Collimators capable of higher resolution and optimized for greater sensitivity can significantly improve the imaging quality of gamma-cameras for single-photon-emission computed tomography of small animals. We are applying deep x-ray lithography and gold electroforming techniques to fabricate high-resolution collimators with continuous, smooth, and thin septa. Negative SU-8 photoresist was used for mold fabrication. To be efficient, collimators for gamma-cameras designed to image 140 keV gamma-rays should be over 1.5 cm tall. The height of the collimator can be achieved by stacking the appropriate number of layers.
We are developing freestanding high-aspect-ratio, focused, two-dimensional antiscatter grids for mammography using deep x-ray lithography and copper electroforming. The exposure is performed using x-rays from bending magnet beamline 2-BM at the Advanced Photon Source (APS) of Argonne National Laboratory. A 2.8-mm-thick prototype freestanding copper antiscatter grid with 25μm-wide parallel cell walls and 550 μm periodicity has been fabricated. The progress in developing a dynamic double-exposure technique to create the grid with the cell walls aligned to a point x-ray source of the mammography system is discussed.
The paper presents the results of theoretical and experimental investigations of static deformations in homeotropic Nematic Liquid Crystal layers, taken place in a spatially nonuniform radial symmetric electric field. The calculations take into account both dielectric and flexoelectric torques. The nonuniform electric field is created by a charge disk of a various size.