Multilayer-based soft X-ray polarimeter at the Beijing Synchrotron Radiation Facility

A compact high precision eight-axis automatism and two-axis manual soft-ray polarimeter with a multilayer has been designed, constructed, and installed in 3W1B at the Beijing Synchrotron Radiation Facility (BSRF). Four operational modes in the same device, which are double-reflection, double-transmission, front-reflection-behind-transmission and front-transmission-behind-reflection, have been realized. It can be used for the polarization analysis of synchrotron radiation. It also can be used to characterize the polarization properties of the optical elements in the soft X-ray energy range. Some experiments with Mo/Si and Cr/C multilayers have been performed by using this polarimeter with good results obtained.     

Beam test of a one-dimensional position sensitive chamber on synchrotron radiation

A one-dimensional single-wire chamber was developed to provide high position resolution for powder diffraction experiments with synchrotron radiation. A diffraction test using the sample of SiO₂ has been accomplished at 1W2B laboratory of Beijing Synchrotron Radiation Source. The data of the beam test were analyzed and some diffraction angles were obtained. The experimental results were in good agreement with standard data from ICDD powder diffraction file. The precision of diffraction angles was 1% to 4.7%. Most of the relative errors between measured values of diffraction angles and existing data were less than 1%. As for the detector, the best position resolution in the test was 138 μm (σ value) with an X-ray tube. Finally, discussions of the results were given. The major factor that affected the precision of measurement was deviation from the flat structure of the detector. The effect was analyzed and the conclusion was reached that it would be the optimal measurement scheme when the distance between the powder sample and detector was from 400 mm to 600 mm.     

Investigation of GEM-Micromegas detector on X-ray beam of synchrotron radiation

To reduce the discharge of the standard bulk Micromegas and GEM detectors, a GEM-Micromegas detector was developed at the Institute of High Energy Physics. Taking into account the advantages of the two detectors, one GEM foil was set as a preamplifier on the mesh of Micromegas in the structure and the GEM preamplification decreased the working voltage of Micromegas to significantly reduce the effect of the discharge. At the same gain, the spark probability of the GEM-Micromegas detector can be reduced to a factor 0.01 compared to the standard Micromegas detector, and an even higher gain could be obtained. This paper describes the performance of the X-ray beam detector that was studied at 1W2B Laboratory of Beijing Synchrotron Radiation Facility. Finally, the result of the energy resolution under various X-ray energies was given in different working gases. This indicates that the GEM-Micromegas detector has an energy response capability in an energy range from 6 keV to 20 keV and it could work better than the standard bulk-Micromegas.     

上海软X光胶片响应的相对标定

介绍了在同步辐射源上用透射光栅对“上海”软Ｘ光胶片进行相对标定的方法，初步研究了“上海”胶片的特性，得到了在２７６ｅＶ和９３０ｅＶ两能点的胶片黑密度与相对曝光量的关系曲线；应用标定结果。     

Hard X-ray optics simulation using the coherent mode decomposition of the Gaussian Schell model

The propagation of a hard X-ray beam from a partially coherent synchrotron source is simulated by using the novel method based on the coherent mode decomposition of Gaussian Schell model and wave-front propagation. We investigate how the coherency properties and intensity distributions of the beam are changed by propagation through optical elements. Here, we simulate and analyze the propagation of the partially coherent radiation trans- mitted through an ideal slit. We present the first simulations for focusing partially coherent synchrotron hard X-ray beams using this novel method. And when compared with the traditional method which assumes the source is a totally coherent point source or completely incoherent, this method is proved to be more reasonable and can also demonstrate the coherence properties of the focusing beam. We also simulate the Young’s double slit experiment and the simulated results validate the academic analysis.     

Polycapillary X-ray lens for the secondary focusing Beijing synchrotron radiation source

According to intensity distribution of the synchrotron radiation source focused by a toroidal mirror at the Beijing synchrotron radiation biological macromolecule station, theoretical modeling of the Beijing synchrotron radiation source is developed for capillary optics. Using this theoretical modeling, the influences of the configuration curve of the polycapillary X-ray lens on transmission efficiency and working distance are analyzed. The experimental results of the transmission efficiency and working distance at the biological macromolecule station are in good agreement with the theoretical results.     

DEIReconstructor:a software for diffraction enhanced imaging processing and tomography reconstruction

Diffraction enhanced imaging (DEI) has been widely applied in many fields, especially when imaging low-Z samples or when the difference in the attenuation coefficient between different regions in the sample is too small to be detected. Recent developments of this technique have presented a need for a new software package for data analysis. Here, the Diffraction Enhanced Image Reconstructor (DEIReconstructor), developed in Matlab, is presented. DEIReconstructor has a user-friendly graphical user interface and runs under any of the 32-bit or 64-bit Microsoft Windows operating systems including XP and Win7. Many of its features are integrated to support imaging preprocessing, extract absorption, refractive and scattering information of diffraction enhanced imaging and allow for parallel-beam tomography reconstruction for DEI-CT. Furthermore, many other useful functions are also implemented in order to simplify the data analysis and the presentation of results. The compiled software package is freely available.     

Pressure-induced phase transition of wulfenite

The in-situ high-pressure structures of wulfenite have been investigated by means of angular dispersive X-ray diffraction with diamond anvil cell and synchrotron radiation. In the pressure up to 22.9 GPa, a pressure-induced scheelite-to-fergusonite transition is observed at about 10.6 GPa. The pressure dependence for the lattice parameters of wulfenite is reported, and the axial compression coefficients Ka₀=－1.36×10^－3 GPa^－1 and Kc₀= －2.78×10^－3 GPa^－1 are given. The room-temperature isothermal bulk modulus is also obtained by fitting the P-V data using the Murnaghan equation of state.     

Hard X-ray one dimensional nano-focusing at the SSRF using a WSi2 /Si multilayer Laue lens

The multilayer Laue lens (MLL) is a novel diffraction optics which can realize nanometer focusing of hard X-rays with high efficiency. In this paper, a 7.9 μm-thick MLL with the outmost layer thickness of 15 nm is designed based on dynamical diffraction theory. The MLL is fabricated by first depositing the depth-graded multilayer using direct current (DC) magnetron sputtering technology. Then, the multilayer sample is sliced, and both cross-sections are thinned and polished to a depth of 35-41 μm. The focusing property of the MLL is measured at the Shanghai Synchrotron Facility (SSRF). One-dimensional (1D) focusing resolutions of 205 nm and 221 nm are obtained at E=14 keV and 18 keV, respectively. It demonstrates that the fabricated MLL can focus hard X-rays into nanometer scale.     

Upgrading design of the 3B1A beamline for x-ray nanometre lithography of microelectronic devices at BSRF

Beijing Synchrotron Radiation Facility is a partly dedicated synchrotron radiation source operated in either parasitic or dedicated mode. The 3B1A beamline, extracted from a bending magnet, was originally designed as a soft x-ray beamline for submicro x-ray lithography with critical lateral size just below 1μm in 1988 and no change has been made since it was built. But later the required resolution of x-ray lithography has changed from sub-micrometre to the nanometre in the critical lateral size. This beamline can longer more meet the requirement for x-ray nano lithography and has to be modified to fit the purpose. To upgrade the design of the 3B1A beamline for x-ray nano lithography, a mirror is used to reflect and scan the x-ray beam for the nano lithography station, but the mirror's grazing angle is changed to 27.9mrad in the vertical direction, and the convex curve needs to be modified to fit the change; the tiny change of mirror scanning angle is firstly considered to improve the uniformity of the x-ray spot on the wafer by controlling the convex curve.     

Time-compensated grazing-incidence monochromator for extreme-ultraviolet and soft X-ray high-order harmonics

The use of a grating monochromator for the selection of one or more high-order laser harmonics produced by a femtosecond pulse interacting with a gas jet may alter the duration of the pulse itself. This is due to the differences in the optical paths of the rays caused by ordinary diffraction when a grating is used. The time stretching can be almost eliminated by using two gratings in time-compensated configurations. Unfortunately, the classical diffraction mounting has low efficiency, overall in the extreme-ultraviolet region. High broadband efficiency can be obtained by using the conical diffraction mounting. A time-compensated monochromator with toroidal gratings used in conical diffraction is here presented. It is shown that the time compensation is very effective in a broad spectral region, ranging from VUV to soft X-rays, with much higher efficiency than the classical diffraction mounting. PACS 42.65.Ky; 42.79.Dj; 42.65.Re; 41.85.Si     

An analytical model for the polarization of synchrotron radiation in a soft X-ray region

Conventionally, the polarization of a synchrotron soft X-ray beam is measured through a polarimeter based on multilayer optical elements. The major drawback of the traditional approach is the difficulty in comparing different configurations due to the misalignment of each incident angle. In this paper, a new analytical model, based on the variation of reflectivity for different incident angles, is established to facilitate the extraction of important polarization-related information, i.e. angular distribution of polarization components, a tiny change of the direction of azimuth rotation axis of polarizer, etc.     

一种透射式软X光带通方法研究

基于微通道板(MCP)X射线光学, 提出了一种透射式软X光带通方法. 通过三种通道结构的MCP-X光传输特性比较, 给出了带通设计方法. 利用北京同步辐射装置开展了方孔MCP和滤片标定. 结果表明, MCP透射谱具有宽能带选择范围和高效率的特点, 并且在1 keV以下可以在多个多能点实现100 eV带宽的带通设计. 关键词： X射线光学 微通道板 软X光带通     

Partial contributions of individual harmonics to the power of synchrotron radiation

For synchrotron radiation, the partial contribution is defined as the ratio of the power radiated by an individual spectral harmonic, ν = 1, 2, 3 …, to the total (summed over ν) radiated power. A complete analysis of the dependence of the partial contribution on ν, polarization of the radiation, and energy of the particle is given. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–10, July, 2006.     

A new method of creating minibeam patterns for synchrotron radiation therapy: a feasibility study

Several synchrotrons around the world are currently developing innovative radiotherapy techniques with the aim of palliating and possibly curing human brain tumors. Amongst them, microbeam radiation therapy (MRT) and, more recently, minibeam radiation therapy (MBRT) have shown promising results. In MBRT the beam thickness ranges from 500 to 700 µm with a separation between two adjacent minibeams of the same value, whilst in MRT the thickness is of the order of 25–50 µm with a distance between adjacent microbeams of the order of 200 µm. An original method has been developed and tested at the ESRF ID17 biomedical beamline to produce the minibeam patterns. It utilizes a specially developed high‐energy white‐beam chopper whose action is synchronized with the vertical motion of the target moving at constant speed. Each opening of the chopper generates a horizontal beam print. The method described here has the advantage of being simple and reliable, and it allows for an easy control of the patient safety in future clinical trials. To study the feasibility of the method, dosimetric measurements have been performed using Gafchromic HD‐810 films and compared with Monte Carlo simulations. The results of this comparison are discussed.     

软X光能谱仪求辐射能流的改进方法

使用多道软X光能谱仪测量黑腔辐射能流时间过程并使用最小二乘法将多道谱仪的响应函数线性组合为等效平响应。针对惯性约束聚变实验中软X光能谱强度分布不均匀、等效平响应局部不平带来的误差,提出了辐射能流求解的加权改进算法。对不同谱形和等效积分温度的能谱进行了计算,比较了不同方法得到的能流还原能力。改进后的方法应用于实验数据的处理,得到了修正后的等效积分温度随时间的演化过程。     

A new soft X-ray magnetic circular dichroism facility at the BSRF beamline 4B7B

X-ray magnetic circular dichroism (XMCD) has become an important and powerful tool because it allows the study of material properties in combination with elemental specificity, chemical state specificity, and magnetic specificity. A new soft X-ray magnetic circular dichroism apparatus has been developed at the Beijing Synchrotron Radiation Facility (BSRF). The apparatus combines three experimental conditions: an ultra-high-vacuum environment, moderate magnetic fields and in-situ sample preparation to measure the absorption signal. We designed a C-type dipole electromagnet that provides magnetic fields up to 0.5 T in parallel (or anti-parallel) direction relative to the incoming X-ray beam. The performances of the electromagnet are measured and the results show good agreement with the simulation ones. Following film grown in situ by evaporation methods, XMCD measurements are performed. Combined polarization corrections, the magnetic moments of the Fe and Co films determined by sum rules are consistent with other theoretical predictions and experimental measurements.     

Nuclear Bragg diffraction using synchrotron radiation — A new method for hyperfine spectroscopy

Nuclear Bragg diffraction with synchrotron radiation as source will become a powerful new X-ray source in the Å-region. This source exceeds by now the brilliance of conventional Mössbauer sources giving hyperfine spectroscopy further momentum. As examples applications to yttrium iron garnel (YIG) and iron horate will be discussed.     

Coplanar monolithic resonator for X-ray and synchrotron radiation

A scheme of a three-block monolithic X-ray resonator with Si \((04\bar 4,40\bar 4)\)-configuration single crystal for NiKα₂ and synchrotron radiation is proposed and realized experimentally. Specialties and advantages of the proposed scheme are given. It is shown that using asymmetric Bragg reflections makes possible to solve one of the basic problems of X-ray resonators, that of the input of radiation into the resonator and creation of the lossless cycle. The technology of fabrication of the resonator is described and the problems of raising the efficiency of its operation are considered.     

软X射线测量用电阻式薄膜量热计

介绍了一种用于软X射线辐射能量测量的电阻式薄膜量热计。利用电流的欧姆热效应对薄膜量热计的灵敏度进行了标定。在有基底薄膜的标定过程中,采用一维热扩散模型,考虑了金属薄膜向基底的传导热损失。利用电阻式薄膜量热计对聚龙一号装置钨丝阵Z箍缩产生的软X射线进行了测量,并与平响应X射线二极管(XRD)探测器的测量结果进行了比较。实验结果表明,电阻式薄膜量热计测量的软X射线辐射能量和辐射功率与平响应XRD探测器结果在测量不确定度范围内合理地一致。