A device for measuring the 2.45 GHz low hybrid wave spectrum in plasma.

Abstract

This invention discloses a device for measuring the 2.45 GHz low-hybrid wave spectrum in plasma. It can be used for experimental research on low-hybrid wave current-driven processes in tokamaks, qualitatively analyzing boundary parasitic effects, such as wave scattering caused by density fluctuations and the influence of parametric decay processes on low-hybrid wave spectral broadening. The device includes a rectangular copper ring antenna, a shielded coaxial cable, an attenuator, a DC blocker, a spectrum analyzer, and a host computer system for data acquisition. The rectangular copper ring antenna is vertically attached to the tokamak glass or PTFE dielectric window to receive the 2.45 GHz low-hybrid wave propagating from the plasma. The signal is then transmitted to the spectrum analyzer via the attenuator and DC blocker, and finally, the host computer acquires the spectral evolution data over time. This invention can measure the low-hybrid wave spectral broadening information under different plasma parameter conditions in low-hybrid wave current-driven experiments, and can be used to qualitatively analyze the relationship between low-hybrid wave driving efficiency and spectral broadening.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology, specifically relating to a device for measuring the 2.45 GHz low hybrid wave spectrum in plasma. Background Technology

[0002] Low-hybrid current drive (LHCD) is a crucial method for maintaining long-pulse steady-state operation in existing tokamak devices, characterized by its extremely high drive efficiency. However, almost all LHCD experiments have shown that the LHCD drive efficiency decreases with density much faster than theoretically predicted. Furthermore, when the density exceeds a certain critical value, no drive effect is observed—the so-called "density limit." This phenomenon is a bottleneck limiting the application of LHCD in future reactors, as future reactor operating environments will typically have very high densities. Recent research suggests that the anomalous decrease in LHCD drive efficiency at high densities is likely related to spectral broadening. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a device for measuring the 2.45 GHz low hybrid wave spectrum in plasma. This device can measure the low hybrid wave spectrum broadening information under different plasma parameter conditions in low hybrid wave current-driven experiments, and is used to qualitatively analyze the relationship between low hybrid wave driving efficiency and spectrum broadening. This provides crucial data support for experiments exploring the mechanism of anomalous decline in low hybrid wave driving efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A device for measuring the 2.45 GHz low-hybrid wave spectrum in plasma includes a rectangular copper ring antenna, a shielded coaxial cable, an attenuator, an SMA connector, a DC blocker, a spectrum analyzer, a standard network cable, and a host computer acquisition system. The rectangular copper ring antenna is vertically attached to a glass or PTFE window. The rectangular copper ring antenna is connected to the spectrum analyzer via the shielded coaxial cable, attenuator, SMA connector, and DC blocker. The spectrum analyzer is placed around a tokamak. The host computer acquisition system remotely controls the spectrum analyzer via the standard network cable. The 2.45 GHz low-hybrid wave in the plasma propagates through the glass or PTFE window, is coupled by the rectangular copper ring antenna, and then passes through the attenuator and DC blocker before being connected to the spectrum analyzer. Finally, the host computer acquisition system acquires and stores the spectrum data.

[0006] Furthermore, the rectangular copper loop antenna includes copper wire, and the size of the rectangular copper loop antenna is 3.7cm×5.3cm to ensure that there is no resonance phenomenon for radio frequency waves in the frequency range of 2450±30MHz; one end of the rectangular copper loop antenna is welded to the flange of the N-type connector, and the other end is welded to the inner conductor of the N-type connector, and then connected to the spectrum analyzer through a coaxial cable.

[0007] Furthermore, the 2.45GHz radio frequency wave received by the rectangular copper ring antenna is connected to the spectrum analyzer via a shielded coaxial cable after passing through a -10dB attenuator and a double-isolated DC blocker.

[0008] Furthermore, the attenuator is used to prevent the coupled signal from being too strong in the high-power low-spurious wave experiment, which could damage the spectrum analyzer; the DC blocker is used to prevent DC voltage from damaging the spectrum analyzer.

[0009] Furthermore, the spectrum analyzer has a scanning time of ≤20ms, an operating frequency of greater than 2.5GHz, and a remote connection function; the spectrum analyzer and the rectangular copper ring antenna 2 are connected by a coaxial cable, which is less than 15 meters long.

[0010] Furthermore, the host computer acquisition system is connected to the spectrum analyzer via a standard network cable to enable remote control of the spectrum analyzer and data acquisition functions.

[0011] Beneficial effects:

[0012] The technical means employed in this invention can measure the spectral broadening information of low-hybrid current drive in tokamak low-hybrid current drive experiments, and can be used to study the relationship between the anomalous decrease in low-hybrid current drive efficiency and spectral broadening. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the main structure of a device for measuring the 2.45 GHz low hybrid wave spectrum in plasma according to the present invention.

[0014] Figure 2 This is a schematic diagram of a copper ring antenna structure.

[0015] Figure 3 For copper ring antenna S 11 Parameter test results graph.

[0016] Figure 4 The image shows the 2.45 GHz spectrum results measured under different plasma density conditions according to the present invention; where (a) represents the plasma density. The spectrum diagram, (b) is the plasma density. The spectrum diagram. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0018] like Figure 1 As shown, the device for measuring the 2.45 GHz low-hybrid wave spectrum in plasma according to the present invention includes a rectangular copper ring antenna 2, a shielded coaxial cable 3, an attenuator 4, an SMA connector 5, a DC blocker 6, a spectrum analyzer 7, a standard network cable 8, and a host computer acquisition system 9. The rectangular copper ring antenna 2 is vertically attached to a glass or polytetrafluoroethylene window 1. The rectangular copper ring antenna 2 is connected to the spectrum analyzer 7 via the shielded coaxial cable 3, attenuator 4, SMA connector 5, and DC blocker 6. The spectrum analyzer 7 is placed around the tokamak. The host computer acquisition system 9 remotely controls the spectrum analyzer 7 via the standard network cable 8.

[0019] like Figure 2 As shown, the rectangular copper loop antenna 2 includes copper wire and measures 3.7cm × 5.3cm to ensure no resonance for radio frequency waves in the frequency range of 2450±30MHz. One end of the rectangular copper loop antenna 2 is soldered to the flange of an N-type connector, and the other end is soldered to the inner conductor of the N-type connector. It is then connected to the spectrum analyzer 7 via a coaxial cable.

[0020] like Figure 3 As shown, the copper ring test results indicate that within the frequency range of interest (2450±30MHz), S 11 The parameters were -6.5 ± 0.4 dB, and no resonance was observed. This indicates that 78% of the power was radiated, the copper ring exhibited excellent coupling, and the coupling was comparable within the frequency range of interest.

[0021] The 2.45GHz radio frequency wave received by the rectangular copper loop antenna 2 passes through a -10dB attenuator 4 and a double-isolated DC blocker 6, and is then connected to the spectrum analyzer 7 via a shielded coaxial cable. The attenuator 4 prevents the coupled signal from being too strong and damaging the spectrum analyzer 7 during high-power, low-clutter experiments. The DC blocker 6 prevents DC voltage from damaging the spectrum analyzer 7.

[0022] The host computer acquisition system 9 is connected to the spectrum analyzer 7 via a network cable, remotely controlling parameters such as the scanning time and operating frequency bandwidth of the spectrum analyzer 7, and acquiring spectrum data that evolves over time and saving it to the host computer.

[0023] Figure 4 Different plasma densities measured in low hybrid current driven experiments The spectral data under these conditions show that, under high-density conditions, the 2.45 GHz pump wave spectral broadening (Δf) is observed. PThe frequency response was severe, reaching 3.12 MHz, and new wavelets were generated. This provides crucial data for studying the anomalous decrease in low clutter drive efficiency under high-density conditions, where the spectral width is defined as the full width after a 20 dB drop in peak power.

[0024] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An apparatus for measuring the 2.45 GHz low hybrid wave spectrum in plasma, characterized in that, The system includes a rectangular copper ring antenna, a shielded coaxial cable, an attenuator, an SMA connector, a DC blocker, a spectrum analyzer, a standard network cable, and a host computer data acquisition system. The rectangular copper ring antenna is vertically mounted against a glass or PTFE window. It is connected to the spectrum analyzer via the shielded coaxial cable, attenuator, SMA connector, and DC blocker. The spectrum analyzer is placed around the tokamak, and the host computer data acquisition system remotely controls the spectrum analyzer via the standard network cable. The 2.45 GHz low-spurious wave in the plasma propagates through the glass or PTFE window, is coupled by the rectangular copper ring antenna, and then passes through the attenuator and DC blocker before being connected to the spectrum analyzer. Finally, the host computer data acquisition system collects and stores the spectrum data. The rectangular copper loop antenna includes copper wire and has dimensions of 3.7 cm × 5.3 cm to ensure no resonance phenomenon for radio frequency waves in the frequency range of 2450 ± 30 MHz. One end of the rectangular copper loop antenna is welded to the flange of the N-type connector, and the other end is welded to the inner conductor of the N-type connector. It is then connected to the spectrum analyzer via a coaxial cable.

2. The apparatus for measuring the 2.45 GHz low hybrid wave spectrum in plasma according to claim 1, characterized in that, The 2.45 GHz radio frequency wave received by the rectangular copper ring antenna is passed through a -10 dB attenuator and a double-isolated DC blocker, and then connected to the spectrum analyzer via a shielded coaxial cable.

3. The apparatus for measuring the 2.45 GHz low hybrid wave spectrum in plasma according to claim 1, characterized in that, The attenuator is used to prevent the coupled signal from being too strong in the high-power low-spurious wave experiment, which could damage the spectrum analyzer; the DC blocker is used to prevent DC voltage from damaging the spectrum analyzer.

4. The apparatus for measuring the 2.45 GHz low hybrid wave spectrum in plasma according to claim 1, characterized in that, The spectrum analyzer has a scanning time of ≤ 20 ms, an operating frequency of greater than 2.5 GHz, and a remote connection function; the spectrum analyzer and the rectangular copper ring antenna 2 are connected by a coaxial cable, which is less than 15 meters long.

5. The apparatus for measuring the 2.45 GHz low hybrid wave spectrum in plasma according to claim 1, characterized in that, The host computer acquisition system is connected to the spectrum analyzer via a standard network cable to enable remote control of the spectrum analyzer and data acquisition functions.

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