| With the rapid development of science and technology,it is urgent to fulfill the requirements for the dynamic process investigation of materials at the macro-scale.To solve the many scientific problems appear in complex disordered materials at the nano-to-micron scale,such as phase separation,tissue or molecular structure changes,a new experimental technique has been developed:X-ray Photon Correlation Spectroscopy?XPCS?.XPCS is a new technology which can be used to observe the dynamic processes of large molecules or particle clusters in the micro scale.It has significant advantages,such as large scattering vector,small detection scale,capability to detect opaque material systems,and robust to multiple scattering,and so on.Furthermore,XPCS can also be used to investigate specimen at a nanoscale spatial resolution.XPCS has many applications in soft materials like solution diffusion kinetics and polymer equilibrium transitions,contributing greatly and actively to the exploration of the nanoscale dynamic behavior of hard materials such as semiconductors,ferroelectrics,and magnetic materials.Therefore,XPCS methodology has attracted more and more attention.Before the emergence of third generation synchrotron radiation source,XPCS method developed slowly due to the lack of good coherent x-rays.Visible light?laser?photon correlation spectroscopy technology has been widely used in experiments.With the continuous progress of advanced x-ray light source technology,many third or fourth generation synchrotron radiation sources,and x-ray free electron laser?XFEL?have been put into operation.XPCS technology is also in a period of rapid development and continuous improvement.At present,more than 70 synchrotron radiation facilities have been built in more than 20 countries abroad.XPCS has been improved continuously and the XPCS endstations suitable for specific scientific objectives have been gradually established,such as European ESRF?ID 10?,American APS?ID 8?and Japanese Spring-8?BL40XU?.Meanwhile,the energy range of XPCS experiments has been extended,and it is feasible to explore a series of new research subjects,such as structural transformation at atomic scale of metallic glass.Due to the construction and operation of more and more advanced x-ray sources,photon science and technology based on advanced x-ray sources are developing rapidly in China:Shanghai Synchrotron Radiation Facility?SSRF?is the first third-generation synchrotron radiation facility in China,which has been running for nearly 10 years;the construction of Beijing High Energy Photon Source?HEPS?,a fourth-generation synchrotron facility,has been started;and the advanced high-frequency hard X-ray free electron laser?XFEL?facility in Shanghai is also under construction now.However,the XPCS method has not been established in all facilities mentioned above.The purpose of this research is to explore the deployment of prototype XPCS technology at SSRF,including device design,research system and noise suppression scheme,to accumulate necessary experience for the follow-up development of dedicated XPCS endstation.In this paper,some innovative designs of XPCS have been proposed,such as apparatus,application field,system integration and matching,and theoretical analysis,and so on.1.Reflective photon correlation spectroscopy experiment platform,which can make full use of the highly coherent X-ray beams?coherence 94%?at SSRF,has been developed f,which can be used to study the micro-dynamics of hard materials such as ferroelectrics,ferromagnets and semiconductors.2.Designed and built a brand-new soft x-ray photon correlation spectroscopy experimental system,including vacuum,sample preparation and transfer,sample testing and signal processing subsystems.Innovations in the design are as follows:?1?selecting scattering vectors with replaceable apertured baffles to meet the measurement scale requirements of different sample systems;?2?to suppress the system noise when a single detector is used,a new scheme of adding a multilayer film between detector and sample to suppress noise is proposed.3.In the system device integration,the matching between the system is realized:?1?the matching between the wavelength response range of incident light and the response time of the correlator?the magnitude of ns?is realized by the microchannel plate detector?MCP?in the vacuum ultraviolet;?2?matching of signal processing between MCP detector collect signal with amplifier and converter;?3?matching of the cavity design with the existing layout of the beam line,and realizing the functions of the XPCS system without affecting the existing beam line function;?4?to achieve the matching of the vacuum system,the sample preparation chamber with low vacuum?10-66 torr?and thesample experimental chamber with ultra-high vacuum(10-9torr)are incorporated into the vacuum interlock system of beam line.4.A preliminary exploration of data analysis is carried out:?1?theoretical calculations were carried out on the appropriate sample detection scales.The effects of scattering angle and incident wavelength on the sample period size and scattering vector were investigated:when fundamental energy is 92.5 eV,within the range of the full-width spectral energy at half maximum,assuming the deflection angle is 34.9mrad,the calculation result shows that the sample size range is approximately 10 to60 nm,which is suitable for studying the dynamics information of the nano-region;?2?by extending the general theory of second-order coherence functions of light,a new theoretical model of second-order coherent light for curved small holes is obtained based on typical Gaussian beams.5.On the basis of completing the design and construction of the device,the signal processing system,including the amplifier,converter,and digital correlator,was tested offline,and the offline test signals of each device in the system were collected to confirm that the instruments can work normally after being connected.For the system noise,the system performs well after 30 ms,and the system noise below 30ms can be eliminated clearly.For the heating system,the infrared thermometer was used to compare the temperature of the heating piece under the room temperature condition and the cavity environment,obtained the maximum temperature that can be withstood in the sample vacuum experimetal chamber was 547.9K,which can be maintained for a long time.It can meet the basic temperature control range and accuracy requirements of the XPCS experiment.This project completed the design and construction of the XPCS device,and carried out preliminary theoretical research on its research system.These work laid the foundation for future on-line experiment and the realization of the new XPCS method in China. |
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