GEM Software for use during the experiment

This page describes software for use during the experiment which may be of use for either crystallography or experiments on disordered materials.

The software has been written to be used on VMS ALPHA computers.

GEMSQRAW

The GEMSQRAW program calculates (sample-can)/(vanadium-background) for each currently-existing GEM detector bank.

The program is run inside Open Genie: Type OGEN to start Open Genie if it's not already running. (If this does not work, type OPENGENIE -L.) Note that Open Genie will not produce graphical output unless a display has been created before starting Open Genie. Type SH DISPLAY to find out if a display has been setup.

To run GEMSQRAW inside Open Genie, simply type GEMSQRAW. If this does not work, then type LOAD "GCL:GEMSQRAW.GCL" first, but be very careful to type this command within Open Genie and not at the VMS operating system prompt (e.g. GEM> ) because this will disrupt data collection.

The results for the 3 currently-existing GEM detector banks are placed in workspaces called bank2, bank4 and bank5. The output can be on either a Q or a d-spacing x-axis; however, the units can subsequently be changed by using an Open Genie command like this: bank5=units:d(bank5).

The vanadium data can be either raw data from a .RAW file or, smoothed & corrected data from a .SMO file. Smoothed vanadium data may be produced by running the VANSM program from the ATLAS suite. Click here for further information on running this program. The .SMO smoothed vanadium file must be copied to the vansm area, gem$disk0:[gem.vansm], before running GEMSQRAW. There may already be a suitable file in this area, placed there by an instrument scientist. The advantages of using the smoothed vanadium data are firstly that the result is smoother, and secondly that the sharp negative spikes in the result due to the vanadium Bragg peaks are removed. Here are examples of the output from GEMSQRAW:

vitreous silica, bank5, raw vanadium data

vitreous silica, bank5, smoothed vanadium data

Last updated on 25 Feb 2000 by Alex Hannon (a.c.hannon@rl.ac.uk)