Focusing slits

A well-known device that performs a 2D projection of the scattering pattern is the Kratky camera. By integrating the intensity along the direction of the focus slit, it is collapsing the SAXS intensity on the plane that is normal to the slit direction. In general, 2D projections collapse the measured complete intensity not on a line, but on a plane. As in the case of the ID projections, the orientation of this plane can freely be chosen. The result of such a projection / 2 (Sj,Sk) is not a curve as was the case with the ID projection, but a 2D scattering pattern. Only in the case of 2D isotropy (i.e., / 2 (sjk) with sjk = Js2, + s ) the scattering pattern can be represented by a curve. 

The main advantages of quadrupoles are their small size and absence of small focusing slits, i.e. high transmission properties, and also the relative cheapness. It is predicted that in the future quadrupoles will become the most commonly used detector (see, for example, refs. 177 and 227-229). 

When we do a line scan , we move a focused slit of energy across a detector. In Figure 15.8, g(x) is the irradiance profile of the focused slit, and/t(x) is the nonuniform responsivity of the detector. Let p represent the position of thex-origin for the slit with respect to the x-origin for the detector. We want to see how the signal varies with p as we move the slit - starting at the far left (p = -20, for example), then over the detector, and finally to the far right (p = -Fl5, for example). 

Fig. 5.1 Schematic illustration of an electron impact ionization ion source with the ionizing beam passing at right angles to the page. 1, Effluent line from gas chromatograph 2, direct insertion probe carrying sample crucible 3, ion source block held at high positive potential 4, sample molecules 5, ionization region 6, extraction plates 7, focusing slits 8, beam centering plates 9, source slit 10, ion beam.

Figure Bl.7.4. Schematic diagram of a reverse geometry (BE) magnetic sector mass spectrometer ion source (1) focusing lens (2) magnetic sector (3) field-free region (4) beam resolving slits (5) electrostatic sector (6) electron multiplier detector (7). Second field-free region components collision cells (8) and beam deflection electrodes (9).

SOURCE SLIT (FIXED) FOCUS (BEAM CENTRE) SOURCE EI/CI... 

Through the use of sequential electric (electrostatic) and magnetic fields (sectors) and various correcting lenses, the ion beam leaving the ion source can be adjusted so that it arrives at the collector in focus and with a rectangular cross-section aligned with the collector slits. For the use of crossed electromagnetic fields. Chapter 25 ( Quadrupole Ion Optics ) should be consulted. 

A simple spectrometer that we have used successfully is shown in Figure 2. Electrons from an electron microscope hairpin tungsten filament are focused with an Einzel lens onto the monochromator entrance slit, pass through the monochromator and exit slit, and are focused on the sample s surface by additional electrostatic... 

---