Beams divergence

In traditional Fan-Beam CT the radiation emitted from the X-ray tube is collimated to a planar fan, and so most of the intensity is wasted in the collimator blades (Fig. 2a). Cone-Beam CT, where the X-rays not only diverge in the horizontal, but also in the vertical direction, allows to use nearly the whole emitted beam-profile and so makes best use of the available LINAC photon flux (Fig. 2b). So fast scanning of the samples three-dimensional structure is possible. For Cone-Beam 3D-reconstruction special algorithms, taking in consideration the vertical beam divergence of the rays, were developed. 

Wafer charging is becoming a critical issue as new MOS devices are designed with thinner (<10 mm) gate dielectrics. Lower energy implanters require optics that compensate for beam divergence which occurs at low energeries (32). 

The value of the beam divergence angle given by equation 3 corresponds to that emerging from the laser. The beam may be collimated further by a telescope. The improvement of the coUimation is the inverse of the magnification of the telescope ... 

A hollow waveguide (HWG) is essentially a hollow tube that transports light from one end to the other either by multiple mirror reflection or by total internal reflection. The hollow structure gives them several advantages (i) a high power threshold, (ii) low insertion losses, (iii) no end reflections, (iv) a small beam divergence, (v) robustness and - especially important for sensor applications - (vi) a wide spectral transmission range. 

In terms of directionality, an off-the-shelf laser may have a beam divergence of 0.5 milliradians. Such a laser, shone on the moon from the surface of Earth, would project a spot approximately 120 miles in diameter. Very special optics, e.g. colli-mation of the laser beam by a large optical telescope, can decrease the beam divergence by a factor of ten. 

Electron beam divergence, 173 Electron beam pointing, 173 Electron density, 91 Electronic softening, 32 Emittance, 152 Energy resolved images, 134 Excimers, 20... 

The nature of the optical signal generation and extraction gives a high beam divergence, as high as 30° in many cases. Hence some external focusing is often desirable. 

We do not consider here the dependence of the group velocity on the beam divergence and the related spatiotemporal effeets in the nonlinear medium leading to additional changes in the pulse shape. In the region of the core, these effects are small, and the radiation field power for the levels of the input pulse power considered here is low. 

As we have seen in Chapter 1, we need something near a plane wave in order to see the finest details of the specimen stracture. A single-axis diffractometer utilises a beam that is very far from a plane wave. Thus, single-crystal rocking curves are broadened due to the beam divergence, and the spectral width of the characteristic X-ray lines. 

We first consider the beam divergence. As discussed in Chapter 2 we must perform a mathematical correlation (often miscalled convolution) between the plane wave rocking curves of the beam conditioner and of the sample crystals. If R (, ) and R 2 ( > j are the reflectivities (in intensity) of the first and... 

Air pollutants can be identified by recording the absorption of selected infrared laser lines and their concentration and its local dependence determined. The small beam divergence allows long light paths and therefore high sensitivity 253 a)... 

More seriously, the effect of the above beam divergence also impacts wavenumber accuracy, and the deviation in measured wavenumber for the extreme ray versus the central ray is approximated by ... 

S)mchrotron X-ray sources include both bending magnets and insertion devices. For protein crystallography, an undulator insertion device is preferred because it provides greater intensity at a specific wavelength and has lower beam divergence. This latter property results in smaller X-ray reflections. 

One problem of the measurement of weak absorption in the far IR is that short absorption paths must be used. At wavelengths comparable to the beam apertures diffraction effects lead to beam divergence [252]. (The combination of high gas pressures and short absorption paths may not be useful if many-body induction effects must be avoided, and an accurate measurement of a under conditions of weak absorption, I/Iq 1, is difficult [368].)... 

Among the first practical applications, research studies have been interested to fathom possible potentials and limitations of LAPS-based measurements. One distinguishing feature of the LAPS is its spatial resolution. The resolution of a LAPS system is limited by several factors such as the definition of the light source (e.g., wavelength, beam diameter, beam divergence, beam intensity, etc.) and the LAPS geometry of the build-up (layer scheme, layer thickness, material properties,... 

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