Accelerating ultrasound speed of sound tomography through reflection and transmission imaging

Investigation of the particulate matter contained in the water sample, revealed the presence of a number of different types and certain of these were selected for analysis.An A.E.I. Corinth electron microscope was modified to accept a Kevex Si (Li) detector. To allow for existing instruments to be readily modified, this was kept to a minimum. An additional port is machined in the specimen region to accept the detector, with the liquid nitrogen cooling dewar conveniently housed in the left hand cupboard adjacent to the microscope column. Since background radiation leads to loss in the sensitivity of the instrument, great care has been taken to reduce this effect by screening and manufacturing components that are near the specimen from material of low atomic number. To change from normal transmission imaging to X-ray analysis, the special 4-position specimen rod is inserted through the normal specimen airlock.

Download Full-text

X-ray Gabor holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100139433 ◽

1995 ◽

Vol 53 ◽

pp. 612-613

Author(s):

Steve Lindaas ◽

Chris Jacobsen ◽

Alex Kalinovsky ◽

Malcolm Howells

Keyword(s):

Surface Relief ◽

Biological Imaging ◽

Specimen Preparation ◽

X Rays ◽

X Ray ◽

Water Window ◽

Biological Objects ◽

Transmission Imaging ◽

Atomic Force ◽

Electron Microscopes

Soft x-ray microscopy offers an approach to transmission imaging of wet, micron-thick biological objects at a resolution superior to that of optical microscopes and with less specimen preparation/manipulation than electron microscopes. Gabor holography has unique characteristics which make it particularly well suited for certain investigations: it requires no prefocussing, it is compatible with flash x-ray sources, and it is able to use the whole footprint of multimode sources. Our method serves to refine this technique in anticipation of the development of suitable flash sources (such as x-ray lasers) and to develop cryo capabilities with which to reduce specimen damage. Our primary emphasis has been on biological imaging so we use x-rays in the water window (between the Oxygen-K and Carbon-K absorption edges) with which we record holograms in vacuum or in air.The hologram is recorded on a high resolution recording medium; our work employs the photoresist poly(methylmethacrylate) (PMMA). Following resist “development” (solvent etching), a surface relief pattern is produced which an atomic force microscope is aptly suited to image.

Download Full-text

Parabolas from Reconstructed Surfaces Observed in Convergent-Beam RHEED Patterns

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135599 ◽

1990 ◽

Vol 48 (2) ◽

pp. 398-399

Author(s):

M. Gajdardziska-Josifovska

Keyword(s):

Electron Microscopy ◽

High Energy ◽

Two Dimensional ◽

High Energy Electron ◽

Reflection And Transmission ◽

Experimental Diffraction Pattern ◽

Surface Resonance ◽

Reconstructed Surfaces ◽

Reflection Electron Microscopy ◽

Convergent Beam

Parabolas have been observed in the reflection high-energy electron diffraction (RHEED) patterns from surfaces of single crystals since the early thirties. In the last decade there has been a revival of attempts to elucidate the origin of these surface parabolas. The renewed interest stems from the need to understand the connection between the parabolas and the surface resonance (channeling) condition, the latter being routinely used to obtain higher intensity in reflection electron microscopy (REM) images of surfaces. Several rather diverging descriptions have been proposed to explain the parabolas in the reflection and transmission Kikuchi patterns. Recently we have developed an unifying general treatment in which the parabolas are shown to be K-lines of two-dimensional lattices. Here we want to review the main features of this description and present an experimental diffraction pattern from a 30° MgO (111) surface which displays parabolas that can be attributed to the surface reconstruction.

Download Full-text