Experimental Aspects of Reflectometer Operation

Collimating s//ts-these are located on either side of the sample. A beam monitor on the precollimating slit allows the primary detector to be scaled to absolute reflectivites. 

Pre- and post-sample flights-both have LiF slits for collimation of the incident or reflected beam. Flight tubes have 2ec ( Ni) supermirrors and are evacuated to minimize losses. 

Thermal neutron filter-a liquid nitrogen-cooled beryllium filter is placed after the monochromator to remove thermal neutrons. 5. Sample sfoge-available space is approximately 30cm between the collimating slits. 6. Translation 

To improve the statistical quality of data, typical counting times can exceed 8-10 h which requires that systems being studied are sufficiently stable. 

The end points define the lateral distance in the sample plane across which a given spherical wave front becomes out of phase by n degrees. For a spherical wavelength of 5 A emanating from a source 5 m away, the length I is of the order of 100 pm. In practice, the lateral coherence length depends on the energy spread and the wave vector spread of the incident neutron wave front If the instrumental 

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