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PSI sics-cvs-psi-2006

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koennecke
2006-05-08 02:00:00 +00:00
committed by Douglas Clowes
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html><head><title>Conescan.radi</title></head><body>
<h2>Conescan </h2>
<p>A conescan is a possibly useful procedure when setting up a single crystal
diffraction experiment. The first thing which needs to be done when
starting a single crystal experiment is the determination of the UB
matrix. In order to do that at least two reflections need to be
located through a search procedure. Now, consider the situation when
one reflection has been found and indexed. Then it is known that other
reflections can be found on a cone
with an opening angle determined by the lattice parameters and the
indices of the target reflection around the first (center)
reflection. The SICS conescan module allows to do just that, do a scan
around a given center reflection. The syntax is:
</p></p><dl><dt>conescan list
<dd> lists all the parameters of the conescan
<dt>conescan cell
<dd> prints the cell constants.
<dt>conescan cell a b c alpha beta gamma
<dd> sets new cell constants.
<dt>conescan center
<dd> prints the current values for the center reflection
<dt>conescan center h k l
<dd> uses h, k, l as the indices of the center
reflection. Motor positions are read from motors.
<dt>conescan center h k l stt om chi phi
<dd> defines a center position
complete with all angles.
<dt>conescan target
<dd> prints the current target for the conescan
<dt>conescan target h k l
<dd> defines the target indices for the conescan.
<dt>conescan qscale
<dd> prints the Q scale for the conescan. The conescan
module calculates the length of then scattering vector from the
lattice parameters and the indices. When the lattice constants are
only approximatly known it might be useful to vary the scattering
vector length for the conescan a little. This can be doen with the
qscale factor.
<dt>conescan qscale value
<dd> sets a new value for the qscale factor
<dt>conescan run step mode preset
<dd> starts a conescan with the nstep width
step, the couent mode mode and the preset preset.
<dt>conescan run
<dd> starts a conescan with defaults: step = .5,
mode = monitor, preset = 10000
<p></dl>This is the simple usage of the conescan. In fact cone is implemented
as a virtual motor. This means that arbitray scans can be performed on
cone as with any other motor. As with any other motor, cone can also
be driven to a cone angle.
</p></p><h3>Implementation Reference </h3>
<p>The conescan commands are just wrapper routines around the cone and
ubcalc module which actually work together to implement the
conescan. The ubcalc module, documented elsewhere, holds the cell
constants and the center reflection.
</p></p><p>The cone module does the actual cone calculation. Cone can be
configured with commands:
<dl></p><dt>cone center
<dd> prints the number of the reflection in ubcalc to use as
a center.
<dt>cone center num
<dd> sets the reflection in ubcalc to use a the center
for driving on the cone. Set to 0 to use the first reflection in
ubcalc.
<dt>cone target
<dd> prints the target reflection indices for the cone.
<dt>cone target h k l
<dd> sets the target reflection indices.
<dt>cone qscale
<dd> prints the current value of the scattering vector scale.
<dt>cone qscale val
<dd> sets a value for the scaling factor for the
scattering vector. Values should be close to 1.0;
</dl></body></html>