The investigation of the features optical vortices focusing by ring gratings with the variable height using high-performance computer systems

The diffraction of vortex laser beams with circular polarization by ring gratings with the variable height was investigated in this paper. Modelling of near zone diffraction is numerically investigated by the finite difference time domain (FDTD) method. The changes in the length size of the light needle and focal spot size are shown depending on the type of the ring grating.

Improve X-ray images using quality assurance tests

In this research, entrance surface doses of patients which are resulted from a classical radiograph in most widespread tests (Chest, skull, abdomen, limbs, …) have been measured with selected instruments in (Specialized surgeries hospital) and one of the private clinic in Baghdad, the instruments are of various origins and different make date. A group of patients (10 patients) for each test and according the average of the resulted doses. Comparison of the patient’s doses, in this research, has been close with the reliable International standards and it has been found that radiological doses are bigger than reference doses ranging (132–1.79) in most of the appliance and the range doses to one whenever the instrument is new and the radiographer has good experience, this increase relates to several functions discussed in the research in detail For the importance of the quality assurance of x-ray instruments, three tests have been performed by three of the instruments only, and these tests are : Beam Alignment test : The Beam Alignment was measured and the x-ray radiograph was found symmetrical round the two axes of the instruments (A, B) but it is about 3 ° away from the vertical axis of the instrument (C). Optical and Radiation Field Congruence Test: The light field coincides with the radiative field in a and b and their mismatch in c. Focal Spot Size Test: The radiation focus area was measured by the star tool and what appeared is that the focus of the x-ray instrument (C) is smaller than the international standards on the contrary of the focus area of the x-ray instrument (E) which is identical with the international standards. From these results reached is that the instruments (A, B) have passed quality assurance tests and they are suitable for work in the present, but the instrument (C) has not passed most of the quality assurance tests, so this instrument should not be used for medical tests This in research is considered the first one for these instruments to evaluate their doses or measure a quality assurance.

High-energy high-dose microfocus X-ray computed tomography driven by high-average-current photo-injector

High-energy, high-dose, microfocus X-ray computed tomography (HHM CT) is one of the most effective methods for high-resolution X-ray radiography inspection of high-density samples with fine structures. Minimizing the effective focal spot size of the X-ray source can significantly improve the spatial resolution and the quality of the sample images, which is critical and important for the performance of HHM CT. The objective of this study is to present a 9 MeV HHM CT prototype based on a high-average-current photo-injector in which X-rays with about 70μm focal spot size are produced via using tightly focused electron beams with 65/66μm beam size to hit an optimized tungsten target. In digital radiography (DR) experiment using this HHM CT, clear imaging of a standard 0.1 mm lead DR resolution phantom reveals a resolution of 6 lp/mm (line pairs per mm), while a 5 lp/mm resolution is obtained in CT mode using another resolution phantom made of 10 mm ferrum. Moreover, comparing with the common CT systems, a better turbine blade prototype image was obtained with this HHM CT system, which also indicates the promising application potentials of HHM CT in non-destructive inspection or testing for high-density fine-structure samples.

Study of Superoscillating Functions Application to Overcome the Diffraction Limit with Suppressed Sidelobes

The problem of overcoming the diffraction limit does not have an unambiguously advantageous solution because of the competing nature of different beams’ parameters, such as the focal spot size, energy efficiency, and sidelobe level. The possibility to overcome the diffraction limit with suppressed sidelobes out of the near-field zone using superoscillating functions was investigated in detail. Superoscillation is a phenomenon in which a superposition of harmonic functions contains higher spatial frequencies than any of the terms in the superposition. Two types of superoscillating one-dimensional signals were considered, and simulation of their propagation in the near diffraction zone based on plane waves expansion was performed. A comparative numerical study showed the possibility of overcoming the diffraction limit with a reduced level of sidelobes at a certain distance outside the zone of evanescent waves.

Minimal Focal Spot Size Measured Based on Intensity and Power Flow

It is shown, theoretically and numerically, that the distributions of the longitudinal energy flow for tightly focused light with circular and linear polarization are the same, and that the spot has circular symmetry. It is also shown that the longitudinal energy flows are equal for optical vortices with unit topological charge and with radial or azimuthal polarization. The focal spot has a minimum diameter (all other characteristics being equal), which is measured based on the intensity of an optical vortex with azimuthal polarization. The diameter of the focal spot calculated from the energy flow for light with circular or linear polarization is slightly larger (by a fraction of a percentage). The magnitude of the diameter based on the intensity plays a role in the interaction of light with matter, and the magnitude of the diameter based on the energy flux affects the resolution in optical microscopy which is crucial in sensorial applications.