Metamaterial resonant cavity and accelerator beam flow intensity measuring device and method

Abstract

The invention discloses a metamaterial resonant cavity and an accelerator beam flow intensity measuring device and method, and relates to the field of particle acceleration equipment, the metamaterial resonant cavity comprises an insulator and an electrode body formed by a substrate and a metamaterial unit array arranged on the substrate; the electrode body is disposed in the cavity, and the insulator is disposed between the electrode body and the cavity. The metamaterial resonant cavity provided by the invention can greatly improve the signal-to-noise ratio of a signal, is applied to beam current intensity measurement, and aims to overcome the contradiction between the sensitivity and the time resolution of a traditional non-interception type measurement method so as to thoroughly solve the problems of the acceleration and the time resolution of an accelerator. And particularly, the problem of real-time accurate monitoring in a low-flow-intensity and short-pulse beam device is solved.

Description

Technical Field

[0001] This application relates to the field of particle acceleration equipment, and in particular to a metamaterial resonant cavity and an accelerator beam current measurement device and method. Background Technology

[0002] The stable and efficient operation of particle accelerators heavily relies on the accurate diagnosis of beam parameters, among which beam current is one of the most critical parameters. Traditional current measurement techniques each have their advantages, but they all have significant limitations when facing the stringent requirements of high sensitivity, high time resolution, miniaturization, and non-interception for diagnostic equipment in next-generation accelerator devices (such as miniaturized ion accelerators and energy recovery linear accelerators, ERLs).

[0003] Currently widely used technologies mainly include Direct Current Transformer (DCCT) and Alternating Current Transformer (ACCT), which utilize the magnetic field generated by the beam current induced by the magnetic core for measurement. Although the technology is mature and has a large measurement range, it is susceptible to external electromagnetic interference. Wall Current Monitors have an extremely wide response bandwidth and can capture rapidly changing beam current signals. However, the output signal of the wall current monitor is closely related to the beam impedance matching and the pipe environment, making absolute current intensity calibration complex, and the signal is susceptible to reflection interference. The Faraday Cup, as the absolute reference for current intensity measurement, has a direct and reliable principle, but its essence is interception measurement, which completely blocks the beam current, resulting in severe heat dissipation and secondary electronic effects, making it unsuitable for online, real-time, and non-destructive diagnostic scenarios. The above traditional methods struggle to achieve high-sensitivity measurement of weak beams without intercepting the beam current. When a charged particle beam (such as electrons or protons) passes through a resonant cavity in a vacuum, it induces an electromagnetic field on the cavity wall; this phenomenon is called "wake field loading." The amplitude and phase of the induced field are closely related to the beam intensity, energy, lateral dimensions, and bundle length. Placing a specially designed high-quality factor resonant cavity in the beam path (non-interceptor type) induces a stable intrinsic electromagnetic mode within the cavity as the beam passes through. This microwave signal is coupled out of the cavity via a coupler, and its amplitude is proportional to the beam intensity. Therefore, this device can be used to measure the average beam intensity; however, current resonant cavities have low signal-to-noise ratios, severely impacting the accuracy of average beam intensity detection. Cavity detectors are crucial beam diagnostic devices in modern particle accelerators, especially electron linear accelerators and energy recovery linear accelerators. Their main applications include real-time beam intensity monitoring, beam position monitoring, and bundle length diagnosis. They have been widely used in many large accelerator facilities known to the inventors, such as the linear accelerator section of the Shanghai Synchrotron Radiation Facility (SSRF) and its upgraded project, SSRF II; the linear accelerator of the China Spallation Neutron Source (CSNS); and free-electron laser devices, which require extremely high beam quality and precise beam diagnostics. Examples include the Swiss Light Source at the Paul Scherer Institute in Switzerland and the CLIC testing facility at CERN. The Pillbox cavity is the simplest and most classic resonant cavity design. It boasts a mature theory, simple design, high quality factor, and good mechanical stability. However, its lack of compactness (large lateral space requirement) limits its use in space-constrained modern accelerators.

[0004] Therefore, based on the above description, traditional non-interception measurement methods have a contradiction between sensitivity and time resolution, and cannot fundamentally solve the problem of real-time accurate monitoring in particle accelerators, especially in low-current, short-pulse beam devices. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a metamaterial resonant cavity and an accelerator beam current measurement device and method.

[0006] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a metamaterial resonant cavity, comprising: an insulator, and an electrode body composed of a substrate and an array of metamaterial units disposed on the substrate; The electrode body is disposed in the cavity, and the insulator is disposed between the electrode body and the cavity.

[0007] Optionally, the structure and size of the metamaterial units in the metamaterial unit array, as well as the arrangement of each metamaterial unit, are determined by simulation software based on user requirements.

[0008] Optionally, the metamaterial units in the metamaterial unit array are complementary open-loop resonators or electric LC resonators.

[0009] Optionally, the insulator is made of zirconia ceramic or plastic for a vacuum environment; the electrode body and the cavity body are both made of oxygen-free copper, electrolytic copper, or aluminum alloy.

[0010] Optionally, the size of the metamaterial resonant cavity is on the order of centimeters.

[0011] Optionally, both the cavity and the electrode body are provided with through holes; the center point of the through hole on the cavity and the center point of the through hole on the electrode body are located on the same straight line.

[0012] Optionally, the metamaterial resonant cavity further includes at least two probes; the probes are used to extract the resonant signal generated by the metamaterial resonant cavity.

[0013] Secondly, this application provides an accelerator beam current measurement device, including: a particle accelerator, a differential, a mixer, a low-pass filter, a data acquisition unit, and the metamaterial resonant cavity provided above; The metamaterial resonant cavity is fitted onto the beam channel of the particle accelerator; The mixer, the low-pass filter, and the data acquisition unit are connected in series; the differential is connected in parallel between the metamaterial resonant cavity and the mixer.

[0014] Optionally, the accelerator beam current measurement device provided in this application further includes: an amplifier; The amplifier is positioned between the low-pass filter and the data acquisition unit.

[0015] Thirdly, this application provides a method for measuring accelerator beam current intensity, including: The resonant signal generated by the metamaterial resonant cavity is differentially amplified in real time and then mixed to obtain a mixed signal. The mixed signal is low-pass filtered to obtain an intermediate frequency signal; The intermediate frequency signal is digitally sampled, and the amplitude of the intermediate frequency signal is extracted; The beam current intensity is obtained based on the amplitude of the intermediate frequency signal using the beam current intensity-cavity field amplitude curve.

[0016] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a metamaterial resonant cavity and an accelerator beam current measurement device and method. By utilizing the field enhancement effect of metamaterials to set up the metamaterial resonant cavity, the signal-to-noise ratio can be greatly improved. Furthermore, this application applies the metamaterial resonant cavity to the beam current measurement of an accelerator, aiming to overcome the contradiction between sensitivity and time resolution in traditional non-interception measurement methods, thereby completely solving the problem of real-time accurate monitoring in particle accelerators, especially low-current, short-pulse beam devices. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is an axial half-sectional view of a metamaterial resonant cavity provided in an embodiment of this application; Figure 2 A radial half-sectional view of a metamaterial resonant cavity provided in an embodiment of this application; Figure 3 A front view of a metamaterial resonant cavity provided in an embodiment of this application; Figure 4 A top view of a metamaterial resonant cavity provided in an embodiment of this application; Figure 5 A side view of a metamaterial resonant cavity provided in an embodiment of this application; Figure 6 This is a schematic diagram of the structure of an electrode body provided in an embodiment of this application; Figure 7This is a flowchart of an accelerator beam current measurement method provided in an embodiment of this application.

[0019] Figure label: 1-Cavity, 2-Insulator, 3-Electrode, 4-Through hole, 5-First probe, 6-Second probe, 7-Metamaterial unit array, 8-Positioning pin hole, 9-Substrate. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Metamaterials are composite materials that achieve extraordinary physical properties (such as negative refractive index and anomalous transmission) through artificially designed structural units rather than the inherent material properties. In the microwave field, precise manipulation of electromagnetic wave propagation can be achieved by designing arrays of subwavelength metallic resonant units (such as complementary split-ring resonators, SRRs). In recent years, the concept of metamaterials has been introduced into the accelerator field, demonstrating enormous potential. Its core value lies in its ability to generate extremely strong electromagnetic field localization and enhancement effects within physical dimensions much smaller than the operating wavelength.

[0022] The aforementioned properties of metamaterials have been explored for use in novel acceleration structures, radiation sources, and beam manipulation devices. This suggests that metamaterial-based resonant cavities hold the potential to bring revolutionary breakthroughs to beam diagnostics. Based on this, this application innovatively proposes the application of metamaterial resonant cavities to beam current measurement. This approach aims to simultaneously overcome the contradiction between sensitivity and time resolution in traditional non-interception measurement methods and provide a compact and easily integrated solution to address the challenge of real-time monitoring in accelerators, particularly in low-current, short-pulse beam devices.

[0023] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] In one exemplary embodiment, this application provides a metamaterial resonant cavity, such as Figures 1-6 As shown, it includes: an insulator 2, and an electrode body 3 composed of a substrate 9 and a metamaterial unit array 7 disposed on the substrate 9.

[0025] Electrode 3 is disposed in cavity 1, and insulator 2 is disposed between electrode 3 and cavity 1.

[0026] In practical applications, insulator 2 can be an insulating disc. Figure 6 As shown, electrode body 3 can also be an electrode disk.

[0027] In an exemplary embodiment, in order to flexibly design parameters such as resonant frequency (e.g., on the order of 10~1000MHz), Q value (e.g., on the order of 10^2~10^3), and coupling coefficient (β≈1) by changing the structure, arrangement, and substrate of the metamaterial units, in order to adapt to beam measurement requirements of different energies (e.g., on the order of 1~1000MeV) and different bundle lengths (e.g., on the order of 1~10mm), the structure and size of the metamaterial units in the metamaterial unit array 7 used in this application, as well as the arrangement of each metamaterial unit, can all be determined by simulation software based on user requirements. For example, its geometric parameters can be optimized using CST electromagnetic simulation software to obtain a high Q value and high shunt impedance at the required frequency.

[0028] In an exemplary embodiment, in order to improve sensitivity, the metamaterial units in the metamaterial unit array 7 provided in this application can be configured as complementary open-ring resonators (CSRR), electric LC resonators (ELC), or other structures.

[0029] In one exemplary embodiment, to further improve the performance of the metamaterial resonant cavity, the insulator material can be zirconia ceramic or plastics suitable for vacuum environments such as PEEK, PPS, and PTFE. The electrode body and cavity body materials can both be oxygen-free copper or electrolytic copper, aluminum alloys, or other good conductors.

[0030] In one exemplary embodiment, based on metamaterial design, the lateral physical dimensions (on the order of centimeters) of the metamaterial resonant cavity can be made extremely small to facilitate installation within the limited space of an application device (e.g., an accelerator vacuum tube). Furthermore, to facilitate beam reception, such as... Figure 2 and Figure 3 As shown, both the cavity 1 and the electrode body 3 are provided with through holes 4. The center point of the through hole on the cavity 1 and the center point of the through hole on the electrode body 3 are on the same straight line.

[0031] In one exemplary embodiment, for ease of detection, such as Figure 1 , Figure 3 and Figure 4 As shown, the metamaterial resonant cavity provided in this application may further include at least two probes (i.e., the first probe 5 and the second probe 6). The probes are used to extract the resonant signal generated by the metamaterial resonant cavity.

[0032] Based on the above description, the metamaterial resonant cavity provided in this application can integrate the advantages of high sensitivity, high time resolution, non-interception and miniaturization, effectively overcoming the limitations of traditional technologies and providing key technical support for beam diagnostics of next-generation accelerators.

[0033] In an exemplary embodiment, to utilize the passive resonant cavity based on artificial metamaterial units provided above, it is non-interceptively mounted on a beam channel. The cavity is excited by the beam to generate a wake field. The beam intensity is obtained by inverting the amplitude of the amplified microwave signal through high-precision measurement. This application provides an accelerator beam intensity measurement device, which includes: a particle accelerator, a differential converter, a mixer, a low-pass filter, a data acquisition unit, and the metamaterial resonant cavity provided in the above embodiment. The metamaterial unit array employs a field enhancement effect based on metamaterials, which can amplify the beam signal by several orders of magnitude to resolve beam intensity changes on the order of μs or even shorter (i.e., it has high time resolution), greatly improving the signal-to-noise ratio, and is particularly suitable for measuring low-intensity beams.

[0034] The metamaterial resonant cavity is housed within the beam channel of the particle accelerator, meaning it surrounds the accelerator's vacuum beam channel. The cavity is connected to an external excitation / signal acquisition system (including a data acquisition unit) via a microwave coupling structure. In practical applications, such as... Figure 4 As shown, the metamaterial resonant cavity can be fixed to the beam pipe of the particle accelerator by setting the positioning pin hole 8. The mixer, low-pass filter, and data acquisition unit are connected in series. A differential circuit is connected in parallel between the metamaterial resonant cavity and the mixer. There can be a pair of differential circuits.

[0035] In the device provided in this application, the signal-to-noise ratio can be significantly improved by utilizing the strong field enhancement characteristics of metamaterials. Furthermore, by setting up a compact metamaterial resonant cavity that can be installed online (i.e., compact structure and easy integration), non-destructive, real-time, and high-precision current intensity monitoring is achieved. This solves the problems in existing accelerator beam measurements, such as the difficulty in balancing high time resolution and high sensitivity, low signal-to-noise ratio in low current intensity measurements, excessively large volume of traditional resonant cavities, inability to perform online measurements with Faraday cylinders, and excessively large size of traditional cavities.

[0036] Based on the above description, the core of the accelerator beam current measurement device provided in this application lies in a passive resonant cavity (i.e., a metamaterial resonant cavity) constructed based on metamaterial units. When a charged beam passes through this resonant cavity at near-light speed, its electromagnetic field excites the eigenmodes of the cavity. Through the resonance of its subwavelength units, the metamaterial units can highly localize the electromagnetic field energy in a specific region, generating a very strong field enhancement effect. As an excitation source, when the charged particle beam passes through the beam channel at the center of the cavity, its transient electromagnetic field excites the metamaterial resonant cavity to generate a specific mode of wake field. The amplitude of the induced electromagnetic field is linearly related to the beam intensity (charge) passing through the cavity (i.e., the wake field amplitude and the beam current intensity are linearly related). Finally, by performing simulation calculations and calibrations on the system beforehand, establishing the correspondence between the wake field signal amplitude and the beam current intensity, and accurately calibrating, the absolute beam current intensity can be calculated (i.e., inverted) by measuring the characteristics of the resonant signal. It features non-interference and non-destructive measurement characteristics, does not interfere with the beam itself, and can be monitored online in real time.

[0037] In one exemplary embodiment, this application can utilize the high sensitivity of metamaterials to beam intensity by designing a metamaterial structure probe for beam intensity measurement. For example, a metamaterial resonant cavity is used to measure the TM010 signal, and the beam intensity is obtained after mixing and low-pass filtering the TM010 signal.

[0038] The amplitude of the TM010 signal obtained by the metamaterial resonant cavity during the current intensity measurement is not significantly affected by the beam position and is proportional to the beam current intensity. Therefore, the TM010 signal can be used to measure the beam current intensity.

[0039] It is known that the TM010 signal is a radio frequency signal, and its expression is as follows: .

[0040] In the formula, yes The TM010 signal at time 10. It is the scaling factor of the sensing signal of the metamaterial resonant cavity probe, which can be calculated through beam load effect theory and radio frequency cavity theory. It is the beam current intensity. It is the signal phase. It is the signal decay time. It is the resonant signal frequency. It is the initial moment.

[0041] In one exemplary embodiment, to further improve measurement sensitivity, the accelerator beam current measurement device provided in this application may also include an amplifier. The amplifier is positioned between the low-pass filter and the data acquisition unit.

[0042] In an exemplary embodiment, in order to ensure the stability of long-term measurements, the accelerator beam current measurement device provided in this application may also be equipped with a temperature control and compensation module to suppress the drift caused by ambient temperature fluctuations on the resonant characteristics of the metamaterial resonant cavity.

[0043] Based on the above description, the accelerator beam current measurement device provided in this application can measure the particle accelerator beam current using the TM010 signal of the cavity BCM, thereby significantly reducing the lateral dimension of the cavity BCM.

[0044] In one exemplary embodiment, an accelerator beam current measurement method is provided, such as... Figure 7 As shown, the method includes: Step 100: The resonant signal generated by the metamaterial resonant cavity is differentially amplified in real time and then mixed to obtain a mixed signal. Specifically, the resonant signal is extracted from two probes on the metamaterial resonant cavity set on the particle accelerator. The resonant signal output from the probes is differentially amplified by a pair of differential amplifiers, and then the differential signal output from the differential amplifiers is mixed by a mixer.

[0045] Step 101: Perform low-pass filtering on the mixing signal to obtain the intermediate frequency (IF) signal. Specifically, the IF signal is obtained by low-pass filtering the mixing signal using a low-pass filter.

[0046] Step 102: Digitally sample the intermediate frequency (IF) signal and extract its amplitude. This involves using a data acquisition unit to digitally sample the IF signal and extract its amplitude.

[0047] Step 103: Using the beam current intensity-cavity field amplitude curve, the beam current intensity is obtained based on the amplitude of the intermediate frequency signal.

[0048] By repeatedly executing steps 100-103 above, this application can obtain the amplitude of the intermediate frequency signal output by the low-pass filter at different times, and then obtain the beam current intensity at different times based on the correspondence between the amplitude of the intermediate frequency signal and the beam current intensity.

[0049] In summary, compared with the prior art, the solution provided in this application has at least the following advantages: 1) Ultra-high sensitivity: This application utilizes the field enhancement effect of metamaterials to amplify the beam signal, which greatly improves the signal-to-noise ratio.

[0050] 2) High time resolution: This application can design the signal sampling frequency in the MHz range, with extremely fast response speed, and can distinguish current intensity changes in the μs time range.

[0051] 3) Compact and integrated structure: This application can significantly reduce the physical size (centimeter level) of the A-band resonant cavity (i.e., metamaterial resonant cavity), making it easy to embed into the limited space of existing accelerator beam channels and achieve seamless integration.

[0052] 4) True non-interference and non-destructive measurement: This application can achieve 100% online, real-time and continuous monitoring of the duty cycle without any interference to the beam operation.

[0053] 5) Design flexibility and adjustability: By changing the topology, size and arrangement of metamaterial units, the operating frequency, coupling degree and sensitivity of metamaterial resonant cavities can be flexibly customized to meet the beam measurement requirements of different energies and different pulse structures.

[0054] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A metamaterial resonant cavity characterized by, The application relates to a super material resonant cavity, which comprises the following parts: an insulator and an electrode body composed of a substrate and an array of super material units arranged on the substrate; the electrode body is arranged in a cavity, and the insulator is arranged between the electrode body and the cavity.

2. The metamaterial resonant cavity of claim 1, wherein, The structure and size of the super material units in the array of super material units and the arrangement mode of the super material units are determined by simulation software based on user requirements.

3. The metamaterial resonant cavity of claim 1, wherein, The super material units in the array of super material units are complementary split ring resonators or electric LC resonators.

4. The metamaterial resonant cavity of claim 1, wherein, The material of the insulator is zirconium oxide ceramic or plastic used in a vacuum environment; the material of the electrode body and the material of the cavity are oxygen-free copper, electrolytic copper or aluminum alloy.

5. The metamaterial resonant cavity of claim 1, wherein, The size of the super material resonant cavity is in the order of centimeters.

6. The metamaterial resonant cavity of claim 1, wherein, Holes are arranged on the cavity and the electrode body; the center points of the holes on the cavity and the center points of the holes on the electrode body are located on the same straight line.

7. The metamaterial resonant cavity of claim 1, wherein, The super material resonant cavity further comprises at least two probes; the probes are used for leading out resonant signals generated by the super material resonant cavity.

8. An accelerator beam current measuring device characterized by comprising: The application further relates to a particle accelerator system, which comprises the following parts: a particle accelerator, a differentiator, a mixer, a low-pass filter, a data collector and the super material resonant cavity as claimed in any one of claims 1-7; the super material resonant cavity is sleeved on a beam pipe of the particle accelerator; the mixer, the low-pass filter and the data collector are sequentially connected in series; and the differentiator is connected in parallel between the super material resonant cavity and the mixer.

9. The accelerator beam current measuring device of claim 8, wherein The application further relates to a particle accelerator system, which comprises the following parts: an amplifier; the amplifier is arranged between the low-pass filter and the data collector.

10. An accelerator beam current measurement method characterized by comprising: The application further relates to a particle accelerator system, which comprises the following steps: real-time differential amplification and mixing frequency processing are performed on resonant signals generated by the super material resonant cavity to obtain mixed frequency signals; low-pass filtering is performed on the mixed frequency signals to obtain intermediate frequency signals; the intermediate frequency signals are digitally sampled, and the amplitudes of the intermediate frequency signals are extracted; beam current intensity is obtained based on the amplitudes of the intermediate frequency signals by using a beam current intensity-cavity field amplitude curve.

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