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Reflectometer D17

D17 is the first ILL dedicated reflectometer and it has been designed to be as flexible as possible in resolution and modes of operation. The instrument is suitable for the analysis of surface structures in solids and solid/liquid interfaces. Horizontal surface experiments, such as free liquids, will suffer from a severe restriction in Q-range and flux and are thus not recommended for this instrument.

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www > Instruments & Support > Instruments & groups > D17 > Documentation > D17 LAMP Book > COSMOS > Detector Ranges

D17 LAMP Book

Clicking this button will open a window that allows you to select the areas of the detector where COSMOS will search for the specular reflection.  This is a useful option if there is strong, structured off-specular scattering, or for weak reflectivity.


Useful Range in x:  Specify here the first and last x-pixels in the detector range to be used, separated by a comma.

The D17 detector has 286 pixels in the x-direction.  Look closely, and you will see that the first and last 20 or so pixels have zero intensity.  In other words, the x-range is larger than the range on the detector.  For this reason, it is best to always have an x-range of something like 30 ≥ x ≥ 255.

Search Range for Peak:  Specify the ranges of the detector that will be used to calculate the specular reflectivity.  The minimum and maximum pixels for x (labeled x:) and y (labeled t:) are to be inserted in their respective fields, separated  by a comma.

In time-of-flight, the specular reflectivity corresponds to a vertical line on the detector.  COSMOS will look for a peak in x within the range that defined in x:, and will calculate the reflectivity over the wavelength range defined by the range in t:.

Leaving the fields blank means that no limits will be adopted.

Inserting auto in the t: field means that the reflectivity will be calculated over the wavelength range defined  in the Calculation Options.