714b8ae84d
- Fixed many things in DIFRAC subsystem:
* Recoded tcentr.f etc so that the course centering will work and will not
go into an endless loop.
* fixed boundary overwrites which occurred when yesno or alfnum where
uset to get a single character and several were given.
* Addeded documentation for DIFRAC
- Added tcl-files which support the WWW status system
105 lines
3.7 KiB
HTML
105 lines
3.7 KiB
HTML
<HTML>
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<HEAD>
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<TITLE>Running TRICS with a Single Counter</TITLE>
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</HEAD>
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<BODY>
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<H1>Running TRICS with a Single Counter</H1>
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<P>
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In this mode TRICS simulates a conventionell four circle diffractometer much
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like a x-ray diffractometer as commercially available. The tasks which have
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to be solved are:
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<ul>
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<li>Locate Reflections
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<li>Index reflections and refine a UB-matrix.
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<li>Measure a couple of reflections.
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<li>Furthermore there are some specialities.
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</ul>
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There are two ways to achieve all this:
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The older way uses some built in SICS functionality plus some external
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programs inherited from the ILL. This is called the ILL operation.
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Then a complete
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four circle package called DIFRAC from P. White and Eric Gabe was
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integrated into SICS.
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This is The Difrac way of operation.
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</p>
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<h2>DIFRAC</h2>
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<p>
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The DIFRAC commands are accessed by prepending the difrac commands
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with <b>dif</b>. For example: "dif td" calls the difrac td
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command. For more information on DIFRAC commands see the separate
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<a href="diftrics.htm">DIFRAC manual</a>.
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</p>
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<h2>ILL operation</h2>
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<h3>Locate Reflections</h3>
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<p>
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If you know x-ray single crystal diffractometers you'll expect sophisticated
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reflection search procedures here. Nothing is available in this field in
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SICS. It was deemed inapropriate for neutron research. The first reflections
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must be found by hand. Something which may help in this is a quick scan
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facility which allows to run a motor and print counts while the motor is
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moving. This can be invoked by a command like this:
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<pre>
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susca var start end time
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</pre>
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The parameters are:
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<ul>
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<li>var: the motor or variable to scan.
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<li>start: the start position from which to scan.
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<li>end: the end position for this scan.
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<li>time: The maximum counting time.
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</ul>
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Be aware that this is inprecise and liable to changes in the source current.
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But it may help to locate the aproximate position of a peak.
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</p>
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<p>
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Once a peak has been found, its position can be optimised and centered with the
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<a href="optimise.htm">peak optimiser</a>.
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</p>
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<P>
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The next thing to do is to store the reflection and find other ones. Once a
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few reflections have been found, the need to be written to disk. This can be
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accomplished with the object rliste which has the following subcommands:
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<DL>
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<DT>rliste clear
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<DD> clears all entries from the list
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<DT>rliste store
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<DD>saves the current diffractometer position into the list
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<DT>rliste write file
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<DD>Writes the contents of the reflection list to the file specified.
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</DL>
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</p>
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<h3>Indexing Reflections and Refining UB-Matrix</h3>
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<p>
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For these purposes the external programs <a href="illprog.txt">INDEX and
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RAFIN </a> are provided. These programs are courtesy of the ILL, France.
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</p>
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<h3>Measuring Reflections</h3>
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<p>
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Before measuring reflections a list of reflections to measure must be
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created. This is done with the external program
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<a href="illprog.txt">HKLGEN</a>. Then reflections this reflection list can
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be fed into SICS using the <a href="mesure.htm">mess </a> command. mess
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creates two output files: a .col file containing the reflection profiles of
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all the relfections and a .dat files which contains the
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HKL,F,sig(F),TH,OM,CH,PH for each reflection. Intensity has then be
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integrated within SICS. The .col files can be processed by the program
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REFRED which allows to perform more advanced data reduction chores and has a
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choice of integration methods for reflection data. Please note, that SICS
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does not automatically measure standard reflections. It is your task to add
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suitable standard reflections into the reflection list.
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</p>
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<h2>Special Commands</h2>
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<p>
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As of current this section only holds the <a href="hklscan.htm">hklscan
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commmand</a> which allows to express a scan in Miller indizes. This is
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in fact a scan in reciprocal space.
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</p>
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</BODY>
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</HTML>
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