164 lines
7.1 KiB
HTML
164 lines
7.1 KiB
HTML
<HTML>
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<HEAD>
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<TITLE>Four Circle Diffractometer Measurements in Single Counter Mode</TITLE>
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</HEAD>
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<BODY>
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<H1>Reflection List Processor</H1>
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<P>
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This module performs four circle diffractometer measurements with a single
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counter . In a first view this
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module takes a list of reflections as input, drive to each reflection in the list
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and performs a scan for each reflection. Some more feautures are supported:
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<ul>
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<li>Two different input file formats are supported: the simplest contains a three
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values for H,K,L per line. Some users prefer to perform the angle calculations
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themselves; for such cases the input list can contain four values: two theta, omega, chi
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and phi per line.
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<li>This module supports phi scans: the reflection list must then contain H,K,L and phi
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per line.
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<li>Both measurements in normal bisecting mode and normal beam mode are supported.
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<li>Optionally weak reflections can be remeasured with the preset multiplied by 5.
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<li>Optionally scans are performed in fastscan mode: Between steps, the motor and the
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counter are started at the same time. The step is finished when both operations terminate.
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<li>The module maintains a table of two theta ranges and scan step widths and scan
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variables. This allows to perform scans with varying step widths with two theta and to
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switch between omega and omega - two theta scan mode.
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</ul>
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</p>
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<p>
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Three files will be written starting from a root such as tricsyearnnumber.
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For instance trics1998n000560 means file number 560 in 1998. The file ending in
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.log will contain the console log. This is extremely verbose. Another file
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ending with .col will contain the reflection, diffractometer settings and
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the measured profile. The third file, ending with .rfl will contain for each
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refelction, the HKL, the diffractometer settings and the intensity and sigma
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intensity as calculated by the SICS internal integration routine. A
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Grant Gabe integration (see J.Appl. Cryst (1978), 11, 114-120) is performed.
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</p>
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<p>
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For the purpose of the command description it is assumed, that this facility
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is accessible as object dataset within SICS.
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Interaction with this object happens through the following commands:
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<dl>
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<DT>dataset open
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<DD>Creates a new set of files and writes some header info.
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<DT>dataset measure filename iSkip
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<DD>Starts a measurement. Reads reflections from the file filename. iSkip is
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an optional parameter which allows to skip iSkip lines in the file. This
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is for recovery in cases of accidental or purposeful interruption
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of the measurement.
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<DT>dataset genlist filename iSkip
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<DD>Mesures reflection from filename. The file is expected to have been
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created by hklgen and to include all the angle settings. The optional
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parameter iSkip determines the number of lines to skip in the file. This
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feature allows to continue measurement on not fully processed files.
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<DT>dataset reopen filename
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<DT>dataset reopen 001/trics2005n000051
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<DD>Reopens an already existing file set for appending. Only the file root
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without directory info or endings needs to be given.
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<DT>dataset close
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<DD>Closes the current data file set.
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<DT>dataset file
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<DD>Prints the current data file name.
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<dt>dataset list
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<dd>prints the current parameters.
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<dt>dataset calc file
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<dd>Tries to calculate all the reflections listen in file and prints an estimate how
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many reflections are within limits. As file format only a H,K,L type file is
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supported.
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</dl>
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Then there are a few parameter commands. They follow the general scheme:
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<dl>
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<DT>dataset parameter
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<DD>Prints the current value of the parameter
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<DT>dataset parameter value
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<DD>Sets the parameter to the new value.
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</dl>
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This object knows about the following parameters:
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<dl>
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<DT>countmode
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<DD>The counting mode to use. Possible values are timer or monitor.
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<DT>preset
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<DD>The preset to use for counting
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<DT>np
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<DD>number of points to collect for each profile.
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<DT>step
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<DD>The step width in omega to use for scanning.
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<DT>compact
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<DD>Determines if the scan data output to the SICS is in normal
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(compact = 0) or condensed (compact = 1) form. The default is 1.
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<DT>weak
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<DD>0 or 1: switches on special processing of weak reflections.
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<DT>weakthreshold
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<dd>The threshold used to decide what constitues a weak reflection. The test is:
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max count in scan - 2* min count in scan.
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<dt>fastscan
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<dd>0 or 1: switches fastscan mode.
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<dt>psimode
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<dd>0 or 1: switches psi scanning mode. Please note that suitable HKL input files for this mode
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must contain four numbers: H, K, L and psi.
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<dt>psd
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<dd>0 or 1: switches on PSD mode for measuring with the area detector. Currently this is mapped
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to doing a tricsscan with the scan parameters as evaluted from the two theta range table. The
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psi, compact and weak flags are ignored in PSD mode. Only a log file is openend, the rest of
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the file management is done by tricsscan.
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</dl>
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</p>
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<p>
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Then there are command which allow to configure the table of two theta ranges and
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scan parameters. All table related commands start with: dataset table. The following
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commands are supported:
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<dl>
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<dt>dataset table list
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<dd>prints the content of the table.
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<dt>dataset table add end scanvar step np
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<dd>configures a two theta range. The end parameter describes the end of the two theta range to
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which these parameters can be applied. Scanmode can either
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be om for omega scans or o2t for omega 2 theta scans. step is the step width to use. np is the
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number of points in the scan.
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<dt>dataset table del num
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<dd>deletes the entry num from the table. Counting starts with 0!
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<dt>dataset table clear
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<dd>clears the whole table.
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</dl>
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When there is no two theta range configured for a given two theta value, the omega scan
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mode applies with the step width given as a parameter to dataset.
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</p>
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<p>
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dataset supports two geometries: the first is the usual bisecting geometry. The
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second is the normal beam geometry where the detector is moved out of plane.
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This is accounted for by two switches:
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<dl>
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<dt>dataset bi
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<dd>switches into bissecting mode. This is the default.
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<dt>dataset nb
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<dd>switches into normal beam mode.
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</dl>
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</p>
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<p>
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This object supports some file management functionality. It caters
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for the problem that experiments may need to be continued. Thus reopening
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files and continuation of reflection processing at a point way down the
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reflection file is supported. Consequently the start of a new experiment
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requires the following steps:
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<ul>
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<li>Create a new set of files with <b>dataset start</b>.
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<li>Configure the scans with the parameter commands.
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<li>Start processing a reflection file with either the <b>dataset genlist</b>
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or <b>dataset measure</b> commands.
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</ul>
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If you need to continue reflection file processing after an abort or after
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solving a problem the following steps are required:
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<ul>
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<li>Determine the file number you were working at and the line number in the
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reflection file where you wish to continue processing.
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<li>Set the file root with the <b>dataset reopen</b> command.
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<li>Configure the scan parameters again.
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<li>Restart the measurement with either <b> dataset genlist</b> or <b> dataset
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measure</b> but specify the iSkip parameter according to the position in
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the reflection file where processing should continue.
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</ul>
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</p>
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</BODY>
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</HTML>
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