An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulatio...An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulations and careful mechanical designs,a shielding configuration has been successfully developed to satisfy safety requirements of below 3μSv/h dose rate at its exterior,meanwhile fulfilling space,floor load and nonmagnetic requirements.Composite materials are utilized to form the sandwich-type shielding walls:the inner layer of boron carbide rubber,the middle layer of steel-encased lead and the outer layer of borated polyethylene.Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage.Our work has demonstrated that by utilizing composite shielding materials,along with the sandwich structure and liftable shielding blocks,a compact and lightweight shielding solution can be achieved.This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement,larger energy and momentum coverage,and higher flux on the sample.This shielding represents the first of its kind in neutron scattering instruments in China.Following its successful operation,it has been subsequently employed by other neutron instruments across the country.展开更多
This study presents a new method for characterizing the thermal lattice deformation of a monochromator with high precision under service conditions and first reports the operando measurements of nanoscale thermal latt...This study presents a new method for characterizing the thermal lattice deformation of a monochromator with high precision under service conditions and first reports the operando measurements of nanoscale thermal lattice deformation on a double-crystal monochromator at different incident powers.The nanoscale thermal lattice deformation of the monochromator first crystal was obtained by analyzing the intensity of the distorted DuMond diagrams.DuMond diagrams of the 333 diffraction index,sensitive to lattice deformation,were obtained directly using a 2D detector and an analyzer crystal orthogonal to the monochromator.With increasing incident power and power density,the maximum height of the lattice deformation increased from 3.2 to 18.5 nm,and the deformation coefficient of the maximum height increased from 1.1 to 3.2 nm/W.The maximum relative standard deviation was 4.2%,and the maximum standard deviation was 0.1 nm.Based on the measured thermal deformations,the flux saturation phenomenon and critical point for the linear operation of the monochromator were predicted with increasing incident power.This study provides a simple solution to the problem of the lower precision of synchrotron radiation monochromator characterizations compared to simulations.展开更多
In SSRF, the design of 1st crystal cooling geometry of double crystal monochromator with sagittal focus is mainly reported by China. Our simulation indicates that the broadening of the full width at half maximum of th...In SSRF, the design of 1st crystal cooling geometry of double crystal monochromator with sagittal focus is mainly reported by China. Our simulation indicates that the broadening of the full width at half maximum of the rocking curve of the double crystal monochromator induced by the heat load is about 3.7 μrad, and is in agreement with the experimental value of 5 μrad. Our scheme showed that the photon flux is reliably linear with electron current of the storage ring, which is extracted from the monochromator.展开更多
The variable-included angle plane-grating monochromator is a homemade key equipment of the scanning transmission X-ray microscopy (STXM) beamline at Shanghai Synchrotron Radiation Facility (SSRF).Monochromatic light o...The variable-included angle plane-grating monochromator is a homemade key equipment of the scanning transmission X-ray microscopy (STXM) beamline at Shanghai Synchrotron Radiation Facility (SSRF).Monochromatic light of various wavelengths is achieved by an effective control system that handles the rotation of the plane mirror and plane grating mounted in a high vacuum chamber.M511.DDB made by PI Corp.is used as motion stage which has a DC servo motor controlled by a C862 controller based on RS232 protocol.The software platform of STXM is EPICS,so the local control functions are implemented by LabVIEW program to satisfy physics control.For the remote control functions,the program is integrated into EPICS with ShareMemoryIOC.Experimental tests show that the repeat precision of motion control is less than 0.2μm,which meets the control demand.展开更多
遥感图像在成像过程中,容易受到云层和雾霾天气的影响,形成带雾图像;同时在下传时,会受到多种因素影响(如发送接收误码、电离层和对流层的随机变化对信号形成扰动等),使图像信息丢失或掺杂噪声。本文针对信息丢失的带雾单色遥感图像,提...遥感图像在成像过程中,容易受到云层和雾霾天气的影响,形成带雾图像;同时在下传时,会受到多种因素影响(如发送接收误码、电离层和对流层的随机变化对信号形成扰动等),使图像信息丢失或掺杂噪声。本文针对信息丢失的带雾单色遥感图像,提出了基于矩阵复原和暗通道理论的单色遥感图像去雾算法,通过基于交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)的矩阵复原算法与传统暗通道理论相结合,有效实现了信息丢失下的遥感雾图复原。通过主观评价和客观评价相结合的方式,将本文算法与经典算法对比。结果表明,本文算法得到的结果在直观视觉上效果更好,且相对于信息丢失30%的雾图,6个场景的平均信息熵提升1.6652,平均峰值信噪比提升11.7029,平均结构相似性提升0.8146,客观评价指标结果优异。进一步在不同比例信息丢失情况下进行实验,结果表明,即使在信息大量丢失的情况下,依然能够得到清晰的复原去雾图像。展开更多
透射电子显微镜(transmission electron microscope,TEM)具有超高的空间分辨率,是化学、材料科学、物理学、生物科学等领域最重要的研究手段之一.影响TEM空间分辨率的因素众多,不仅包括电镜自身结构和成像原理等,还有样品性质等原因.为...透射电子显微镜(transmission electron microscope,TEM)具有超高的空间分辨率,是化学、材料科学、物理学、生物科学等领域最重要的研究手段之一.影响TEM空间分辨率的因素众多,不仅包括电镜自身结构和成像原理等,还有样品性质等原因.为系统且全面地了解TEM分辨率的涵义、原理与应用,本文通过回顾TEM空间分辨率的发展历史,从理论上厘清了TEM空间分辨率的概念、物理涵义、影响因素和适用范围;从电镜装置角度,分别概述了电子枪、磁透镜、图像探测器和电镜内外部环境对空间分辨率的影响规律,以及单色器、像差校正器和新型图像探测器的发展现状;从实际应用角度,重点介绍了样品过厚、电子束损伤、积碳和原子振动等降低空间分辨率的作用机理及解决途径.本文可为非电子显微学研究者们正确使用TEM提供参考.展开更多
针对新型多通道双晶单色器系统易受晶体片平行度误差影响导致性能失效的问题,提出一种迭代学习模型预测控制器(Iterative Learning Model Predictive Control,ILMPC)策略。该策略将主-从轴晶体片平行度误差转换为从轴电机的重复参考运...针对新型多通道双晶单色器系统易受晶体片平行度误差影响导致性能失效的问题,提出一种迭代学习模型预测控制器(Iterative Learning Model Predictive Control,ILMPC)策略。该策略将主-从轴晶体片平行度误差转换为从轴电机的重复参考运动轨迹,采用ILC迭代消除周期性机械安装误差,再利用MPC对单个转动周期内从轴电机的随机性误差进行抑制。最终在单轴电机运动实验平台上对该策略进行轨迹跟踪验证。实验结果表明,在晶体片有效工作区间内从轴电机的位置跟踪误差达到1.44″,相比于PID控制、MPC、DOB+MPC以及ILC+PID组合控制器策略,分别降低了99.64%,98.52%,98.26%和73.33%。研究结果验证了所提出的ILMPC策略在补偿晶体片平行度误差和提高平行对准精度方面的有效性,该策略对于改善新型多通道双晶单色器性能具有较好的实际应用价值。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004426,U2030106,and 12304185)the National Key Scientific Instrument and Equipment Development Project of NSFC(Grant No.11227906)the National Key R&D Program of China(Grant No.2023YFA1406500)。
文摘An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulations and careful mechanical designs,a shielding configuration has been successfully developed to satisfy safety requirements of below 3μSv/h dose rate at its exterior,meanwhile fulfilling space,floor load and nonmagnetic requirements.Composite materials are utilized to form the sandwich-type shielding walls:the inner layer of boron carbide rubber,the middle layer of steel-encased lead and the outer layer of borated polyethylene.Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage.Our work has demonstrated that by utilizing composite shielding materials,along with the sandwich structure and liftable shielding blocks,a compact and lightweight shielding solution can be achieved.This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement,larger energy and momentum coverage,and higher flux on the sample.This shielding represents the first of its kind in neutron scattering instruments in China.Following its successful operation,it has been subsequently employed by other neutron instruments across the country.
基金National Natural Science Foundation of China(No.12205360)Shanghai Pilot Program for Basic Research-Chinese Academy of Science,Shanghai Branch(No.JCYJ-SHFY-2021-010).
文摘This study presents a new method for characterizing the thermal lattice deformation of a monochromator with high precision under service conditions and first reports the operando measurements of nanoscale thermal lattice deformation on a double-crystal monochromator at different incident powers.The nanoscale thermal lattice deformation of the monochromator first crystal was obtained by analyzing the intensity of the distorted DuMond diagrams.DuMond diagrams of the 333 diffraction index,sensitive to lattice deformation,were obtained directly using a 2D detector and an analyzer crystal orthogonal to the monochromator.With increasing incident power and power density,the maximum height of the lattice deformation increased from 3.2 to 18.5 nm,and the deformation coefficient of the maximum height increased from 1.1 to 3.2 nm/W.The maximum relative standard deviation was 4.2%,and the maximum standard deviation was 0.1 nm.Based on the measured thermal deformations,the flux saturation phenomenon and critical point for the linear operation of the monochromator were predicted with increasing incident power.This study provides a simple solution to the problem of the lower precision of synchrotron radiation monochromator characterizations compared to simulations.
基金Supported by cooling research of double crystal monochromator used by synchrotron radiation(10205024)
文摘In SSRF, the design of 1st crystal cooling geometry of double crystal monochromator with sagittal focus is mainly reported by China. Our simulation indicates that the broadening of the full width at half maximum of the rocking curve of the double crystal monochromator induced by the heat load is about 3.7 μrad, and is in agreement with the experimental value of 5 μrad. Our scheme showed that the photon flux is reliably linear with electron current of the storage ring, which is extracted from the monochromator.
基金Supported by Shanghai Synchrotron Radiation Facility project
文摘The variable-included angle plane-grating monochromator is a homemade key equipment of the scanning transmission X-ray microscopy (STXM) beamline at Shanghai Synchrotron Radiation Facility (SSRF).Monochromatic light of various wavelengths is achieved by an effective control system that handles the rotation of the plane mirror and plane grating mounted in a high vacuum chamber.M511.DDB made by PI Corp.is used as motion stage which has a DC servo motor controlled by a C862 controller based on RS232 protocol.The software platform of STXM is EPICS,so the local control functions are implemented by LabVIEW program to satisfy physics control.For the remote control functions,the program is integrated into EPICS with ShareMemoryIOC.Experimental tests show that the repeat precision of motion control is less than 0.2μm,which meets the control demand.
文摘遥感图像在成像过程中,容易受到云层和雾霾天气的影响,形成带雾图像;同时在下传时,会受到多种因素影响(如发送接收误码、电离层和对流层的随机变化对信号形成扰动等),使图像信息丢失或掺杂噪声。本文针对信息丢失的带雾单色遥感图像,提出了基于矩阵复原和暗通道理论的单色遥感图像去雾算法,通过基于交替方向乘子法(Alternating Direction Method of Multipliers,ADMM)的矩阵复原算法与传统暗通道理论相结合,有效实现了信息丢失下的遥感雾图复原。通过主观评价和客观评价相结合的方式,将本文算法与经典算法对比。结果表明,本文算法得到的结果在直观视觉上效果更好,且相对于信息丢失30%的雾图,6个场景的平均信息熵提升1.6652,平均峰值信噪比提升11.7029,平均结构相似性提升0.8146,客观评价指标结果优异。进一步在不同比例信息丢失情况下进行实验,结果表明,即使在信息大量丢失的情况下,依然能够得到清晰的复原去雾图像。
文摘透射电子显微镜(transmission electron microscope,TEM)具有超高的空间分辨率,是化学、材料科学、物理学、生物科学等领域最重要的研究手段之一.影响TEM空间分辨率的因素众多,不仅包括电镜自身结构和成像原理等,还有样品性质等原因.为系统且全面地了解TEM分辨率的涵义、原理与应用,本文通过回顾TEM空间分辨率的发展历史,从理论上厘清了TEM空间分辨率的概念、物理涵义、影响因素和适用范围;从电镜装置角度,分别概述了电子枪、磁透镜、图像探测器和电镜内外部环境对空间分辨率的影响规律,以及单色器、像差校正器和新型图像探测器的发展现状;从实际应用角度,重点介绍了样品过厚、电子束损伤、积碳和原子振动等降低空间分辨率的作用机理及解决途径.本文可为非电子显微学研究者们正确使用TEM提供参考.
文摘针对新型多通道双晶单色器系统易受晶体片平行度误差影响导致性能失效的问题,提出一种迭代学习模型预测控制器(Iterative Learning Model Predictive Control,ILMPC)策略。该策略将主-从轴晶体片平行度误差转换为从轴电机的重复参考运动轨迹,采用ILC迭代消除周期性机械安装误差,再利用MPC对单个转动周期内从轴电机的随机性误差进行抑制。最终在单轴电机运动实验平台上对该策略进行轨迹跟踪验证。实验结果表明,在晶体片有效工作区间内从轴电机的位置跟踪误差达到1.44″,相比于PID控制、MPC、DOB+MPC以及ILC+PID组合控制器策略,分别降低了99.64%,98.52%,98.26%和73.33%。研究结果验证了所提出的ILMPC策略在补偿晶体片平行度误差和提高平行对准精度方面的有效性,该策略对于改善新型多通道双晶单色器性能具有较好的实际应用价值。