Specimen stage

The specimen holder is a sophisticated, rod-like device that not only holds the specimen but also is able to tilt it for better viewing inside the TEM column. Types of specimen holders used include single-tilt and double-tilt. The single-tilt holder allows a specimen to be titled along one axis in the disc plane. The double-tilt holder allows the specimen be tilted independently along two axes in the disc plane. The double-tilt holder is necessary for analytical studies of crystalline structures. 

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The beam next arrives at the final lens-aperture combination. The final lens does the ultimate focusing of the beam onto the surface of the sample. The sample is attached to a specimen stage that provides x- and j>-motion, as well as tilt with respect to the beam axis and rotation about an axis normal to the specimen s surface. A final z motion allows for adjustment of the distance between the final lens and the sample s surface. This distance is called the working distance. 

A computer system to control the beam, spectrometers, specimen stage, and... 

The specimen stage usually holds several specimens and standards, with dimensions typically 20-30 mm, although for special purposes extra-large specimen stages are available - Matsuya et al. (1988) describe a holder with a working area of 300 x 300 mm. An airlock isolated from the main vacuum chamber reduces the time taken to change specimens. 

Procedure Water was taken as an immersion medium. The object under study was placed on a wet specimen stage so that the section of its surface to be investigated should be above the scanning zone and was clamped by a slide. After that OCM images of the biological object were acquired. The images were recorded and stored in the personal computer for further analysis. 

Specimen stage in single-or multiple-sample configurations accepts mounts from the Introduction system and positions them for analysis. 

Drive mechanism can be used to automate the specimen stage sample advance and tilt motions. 

The most recent developments in TEM also include the Environmental mode. In dedicated TEM, a differential pumping between the electron gun and the specimen stage allows the specimen to be surrounded by a gaseous atmosphere, with a pressure of a few millibars. Interestingly, the spatial resolution of the TEM is not seriously affected since atomic resolution is still attainable (31) and chemical reactions can be followed in situ. 

Mechanical Stability.—Finally, we note mechanical constraints on system construction which may be more severe in the case of STEM than CTEM. In either type of instrument the user is accustomed to extreme mechanical stability in the specimen stage region exposure times measured in seconds at resolutions of 2 A or so require drift and vibrational stability in the stage at a commensurate level. In the STEM, however, an extra constraint exists. As a consequence of passing through an aperture the emitted electron beam from the field emission tip, the effective electron source size... 

We can conclude that white light will not be extinguished for any combination of polar vibration directions. If a specimen is viewed between crossed polars in white light, and a region fails to go into extinction as the specimen stage is rotated, the optical orientation in that region is not constant through the specimen thickness. 

What contrast is obtained when the analyzer is withdrawn and the specimen stage is rotated ... 

It is equipped with field emission gun (PEG), helium temperature specimen stage, omega-type energy filter and Gatan MegaScan 795 2Kx2K CCD camera. For improved contrast of ice-embedded specimens we employed a novel Zernike-type... 

The most effective means to reduce mass loss appears to be with the use of a cold specimen stage. Different samples lose mass at different rates, but most lose some percent and then are quite stable thereafter. Mass loss becomes important in several quantitative procedures, such as mass mapping of macromolecules and elemental analysis. 

Mass mapping is not without possible errors in accuracy. Mass loss accounts for inaccuracies, especially in proteins. Wall and Hainfield (17) report that a dose of 10e /0.1nm2 is a reasonable compromise between structural preservation and accuracy of mass measurements. Use of a cold specimen stage is requisite. Since proteins, nucleic acids, and lipids suffer mass loss at different rates, a dose-... 

As shown in Figure 21-16, the specimen stage is provided with a mechanism to move the sample in two mutually perpendicular directions and rotate it as well, which permits the surface to be scanned. 

The X-ray analysis system for the EMA is a wavelength dispersive spectrometer with gas proportional counter detectors. In the SEM, an energy dispersive X-ray spectrometer with a Si(Li) detector is used. The entire electron and X-ray optical systems are operated under a vacuum of about 10 torr. Modem systems are completely automated with computer control of the instmment parameters, specimen stage movement, data collection and data processing. 

For Raman load transfer experiments one end of a 10 mm fiber sample was fixed to the Raman specimen stage, whilst the other end was attached to a metallic wire which... 

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