Running TRICS with a Single Counter

In this mode TRICS simulates a conventionell four circle diffractometer much like a x-ray diffractometer as commercially available. The tasks which have to be solved are:

Locate Reflections
Index reflections and refine a UB-matrix.
Measure a couple of reflections.
Furthermore there are some specialities.

There are two ways to achieve all this: The older way uses some built in SICS functionality plus some external programs inherited from the ILL. This is called the ILL operation. Then a complete four circle package called DIFRAC from P. White and Eric Gabe was integrated into SICS. This is The Difrac way of operation.

DIFRAC

The DIFRAC commands are accessed by prepending the difrac commands with dif. For example: "dif td" calls the difrac td command. For more information on DIFRAC commands see the separate DIFRAC manual.

ILL operation

Locate Reflections

If you know x-ray single crystal diffractometers you'll expect sophisticated reflection search procedures here. Nothing is available in this field in SICS. It was deemed inapropriate for neutron research. The first reflections must be found by hand. Something which may help in this is a quick scan facility which allows to run a motor and print counts while the motor is moving. This can be invoked by a command like this:

susca var start end time

The parameters are:

var: the motor or variable to scan.
start: the start position from which to scan.
end: the end position for this scan.
time: The maximum counting time.

Be aware that this is inprecise and liable to changes in the source current. But it may help to locate the aproximate position of a peak.

Once a peak has been found, its position can be optimised and centered with the peak optimiser.

The next thing to do is to store the reflection and find other ones. Once a few reflections have been found, the need to be written to disk. This can be accomplished with the object rliste which has the following subcommands:

rliste clear: clears all entries from the list
rliste store: saves the current diffractometer position into the list
rliste write file: Writes the contents of the reflection list to the file specified.

Indexing Reflections and Refining UB-Matrix

For these purposes the external programs INDEX and RAFIN are provided. These programs are courtesy of the ILL, France.

Measuring Reflections

Before measuring reflections a list of reflections to measure must be created. This is done with the external program HKLGEN. Then reflections this reflection list can be fed into SICS using the mess command. mess creates two output files: a .col file containing the reflection profiles of all the relfections and a .dat files which contains the HKL,F,sig(F),TH,OM,CH,PH for each reflection. Intensity has then be integrated within SICS. The .col files can be processed by the program REFRED which allows to perform more advanced data reduction chores and has a choice of integration methods for reflection data. Please note, that SICS does not automatically measure standard reflections. It is your task to add suitable standard reflections into the reflection list.

Special Commands

As of current this section only holds the hklscan commmand which allows to express a scan in Miller indizes. This is in fact a scan in reciprocal space.