X-ray Focusing Research Articles

Features of multilayer mirror application for focusing and collimating X-rays from inverse Compton scattering sources

We have analysed the use of X-ray interference multilayer mirrors as the elements of a focusing scheme for a compact source based on inverse Compton scattering. An algorithm is proposed for selecting mirror parameters, which takes into account the properties of the radiation source. The dependence of wavelength on the viewing angle and the energy line broadening for a fixed viewing angle are found to be the main limitations in the use of multilayer mirrors. Efficient radiation collection calls for the application of broadband mirrors. It is shown that the efficiency of multilayer mirrors in a Kirkpatrick – Baez X-ray focusing setup exceeds that of total external reflection mirrors by an order of magnitude, and that stack multilayer mirrors offer a small advantage over the periodic ones. The overall efficiency of source radiation collection in the photon energy range ΔE = 10 – 12 keV amounts to 12 % for the two-mirror Kirkpatrick – Baez setup. For a spectral region with a bandwidth ΔE/E = 3 %, the efficiency ranges up to 69 %.

Soft x-ray nanobeam formed by an ellipsoidal mirror

Ellipsoidal mirrors are promising optical devices for soft x-ray focusing. A fabrication process consisting of master fabrication and replication has been developed to produce ellipsoidal mirrors with wide apertures of approximately 10 mm. In the present study, the focusing performance of an ellipsoidal mirror was evaluated using soft x-rays in the soft x-ray beamline BL25SU-a of SPring-8. The focus sizes were measured at photon energies of 300, 400, and 500 eV. A quantitative figure error of the ellipsoidal mirror was also evaluated by analyzing the wavefield of the focused beam retrieved using ptychography. The figure error distributions measured at different photon energies agreed with each other at a root mean square level of 1 nm. The developed focusing system can be used for various types of microscopy, allowing the use of a wide range of x-ray energies.

Direct measurement method of micro-beam X-ray focus based on array detector

A method for directly measuring the focal spot size and minimum focus position output by micro-beam X-ray is proposed. An experimental device based on portable micro X-ray source and capillary X-ray lens is built, and the experiments are carried out at different distances and under different tube voltages. The measured results are compared with the knife-edge scanning method. The results show: the focal spot size and minimum focus position of X-ray lens are 87μm and 9.798 cm respectively by using an array detector. X-ray array detector can directly measure the size of focal spot and predict the position of the minimum focus. It has the advantages of real-time measurement, available two-dimensional distribution, high cost performance and high efficiency. The device can predict the minimum focus position better, but the measured focal spot size is larger than it measured by knife-edge scanning method due to the influence of the pixel size and energy response of the array detector. The measurement results are related to the size of the pixel unit, measurement threshold and exposure time of an array detector.

Development of a Fast Sample-exchange System for Fixed Target Single-shot Imaging at PAL-XFEL

This paper describes the development of a fast exchange system to exchange thin membrane containing samples for single-shot experiments using micron focusing X-ray pulses at Pohang Accelerator Laboratory X-ray free electron laser (PAL-XFEL). The mechanism uses a compact gripper that can remove used samples and mount new ones in a vacuum chamber. The lead time of sample exchange is reduced more than half and increases data-collection time during limited beamtime. We believe that this

Effect of tilt on circular zone plate performance.

Fresnel zone plates are frequently used as focusing and imaging optics in x-ray microscopy, as they provide the ease of use of normal incidence optics. We consider here the effects of tilt misalignment on their optical performance, both in the thin optics limit and in the case of zone plates that are sufficiently thick so that volume diffraction effects come into play. Using multislice propagation, we show that simple analytical models describe the tilt sensitivity of thin zone plates and the thickness at which volume diffraction must be considered, and examine numerically the performance of example zone plates for soft x-ray focusing at 0.5 keV and hard x-ray focusing at 10 keV.

Diamond refractive micro-lenses for full-field X-ray imaging and microscopy produced with ion beam lithography.

We demonstrate that ion-beam lithography can be applied to the fabrication of rotationally parabolic refractive diamond X-ray micro-lenses that are of interest to the field of high-resolution X-ray focusing and microscopy. Three single half-lenses with curvature radii of 4.8 µm were produced and stacked to form a compound refractive lens, which provided diffraction-limited focusing of X-ray radiation at the P14 beamline of PETRA-III (DESY). As shown with SEM, the lenses are free of expressed low- and high-frequency shape modulations with a figure error of < 200 nm and surface roughness of 30 nm. Precise micro-manipulation and stacking of individual lenses are demonstrated, which opens up new opportunities for compact X-ray microscopy with nanometer resolution.

A simulation model and experimental study of X-ray transmission through a polycapillary focusing X-ray lens

A simulation model is established to simulate the X-ray transmission performance through a polycapillary focusing X-ray lens whose configuration curve was described by a piecewise function. The shape of the lens is segmented, and each segment uses different function curve. The ray tracing principle is used to simulate the transmission performance of X-rays through the polycapillary focusing X-ray lens. And the simulation results were compared with the experimental results.

Method and application of fast estimating particle background level for space-based focusing X-ray instruments

Instrument background is an important content in implementing the space-based astronomical mission. For the focusing X-ray telescope, the observation ability is affected by the particle background, which is directly related to the sensitivity of the instrument and the systematic error of background reproducibility. In the iterative process of instrument design and engineering implementation, it is necessary to make sure that the particle background level is within the acceptable level. In this paper, we propose a method of fast estimating the particle background of the space-based focusing X-ray telescope, which is based on interpolation of planar density distribution. With acceptable accuracy and efficiency, this method is suitable for rapidly estimating the background shielding effects of various design schemes, especially in the early stage of telescope scheme design. This can greatly improve the availability of early scheme design. This method has a certain reference significance for developing the focusing space high-energy astronomical instruments and other similar instruments. The commonly used method of estimating the particle background of space X-ray instruments is the Monte Carlo method, which relies on constructing an overall mass model of instrument and simulating the response of the detectors to the space radiation environment, but the calculation efficiency of this method is lower. In order to meet the needs of instrument design optimization of mission during initial stage, we simulate the responses of simplified aluminum spherical shells with different sizes and planar desities to the space radiation environment, and count energy depositing events in a concerned energy range. Then we obtain the relationship between the particle background caused by various spatial radiation components and the thickness of the simplified aluminum spherical shell after being normalized. The particle track tracking method is used to calculate the area density distribution of the equivalent aluminum around the sensitive detectors of the telescope. Finally, the average particle background level of each component is obtained by interpolating calculation according to the relationship between equivalent thickness and the particle background. The method is verified through the simulation of the payload SFA onboard eXTP satellite by comparing the results of the simulation calculation of the whole star mass model with the results from the area density distribution interpolation method, and good consistency is obtained. The method based on the interpolation of the planar density distribution can well depict the relationship between the whole structure and the particle background level, which can be applied to the particle background estimation and shielding optimization for X-ray focusing instruments in different orbital space radiation environments.

Impact of beryllium microstructure on the imaging and optical properties of X-ray refractive lenses.

Beryllium is one of the most transparent materials to hard X-ray radiation and, as a direct consequence, it is the main material for the fabrication of X-ray refractive optics and instrumentation for synchrotron radiation sources and free-electron laser facilities. However, it is known that almost all beryllium currently in use is polycrystalline material. In this paper, the influence of the microstructure of different beryllium grades on the optical properties of X-ray refractive lenses is studied. The experiments were performed at the ESRF ID06 beamline in X-ray coherent transmission microscopy mode in the near- and far-fields. Two sets of refractive lenses made of beryllium O-30-H and IS-50M grades with different internal microstructure were used. It was found that both beryllium grades have a strongly inhomogeneous structure, which inevitably produces speckle patterns under coherent illumination in imaging experiments. It was shown that fine-grained beryllium O-30-H is better suited for imaging applications, whereas beryllium IS-50M with a relatively large grain microstructure is more appropriate for focusing and collimation of X-rays. A discussion on the requirements for X-ray optical materials used at the third- and fourth-generation synchrotrons is also presented.

Nanoscopic X-ray imaging and quantification of the iron cellular architecture within single fibroblasts of Friedreich's ataxia patients.

Friedreich's ataxia (FRDA) is a neurodegenerative disease characterized by an increase in intracytoplasmic iron concentration. Here the nanoscale iron distribution within single fibroblasts from FRDA patients was investigated using synchrotron-radiation-based nanoscopic X-ray fluorescence and X-ray in-line holography at the ID16A nano-imaging beamline of the ESRF. This unique probe was deployed to uncover the iron cellular two-dimensional architecture of freeze-dried FRDA fibroblasts. An unsurpassed absolute detection capability of 180 iron atoms within a 30 nm × 50 nm nanoscopic X-ray beam footprint was obtained using state-of-the-art X-ray focusing optics and a large-solid-angle detection system. Various micrometre-sized iron-rich organelles could be revealed for the first time, tentatively identified as endoplasmic reticulum, mitochondria and lysosomes. Also a multitude of nanoscopic iron hot-spots were observed in the cytosol, interpreted as chaperoned iron within the fibroblast's labile iron pool. These observations enable new hypotheses on the storage and trafficking of iron in the cell and ultimately to a better understanding of iron-storage diseases such as Friedreich's ataxia.

International Axion Observatory (IAXO) status and prospects

International Axion Observatory (IAXO) is a new generation axion helioscope aiming to search for solar axions and axion-like particles (ALPs) with a signal to background ratio of about 5 orders of magnitude higher than the one achieved by currently the most sensitive axion helioscope, CAST. IAXO relies on large improvements in magnetic field volume and extensive use of X-ray focusing optics combined with low-background detectors. IAXO will probe a substantial unexplored region of the axion and ALP parameter space which is theoretically and cosmologically motivated, and thus will have significant discovery potential. IAXO could also be used to test models of other proposed particles at the low energy frontier of particle physics, like hidden photons or chameleons. In addition, the IAXO magnet could accommodate new equipment to search for relic axions or ALPs potentially composing the galactic halo of dark matter.

面向脉冲星导航的聚焦型X射线探测器测试标定方法研究

面向脉冲星导航的聚焦型X射线探测器测试标定方法研究

X-ray diffraction methods for structural diagnostics of materials: progress and achievements

The development of X-ray diffractometry at the turn of the 21st century is presented. The review covers instrumentation development for structural studies based on the use of both standard continuously radiating X-ray generators and state-of-the-art sources of ultrashort and ultra-bright X-ray pulses. The latter technique enables investigation of the structural dynamics of condensed matter in a 4D space–time continuum with a resolution reaching a tenth of a femtosecond. New engineering approaches to enhancing the sensitivity, accuracy, and efficiency of X-ray diffraction experiments are discussed, including new and promising X-rays sources, reflective collimating and focusing X-ray optical devices, and fast low-noise and radiation-resistant position-sensitive X-ray detectors, as well as a new generation of X-ray diffractometers developed based on these elements. The presentation is focused on modern engineering solutions that enable academic and applied-research laboratories to perform X-ray diffraction studies on-site, which earlier were only feasible using synchrotron radiation sources at international resource sharing centers.

NI-23 ULTRA-HIGH-RESOLUTION CT ANGIOGRAPHY FOR BRAIN TUMOR SURGERY

BACKGROUNDPreoperative accurate evaluation of arteries and veins can help avoid ischemic complication of brain tumor surgery. The latest ultra-high-resolution CT (UHRCT) angiography (Aquilion PrecisionTM; Canon Medical Systems) has recently become available for clinical testing of the main arteries and critical perforating arteries by brain CTA, compared to conventional CT.METHODSUHRCT provides slice collimation of 0.25 mm x 160 and matrix size of 1024 x 1024 or 2048 x 2048. Major features of this CT scanner include an improved detector system (the minimal slice thickness, 0.25 mm; the maximal channel number, 1792) and a small x-ray focus (the smallest size, 0.4 x 0.5 mm) compared to a standard multi-detector CT (MDCT) scanner (the minimal slice thickness, 0.5 mm; the maximal channel number, 896; the smallest x-ray focus size, 0.8 x 0.9 mm).RESULTSUntil July 2019, 168 patients with brain tumor underwent UHRCT angiography. As high resolution image could visualize cortical arteries and cortical veins clearly, it helped to decide approach route to the tumor and achieve accurate biopsy of even small lesion. Identification of tumor feeders and passing arteries allowed for efficient feeder coagulation and preservation of passing artery, avoiding the ischemic change of surrounding brain. Improved image reconstruction could visualize perforating arteries, which helped to preserve perforator by predicting the location during tumor removal.CONCLUSIONUHRCT angiography can visualize even tiny arteries and veins around the tumor, and contributes to avoid the risk of ischemic complication.

NI-22 IMPROVED DELINEATION OF THE SUPERFICIAL CEREBRAL VENOUS SYSTEM IN BRAIN CT ANGIOGRAPHY BY ULTRAHIGH-RESOLUTION CT FOR ASSISTING BRAIN TUMOR SURGERY

BACKGROUNDIn brain CT angiography (CTA) for assisting brain tumor surgery, delineation of the superficial cerebral venous system is critical for selecting the optimal surgical approach. This delineation is, however, limited using conventional CT scanners, including an area-detector CT (ADCT) scanner, due to their insufficient spatial resolution. Since March 2017, a state-of-the-art ultrahigh-resolution CT (UHRCT) scanner has been clinically available to improve in- and through-plane spatial resolution compared with conventional CT scanners, mainly due to smaller slice thickness from 0.5 mm to 0.25 mm, larger channel number from 896 to 1792, and smaller x-ray focus from 0.9 x 0.8 mm to 0.4 x 0.5 mm.PurposeWe assessed usefulness of UHRCT to improve delineation of the superficial cerebral venous system in brain CTA for assisting brain tumor surgery compared with conventional ADCT.METHODSWe retrospectively enrolled patients with intra- and/or extra-axial brain tumors who underwent preoperative brain CTA for assisting brain tumor surgery by UHRCT or ADCT using our routine technique and generated the CTA to delineate the superficial cerebral venous system using the same technique. Two reviewers by consensus subjectively counted the number of the superficial sylvian veins and the cortical veins draining into these veins and the maximal bifurcation order of the cortical veins draining into the superior sagittal sinus. We compared these numbers and the maximal bifurcation order in the CTA between the UHRCT and ADCT groups using the intraoperative findings as the reference.RESULTSThe numbers and the maximal bifurcation order in the UHRCT group were significantly greater and more accurate than those in the ADCT group.CONCLUSIONSUse of UHRCT can be clinically useful for better delineating the superficial cerebral venous system in brain CTA and assisting brain tumor surgery.

Unravelling the unusually curved X-ray spectrum of RGB J0710 + 591 using AstroSat observations

ABSTRACT We report the analysis of simultaneous multiwavelength data of the high-energy-peaked blazar RGB J0710 + 591 from the Large Area X-ray Proportional Counters, Soft X-ray focusing Telescope, and Ultraviolet Imaging Telescope (UVIT) instruments onboard AstroSat. The wide band X-ray spectrum (0.35–30 keV) is modelled as synchrotron emission from a non-thermal distribution of high-energy electrons. The spectrum is unusually curved, with a curvature parameter βp ∼ 6.4 for a log parabola particle distribution, or a high-energy spectral index p2 &amp;gt; 4.5 for a broken power-law distribution. The spectrum shows more curvature than an earlier quasi-simultaneous analysis of Swift–XRT/NuSTAR data where the parameters were βp ∼ 2.2 or p2 ∼ 4. It has long been known that a power-law electron distribution can be produced from a region where particles are accelerated under Fermi process and the radiative losses in acceleration site decide the maximum attainable Lorentz factor, γmax. Consequently, this quantity decides the energy at which the spectrum curves steeply. We show that such a distribution provides a more natural explanation for the AstroSat data as well as the earlier XRT/NuSTAR observation, making this as the first well-constrained determination of the photon energy corresponding to γmax. This in turn provides an estimate of the acceleration time-scale as a function of magnetic field and Doppler factor. The UVIT observations are consistent with earlier optical/UV measurements and reconfirm that they plausibly correspond to a different radiative component than the one responsible for the X-ray emission.

A Reconstruction Method Through Projection Data Conversion Under the Displaced Detector Scanning for Industrial Cone-Beam CT

In the application of industrial cone-beam computed tomography (CBCT), the displaced detector scanning mode can significantly enlarge the field of view (FOV) of the CT system. However, when this mode is applied to inspect a large object, the connecting line between the X-ray focus and the center-of-rotation projection may not be perpendicular to the real flat-panel detector, which makes most of the existing reconstruction methods impractical. The purpose of this article is to explain the work done in developing an image reconstruction method under the displaced detector scanning mode. We first establish a virtual detector to make the connecting line be perpendicular to the virtual detector, and the real projection data are then converted into the virtual detector. The geometrical parameters of the real CT system are converted into the CT system with the virtual detector, in which the virtual detector and the twist angles of the reconstructed images are effectively corrected by adjusting angles of the projection sequence. Based on the corrected projection data and the converted geometry parameters, the cross sections of the object are accurately reconstructed through the FDK reconstruction algorithm combined with the Wang weighting function. Computer simulation results and CBCT experiment results demonstrate that the image artifacts and the twist angles of the reconstructed images are well corrected. Through this method, the FOV of the CT system is enlarged by 78% without changing the original geometric layout of the system, which is significant for engineering applications.

Effect of external pressure on β-NiAl phase transformation of Co-base alloy at 1323 K

To study the effect of pressure on the oxidation behavior of cobalt base super alloys at high temperature, the alloys were oxidized by using a muffle furnace under the constant pressure of 0.0 MPa, 0.5 MPa and 1.5 MPa at 1323 K. Specimens were investigated using scanning electronic microscopy (SEM), coupled with energy dispersive x-ray (EDX), focus ions beam (FIB) and x-ray diffraction (XRD). The results revealed that under pressure continue protective oxides scales of Al2O3 were formed on the surface of the super alloys. In the substrate, the β-NiAl phase shows a different transform behavior compared to the alloy without pressure. The theoretical mechanism was also assessed based on Density Functional Theory (DFT) to calculate the coefficient of thermal expansion (CTE) of α-Al2O3 and γ′-Ni3Al and enthalpy, entropy of β-NiAl under pressure at high temperature. The difference within CTE between the alumina scale and substrate decreased under pressure as well as enthalpy value. A theoretical analysis has been proposed to explain the experimental results.

TAGUCHI METHOD-BASED OPTIMIZATION OF THE MINIMUM DETECTABLE DIFFERENCE OF A CARDIAC X-RAY IMAGING SYSTEM USING A PRECISE LINE PAIR GAUGE

Objective: To optimize the minimum detectable difference (MDD) of a cardiac X-ray imaging system using the Taguchi L8(27) analysis and a precise line pair (LP) gauge. Methods: The optimal combination of the four critical factors of the cardiac X-ray imaging system, namely X-ray focus, kilovoltage (kVp), milliamper-seconds (mAs) and source image distance (SID), providing the MDD was calculated via the Taguchi analysis and experimentally verified. Two (low and high) levels were assigned for each factor, and eight combinations of four factors were used to acquire instant X-ray images using an NDT commercial LP gauge (with a gauge length of 64[Formula: see text]mm and a width of [Formula: see text][Formula: see text]mm). The latter had five lines and was split gradually from top to bottom for the inspection of X-ray images, whose quality was ranked by three well-trained radiologists according to the double-blind criterion. The ranking grade was given by sharp contrast, low noise and precision to distinguish the LP. Accordingly, the MDD was derived to represent the spatial resolution of instant X-ray images by the revised Student’s [Formula: see text]-test analysis. The optimal combination of factors was experimentally identified and clinically verified in the follow-up inspections. Results: For the conventional setting, Group No. 7 (which obtained the highest grade among eight groups) and the optimal setting, the obtained MDD values were [Formula: see text], [Formula: see text] and [Formula: see text][Formula: see text]mm, respectively, while the LP (line pair/mm) interpolated from the gauge scale amounted to [Formula: see text], [Formula: see text] and [Formula: see text][Formula: see text]LP/mm, respectively. Conclusion: The Taguchi L8 analysis was proved to be instrumental in optimizing the cardiac X-ray imaging system MDD and is recommended to be used jointly with the revised Student’s [Formula: see text]-test analysis for improving the spatial resolution of instant X-ray images.

An X-ray focusing monochromator composed of poly-capillary X-ray lenses and highly oriented pyrolytic graphite

An X-ray focusing monochromator is proposed, which is composed of an X-ray source, a highly oriented pyrolytic graphite and two poly-capillary X-ray lenses. Through the function of the front poly-capillary X-ray lens, the X-ray beams diffracted by the highly oriented pyrolytic graphite changed from a linear pattern with high divergence in the vertical direction, to a circular pattern with low divergence, and more X-rays are diffracted than the conventional monochromator of combining an X-ray source with a flat crystal. The post poly-capillary X-ray lens can focus the diffracted X-ray beams with low divergence into a small focal spot with high gain in power density. The results show that the gains of circular apertures with diameters of 320 and 100 μm are 12 and 22, respectively, at a distance of 221.5 mm away from the center of the highly oriented pyrolytic graphite.