Coherent Backscattering from Multiple Scattering Systems - KOPS ...
Coherent Backscattering from Multiple Scattering Systems - KOPS ...
Coherent Backscattering from Multiple Scattering Systems - KOPS ...
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5.2 The coherent backscattering cone in high resolution<br />
3.25 x 104 scattering angle θ CCD<br />
[deg]<br />
3.2<br />
3.15<br />
3.1<br />
f = 58%<br />
f = 49%<br />
f = 47%<br />
f = 43%<br />
f = 39%<br />
intensity [a.u.]<br />
3.05<br />
3<br />
2.95<br />
2.9<br />
2.85<br />
2.8<br />
0 0.05 0.1 0.15 0.2 0.25 0.3<br />
Figure 5.19: <strong>Backscattering</strong> for various volume fractions. The transport mean free path<br />
is expected to be proportional to the volume fraction of the fluidized bed. However, due<br />
to strong fluctuations in the data no real trend in the width of the backscattering cone<br />
can be observed.<br />
For the fluidized bed with f = 43% one reads <strong>from</strong> fig. 5.18 and with eqn. 2.16 a transport<br />
mean free path between 50 µm and 60 µm. This would mean that l ∗ is significantly shorter<br />
than the diameter of the particles in the fluidized bed, and it stands in strong contrast to<br />
reported mean free paths <strong>from</strong> similar experiments (e.g. [52, 17, 39, 41, 46, 51, 57]), which are<br />
all of the order of several particle diameters.<br />
As the present data are only first results and the experiments are still ‘work in progress’,<br />
there are all kinds of possible explanations for this surprising result, of both theoretical and<br />
experimental nature. These will have to be discussed and investigated if further experiments<br />
on fluidized beds or similar systems are planned for the future.<br />
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