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At least 37 records · Page 2

Implosion simulations and optimum times of radiographic Images in OMEGA high-density-carbon cylinder experiments

The Los Alamos Ignition Threshold team is planning direct-drive cylinder implosion experiments (CylDRT24B) at the OMEGA laser, scheduled for Thursday 23 May 2024, to investigate the effect of granular microstructure in high density carbon (HDC) shells. Granular microstructure is believed to play a crucial role in seeding perturbations, reducing compression, and enhancing mix in the implosion of HDC shells at the National Ignition Facility (NIF). But the ICF community lacks a detailed understanding of how grains induce these effects, owing partly to the practical difficulty of numerically simulating the behavior of tiny nanometer-scale granular structures in laboratory-scale experiments. Our planned experiments are aimed at acquiring data to help constrain simulations and calibrate reduced models.

36 MATERIALS SCIENCE↗

Characterization of the Bridgman crystal growth process by radiographic imaging

Elemental (Ge) and alloy (PbSnTe) crystal growth that is monitored via radiography to reveal both the interface position and the shape in real time is discussed for both seeded and unseeded growth. It is concluded that the interface position and the actual growth rate of a Bridgman grown crystal is dependent on the growth conditions. The actual growth rate which is a strong function of the degree of supercooling exceeded the pull rate by a factor of greater than two. The interface shape changed from concave to flat to convex during the growth.

Fripp, Archibald L.↗

Multiwire Gamma Camera for Radionuclide and Radiographic Imaging in the Space environment

Unique multiwire proportional counter technology has been developed at the Johnson Space Center over the past several years. The technology will be described and how it may apply both in near- and long-term NASA efforts. In the near-term, I feel that the technology will provide a significant tool for the cardiovascular research area. In particular, low-dose nuclear medicine and tissue densitometry techniques of expanded scope will be supplied. In the longer term, the multiwire technique can provide a general purpose radiology and nuclear medicine facility for use in the space station which would be difficult and costly to provide by other means.

Lacy, Jeffrey L.↗

Investigation of an electronic image enhancer for radiographs

Radiographs of nuclear and aerospace components were studied with a closed-circuit television system to determine the advantages of electronic enhancement in radiographic nondestructive evaluation. The radiographic images were examined on a television monitor under various degrees of magnification and enhancement. The enhancement was accomplished by generating a video signal whose amplitude is proportional to the rate of change of density. Points, lines, edges, and other density variations that are faintly registered in the original image are rendered in sharp relief. Examples of the applications of this mode of enhancement are discussed together with the system's dynamic response and resolution.

Vary, A.↗

Investigation of an electronic image enhancer for radiographs.

Radiographs of nuclear and aerospace components were studied with a closed-circuit television system to determine the advantages of electronic enhancement in radiographic nondestructive evaluation. The radiographic images were examined on a television monitor under various degrees of magnification and enhancement. The enhancement was accomplished by generating a video signal whose amplitude is proportional to the rate of change of density. Points, lines, edges, and other density variations that are faintly registered in the original image are rendered in sharp relief. Examples of the applications of this mode of enhancement are discussed together with the system's dynamic response and resolution.

Vary, A.↗

Fabrication and characteristics of experimental radiographic amplifier screens

The fabrication process and transfer characteristics for solid state radiographic image transducers (radiographic amplifier screens) are described. These screens are for use in realtime nondestructive evaluation procedures that require large format radiographic images with contrast and resolution capabilities unavailable with conventional fluoroscopic screens. The screens are suitable for in-motion, on-line radiographic inspection by means of closed circuit television. Experimental effort was made to improve image quality and response to low energy (5 kV and up) X-rays.

Szepesi, Z.↗

Radiographic amplifier screens: Fabrication process and characteristics

The fabrication process and transfer characteristics for solid state radiographic image transducers (radiographic amplifier screens) is described. These screens were developed for use in real time nondestructive evaluation procedures that require large format radiographic images with contrast and resolution capabilities unavailable with conventional fluoroscopic screens. This work was directed toward screens usable for inmotion, on-line radiographic inspection by means of closed circuit television.

Szepesi, Z. P.↗