Probe diameter

In this case the probe diameter and the slot length are of similar size. The material chosen has penetration depth of 0.7 ram at the given frequency of 16.9 kHz. The slot depth is 7 times larger than the penetration depth. 

We improve the penetration of eddy currents by increasing the probe diameter. The useful diameter is generally equal to the coil diameter to which we add four times the standard thickness 8. 

By increasing the probe diameter, we bring down tlie impedance point along the impedance curve with the same way as the electrical frequency or conductivity. We will describe only one type of probes, namely, the probe with ferritic circular section that we could qualify as punctual with an optimal sensibility. In order to satisfy these conditions, tests will be made to confirm these results by ... 

The usual source of electrons is a tungsten filament electron gun held at a negative potential (typically 10-30 kV), and magnetic lenses focus the beam into a fine probe incident on the surface of the specimen. A probe diameter of 0.2-1 pm is typical, with a current of 1-100 nA. 

Probe diameter Description Total power dissipated into the reactor (W/m3) Crystallite size (nm) Particle size distribution (nm) Induction time (min)... 

Puncture probe diameter should be held constant during a given series of tests. 

The general experimental setup is shown in Fig. 37.1. The probe is an amperometric disk-shaped UME that is embedded in an insulating sheath, typically made from glass. Most often the electrode is made from Pt but electrodes from Au and carbon fibers have been used as well. Typical probe diameters are 10 or 25 pm. Of course, smaller electrodes may be used and this area is currently extensively explored. As it will be evident later, it is convenient to characterize the probe by two important radii the radius rT of the active electrode area and... 

A consistent protocol for the collection and analysis of thin-film EDS data requires an assessment of both instrument and specimen dependent parameters. Major parameters which should be considered for thin-film analyses include spurious X-rays, spectral artifacts, detector geometry, probe diameter, beam broadening, contamination, sample preparation artifacts, sample orientation and temperature and X-ray absorption. Many of these parameters are interdependant during an analysis and the prudent operator will evaluate as many as possible before routine use of an AEM. Further explanations of these parameters can be found in a number of publications [4,6.,9.,7] Only selected parameters are discussed below. 

FIGURE 5.5 The secondary x-ray information will emerge from cellular structures in the depth of the section within volume of the proton beam volume of excitation. In addition, a probe diameter of 5 /im will result in lateral overlap of cellular compartments. Hence, the spatial resolution of the proton probe is restricted to strata rather than single cells. The resolution can be improved by diminishing the probe diameter (<2 //m) and the section thickness (<6 //m) at the cost of a substantial increase in acquisition time. 

Another application of direct e-beam irradiation is given in [20]. In this paper, non-ferromagnetic Co-C thin films were magnetically patterned using a focused electron beam with a probe diameter of less than 0.1 pm. The... 

Example 8.4 It is desired to sample fume particles (d = 0.1 pm) that are emitted horn a stack at a velocity of 100 cm/s and a temperature of 200°C. (Assume a particle density of 1 g/cm3 and a sample probe diameter of 1 cm.) Determine the sampling error when the sampling velocity is 0.01 of the stream velocity. 

As with optical lenses, electromagnetic lenses have aberrations (chromatic aberration, spherical aberration, electron diffraction limit, astigmatism, etc.) each entailing an enlargement of the electron probe expressed by the diameter of a circle of least confusion. Under standard operating conditions, when the astigmatism has been adjusted, only spherical aberration plays a significant role. The expression of the probe diameter becomes ... 

The electron probe is the reduced image of an electron source supplied by a gun. The tungsten filament thermionic emission gun is currently the most suitable source for X-ray microanalysis. It is not very expensive to run, can be easily aligned and offers satisfactory stability. It delivers high current intensities (1 to 1000 nA) for probe diameters of the order of a micrometre. 

Resolution in the STEM is limited by the probe diameter, which is about 1 nm in equipment dedicated to this operating mode, at the cost of using a cold field emission gun requiring an ultravacuum. Because of the high-precision optics and the point-by-point image formation principle, the STEM combines the advantages of scanning electron microscope analysis with resolution performance levels similar to the transmission electron microscope. 

Various Definitions of Protein Surfaces. It is crucial that the size of the probe is small enough so that the small detail of surface irregularities (hills and valleys) can be resolved. Because of different probe sizes, different definitions of protein surface arose. Contact surface would be used if the probe were not small enough to resolve every hills and valleys of the protein surface. It refers to the contact area of the probe with the protein surface. Accessible surface is not preferred for Ds determination because it includes both protein and solvent atoms surfaces. It is more suitable to describe properties of protein packing. Molecular surface is favored to represent protein-solvent interaction because it describes area inaccessible to the solvent.f It is this surface that claimed to best describe self-similarity. Eq. (11) can be employed to obtain after replacing d with the probe diameter. When the molecular surface (Am) is used, Ds can be determined as follows ... 

Figure 3 Current versus probe diameter FWHM estimated) for a dedicated field omission...

The Raman spectra of DWCNT s were analysed in terms of chiral, (n,m) assignments for these tubes.266 The Raman spectrum of I2-doped DWCNT gave assignments to radial breathing and tangential modes.267 Resonance Raman spectra of DWCNT were analysed to probe diameters and chiralities.268 The Raman spectra of DWCNT (from fullerene peapods annealed at high temperatures) show that the inner tubes are remarkably defect-free.269 Very low levels of defects were also observed from the Raman spectra of DWCNT produced by the catalytic decomposition of benzene over Fe-Mo/ A1203 catalysts at 900°C (i.e. very weak D-band at 1265.5 cm-1).270... 

A similar study was carried out by Fai d [ 129] with an immersed probe (diameter 12 mm). The reactor was a large beaker (25 cm in diameter). The probe was located at the center and the tip of the horn was immersed to a depth 2 cm below the surface of the liquid as shown in Figure 26. 

The resolution of SEM imaging is determined by the cross-sectional diameter of the scanning probe. Thus, the size of the probe limits the size of features on the specimen surface to be resolved. To obtain high resolution, we should know how to minimize probe size. The probe diameter is approximately expressed as dp. 

Figure 4.4 Relationship between the probe diameter, convergence angle and working distance.

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