Focusing geometry

J. Mattauch and R. F. K. Herzog. Z. Physik. 89,786, 1934. This is the original paper showing the double-focusing geometry necessary to focus onto a plane rather than at a single point. 

Potma and Krishnamachari (Chapter 9) explore the effects of spatial beam shaping on the generated nonlinear Raman signals in a tightly focused geometry, demonstrating its enhanced ability to image chemical interfaces. 

Figure 1.77 A triangular focusing geometry for multi lamellae flows (source IMM).

The so-called Bragg-Brentano focusing geometry is the most commonly used technique in modern powder diffractometry. It is briefly discussed later in this chapter and in greater depth in the next chapter. 

For the most commonly used Bragg-Brentano focusing geometry (see Chapter 3), the overall correction is generally a sum of six factors ... 

Here the surface represents the probability to find the reciprocal lattice point (100) in the diffractometer coordinate system assuming Bragg-Brentano focusing geometry. The Z-axis is perpendicular to the sample, and X- and 7-axes are located in the plane of the sample. 

Figure 3.8. The schematic of the Bragg-Brentano focusing geometry using a flat sample when the self-focused diffracted beam is registered by the detector after reflection from the sample. F - focus of the x-ray source, DS - divergence slit, RS - receiving slit, D - detector, 0 -Bragg angle.

Fig. 7-6 Focusing geometry for flat specimens in (a) forward reflection and (b) back reflection.

Figure 4. The T-junction [9] (Adapted from Ref [13]). An axisymmetric flow-focusing geometry [10] (Adapted from Ref [14]). A planar flow-focusing device [12] (Adapted from Ref [15]).

FORMATION OF BUBBLES AND DROPLETS IN A PLANAR FLOW-FOCUSING GEOMETRY... 

In our experiments [15] on using the microfluidic flow-focusing geometry for formation of monodisperse bubbles of Nitrogen in a continuous liquid of aqueous solutions of surfactant and glycerin we found that the volume of the bubbles (V) depended on the pressure (p) applied to the stream of gas, the rate of flow (Q) of the continuous liquid and its viscosity (p) (Fig. 5) ... 

The usual way of feeding the microfluidic systems with fluids is to apply either a constant rate of inflow into the chip, or a constant pressirre at the inlet [20]. Formation of droplets or bubbles in systems with such, fixed, boundary conditions for flow is realtively well understood. Two microfluidic geometries are most commonly used a microfluidic T-junction [1] or a microfluidic flow-focusing geometry [6]. 

The flow focusing geometry was first introduced in an axi-s5mimetric system by Ganan-Calvo [22]. Later, the same concept was succesfiilly used in a - typical to current microfluidic techniques - planar chip by Anna et al. 

In order to develop high harmonics into an attractive general purpose source of spectroscopic radiation it is necessary to optimise the generation efficiency with regard to focus geometry, gas density etc., and many studies along these lines as well as for the temporal and spatial characterisation have been performed [19-24]. 

Fig. 2 a. Focusing geometry of a SAXS-camera [11, 32]. b. Schematic design of a focussing SAXS-camera with a pinhole geometry. S, and S2 are the aperture and guard slits. The optical element could be a mirror or a monochromator, m corresponds to the — idealized — extension of the diffuse scattering in the detector plane. as is the size of the source point and and a that of the focus. Note that the calculations of SAXS-resolution assume that F2 L, + L2... 

Yobas L, Martens S, Ong W, Ranganathan N (2006) High-performance flow-focusing geometry for spontaneous generation of monodispersed droplets. Lab Chip 6(8) 1073-1079. http //dx.doi.org/10.1039/B602240E... 

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