Moving slit device

The moving slit device is designed to directly measure the primary beam intensity without overloading the detector. It works like a slit shutter of a photographic camera a narrow slit is moved along the primary beam. If a sample is in the beam, the absorption of the primary beam by the sample can be directly measured. 

General Routes. If a SAXS beamline in normal transmission geometry is used, calibration to absolute intensity is, in general, carried out indirectly using secondary standards. Direct methods require direct measurement of the primary beam intensity under consideration of the geometrical setup of the beamline. On a routine basis such direct calibration was commercially available for the historic Kratky camera equipped with zero-dimensional detector and moving slit device 14. 

J (s) = Jl (s) dsi is the slit-smeared scattering intensity, P(t is the total primary beam intensity per slit-length element - a quantity determined by the moving slit device. R is the distance between sample and detector slit as measured on the optical axis of the camera. L is the (fixed and known) length of the detector slit in the registration plane. H is the (adjustable) height of the detector slit. exp(—jut) is the linear absorption factor of the sample19. 

The absorption factor of the studied sample is measured by means of the moving slit device, as well. For this purpose the sample is mounted in the sample holder and the moving slit measurement is performed. We measure Ns = 50031 in 16 scans. Because the heights of the moving and the fixed vertical slits are 2 cm, the moving slit registers the SAXS as well - as is required from the definition of absorption. Then... 

Thus, information concerning size and arrangement of domains in the cross-sectional plane of the fiber are accessible with classical laboratory equipment. Moreover, since the projection /(s) 2 ( 12) is complete and a normalization /(s) 2 (512) /(s) 2 ( 12) /T to absolute intensity units is readily established by employment of the moving slit device without the need to resort to a secondary standard, the invariant... 

Design of the SAXS camera. Figure 8 shows a diagram of the SAXS-camera. As in the case of a conventional Kratky-camera [71] it consists of a block collimation system, a sample holder, and a primary beam stop. The intensity of the primary beam is measured by a moving slit device [75]. The intensity is recorded by a linear position-sensitive counter (Braun, OED-50m) the spatial resolution of which is given by approximately 80 pm. 

The main error incurred when determining absolute scattering intensities by the moving slit device is given by the insecure determination of the resolution function of the position-sensitive counter. Here a width of 80 pm has been used which is supplied by the manufacturer. To check this problem in more detail, the scattering intensities of water, toluene, and ethanol have been measured at 25 °C and compared to the theoretical result deriving from classical fluctuation theory [1] ... 

Equation 8.53 predicts that the fastest moving fluid will experience two-thirds of the mean residence time, 0.67F. This is a worthwhile improvement in uniformity compared to a mbe where the fastest fluid has only half the mean residence time. However, the major advantage of duct and slit devices is that they can be fabricated... 

The Spectronic 20 reads out in transmittance or in absorbance on a light-emitting diode display (LED). The instrument is equipped with an occluder, which is a vane that automatically falls between the beam and the detector whenever the cylindrical cell is removed from its holder. The light-control device is a V-shaped aperture that is moved in and out of the beam to control the amount of light reaching the exit slit. 

The travel of the film through the blown film tower is aided by various guiding and sizing devices. The film turns from molten to semisolid at the frostline but is still easily deformed as it moves up the tower. However, the orientation of the film is generally complete at this point. When the film is cool enough, the bubble is collapsed by plates and rollers (pinch rollers), and then wound up with or without slitting, gusseting, or other treatment. Thus, the blown film process can produce tubular as well as flat film. 

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