X-ray Lens Research Articles

Benzylidene Cyclopentanone Derivative Photoinitiator for Two-Photon Photopolymerization-Photochemistry and 3D Structures Fabrication for X-ray Application.

Micron- and submicron-scale 3D structure realization nowadays is possible due to the two-photon photopolymerization (TPP) direct laser writing photolithography (DLW photolithography) method. However, the achievement of lithographic features with dimensions less than 100 nm is in demand for the fabrication of micro-optical elements with high curvature values, including X-ray microlenses. Spectroscopic and photochemical study of a photoinitiator (PI) based on a methyl methacrylate derivative of 2,5-bis(4-(dimethylamino)benzylidene) cyclopentanone was performed. Enhanced intersystem crossing in the methyl methacrylate derivative results in increased radical generation for the subsequent initiation of polymerization. A comprehensive study of the new photocompositions was performed, with particular emphasis on photochemical constants, the degree of photopolymerization, and topology. The optimal parameters for the fabrication of mechanically stable structures were determined in this research. The threshold dose parameters for lithography (radiation power of 5 mW at a speed of 180 µm/s) when trying to reach saturation values with a conversion degree of (35 ± 1) % were defined, as well as parameters for sub-100 nm feature fabrication. Moreover, the 45 nm feature size for elements was reached. Fabrication of X-ray lens microstructures was also demonstrated.

Phase-retrieval algorithm based on Kramers–Kronig relations in coherent diffraction imaging

Coherent diffraction imaging (CDI) is a high-resolution technique that does not require x-ray lenses. With advances in scientific technology, such as synchrotron radiation, x-ray free-electron lasers, and coherent electron sources, CDI has been applied to diverse fields, such as biology, medicine, and semiconductors, as a high-resolution, nondestructive measure. With the rapid increase in demand for these applications, enhancing the efficiency of processing high-volume data has become a significant challenge for promotion. In this study, we proposed an algorithm that combines Kramers–Kronig (KK) relations with oversampling smoothness (OSS). The results were evaluated by introducing an error coefficient. We found that the error of the KK-OSS algorithm is always reduced by approximately 50% compared with the error reduction (ER) algorithm, hybrid input–output (HIO) algorithm, and OSS in real space. In the diffraction space, the error in the KK-OSS can be decreased to 0.11. With 100 iterations, KK-OSS spent 218.3 s on reconstructing most of the sample information, while ER was 258.1 s, HIO algorithm took 296.7 s and the reconstruction was still a random value. In Fraunhofer diffraction, it cost KK-OSS 58.8 s to reconstruct, while OSS took 61.9 s. Therefore, this method can reduce the reconstruction error, shorten the reconstruction time, and improve the efficiency compared with the ER, HIO, and OSS algorithms using a random phase as the initial value.

Fine Structure of Diffraction Losses in Single-Crystal X-Ray Lenses

Fine Structure of Diffraction Losses in Single-Crystal X-Ray Lenses

Erratum to: Refractive X-Ray Lenses Made by the Two-Photon Laser Lithography Method

An Erratum to this paper has been published: https://doi.org/10.3103/S1541308X22060085

XCT and DLW: Synergies of Two Techniques at Sub-Micrometer Resolution

Direct Laser Writing (DLW) and X-ray computed tomography (XCT) both offer unique possibilities in their respective fields. DLW produces full three-dimensional (3D) polymer structures on the microscale with resolutions below 100 nm. The fabricated structures can be analysed by XCT or X-ray microscopy (XRM), which incorporates additional X-ray lenses, in three dimensions down to a minimal basic spatial resolution of about 500 nm or 50 nm, respectively. In this work, two different DLW structures are analysed via XCT. Internal defects are detected and analysed for the purpose of quality control. Defects and structures with sizes down to 1.5 µm are successfully analysed. A 3D reconstruction and internal, hidden features of the fabricated structures are shown and discussed. In a first-of-its-kind study, we demonstrate the detectability of a single-voxel line inside a fabricated structure that would not be detectable with SEM or light microscopy. Furthermore, the direct fabrication on a PET substrate is shown to overcome the high X-ray absorbance of commonly used glass substrates. Attenuation spectra of SZ2080 and glass substrates are compared to a fabrication route direct on a 170 µm PET foil. The practical aspects of XCT measurements for DLW structures on different substrates will be discussed.

Refractive X-Ray Lenses Made by the Two-Photon Laser Lithography Method

Refractive X-Ray Lenses Made by the Two-Photon Laser Lithography Method

Detailed characterization of polycapillary focusing x-ray lenses by a charge-coupled device detector and a pinhole

A method to measure the detailed performance of polycapillary x-ray optics by a pinhole and charge coupled device (CCD) detector was proposed in this study. The pinhole was located between the x-ray source and the polycapillary x-ray optics to determine the illuminating region of the incident x-ray beam on the input side of the optics. The CCD detector placed downstream of the polycapillary x-ray optics ensured that the incident x-ray beam controlled by the pinhole irradiated a specific region of the input surface of the optics. The intensity of the output beam of the polycapillary x-ray optics was obtained from the far-field image of the output beam of the optics captured by CCD detector. As an application example, the focal spot size, gain in power density, transmission efficiency, and beam divergence of different parts of a polycapillary focusing x-ray lenses (PFXRL) were measured by a pinhole and CCD detector. Three pinholes with diameters of 500, 1000, and 2000 μm were used to adjust the diameter of the incident x-ray beam illuminating the PFXRL from 500 μm to the entire surface of the input side of the PFXRL. The focal spot size of the PFXRL, gain in power density, transmission efficiency, and beam divergence ranged from 27.1 μm to 34.6 μm, 400 to 3460, 26.70% to 5.38%, and 16.8 mrad to 84.86 mrad, respectively.

Rapid aberration correction for diffractive X-ray optics by additive manufacturing.

Diffraction-limited hard X-ray optics are key components for high-resolution microscopy, in particular for upcoming synchrotron radiation sources with ultra-low emittance. Diffractive optics like multilayer Laue lenses (MLL) have the potential to reach unprecedented numerical apertures (NA) when used in a crossed geometry of two one-dimensionally focusing lenses. However, minuscule fluctuations in the manufacturing process and technical limitations for high NA X-ray lenses can prevent a diffraction-limited performance. We present a method to overcome these challenges with a tailor-made refractive phase plate. With at-wavelength metrology and a rapid prototyping approach we demonstrate aberration correction for a crossed pair of MLL, improving the Strehl ratio from 0.41(2) to 0.81(4) at a numerical aperture of 3.3 × 10-3. This highly adaptable aberration-correction scheme provides an important tool for diffraction-limited hard X-ray focusing.

A Procedure for the Characterization of Monocapillary X-Ray Lenses as Condensers for Full-Field Transmission X-Ray Microscopes

Monocapillary x-ray lenses (MXRLs) are mostly used as condensers in full-field transmission x-ray microscopy (TXM) based on synchrotron radiation or laboratory x-ray tubes. The performance of the condenser has a significant impact on the imaging quality of the TXM. In this paper, a procedure for the characterization of the MXRL as a condenser is presented. The procedure mainly includes two parts: optical measurement and x-ray tests. From the test results of the characterization procedure, it can be seen that a relatively high-performance condenser can be screened out from a series of MXRLs drawn by an electric furnace. This is also fed back to the manufacturing process, and therefore, the technology of manufacturing the condenser can be gradually optimized. Moreover, the method of characterizing the performance of the condenser designed for synchrotron radiation TXM by laboratory x-ray tubes is proposed to be used in this procedure, which effectively reduces the manufacturing time of high-performance condensers for synchrotron radiation TXM.

Polished diamond X-ray lenses.

High-quality bi-concave 2D focusing diamond X-ray lenses of apex-radius R = 100 µm produced via laser-ablation and improved via mechanical polishing are presented here. Both for polished and unpolished individual lenses and for stacks of ten lenses, the remaining figure errors determined using X-ray speckle tracking are shown and these results are compared with those of commercial R = 50 µm beryllium lenses that have similar focusing strength and physical aperture. For two stacks of ten diamond lenses (polished and unpolished) and a stack of eleven beryllium lenses, this paper presents measured 2D beam profiles out of focus and wire scans to obtain the beam size in the focal plane. These results are complemented with small-angle X-ray scattering (SAXS) measurements of a polished and an unpolished diamond lens. Again, this is compared with the SAXS of a beryllium lens. The polished X-ray lenses show similar figure errors to commercially available beryllium lenses. While the beam size in the focal plane is comparable to that of the beryllium lenses, the SAXS signal of the polished diamond lenses is considerably lower.

High-quality quasi-parallel X-ray beam obtained by a parabolic monocapillary X-ray lens with a square beam stop

Parabolic monocapillary X-ray lens (PMXRL) is an ideal optical device for constraining the point divergent X-ray beams to quasi-parallel beams, but the overlap of direct X-rays and reflected X-rays through PMXRL deteriorates the outgoing beam divergence. Aiming to solve this problem, this study designs and tests a square-shaped lead occluder (SSLO) embedded in PMXRL to block the direct X-rays passing through the PMXRL. Python simulations are employed to determine the geometric parameters of the SSLO as well as the optimal position of the SSLO in the PMXRL according to our proposed model. The PMXRL with a conic parameter p of 0.000939 mm and a length L of 60.8 mm is manufactured and the SSLO with a size of 0.472 mm×0.472 mm×3.4 mm is embedded into it. An optical path system based on this PMXRL is built to measure the divergence of the outgoing X-ray beam. The experimental results show that the quasi-parallel X-ray beam reaches a divergence of 0.36 mrad in the range from 15-45 mm at the PMXRL outlet. This divergence is 10 times lower than the theoretical divergence without SSLO. Our work provides an alternative method for obtaining highly parallel X-ray beam and is beneficial to generate or facilitate new applications of monocapillary optics in X-ray technology.

Trapezoid-kinoform zone plate lens - a solution for efficient focusing in hard X-ray optics.

X-ray microscopes are powerful tools in the nano-inspection of materials owing to their ultra-high resolution at the molecular level. However, the focusing efficiency of binary zone plate lenses as key components in such probes is merely 5% in practice, hindering their application in advanced scientific research. Although kinoform zone plate lenses are in principle supposed to possess high efficiency beyond binary ones, little progress has been reported so far due to the shortage of both a theoretical calculation approach and greyscale lithography for generating fine three-dimensional (3D) kinoform zones of the lenses. This paper reports our theoretical work for a modified beam propagation method to compute the focusing performance and state-of-the-art 3D greyscale electron beam lithography for kinoform zone plate lenses. Three different zone shapes - binary, kinoform and top-flat kinoform (nicknamed the trapezoid-kinoform) - were compared both theoretically and experimentally. Theoretical calculations suggest, for the first time, that the trapezoid-kinoform zone plate gives rise to the highest focusing efficiency among the three lenses, which was proved by optical characterization of the fabricated lens with hard X-rays. As high as 40% of the focusing efficiency by Au trapezoid-kinoform lenses with resolution of 250 nm at 8 keV has been achieved, which is two times higher than that of binary zone plate lenses. The origin of the enhanced efficiency in the trapezoid-kinoform zone plate lens was explained by the joint contributions from both the refraction through the kinoform slope and the diffraction through the top flat part of the trapezoid-kinoform zone plate. Such a breakthrough in focusing efficiency sheds light on the further development of X-ray lenses with both high resolution and high efficiency.

Using diffraction losses of X-rays in a single crystal for determination of its lattice parameters as well as for monochromator calibration.

A way has been developed to measure the unit-cell parameters of a single crystal just from an energy scan with X-rays, even when the exact energy of the X-rays is not well defined due to an error in the pitch angle of the monochromator. The precision of this measurement reaches da/a ∼ 1 × 10-5. The method is based on the analysis of diffraction losses of the beam, transmitted through a single crystal (the so-called `glitch effect'). This method can be easily applied to any transmissive X-ray optical element made of single crystals (for example, X-ray lenses). The only requirements are the possibility to change the energy of the generated X-ray beam and some intensity monitor to measure the transmitted intensity. The method is agnostic to the error in the monochromator tuning and it can even be used for determination of the absolute pitch (or 2θ) angle of the monochromator. Applying the same method to a crystal with well known lattice parameters allows determination of the exact cell parameters of the monochromator at any energy.

Simulation and Characterization on Tapered Monocapillary High-Energy X-Ray Lens with Microfocal Spot

Simulation and Characterization on Tapered Monocapillary High-Energy X-Ray Lens with Microfocal Spot

Capillary X-Ray Lens Technology and Its Applications

Capillary X-Ray Lens Technology and Its Applications

Analysis of a novel X-ray lens for converging beam radiotherapy

We describe the development and analysis of a new teletherapy modality that, through a novel approach to targeted radiation delivery, has the potential to provide greater conformality than conventional photon-based treatments. The proposed system uses an X-ray lens to reflect photons from a conventional X-ray tube toward a focal spot. The resulting dose distributions have a highly localized peak dose, with lower doses in the converging radiation cone. Physical principles governing the design of this system are presented, along with a series of measurements analyzing various characteristics of the converging beam. The beam was designed to be nearly monoenergetic (~ 59 keV), with an energy bandwidth of approximately 10 keV allowing for treatment energies lower than conventional therapies. The focal spot was measured to be approximately 2.5 cm long and 4 mm wide. Mounting the proposed X-ray delivery system on a robotic arm would allow sub-millimeter accuracy in focal spot positioning, resulting in highly conformal dose distribution via the optimal placement of individual focal spots within the target volume. Aspects of this novel radiation beam are discussed considering their possible clinical application as a treatment approach that takes maximum advantage of the unique properties afforded by converging X-ray beam therapy.

Multi-Lens Array Full-Field X-ray Microscopy

X-ray full-field microscopy at laboratory sources for photon energies above 10 keV suffers from either long exposure times or low resolution. The photon flux is mainly limited by the objectives used, having a limited numerical aperture NA. We show that this can be overcome by making use of the cone-beam illumination of laboratory sources by imaging the same field of view (FoV) several times under slightly different angles using an array of X-ray lenses. Using this technique, the exposure time can be reduced drastically without any loss in terms of resolution. A proof-of-principle is given using an existing laboratory metal-jet source at the 9.25 keV Ga Kα-line and compared to a ray-tracing simulation of the setup.

X-ray focusing using an x-ray lens composed of multi-square polycapillary slices

A new type of x-ray lens composed of multi-square polycapillary slices (ASPXRL) used in focusing parallel x-ray beam was presented in this paper. Compared with conventional x-ray polycapillary lens, ASPXRL can provide smaller and brighter focus. The effects of the manufacturing imperfections on focusing quality of ASPXRL were evaluated with the values of transmission efficiency and discussed. It is suggested that ASPXRL has application prospects as a condenser lens for x-ray microscopy and flux collectors for x-ray analytical instruments.

Simulation of X-Ray Television System Output Signal Based on CMOS-Matrixes

Various X-ray television systems are used for radiation control of materials and products, both indirect conversion of radiation images and direct conversion systems. X-ray television system type "X-ray screen - optics - CMOS-matrix" have a number of advantages over others: the ability to change the X-ray scintillation screen, which allows you to change the size of the working field and other system parameters; short image acquisition time; simplicity of construction; small dimensions and weight; low cost. The development of digital X-ray television systems requires the solution of important scientific and technical problems, which include: increasing the signal-to-noise ratio and, accordingly, the sensitivity of control, increasing the quantum efficiency of image converters, optimizing operating modes to ensure high quality radiation images.The aim of this research was to develop a model of X-ray television system. A physical and topological model of X-ray image transformation in X-ray television systems of the “X-ray screen — optics — CMOS-matrix” type has been developed during research. The math model allows to calculate the characteristics of X-rays at the output of the X-ray tube and the object under study, the intensity of the screen, the light intensity on the surface of the CMOS matrix after passing the optics, calculate the charge packet in a pixel and the output signal systems. The block diagram of the X-ray television system includes the following components: X-ray machine, object, scintillator (screen), mirror and lens with CMOS-matrix. The first stage of creating a through mathematical model is to simulate X-rays at a certain distance from the anode of the X-ray tube. The second stage of creating an end-to-end mathematical model of X-ray television system based on CMOS matrices of the optical range is the modeling of the process of converting X-rays, which corresponds to the shadow X-ray image of the object, into visible range radiation.The developed physical and topological model of X-ray image transformation in X-ray television systems of the type "X-ray screen - optics - CMOS-matrix" allows us to calculate the characteristics of X-ray television system at the design stage, which will save time and money on system development and also select the optimal modes of operation for the study of certain materials. The found results are a perspective direction in development of technology of research of materials that will allow to reduce cost of installations for researches.

Lens Flare: Magnified X-Ray Binaries as Passive Beacons in SETI

Abstract Low-mass X-ray binaries (LMXBs) containing neutron stars are both extremely luminous and compact, emitting up to ∼106 within a kilometer-scale boundary layer. This combination allows for easy modulation, motivating an X-ray Search for Extraterrestrial Intelligence. When X-ray lenses with radii magnify the LMXB boundary layer, it brightens by a factor of several thousand for a fraction of a second. In addition, there should be occultation events where the neutron star is blocked out. Passive X-ray lenses could require little internal power, and the LMXB light source itself shines for millions of years, with potential for an effective beacon for interstellar communication. A very large number of lenses would be needed to ensure frequent signals in all directions, however, and gathering material to construct them could be very difficult. Avoiding collisions between lenses, aiming them, and building and maintaining their precise shapes pose additional challenges. “Lens flares” of bright LMXBs are easily detectable in the Galaxy, although they would be rare events, occurring perhaps once per decade. Our more sensitive X-ray instruments could detect the eclipses of Galactic LMXBs and possibly intergalactic flares, but it is unlikely they would be observing the LMXB at the right time.