Low Energy X-ray Photons Induced Changes in Lexan Films

40 keV Synchrotron X-ray photons were made to fall on Lexan polycarbonate films at different exposure time. The low energy X-ray photons assisted modification in terms of physico-chemical properties of Lexan films were studied using Fourier Transform Infrared (FTIR) spectrophotometer, X-Ray Diffractogram (XRD), Vicker’s Microhardness Tester,Scanning Electron Microscope (SEM) and Contact Angle Meter. FTIR result mainly includes decrease in the C=C stretching and C-C stretching of aromatics after irradiation. XRD analysis shows a slight decrease in the crystallinity after irradiation. Vicker’s microhardness test reveals the decrement in microhardness of Lexan films after irradiation. SEM result shows irradiation induced changes in the surface morphology. Contact angle measurement shows increase in the water contact angle in irradiated Lexan films

Low Energy X-ray Photons Induced Changes in Lexan Films

706-71040 keV Synchrotron X-ray photons were made to fall on Lexan polycarbonate films at different exposure time. The low energy X-ray photons assisted modification in terms of physico-chemical properties of Lexan films were studied using Fourier Transform Infrared (FTIR) spectrophotometer, X-Ray Diffractogram (XRD), Vicker’s Microhardness Tester, Scanning Electron Microscope (SEM) and Contact Angle Meter. FTIR result mainly includes decrease in the C=C stretching and C-C stretching of aromatics after irradiation. XRD analysis shows a slight decrease in the crystallinity after irradiation. Vicker’s microhardness test reveals the decrement in microhardness of Lexan films after irradiation. SEM result shows irradiation induced changes in the surface morphology. Contact angle measurement shows increase in the water contact angle in irradiated Lexan films

Correction of the X-ray wavefront from compound refractive lenses using 3D printed refractive structures

A refractive phase corrector optics is proposed for the compensation of fabrication error of X-ray optical elements. Here, at-wavelength wavefront measurements of the focused X-ray beam by knife-edge imaging technique, the design of a three-dimensional corrector plate, its fabrication by 3D printing, and use of a corrector to compensate for X-ray lens figure errors are presented. A rotationally invariant corrector was manufactured in the polymer IP-STM using additive manufacturing based on the two-photon polymerization technique. The fabricated corrector was characterized at the B16 Test beamline, Diamond Light Source, UK, showing a reduction in r.m.s. wavefront error of a Be compound refractive Lens (CRL) by a factor of six. The r.m.s. wavefront error is a figure of merit for the wavefront quality but, for X-ray lenses, with significant X-ray absorption, a form of the r.m.s. error with weighting proportional to the transmitted X-ray intensity has been proposed. The knife-edge imaging wavefront-sensing technique was adapted to measure rotationally variant wavefront errors from two different sets of Be CRL consisting of 98 and 24 lenses. The optical aberrations were then quantified using a Zernike polynomial expansion of the 2D wavefront error. The compensation by a rotationally invariant corrector plate was partial as the Be CRL wavefront error distribution was found to vary with polar angle indicating the presence of non-spherical aberration terms. A wavefront correction plate with rotationally anisotropic thickness is proposed to compensate for anisotropy in order to achieve good focusing by CRLs at beamlines operating at diffraction-limited storage rings

Aberration characterization of x-ray optics using multi-modal ptychography and a partially coherent source

Ptychography is a scanning coherent diffraction imaging technique that provides high-resolution imaging and complete spatial information of the complex probe and object transmission function. The wavefront error caused by aberrated optics has previously been recovered using ptychography when a highly coherent source is used, but has not been demonstrated with partial coherence due to the multi-modal probe required. Here, we demonstrate that partial coherence can be accounted for in ptychographic reconstructions using the multi-modal approach and assuming that decoherence arises from either the probe or the object. This equivalence recovers coherent (or single state) reconstructions of both the probe and the object even in the presence of partial coherence. We demonstrate this experimentally by using hard x-ray ptychography with a partially coherent source to image a Siemens star test object and to also recover the wavefront error from an aberrated beryllium compound refractive lens. The source properties and resolving capabilities are analyzed, and the wavefront error results are compared with another at-wavelength metrology technique. Our work demonstrates the capability of ptychography to provide high-resolution imaging and optics characterization even in the presence of partial coherence

Two-dimensional wavefront characterization of adaptable corrective optics and Kirkpatrick-Baez mirror system using ptychography

Aberrations introduced during fabrication degrade the performance of X-ray optics and their ability to achieve diffraction limited focusing. Corrective optics can counteract these errors by introducing wavefront perturbations prior to the optic which cancel out the distortions. Here we demonstrate two-dimensional wavefront correction of an aberrated Kirkpatrick-Baez mirror pair using adaptable refractive structures. The resulting two-dimensional wavefront is measured using hard X-ray ptychography to recover the complex probe wavefield with high spatial resolution and model the optical performance under coherent conditions. The optical performance including the beam caustic, focal profile and wavefront error is examined before and after correction with both mirrors found to be diffraction limited after correcting. The results will be applicable to a wide variety of high numerical aperture X-ray optics aiming to achieve diffraction limited focussing using low emittance sources

Hard X-ray ptychography for optics characterization using a partially coherent synchrotron source

Ptychography is a scanning coherent diffraction imaging technique which provides high resolution imaging and complete spatial information of the complex electric field probe and sample transmission function. Its ability to accurately determine the illumination probe has led to its use at modern synchrotrons and free-electron lasers as a wavefront-sensing technique for optics alignment, monitoring and correction. Recent developments in the ptychography reconstruction process now incorporate a modal decomposition of the illuminating probe and relax the restriction of using sources with high spatial coherence. In this article a practical implementation of hard X-ray ptychography from a partially coherent X-ray source with a large number of modes is demonstrated experimentally. A strongly diffracting Siemens star test sample is imaged using the focused beam produced by either a Fresnel zone plate or beryllium compound refractive lens. The recovered probe from each optic is back propagated in order to plot the beam caustic and determine the precise focal size and position. The power distribution of the reconstructed probe modes also allows the quantification of the beams coherence and is compared with the values predicted by a Gaussian-Schell model and the optics exit intensity