnostic system is located at the center of the target plasma region.

2. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wave number turbulence monitoring according to claim 1, characterized in that: The first converging convex lens and the second converging convex lens are made of HDPE material, and the first concave mirror, the second concave mirror, the third concave mirror, and the fourth concave mirror are made of non-magnetic aviation aluminum material.

3. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wavenumber turbulence monitoring according to claim 1, characterized in that: The aperture of the first converging convex lens is larger than the aperture of the first high-density polyethylene vacuum window, and the aperture of the second converging convex lens is larger than the aperture of the second high-density polyethylene vacuum window; the apertures of the first concave mirror and the second concave mirror are not smaller than the aperture of the first high-density polyethylene vacuum window, and the apertures of the third concave mirror and the fourth concave mirror are not smaller than the aperture of the second high-density polyethylene vacuum window.

4. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wavenumber turbulence monitoring according to claim 1, characterized in that: The first concave mirror, the second concave mirror, the third concave mirror and the fourth concave mirror are all installed on the plasma side of the tube neck; the first concave mirror is located on the left side of the second concave mirror, and the second concave mirror does not block the incident millimeter wave of the first concave mirror; the fourth concave mirror is located on the left side of the third concave mirror, and the fourth concave mirror does not block the scattered electromagnetic wave signal of the third concave mirror.

5. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wavenumber turbulence monitoring according to claim 1, characterized in that: The reflection angles of the second concave mirror and the third concave mirror do not exceed 90 degrees, and the reflection angles of the first concave mirror and the fourth concave mirror are not less than 45 degrees.

6. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wave number turbulence monitoring according to claim 1, characterized in that: The millimeter wave receiver includes a millimeter wave antenna and a detection electronics system; the millimeter wave receiver detects scattered signals of different frequencies or directions.

7. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wave number turbulence monitoring according to claim 1, characterized in that: The second concave mirror and the fourth concave mirror adjust the radial overlapping area between the incident millimeter wave and the scattered electromagnetic wave by rotation, and the radial overlapping area is the radial position of the scanning target plasma area.

8. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wave number turbulence monitoring according to claim 1, characterized in that: The first concave mirror is a fixed mirror, and the second concave mirror is a rotatable mirror. The second concave mirror adjusts the incident millimeter wave beam waist to different radial positions of the plasma according to experimental needs.

9. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wavenumber turbulence monitoring according to claim 1, characterized in that: The third concave mirror is a rotatable mirror, and the fourth concave mirror is a fixed mirror. By adjusting the third concave mirror, an overlapping area is created between the incident millimeter wave and the scattered signal, namely the target plasma area.

10. The millimeter wave coherent scattering diagnostic system for superconducting tokamak high wave number turbulence monitoring according to claim 1, characterized in that: The positions of the first converging convex lens and the second converging convex lens outside the vacuum of the tokamak device are movable along the direction of the optical path and are used for optical path calibration.

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