Strip-based parallel beam projection model for under-sampling CT system

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.

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100 KV Scanning Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095613 ◽

1972 ◽

Vol 30 ◽

pp. 472-473 ◽

Cited By ~ 3

Author(s):

A. V. Crewe ◽

M. W. Retsky

Keyword(s):

High Voltage ◽

Voltage Divider ◽

Electron Gun ◽

Objective Lens ◽

Parallel Beam ◽

Emission Point ◽

Error Amplifier ◽

External Reference ◽

Scanning Transmission ◽

Transmission Microscope

A 100 kv scanning transmission microscope has been built. Briefly, the design is as follows: The electron gun consists of a field emission point and a 3 cm Butler gun. The beam has a crossover outside the gun and is collimated by a condenser lens.The parallel beam passes through a defining aperture and is focused by the objective lens onto the specimen. The elastic electrons are detected by two annular detectors, each subtending a different angle, and the unscattered and inelastic electrons are collected by a third detector. The spectrometer that will separate the inelastic and unscattered electrons has not yet been built.The lens current supplies are stable to within one part per million per hour and have been described elsewhere.The high voltage is also stable to 1 ppm/hr. It consists of the raw supply from a 100 kv Spellman power supply controlled by an external reference voltage, high voltage divider, and error amplifier.

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Identification by Electron Microdiffraction of Intermetallic Phases in a Duplex Stainless Steel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136076 ◽

1990 ◽

Vol 48 (2) ◽

pp. 494-495

Author(s):

A. Redjaïmia ◽

J.P. Morniroli ◽

G. Metauer ◽

M. Gantois

Keyword(s):

Stainless Steel ◽

Duplex Stainless Steel ◽

Convergent Beam Electron Diffraction ◽

Intermetallic Phases ◽

Small Particles ◽

Parallel Beam ◽

Diffraction Patterns ◽

Average Size ◽

Convergent Beam ◽

Electron Microdiffraction

2D and especially 3D symmetry information required to determine the crystal structure of four intermetallic phases present as small particles (average size in the range 100-500nm) in a Fe.22Cr.5Ni.3Mo.0.03C duplex stainless steel is not present in most Convergent Beam Electron Diffraction (CBED) patterns. Nevertheless it is possible to deduce many crystal features and to identify unambiguously these four phases by means of microdiffraction patterns obtained with a nearly parallel beam focused on a very small area (50-100nm).From examinations of the whole pattern reduced (RS) and full (FS) symmetries the 7 crystal systems and the 11 Laue classes are distinguished without ambiguity (1). By considering the shifts and the periodicity differences between the ZOLZ and FOLZ reflection nets on specific Zone Axis Patterns (ZAP) which depend on the crystal system, the centering type of the cell and the glide planes are simultaneously identified (2). This identification is easily done by comparisons with the corresponding simulated diffraction patterns.

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Examination of Extra Electron Diffraction Spots Observed in Deuterium-Irradiated Silicon by Using Parallel Electron Beam Illumination

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136052 ◽

1990 ◽

Vol 48 (2) ◽

pp. 490-491

Author(s):

Ryuichiro Oshima ◽

Shoichiro Honda ◽

Tetsuo Tanabe

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Silicon Single Crystal ◽

Mixed Solution ◽

Parallel Beam ◽

Defect Clusters ◽

Float Zone ◽

Transmission Electron ◽

Extra Electron ◽

Diffraction Patterns

In order to examine the origin of extra diffraction spots and streaks observed in selected area diffraction patterns of deuterium irradiated silicon, systematic diffraction experiments have been carried out by using parallel beam illumination.Disc specimens 3mm in diameter and 0.5mm thick were prepared from a float zone silicon single crystal(B doped, 7kΩm), and were chemically thinned in a mixed solution of nitric acid and hydrogen fluoride to make a small hole at the center for transmission electron microscopy. The pre-thinned samples were irradiated with deuterium ions at temperatures between 300-673K at 20keV to a dose of 1022ions/m2, and induced lattice defects were examined under a JEOL 200CX electron microscope operated at 160kV.No indication of formation of amorphous was obtained in the present experiments. Figure 1 shows an example of defects induced by irradiation at 300K with a dose of 2xl021ions/m2. A large number of defect clusters are seen in the micrograph.

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