A novel monochromator crystal correction system and method
By setting a resistive heating layer on the surface of the first crystal of the monochromator and using X-ray beam diagnostic feedback control technology, the problem of reduced diffraction efficiency caused by thermal deformation of crystals in synchrotron radiation devices was solved, low-cost and efficient beam transmission was achieved, and operating costs were reduced.
Patent Information
- Application Number
- CN202210291786.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-03-23
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2042-03-23
AI Technical Summary
In the existing technology, when the monochromator of the synchrotron radiation device is irradiated by a high-power light beam, the crystal surface undergoes thermal deformation, resulting in reduced diffraction efficiency. In addition, the liquid nitrogen cooling solution is expensive and difficult to effectively suppress thermal deformation, resulting in loss of light flux and increased operating costs.
By setting a resistance heating layer on the surface of the first crystal of the monochromator and combining X-ray beam diagnosis and feedback control technology, zoned heating and temperature control of the crystal surface can be achieved, thermal deformation can be compensated, and the impact on the beam can be reduced.
Without relying on cryogenic liquid nitrogen cooling, the thermal deformation of the monochromator is effectively reduced, the beam transmission efficiency is improved, the operating cost is reduced, and the changes in different power inputs are adapted.
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Figure CN114877996B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of synchrotron radiation, and in particular relates to a novel monochromator crystal correction system and method. Background Art
[0002] In recent years, in the planning and construction of large scientific facilities such as free electron lasers and synchrotron radiation sources, the characteristics of the output beams are uneven distributions with high power (density) in the center and low power (density) in the periphery. Such beams often need to be processed by optical instruments before use, so high-quality and high-efficiency spectrometers are key components to ensure the performance of the beam line. In the beam line of the synchrotron radiation device, the double-crystal spectrometer (double-crystal monochromator) using crystal diffraction is the core device, and its structure is generally as follows: Figure 1 As shown in the figure, after the incident light undergoes Bragg diffraction in the first crystal, it is diffracted again by the second crystal, becoming monochromatic light. When the lattice planes of the two crystals with the same index are parallel, a specific wavelength can be selected from the incident white light and emitted in the same direction.
[0003] Since the power and power density of synchrotron white light are very high and are Gaussian distributed in the cross-sectional direction of the spectrometer, this means that when the monochromator is subjected to this heat load, the first crystal surface has a heat load distribution corresponding to the power density. Under homogeneous cooling boundary conditions, the heat load distribution on the crystal surface will bring about the surface temperature distribution and the corresponding changes in the crystal surface lattice and surface shape (collectively referred to as thermal deformation, References Zhang, L., Sánchez del Río, M., Monaco, G., Detlefs, C., Roth, T., Chumakov, AI, & Glatzel, P. (2013). Thermal deformation of cryogenically cooled silicon crystals under intense X-ray beams: measurement and finite-element predictions of the surface shape. Journal of synchrotron radiation, 20(4), 567-580.; Mocella, V., Lee, WK, Tajiri, G., Mills, D., Ferrero, C., & Epelboin, Y. (2003). A new approach to the solution of the Takagi–Taupin equations for X-ray optics: application to a thermally deformed crystal monochromator. Journal of applied crystallography, 36(1), 129-136.). Although this change is not very large, under the condition of matching the diffraction of the second crystal with the ideal flat crystal, since the receiving angle of the X-ray crystal diffraction is very small (a few seconds), the thermal deformation of the first crystal will show a curve tangent to the straight line of the second crystal, which will cause a loss of light flux. Therefore, in practice, it is generally required to control the thermal deformation of the first crystal within the area of the irradiation spot size to be below a certain index (for example, for Si111 crystal -3μrad RMS) to ensure that most of the photon flux in the unit bandwidth of the original beam can pass. The greater the power of the incident beam, the greater the thermal load that the monochromator has to bear. However, since the condition that the second crystal is an ideal flat crystal is basically unchanged, in order to achieve higher transmission / splitting efficiency, the index requirements for controlling the thermal deformation of the first crystal will not change. Therefore, the difficulty of cooling the crystal and suppressing its thermal deformation is becoming increasingly greater. In current synchrotron radiation devices, the heat load and power density are generally between 100-300W and 10-102 W / mm 2 To minimize thermal deformation of the first crystal, liquid nitrogen cooling is currently commonly used, as the ratio of thermal expansion coefficient to thermal conductivity of single-crystal silicon is optimal around 100 K. Therefore, cooling the monochromator requires a large initial investment and high operating and maintenance costs.
[0004] Another type of monochromator is called a high-resolution monochromator, which further reduces the bandwidth of a normal light beam (relative bandwidth of about 2e-4, absolute bandwidth of several eV) to the meV level below 1e-6. Figure 2 This is a schematic diagram of the configuration of a high-resolution monochromator, which is generally used downstream of the forward double-crystal monochromator. The upstream monochromator (left side) selects an energy band of approximately 3eV from the quasi-monochromatic incident light, and the downstream four-time continuous diffraction high-resolution monochromator further monochromates the bandwidth to 6meV or lower. Because the bandwidth of the incident light and the outgoing light differ by nearly 1,000 times, the flux loss of the light beam on the surface of the second crystal after passing through the first crystal is much greater than the flux loss on the surface of the third crystal after passing through the fourth crystal in the reverse direction. Therefore, under high-resolution conditions, the third crystal and the second crystal surface, which appear to have the same index, can see the difference in window position due to different thermal power. The window position can be adjusted by slightly heating the third crystal to improve the light flux (Toellner T S. Monochromatization of synchrotron radiation for nuclear resonant scattering experiments [J]. Hyperfine Interactions, 2000, 125 (1): 3-28.).
[0005] For double-crystal monochromators (Laue or Bragg type), thermal deformation caused by the heat load of the first crystal and deformation caused by crystal cooling and clamping can turn the originally flat lattice and surface shape into a surface with a certain curvature, resulting in a loss of flux when matching the diffraction of the flat second crystal.
[0006] Because thermal deformation occurs on the surface of the crystal, and cooling can only be performed on other surfaces, suppressing thermal deformation on the crystal surface is challenging. Numerous proposals have been attempted, including mechanically shaping the single-crystal silicon and using materials with low expansion and high thermal conductivity (diamond). Ultimately, the most effective method was cryogenic cooling with liquid nitrogen, which came with high initial production costs (cryogenic monochromator and cryogenic liquid circulation equipment) and high operating costs (liquid nitrogen).
[0007] For optical devices, suppressing crystal thermal deformation and managing thermal power (cooling) are two independent factors. From a methodological perspective, independently addressing crystal thermal deformation is the correct path for technological development. Liquid nitrogen cryogenic cooling, on the other hand, effectively solves the problem by sidestepping it, at the expense of high manufacturing and operating costs. It's important to note, however, that this successful sidestep isn't a fundamental solution; when beam power increases and nonuniformity becomes apparent, the same problem persists.
[0008] The history of synchrotron radiation technology reveals that in the early days of synchrotron radiation facilities, efficiency and cost were not a major concern due to the prominent / significant scarcity and rarity of beamline resources (a key selling point). However, with the increasing availability of light sources and beamlines, the scarcity and rarity of synchrotron radiation resources are no longer a major issue. However, with the expansion of facility scale and the increase in the number of monochromators, operating costs and experimental efficiency have inevitably become a major concern. Therefore, it is necessary to reconsider and address the issue of thermal deformation of the first crystal after beam irradiation. Summary of the Invention
[0009] To address the problems existing in the prior art, the present invention aims to provide a novel monochromator crystal correction system and method. This invention addresses the effects of non-uniform thermal deformation of the surface lattice on diffracted light caused by incident light with a spatial power distribution on the crystal. The present invention proposes a method to compensate for this non-uniform thermal deformation, thus cost-effectively solving the problem of splitting unevenly distributed high-power beams.
[0010] The present invention mainly completes the correction of the monochromator crystal through the coordination of three aspects:
[0011] 1. By thermally compensating the surface of the monochromator's first crystal, the effect of this deformation on the monochromator's output flux is reduced, allowing the monochromator to be cooled using cryogenic water or other coolants, rather than expensive liquid nitrogen cooling, to cope with high-power synchrotron radiation.
[0012] 2. By modifying the surface of the crystal material and vapor-depositing electrodes, the zoned heating and temperature distribution of the crystal surface are controlled, solving the problem of matching the X-ray diffraction surface of the first crystal with the X-ray diffraction plane of the second crystal under high heat load.
[0013] 3. Feedback control technology based on X-ray beam diagnosis corrects thermal deformation of the crystal surface through precise zoned thermal control.
[0014] The technical solution of the present invention is:
[0015] A novel monochromator crystal correction system is characterized by comprising a correction unit, an X-ray beam detection unit, and a data processing and feedback unit; wherein,
[0016] The correction unit is connected to the first crystal of the monochromator and is used to modulate the lattice of the first crystal by heating the incident surface of the first crystal;
[0017] The X-ray beam detection unit is configured to receive the X-rays emitted by the second crystal of the monochromator, obtain monitoring data of the X-rays based on the received X-rays, and send the data to the data processing and feedback unit;
[0018] The data processing and feedback unit is used to process the monitoring data to obtain the excitation power supply data of the correction unit, and feed back the excitation power supply data to the excitation power supply of the correction unit.
[0019] Furthermore, the first crystal includes a crystal substrate and a resistance heating layer; the crystal substrate is used to receive incident X-rays and to incident X-rays that meet the diffraction conditions onto the second crystal; the resistance heating layer is used to form a surface heat source under the control of the excitation power supply to heat the incident surface of the crystal substrate.
[0020] Furthermore, the resistance heating layer includes multiple independent heating resistor units, each of the heating resistor units includes a heating resistor area and an electrode area, and the excitation power supply of the correction unit is connected to the electrode area for heating the heating resistor area.
[0021] Furthermore, by modifying the crystal substrate, the resistivity of the incident surface of the crystal substrate is reduced, so that the region of the crystal substrate that has not been modified forms a resistance heating layer.
[0022] Furthermore, a resistance film is plated around the working area of the incident surface of the crystal substrate to serve as the resistance heating layer.
[0023] Furthermore, the monitoring data includes spot shape, position, flux and energy spectrum distribution.
[0024] A novel monochromator crystal correction method comprises the following steps:
[0025] 1) X-rays are incident on a first crystal of a monochromator. The first crystal transmits the X-rays that meet the diffraction conditions to a second crystal of the monochromator. Bragg diffraction occurs at the second crystal to form an outgoing beam.
[0026] 2) The X-ray detection unit receives the outgoing light beam, obtains the X-ray monitoring data according to the received outgoing light beam, and sends the data to the data processing and feedback unit;
[0027] 3) The data processing and feedback unit generates a control signal based on the monitoring data and feeds back the control signal to the control correction unit;
[0028] 4) The correction unit heats the incident surface of the first crystal according to the control signal to modulate the lattice of the first crystal and change the thermal deformation distribution of the first crystal.
[0029] The advantages of the present invention are as follows:
[0030] This invention features a scientific and rational design, leveraging the precision machining characteristics of semiconductor technology to spatially overlap the illumination and heating zones, enabling precise control of X-ray optical elements. Based on a compensation approach, it optimizes crystal performance at a low cost, leveraging current crystal processing, monochromator cooling, and clamping technologies. This is particularly effective in adapting to changing operating conditions, such as changes in input power. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 Diagram of the crystal configuration in a double-crystal monochromator.
[0032] Figure 2 Schematic diagram of high-resolution crystal application.
[0033] Figure 3 This is a schematic diagram of the present invention.
[0034] Figure 4 is the heating unit distribution diagram;
[0035] (a) Two-dimensional distribution, (b) one-dimensional distribution.
[0036] Figure 5 A solution for heating on both sides. DETAILED DESCRIPTION
[0037] The present invention will be described in further detail below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.
[0038] This system consists of the following parts:
[0039] (1) Monochromator first crystal and its surface / lattice correction unit
[0040] (2) Second Crystal
[0041] (3) Power supply unit for surface / lattice correction
[0042] (4) X-ray beam detection unit
[0043] (5) Data processing and feedback unit
[0044] (6) Incident white light X-ray beam
[0045] (7) X-ray outgoing beam of the first crystal (also the incident X-ray beam of the second crystal)
[0046] (8) Second crystal X-ray output beam
[0047] like Figure 3 As shown, white light X-rays 6 to be modulated are incident on the first crystal 1 of the monochromator. X-rays that meet the diffraction conditions are output as a modulated X-ray beam 7. This X-ray beam 7 is incident on the second crystal 2, where it undergoes Bragg diffraction to form an output beam 8. Output beam 8 is parallel to white light X-rays 6. Output beam 8 is detected by an X-ray detection unit 3 to monitor parameters such as the beam bandwidth, spot shape, position, and flux. A processing and feedback unit 4 calculates and processes the data provided by the X-ray detection unit 3 to generate a control signal, which is then used to provide feedback control to excite the surface / lattice correction power supply unit 5. The surface / lattice correction power supply unit 5 is used to generate a heating current to change the thermal deformation distribution of the monochromator's first crystal, thereby overcoming surface thermal deformation of the crystal under uneven heat loads and further controlling the energy, flux, and spot size of output beam 8.
[0048] (1) The monochromator's first crystal and its surface / lattice correction unit achieve modulation of the first crystal's lattice by surface heating. The crystal consists of a resistive heating layer and a high-quality crystal substrate. The former forms a surface heat source under power stimulation. The latter acts as an X-ray diffraction device. The resistive heating layer is composed of multiple independent heating resistor units, each of which consists of a heating resistor area and an electrode area. The surface / lattice correction power supply unit is physically connected to the electrode area and controls the current of each heating resistor unit.
[0049] (2) Resistance heating layer: One way to achieve this is to reduce the resistivity of the surface layer by modifying the crystal (such as ion implantation or diffusion process). The spatial distribution of the resistance layer is designed according to different requirements. The advantages of this solution are: Figure 4 As shown, the surface resistivity of the crystal corresponding to each heating zone (i.e., each small square area in the figure) is reduced, and the resistivity of the unmodified crystal area behind is high relative to the surface resistance, becoming a heating resistance zone. The X-ray diffraction zone (dashed part) and the heating zone can overlap without affecting the diffraction of the crystal.
[0050] (3) Resistance heating layer. Another way to achieve this is to plate a resistance film on the surface of the light reflecting area, such as Figure 5 As shown in the figure, the spatial distribution of the resistor layer is designed according to different requirements. The dashed line indicates the X-ray illumination area. When the working area undergoes thermal expansion, the surrounding electrodes are heated, smoothing the deformation of the working area. The expansion is related to the monitoring data, and the amount of expansion can be calculated based on this relationship.
[0051] (4) X-ray beam detection unit, used to measure the parameters of the emitted X-ray spot shape, position, flux and energy spectrum distribution, and send the monitoring data to the data processing unit;
[0052] (5) A data processing and feedback unit receives data from the X-ray detection unit, processes the data to obtain excitation power supply data, and feeds it back to the excitation power supply unit.
[0053] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A novel monochromator crystal correction system, characterized in that: It includes a correction unit, an X-ray beam detection unit, a data processing and feedback unit; wherein, The correction unit is connected to the first crystal of the monochromator and is used to modulate the lattice of the first crystal by heating the incident surface of the first crystal; the first crystal includes a crystal substrate and a resistance heating layer; the crystal substrate is used to receive incident X-rays and direct X-rays that meet the diffraction conditions to the second crystal of the monochromator; the resistance heating layer is used to form a surface heat source under the control of the excitation power supply to heat the incident surface of the crystal substrate; The X-ray beam detection unit is configured to receive the X-rays emitted by the second crystal of the monochromator, obtain monitoring data of the X-rays based on the received X-rays, and transmit the monitoring data to the data processing and feedback unit; the monitoring data includes spot shape, position, flux, and energy spectrum distribution; The data processing and feedback unit is used to process the monitoring data to obtain the excitation power supply data of the correction unit, and feed back the excitation power supply data to the excitation power supply of the correction unit.
2. The monochromator crystal correction system according to claim 1, characterized in that: The resistance heating layer includes multiple independent heating resistor units, each of which includes a heating resistor area and an electrode area. The excitation power supply of the correction unit is connected to the electrode area for heating the heating resistor area.
3. The monochromator crystal correction system according to claim 1 or 2, characterized in that: By modifying the crystal substrate, the resistivity of the incident surface of the crystal substrate is reduced, so that the region of the crystal substrate that has not been modified forms a resistance heating layer.
4. The monochromator crystal correction system according to claim 1 or 2, characterized in that: A resistance film is plated around the working area of the incident surface of the crystal substrate to serve as the resistance heating layer.
5. A novel monochromator crystal correction method, comprising the steps of: 1) X-rays are incident on a first crystal of a monochromator, the first crystal transmits the X-rays that meet the diffraction conditions to a second crystal of the monochromator, and Bragg diffraction occurs at the second crystal to form an outgoing beam; the first crystal includes a crystal substrate and a resistance heating layer; the crystal substrate is used to receive the incident X-rays and transmit the X-rays that meet the diffraction conditions to the second crystal; the resistance heating layer is used to form a surface heat source under the control of the excitation power supply to heat the incident surface of the crystal substrate; 2) an X-ray detection unit receives the outgoing light beam, obtains monitoring data of the X-ray according to the received outgoing light beam, and sends the monitoring data to a data processing and feedback unit; the monitoring data includes spot shape, position, flux, and energy spectrum distribution; 3) The data processing and feedback unit generates a control signal based on the monitoring data and feeds back the control signal to the control correction unit; 4) The correction unit heats the incident surface of the first crystal according to the control signal to modulate the lattice of the first crystal and change the thermal deformation distribution of the first crystal.
6. The method according to claim 5, characterized in that By modifying the crystal substrate, the resistivity of the incident surface of the crystal substrate is reduced, so that the region of the crystal substrate that has not been modified forms a resistance heating layer.
7. The method according to claim 5, characterized in that A resistance film is plated around the working area of the incident surface of the crystal substrate to serve as the resistance heating layer.