Using Open Genie during an experiment

Raw data files from GEM can be viewed during collection to allow the data quality to be checked.

Open Genie is installed on the GEM control PC, NDXGEM, to allow users to take a preliminary look at their data during collection.

To launch Open genie, double click on the icon. 

Quick data reduction can be carried out using the program GSQ

The raw data collected from a sample on GEM has a background which is due to the energy distribution of the time-of-flight neutrons.  This background can be measured using a vanadium rod, which scatters almost completely incoherently.  To remove the time-of-flight background GSQ requires a run number for the sample you are interested in (a run number of 0 should be used if you wish to look at data before the run has finished) and a run number for a vanadium rod.  The vanadium run number only needs to be given once while Open Genie remains open.

GSQ takes the data from each detector and sums it together into the 8 banks.  The vanadium data is saved in vanadium which can be plotted in Open Genie by typing

d/l vanadium[5] 0 100  

This plots the bank 5 data measured for vanadium with an x-axis from 0 to 100 Å-1.

Vanadium rod data

Vanadium rod data
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The sample data is saved in the the work space sample, and can be plotted with the vanadium data by typing

a/pc $red; p/l sample[5]

GSQ then calculates Sample/vanadium to produce a rough approximation to the total scattering data for the sample.  This data is saved in the Bank workspace.

From this, a quick T(r) can be produced using the bank[5] data (90 degree bank).  To do this the data needs to oscillate about zero.  By typing c in Open Genie, a cursor appears in the plotting window.  Place the cursor over the high Q data and hit y.  This prints the y value at the position of the cursor.  Once the correct value has been measured, hit e to return to the Open Genie window.

More instructions on commands in Open Genie such as using the cursor in the plotting window, changing the pen colour, and exporting the data from Open Genie can be found here.

T(r) can be produced by first subtracting the number taken from the plotting window

ioq=bank[5]-0.596

and then using the Fourier transfer command i2t

i2t ioq

Plotting D(r) (d/l dor 0 8) results in the following

lead silicate d(r)

lead silicate d(r)
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