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X-ray differential phase contrast computed tomography imaging based on grating interferometer system can reconstruct not only the linear attenuation coefficient, but also the phase shift coefficient and the linear scattering coefficient of the object. In practical application, it is very difficult to make a large area grating, so the sample is often larger than the grating. When the sample is scanned with a grating smaller than the sample, the part of the sample beyond the field of view of the grating will cause the differential phase projection information to be truncated. In this paper, a method of reconstructing the region of interest for differential phase contrast computed tomography is proposed. The method is based on the approximate linear relation between the phase shift coefficient of the object and the linear attenuation coefficient (i.e. the decrement in the real part of the refractive index and the imaginary part of the refractive index), the phase shift coefficient of the region of interest is approximately reconstructed by the polynomial of Lambda function of the phase shift coefficient and Lambda inverse function of linear attenuation coefficient. In this paper, according to the Fresnel diffraction theory and differential phase grating phase step-by-step method of imaging a simulation experiment is performed. In the experiment, conducted is the approximate reconstruction by using the first order polynomial and quadratic polynomial of Lambda function of the phase shift coefficient and Lambda inverse function of linear attenuation coefficient. The sample size is five times of grating imaging field, and the results show that this method can approximately reconstruct the region of interest for the sample image. We also carry out the actual data experiment. The actual data are obtained by the Talbot grating interferometer system of Shanghai synchrotron radiation BL13W1 station, and the standard model and biological sample are imaged. The method of reconstructing the region of interest is proposed in this paper. This method can be applied to the multi-material samples with a similar relationship between the decrement in the real part of the refractive index and the decrement in the imaginary part of the refractive index, and also to single-material samples. The comparison between the numerical simulations and the actual experimental results verifies the effectiveness of the proposed method.

Sample information-extracting with diffraction enhanced imaging (DEI) has been one of the interesting areas for many years. Using cosine curve to fit rocking curve in DEI, we deduce the equations described by cosine functions for peak-position image, low- and high-angle image. The analytical expressions of absorption image, refractive angle image and scattering image are also developed. Then a simple method is proposed for sample information-extracting with DEI based on those deductions. This method can extract the absorption information, refractive angle information and scattering information of a sample using only three images, i.e. one peak-position, one low-angle image and on high-angle image, resulting in simple experimental process and low radiation dose introduced to sample by imaging process. The experiments are carried out on a standard sample and a real biological sample. For comparison, experiments are also carried out on the same two samples using the common multiple-image radiography (MIR) method, in which at least seven images should be used to extract sample information. Experimental results show that our new method does extract sample information successfully, and the results from our new method are comparable to those from the MIR method.

The parabolic compound X-ray refractive lenses are a kind of novel optical components, especially suitable for hard X-rays. Due to their parabolic profiles they are free of spherical aberration and are proper devices for sub-micrometer focusing and imaging. The focusing performance of the parabolic compound X-ray refractive lenses is studied theoretically and experimentally in this paper. Firstly, the derivation of the exact focal length formula using matrix optics method and a criterion of the thin lens approximation are described. And the intensity distribution near focus, limiting focal spot size, effective aperture and transmittance are deduced based on the diffraction theory. Several parabolic compound X-ray refractive lenses with PMMA material were fabricated by means of deep X-ray lithography. Then the X-ray microbeam experimental system was built on the 4W1A beamline of Beijing Synchrotron Radiation Facility （BSRF） based on the parabolic compound X-ray refractive lenses we fabricated. The focusing performances of three PMMA parabolic compound X-ray refractive lenses were measured and analyzed under 8 keV monochromatic X-rays. According to the experimental results, it is concluded that the PMMA parabolic compound X-ray refractive lenses promises good hard X-ray focusing performance.

X-ray refraction contrast CT is the computer tomography based on phase contrast. When the biological samples are taken from organs or tissues，X-ray refraction contrast CT provides more internal subtle details compared with conventional absorption CT images and it is considered a novel and very promising imaging technique. The iterative and analytical algorithms are the two main strategies in computer tomography. In the field of X-ray refraction contrast CT several analytical algorithms have been reported in the past. However the algorithm using iterative method have not been proposed. In this study，we tested the application of iterative algorithm in X-ray refraction contrast CT image reconstruction，investigated the influence of the order in which data are accessed in algebraic reconstruction techniques，and satisfactory CT images were obtained. Our data demonstrated that when biological samples are imaged or the complete projective data are not available，our iterative algorithm showed significant advantage over the analytical algorithms. It effectively reduces the number of the projection data，exposure time，as well as the radiation damage to the biology samples.

In this work,we make a theoretical analysis of X_ray grating phase contrast imaging (XGPCI) and give an equation to show the relationship between the transmittance and the relative shift of the two gratings,which was named as the shift curve.According to this equation,we develop a new method to retrieve phase information from the experimental data in theory.Finally,we analyze the influence of the experimental setup to the resolution of the image.

Based on the unique advantages of synchrotron radiation X-ray with high resolution and collimation，and the advantage of nondestructive observation of computed-tomography technique，synchrotron radiation computed tomography technique is widely used in many fields. In this paper，the errors caused by light source such as unevenness，supersaturation and super penetration are studied for synchrotron radiation computed tomography technique，and its three basic error forms are given. Numerical simulation results confirm this analysis.

Diffraction enhanced imaging is a new X-ray radiographic imaging method using monochromatic X-rays from a synchrotron source which produces high contrast and spatial resolution images of thick absorbing objects. Use of this method in medicine, material science and industrial applications in non-destructive testing is highlighted at present. The purpose of this study is to discuss diffraction enhanced imaging computer tomography which combines computer tomography (CT) and diffraction enhanced imaging (DEI) method. Comparison between DEI-CT images with conventional X-ray CT images shows that the DEI-CT imaging technique gives not only surface information but also the internal structure of organs or soft tissues with high contrast. The obtained images show the micro-structures details of DEI-CT.

Diffraction enhanced imaging (DEI) with two crystals has been recently performed at the 4W1A beamline at the Beijing Synchrotron Radiation Facility (BSRF). In the first experiments, images collected with a set up where the rotation axis of the crystal was perpendieular to the orbit, show a higher quality with respect to those taken with a geometry with the rotation axis of the monochromatic crystal parallel to the orbit. When the rotation axis of the crystal is perpendicular to the orbit plane, e.g. to the polarization plane of the synchrotron radiation, the influence of both vibration and thermal expansion of the first crystal can be significantly reduced, allowing the collection of better images. In this work, a systematic comparison is male between two geometrical arrangements of crystals in DEI framework with respect to the reflectivity of crystals, spacial resolution, angular resolution and image contrast.

The interactions between X-ray and the sample and crystals were investigated, and the influence of small angle scattering on images was emphatically analyzed in diffraction enhanced imaging in this paper. Not only were the additional noise term caused by small angle scattering introduced, and more general DEI equation established, but also expressions of absorption contrast, extinction contrast and refraction contrast were given for the peak image and the middle slope image. With the new DEI equation, the contrasts of two kinds of resultant images (apparent absorption image and refraction image) were discussed.

A new x_ray imaging technique, diffraction_enhanced imaging, has been recently developed in Beijing Synchrotron Radiation Facility(BSRF). Diffraction_enhanced i maging is a radiographic technique that derives contrast from an object’s absor ption, refraction gradient and small_angle scatter properties(extinction). This imaging method may improve image quality for medical applications, industrial ra diography for non_destructive testing and x_ray computed tomography.

Diffraction_enhanced imaging by using two crystals has been recently developed i n x_ray topogrphy station in Beijing Synchrotron Radiation Facility. In this art icle the analysis for the influence of the thermal expansion of the first crysta l on the diffraction enhanced imaging is presented. The conclusion is that the i nfluence of the thermal expansion of the first crystal can be avoided and much b etter images can be obtained when the axes of crystals are placed vertically to the polarization plane of the synchrotron radiation. The experimental results co nfirmed this analysis.

The inside source hologram reconstruction algorithm based on discrete Fourier transform was investigated in detail, and how to calculate the contribution of whole spherical hologram to the reconstructed image of atoms was demonstrated in this algorithm, which was previously regarded to be capable of calculating only half of the spherical hologram. Using the sampling theorem in this issue, we are able to examine such essential factors as the sampling rate of the hologram, domain and resolution of reconstructed image.

The reflectivity of grazing soft x-ray planar mirror is studied.The Beijing Synchrotron Radiation Facility-3W1B beam line with beam current 40—120 mA,the storage ring electron energy 2 GeV,photon energy 50—1500 eV are used.We have improved the calibration method.The x-ray diode detectors of planar mirror facility are replaced by AXUV-100.Therefore,2 to 3 orders of magnitude for the ratio of signal to noise can be increased,and the calibration region from (150—270 eV)to (50—1500 eV)is expanded.The reflectivity calibration curves for C,Si,Ni,and Au planar mirror in different grazing angles are given.Finally,the values obtained in experiment and calculation are compared and analyzed.

The conventional holography met with three unsolvable difficulties,such as coherence of light source,spatial resolution and sensitivity of detector,when applied in atomic imaging. This paper is intended to explain how the inside source holography can overcome all these difficulties,and to investigate the recording and reconstruction procedures of the inside source holography. The reconstruction formula of inside source spherical hologram and the δ-functions describing reconstructed atomic images in spherical-symmetrical and energy-irrelevent approximations of atomic scattering factor are deduced

Based on the principle of x-ray fluorescence holography, we numerically simulate d an iron single crystal model of a body-centred cubic lattice. From the fluores cence hologram produced numerically, the Fe atomic images were reconstructed. Th e atomic images of the (001),(100),(010) crystallographic planes were consistent with the corresponding atomic positions of the model. The result indicates that one can obtain internal structure images of single crystals at atomic-resolutio n by using x-ray fluorescence holography.

Absolute diffraction efficiencies of a transmission grating at a photon energy of 844eV have been calibrated on synchrotron radiation source.With the aid of grating model,all structure parameters of the grating are obtained and absolute diffraction efficiencies for soft X-rays in the range of 100—2000eV are calculated and discussed.

A theoretical method to obtain the soft X-ray multilayer monochromater of-better energy resolution is put forward. The basic point is to choose the alternating elements with new criterions instead of general choosing method of high-and low z elements. Moreover, a simple and practicable multilayer designing method to achieve high reflectivity was presented. The some results of soft X-ray multilayer monochromater study in recent years on Beijing Synchrotron Radiation Facility (BSRF) have been given out.

Some main factors having influence on the resolution of X-ray holograms are analyzed theoretically. The smalles resolving distance of X-ray lensless Fourier transform holograms can not be less than the radius of the focus spot of the X-ray condenser or the filter aperture used in recording, and the resolution of X-ray in-line holograms can not be higher than the cutoff frequency of recording material, under the condition that X-ray is perfectly coherent. Relationships between the coherent length required by X-ray lensless Fourier transform holography and the resolution, and the radius of the object are quadric; and the coherent length requested by X-ray in-line holography is proportional to the square of the resolution and does not change with the size of object, under the condition that X-ray is partially coherent. With the resolution of X-ray holograms raised, the reguired coherent length will be increased by a large amount.