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