A high-energy non-elastic spectrometer four-chopper linkage control method and control system
By employing a four-chopper linkage control method, the problem of poor resolution in the high-energy region and difficulty in achieving full-spectrum coverage in traditional spectrometers is solved, enabling efficient and flexible neutron scattering measurements and improving experimental efficiency and data quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-08
- Publication Date
- 2026-06-16
AI Technical Summary
Traditional neutron scattering spectrometers have poor resolution in the low-energy region at high incident energies, making it difficult to balance full spectrum range and high resolution, resulting in resource waste and data accuracy issues. Existing chopper systems also struggle to switch flexibly between strict monochromatic and efficient multicolor modes.
A four-chopper linkage control method is adopted, including four choppers: T0, T1, T2, and M. Combined with the neutron kinematics model and the phase angle remainder strategy, it can achieve precise selection of neutron energy and data stream segmentation and splicing, and support flexible switching between strict monochromatic and multi-monochromatic incident modes.
This improves the efficiency of lattice dynamics characterization of the spectrometer, reduces experimental time and cost, enhances data accuracy, expands the scope of application of the spectrometer, and makes full use of neutron source resources.
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Figure CN122224745A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of large-scale scientific facilities for neutron scattering, specifically relating to a method and control system for the linkage control of four choppers in a high-energy inelastic spectrometer applied to the Direct Geometry Spectrometer (DGS) of the Spallation Neutron Source. Background Technology
[0002] Neutron scattering, as a key method for studying the microstructure and dynamic properties of matter, plays an irreplaceable role in many fields such as condensed matter physics and materials science. With the continuous advancement of spallation neutron source technology, inelastic neutron scattering spectrometers based on time-of-flight (TOF) technology, especially direct geometric time-of-flight spectrometers, have become core tools for studying physical phenomena such as lattice dynamics (phonons) and magnetic excitations (magnons).
[0003] In practical applications of direct geometric time-of-flight spectrometers (DFS), the precise selection of the incident neutron energy (Ei) is crucial. However, traditional spectrometer control strategies, such as the classical mode used by the ARCS spectrometer at Oak Ridge National Laboratory (SNS) in the United States, have long faced the dilemma of reconciling resolution and coverage. Specifically, while using high incident energy (High Ei) can cover a larger range of momentum transfer (Q) and energy transfer (E), offering advantages for observing the full spectrum of phonon states or high-energy magnetic excitations, the fixed relative energy resolution ΔE / E means that high Ei leads to a decrease in the absolute energy resolution ΔE in the low-energy region, making it impossible to effectively resolve the fine structures in the low-energy region. Conversely, low incident energy (Low Ei) offers extremely high absolute energy resolution in the low-energy region, suitable for studying soft modes, Bose peaks, and other fine features, but the measured (Q,E) range is extremely narrow, making it difficult to comprehensively acquire overall information on matter dynamics.
[0004] To obtain data with both full spectral range and high resolution, traditional methods necessitate performing multiple experiments on the same sample. First, a high Ei value is used to measure the overall picture, then a low Ei value is used for repeated measurements to obtain details. This "repetitive step-by-step characterization mode" has several serious drawbacks: First, spallation neutron sources are extremely expensive, and multiple measurements significantly increase time costs, resulting in a huge waste of resources; second, in monochromatic mode, the chopper only selects a very narrow subset of neutrons from the source pulse, causing the detector to be idle for most of the source pulse period, resulting in extremely low data acquisition efficiency; furthermore, slight fluctuations in the sample environment (such as temperature and magnetic field) between measurements can severely affect the accuracy of data merging, thus impacting the reliability of the experimental results.
[0005] Although there have been some attempts at repetition rate multiplication (RRM) technology, existing chopper systems are limited by the physical structure of the chopper window and the rigidity of the control algorithm, making it difficult to flexibly switch between "strict monochromatic" and "efficient multichromatic" modes. Especially when handling wide bandwidth passages, frame overlap becomes a difficult technical bottleneck to overcome, severely restricting further improvements in spectrometer performance. Therefore, developing a novel chopper-linked control algorithm and system to fully utilize the temporal structure of the pulsed neutron source and resolve the contradiction between efficiency and resolution has become a key problem urgently needing to be solved in the field of neutron scattering. Summary of the Invention
[0006] To address the aforementioned issues, this invention aims to provide a four-chopper linkage control method and control system for a high-energy inelastic spectrometer applied to the Direct Geometry Spectrometer (DGS) at the Spallation Neutron Source. This invention focuses on utilizing a four-chopper linkage algorithm to achieve high-efficiency, high-resolution full-spectrum measurement, aiming to resolve the contradiction between "resolution" and "coverage" in traditional spectrometers, improve the efficiency of lattice dynamics characterization, and meet the needs of research users for accurate, efficient, and flexible selection of spectrometer parameters.
[0007] The technical solution adopted in this invention is: a four-chopper linkage control method for a high-energy inelastic spectrometer, comprising the following steps: It provides four core choppers: T0 chopper, T1 bandwidth chopper, T2 dual-window bandwidth chopper, and M monochromatic Fermi chopper; A control model based on neutron kinematics is established, and the incident energy Ei set by the user is converted into a velocity and time graph through E=1 / 2mv². The flight time of the neutron to each chopper is calculated by combining the geometric parameters of the spectrometer. By employing a "phase angle remainder" strategy, the optimal turn-on phase delay of each chopper relative to the source pulse trigger signal is precisely calculated, ensuring that neutron packets of different velocities can accurately pass through the opening slits of all choppers. In the multi-monochromatic incident mode, the "neutron time-of-flight slicing" algorithm is applied to pre-calculate the time window for the scattered neutrons to reach the detector for each Ei based on the incident energy and the range of sample scattering dynamics. The continuous data stream is logically cut into multiple independent neutron bands using time stamps.
[0008] The T0 chopper is used to remove transient high-energy neutrons, ensuring that the neutron energy range processed by subsequent choppers is within a controllable range.
[0009] The bandwidth chopper T1 is used to define the full bandwidth of neutron energy, providing a reference range for neutron energy selection for subsequent choppers.
[0010] The dual-window bandwidth chopper T2 is used to select a specific target bandwidth, enabling flexible switching and energy selection between multi-monochromatic incident modes and strictly monochromatic incident neutron modes.
[0011] The monochromatic Fermi chopper M is used to provide a monochromatic incident neutron beam, and to monochromate each neutron band after it is cut.
[0012] The "phase angle remainder" strategy determines the optimal start-up time for each chopper by calculating the phase remainder of the target time point relative to the chopper rotation period.
[0013] The "neutron time-of-flight slicing" algorithm also includes a data stitching step, which reassembles the cut independent neutron bands in chronological order to restore complete scattering signal information.
[0014] A four-chopper linkage control system for a high-energy inelastic spectrometer includes: Four core choppers: T0 chopper, T1 bandwidth chopper, T2 dual-window bandwidth chopper, and M monochromatic Fermi chopper; A control unit is used to execute the high-energy non-elastic spectrometer four-chopper linkage control method as described in any one of claims 1 to 7; The detector is used to receive the neutron scattering signal after it has been processed by the chopper, and then transmit the signal to the control unit for data processing.
[0015] The control unit also includes a user interface that allows users to set the incident energy Ei, select a measurement mode (either a strictly monochromatic incident neutron mode or a multi-monochromatic incident neutron mode), and display the processed scattering signal data.
[0016] The system also has data storage and export functions, allowing users to save processed scattering signal data for subsequent analysis and comparison.
[0017] Compared with the prior art, the present invention has the following significant and outstanding advantages: This invention significantly improves the efficiency of spectrometer lattice dynamics characterization through an innovative four-chopper linkage control algorithm and system, increasing efficiency by more than three times. It allows for the acquisition of complete spectrum data—data that traditional methods require three or more measurements to piece together—within a single experimental measurement. This not only drastically shortens the experimental cycle and reduces the machine time cost of spallation neutron sources, but also significantly improves research efficiency, providing researchers with more time for their studies.
[0018] This invention successfully overcomes the technical challenge of poor low-energy resolution in traditional spectrometers at high Ei. By employing multi-Ei stitching technology, users can simultaneously view high-energy optical phonons under the same experimental conditions and conduct in-depth analysis of low-energy acoustic phonons with extremely high resolution. Unlike traditional methods, it eliminates the need to change experimental conditions, avoiding potential errors caused by variations in experimental conditions. This provides a strong guarantee for the precise study of the microstructure and dynamic properties of matter.
[0019] This invention enables a one-click software-level switch from a "simple and clear monochromatic mode" to a "efficient and complex multicolor mode." This innovative design greatly expands the spectrometer's applicability, easily handling both rapid testing of standard samples and detailed exploration of complex and unknown materials. Researchers can flexibly select experimental modes according to actual needs, improving the relevance and flexibility of experiments and meeting the diverse requirements of different research scenarios.
[0020] This invention fully leverages the potential of existing physical hardware through a unique dual-window configuration and phase modulo algorithm. While ensuring experimental accuracy and effectiveness, it maximizes the utilization of the spallation neutron source pulse beam, making better use of limited resources. This not only improves the cost-effectiveness of the equipment but also provides valuable reference and guidance for subsequent optimization and upgrades of related hardware. Attached Figure Description
[0021] Figure 1 This is a schematic diagram illustrating the working principle of the direct geometric inelastic neutron scattering spectrometer in this invention.
[0022] Figure 2 This is a schematic diagram illustrating the contradiction between "large energy characterization range" and "high energy resolution" in this invention. It includes two figures, b and c, which illustrate the (Q,E) detection range and resolution of a traditional single incident energy spectrometer (showing the trade-off between resolution and range). Traditional methods require multiple measurements to meet the simultaneous requirements of large detection range and high resolution.
[0023] Figure 3 The four diagrams, including dg, represent the key technologies of the four-chopper linkage system, including i) neutron energy representation transformation, ii) phase angle remainder calculation, iii) neutron time-of-flight slicing, and iv) dual-window bandwidth chopper configuration.
[0024] Figure 4 This is a schematic diagram of the strictly monochromatic incident neutron mode in this invention, including two diagrams, h and i, which express the comparison between the simulated and experimentally verified energy spectra under the strictly monochromatic incident mode.
[0025] Figure 5This invention presents the multi-monochromatic incident neutron mode, including two plots, j and k, which compare the simulated and experimentally verified energy spectra under the multi-monochromatic incident mode. On the right side of plot h,j, T0, T1, T2, and M represent the T0 chopper, the bandwidth chopper, the dual-window bandwidth chopper, and the Fermi monochromatic chopper, respectively. Detailed Implementation
[0026] The following detailed description, with reference to the accompanying drawings, provides a specific implementation method for the linkage control of four choppers in a high-energy non-elastic spectrometer according to this application.
[0027] This system mainly consists of four core choppers, a control unit, and a detector. The specific structure is as follows: It includes four core choppers: a T0 chopper, a bandwidth chopper T1, a dual-window bandwidth chopper T2, and a monochromatic Fermi chopper M. The T0 chopper is used to remove transient high-energy neutrons, ensuring that the neutron energy range processed by subsequent choppers remains within a controllable range. The bandwidth chopper T1 defines the full bandwidth of neutron energy, providing a reference range for neutron energy selection by subsequent choppers. The dual-window bandwidth chopper T2 selects a specific target bandwidth, enabling flexible switching and energy selection between multi-monochromatic incident modes and strictly monochromatic incident neutron modes. The monochromatic Fermi chopper M provides a monochromatic incident neutron beam, meeting the requirements of the strictly monochromatic incident neutron mode.
[0028] The control unit is responsible for executing the four-chopper linkage control method, including establishing a control model, calculating the flight time, implementing a phase angle remainder strategy, and applying a neutron time-of-flight slicing algorithm. The control unit also includes a user interface, allowing users to set the incident energy Ei, select the measurement mode (strictly monochromatic incident neutron mode or multi-monochromatic incident neutron mode), and display the processed scattered signal data.
[0029] The detector is used to receive the neutron scattering signal after it has been processed by the chopper, and transmit the signal to the control unit for data processing.
[0030] The working principle and implementation steps of this invention include the following: S1. Establish a control model based on neutron kinematics: Based on the user-defined target incident energy Ei, the control unit uses the formula... , ,and ( : Neutron mass The distance a neutron travels from the moderator to the monochromatic Fermi chopper M. and The corresponding flight time and neutron wavelength, Planck's constant converts energy into velocity and time phenomena, obtaining the accurate neutron flight time at target Ei. This step corresponds to the one shown in the accompanying drawings of the instruction manual. Figure 3 The d-plane diagram illustrates the process of neutron energy appearance transformation.
[0031] S2. Implement the "phase angle remainder" strategy: To fully utilize the pulse characteristics of the spallation neutron source, the frequency of each chopper needs to be a fixed integer multiple of the source frequency, where the frequency value of the Fermi chopper M is... The specific energy resolution requirement is determined by the user. The control unit performs a phase remainder calculation on the target time point, using the formula... The optimal on-phase delay of the Fermi chopper relative to the source pulse trigger signal (at time T0) is precisely calculated. This strategy ensures that the neutron beam of the target energy passes precisely through the opening slit of the Fermi chopper, corresponding to... Figure 3 Display of e-map size.
[0032] S3. Neutron Time-of-Flight Slicing: Since the chopper rotation speed is usually a multiple of the source frequency, multiple degenerate incident neutron beams will be generated within the neutron source's firing cycle (40ms / cycle). According to the formula... In the time-time graph coordinates, it is possible to quickly obtain the time window through which all neutrons pass within a single pulse period, thereby obtaining the energies of all theoretically obtainable incident neutrons. .
[0033] S3. Strictly Monochromatic Incident Neutron Mode: In strictly monochromatic incident neutron mode, it is necessary to ensure that only neutrons within the target incident neutron energy slice can reach the monochromatic Fermi chopper M. In this mode, the system needs to utilize the narrow-angle window of the dual-window bandwidth chopper T2, and determine its distance from the source based on the geometric distance parameter L. T2 Align its phase center with the wavelength center of the target energy neutron. This shields the noise signals that may be caused by other incident neutron energies, enabling monochromatic measurements with a high signal-to-noise ratio. Figure 4 The simulation and experimental verification energy spectra of the strictly monochromatic incident neutron mode are shown, verifying the effectiveness of the mode.
[0034] S4. Multi-monochromatic incident neutron mode: In multi-monochromatic incident neutron mode, not all theoretically obtainable incident neutron energies within the pulse window can be effectively utilized. This presents challenges such as high-energy background differences and low-energy overlap interference. Therefore, four choppers (T0, T1, T2, and M) need to work in tandem. The T0 chopper adjusts its phase according to the required high-energy neutron. The T1 and T2 choppers work together to select several incident neutron energies within a specific range. Specific process: The user determines the required range of multi-monochromatic incident neutron energies, and then uses the wide-angle windows of the T1 and T2 choppers to collaboratively select this range of incident neutron energies, thus obtaining the target multi-monochromatic incident neutron mode. Here, the phase calculations of all T0, T1, and T2 choppers follow the logic in Figures d and e, combined with their respective geometric distance parameters (L). T0 ,L T1 ,L T2 ).
[0035] Figure 5 The simulation and experimental verification energy spectra under the multi-monochromatic incident mode are shown, demonstrating that this mode can simultaneously obtain scattering signals of multiple energies in a single experiment, significantly improving measurement efficiency.
[0036] This embodiment demonstrates through experiments that, by using four choppers in coordinated control, the spectrometer's lattice dynamics characterization efficiency is improved by more than three times, allowing for the acquisition of full-spectrum data that would require multiple measurements to piece together using traditional methods in a single experiment. It successfully solves the problem of poor resolution between high Ei and low energies, enabling users to analyze low-energy acoustic phonons at extremely high resolution while simultaneously viewing high-energy optical phonons. It achieves a software-level one-click switch from a "simple and clear monochromatic mode" to a "efficient and complex multicolor mode," greatly expanding the spectrometer's applicability. Through dual-window configuration and phase remainder algorithms, it fully leverages the potential of existing physical hardware, maximizing the utilization rate of the spallation neutron source pulse beam.
[0037] In summary, the four-chopper linkage control method and control system for high-energy inelastic spectrometers presented in this application effectively solves the contradiction between efficiency and resolution in traditional spectrometers through innovative control algorithms and hardware configurations, providing a powerful tool for neutron scattering research.
Claims
1. A method for coordinated control of four choppers in a high-energy inelastic spectrometer, characterized in that, Includes the following steps: It provides four core choppers: T0 chopper, T1 bandwidth chopper, T2 dual-window bandwidth chopper, and M monochromatic Fermi chopper; A control model based on neutron kinematics is established, and the incident energy Ei set by the user is converted into a velocity and time graph through E=1 / 2mv². The flight time of the neutron to each chopper is calculated by combining the geometric parameters of the spectrometer. By employing a "phase angle remainder" strategy, the optimal turn-on phase delay of each chopper relative to the source pulse trigger signal is precisely calculated, ensuring that neutron packets of different velocities can accurately pass through the opening slits of all choppers. In the multi-monochromatic incident mode, the "neutron time-of-flight slicing" algorithm is applied to pre-calculate the time window for the scattered neutrons to reach the detector for each Ei based on the incident energy and the sample scattering dynamics range, and to logically cut the continuous data stream into multiple independent neutron bands using time stamps.
2. The high-energy inelastic spectrometer four-chopper linkage control method according to claim 1, characterized in that, The T0 chopper is used to remove transient high-energy neutrons, ensuring that the neutron energy range processed by subsequent choppers is within a controllable range.
3. The high-energy inelastic spectrometer four-chopper linkage control method according to claim 1, characterized in that, The bandwidth chopper T1 is used to define the full bandwidth of neutron energy, providing a reference range for neutron energy selection for subsequent choppers.
4. The high-energy inelastic spectrometer four-chopper linkage control method according to claim 1, characterized in that, The dual-window bandwidth chopper T2 is used to select a specific target bandwidth, enabling flexible switching and energy selection between multi-monochromatic incident modes and strictly monochromatic incident neutron modes.
5. The four-chopper linkage control method for a high-energy inelastic spectrometer according to claim 1, characterized in that, The monochromatic Fermi chopper M is used to provide a monochromatic incident neutron beam, extracting a monochromatic neutron bundle from the broadband neutron beam.
6. The four-chopper linkage control method for a high-energy inelastic spectrometer according to claim 1, characterized in that, The "phase angle remainder" strategy determines the optimal start-up time for each chopper by calculating the phase remainder of the target time point relative to the chopper rotation period.
7. The four-chopper linkage control method for a high-energy inelastic spectrometer according to claim 1, characterized in that, The "neutron time-of-flight slicing" algorithm also includes a data stitching step, which reassembles the cut independent neutron bands in chronological order to restore complete scattering signal information.
8. A four-chopper linkage control system for a high-energy inelastic spectrometer, characterized in that, include: Four core choppers: T0 chopper, T1 bandwidth chopper, T2 dual-window bandwidth chopper, and M monochromatic Fermi chopper; A control unit is used to execute the high-energy non-elastic spectrometer four-chopper linkage control method as described in any one of claims 1 to 7; The detector is used to receive the neutron scattering signal after it has been processed by the chopper, and then transmit the signal to the control unit for data processing.
9. The high-energy inelastic spectrometer four-chopper linkage control system according to claim 8, characterized in that, The control unit also includes a user interface that allows users to set the incident energy Ei, select a measurement mode (either a strictly monochromatic incident neutron mode or a multi-monochromatic incident neutron mode), and display the processed scattering signal data.
10. The high-energy inelastic spectrometer four-chopper linkage control system according to claim 8, characterized in that, The system also has data storage and export functions, allowing users to save processed scattering signal data for subsequent analysis and comparison.