cbcd98c10c
This directory was accidentally omitted from the merge-release branch during the PSI code merge.
409 lines
22 KiB
XML
409 lines
22 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<?oxygen RNGSchema="http://www.oasis-open.org/docbook/xml/5.0/rng/docbook.rng" type="xml"?>
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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0">
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<info><title>TASUB: The Triple Axis Calculation Module</title><author>
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<personname>Mark Koennecke</personname>
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</author>
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<date/>
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</info>
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<sect1>
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<title>TASUB: The Triple Axis Calculation Module</title>
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<para>On a triple axis instrument the parameters incoming energy, Q-position in 3D and
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analyzed energy have to be changed frequently. These calculations are the task of the
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TASUB module. This module uses the calculus described by M. Lumsden, J. L. Robertson and
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M. Yethiraj in J. Appl. Cryst. (2005), 38, 405-411. The special feature of this
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algorithm is that the tilt cradles of the sample table are used to help during alignment
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and in order to drive out of plane (within the limits of the tilt cradles). For
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alignment, two reflections must be located and their angles and Q-E parameters entered
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into the module. Then a UB matrix can be calculated. With a UB matrix, the Q-E variables
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ei, ki, ef, kf, en, qh, qk and ql can be driven as virtual motors in SICS. </para>
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</sect1>
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<sect1>
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<title>Commands understood by Tasub</title>
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<sect2>
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<title>Monochromator and Analyzer Parameters</title>
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<para>Incident and scattered energies are defined by monochromator crystals. In order
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for the calculations to work, some parameters need to be configured. Monochromator
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and analyzer parameters can be accessed with the prefixes: The parameter syntax used
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is as usual: giving only the parameter name queries the value, giving the parameter
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plus a value sets the parameter to the new value. The following parameters are
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supported: </para>
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<variablelist>
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<varlistentry>
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<term><command>tasub mono</command>
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</term>
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<listitem>
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<para>Monochromator properties </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub ana</command>
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</term>
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<listitem>
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<para>Analyser properties </para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Allowed <command>properties </command> for <command>tasub mono</command> and
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<command>tasub ana</command> one of:</para>
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<variablelist>
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<varlistentry>
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<term><command>dd</command></term>
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<listitem>
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<para>The d-spacing of the reflection used </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>ss</command>
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</term>
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<listitem>
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<para>The scattering sense, 1 or -1 are possible. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>hb1</command>
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</term>
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<listitem>
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<para>First parameter for the calculation of the horizontal curvature
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>hb2 </command></term>
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<listitem>
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<para>Second parameter for the calculation of the horizontal curvature
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>vb1</command>
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</term>
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<listitem>
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<para>First parameter for the calculation of the vertical curvature </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>vb2</command>
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</term>
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<listitem>
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<para>Second parameter for the calculation of the vertical curvature </para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Examples: </para>
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<variablelist>
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<varlistentry>
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<term><command>tasub mono dd </command></term>
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<listitem>
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<para>will print the current d-spacing of the monochromator </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub mono dd </command><replaceable>4.3</replaceable>
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</term>
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<listitem>
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<para>Will set the d-spacing of the monochromator to 4.3 </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub mono ss </command></term>
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<listitem>
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<para>will print the scattering sense of the monochromator </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub ana ss </command></term>
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<listitem>
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<para>will print the scattering sense of the analyser </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub ana ss 1</command></term>
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<listitem>
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<para>will set the scattering sense of the analyser to 1</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2>
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<title>Cell Parameters</title>
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<para> In order for the UB matrix calculation to work, the cell constants must be known: <variablelist>
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<varlistentry>
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<term><command>tasub cell </command></term>
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<listitem>
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<para>This command prints the current cell parameters. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub cell </command><replaceable>a b c alpha beta
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gamma</replaceable>
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</term>
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<listitem>
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<para>This command sets the new cell parameters. All six values must be
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given. </para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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</sect2>
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<sect2>
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<title>Reflection Management</title>
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<para> In order to calculate a UB matrix a list of reflections must be maintained. This
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is done with the commands in this section: <variablelist>
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<varlistentry>
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<term><command>tasub clear </command></term>
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<listitem>
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<para>Clears all reflections except the first reflection from the
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reflection list </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub clear all</command></term>
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<listitem>
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<para>Clears all reflections</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub listref</command>
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</term>
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<listitem>
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<para>Prints a list of all known reflections. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub del </command><replaceable>num</replaceable>
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</term>
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<listitem>
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<para>Delete the reflection number num from the list </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub addref </command><replaceable>qh qk ql </replaceable></term>
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<listitem>
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<para>Adds a reflection to the list. The indices of the reflections are
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given. The angles and energy values are read from the motors. Use
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this command only when the instrument is positioned right on a
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reflection. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub addref </command><replaceable>qh qk ql a3 a4 sgu sgl ei
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ef </replaceable></term>
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<listitem>
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<para>Add a new reflection to the list. Besides the indices all angles
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are given: a3, the sample rotation, a4, sample two theta, sgu, upper
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tilt cradle, sgl, lower tilt cradle and incoming energy ei and
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outgoing energy ef. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub addauxref </command><replaceable>qh qk ql
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</replaceable></term>
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<listitem>
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<para>Adds an auxiliary reflection with indices qh, qk, ql to the list.
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A4 is calculated from cell constants. A3 is either left alone or is
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calculated to have the correct angular difference to a previous
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reflection. This is a help for setting up the instrument or running
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powder mode. When a UB has been generated from auxiliary
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reflections, a3, sgu and sgl angles will be incorrect. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub repref </command><replaceable>id qh qk ql a3 a4 sgu sgl
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ei ef </replaceable></term>
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<listitem>
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<para>Modifies the reflection with id id to have the values given.
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</para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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</sect2>
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<sect2>
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<title>Calculations</title>
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<para> This section covers the parameters and commands to use to make the module do
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calculations for you. <variablelist>
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<varlistentry>
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<term><command>tasub const ki | kf | elastic </command></term>
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<listitem>
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<para>Sets a parameter to determine if KI or KF is fixed when the energy
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transfer en is being driven. Allowed values: ki, kf, elastic. In
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elastic mode the analyzer is disregarded. This is useful for two
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circle diffractometers. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub const </command></term>
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<listitem>
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<para>Prints if ki or kf is fixed. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub ss </command></term>
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<listitem>
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<para>Prints the sample scattering sense. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub ss 1 | -1 </command></term>
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<listitem>
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<para>Sets the sample scattering sense. Allowed values are either 1 or
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-1. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub silent 0 | 1 </command></term>
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<listitem>
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<para>Prints or sets the silent flag. If this is 0, the messages Driving
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motor .. from .. to .. are suppressed.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub outofplane 0 | 1 </command></term>
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<listitem>
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<para>Prints or sets the outofplane flag. If this flag is 0, the
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instrument will stay in the scattering plane and not move out of it.
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This is here in order to protect those bloody magnets which cannot
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be tilted.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub makeub</command><replaceable> r1 r2 </replaceable></term>
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<listitem>
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<para>Calculate a new UB matrix from the current cell constants and the
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entries r1 and r2 in the reflection list. r1 and r2 are integer
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numbers. This command will not only print the new UB matrix but also
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the results of various back and forth calculations performed with
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the new UB matrix. This can be inspected in order to check the new
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UB. WARNING: The calculation will go wrong if the scattering sense
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at the sample has changed since the reflections used for the UB
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matrix determination have been entered. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub listub </command></term>
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<listitem>
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<para>prints the current UB matrix. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub calcang </command><replaceable>qh qk ql ei ef
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</replaceable></term>
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<listitem>
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<para>Will calculate new angles for the Q-E position specified. The
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angles will be printed in the order: monochromator two theta, sample
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rotation, sample two theta, lower tilt cradle, upper tilt cradle and
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analyzer two theta. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub calcqe </command><replaceable>a2 a3 a4 sgu sgl a6
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</replaceable></term>
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<listitem>
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<para>Calculates and prints the Q-E position from the angles given: a2 =
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monochromator two theta, a3 = sample rotation, a4 = sample tow
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theta, sgu = upper tilt cradle, sgl = lower tilt cradle and a6 =
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analyzer two theta. The Q-E position is printed in the sequence: qh,
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qk, ql, ei, ef. </para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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</sect2>
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<sect2>
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<title>Virtual Motors</title>
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<para> The tasub module also installs the following virtual motors into SICS: ei, ki,
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qh, qk, ql, en, ef, kf and qm. All these motors can be used in SICS drive, run or
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scan commands like real motors. Driving them triggers a recalculation of angles and
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the drives the real motors to appropriate values. The virtual motors have a very
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limited command set (shown at the example of qh): <variablelist>
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<varlistentry>
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<term><command>qh</command>
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</term>
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<listitem>
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<para>The name of the motor alone will print its current position.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>qh</command>
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<replaceable>target</replaceable>
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</term>
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<listitem>
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<para>This will print the last requested target position for this
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virtual motor. </para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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<para> The virtual motor qm implements <emphasis role="b">powder mode</emphasis>. In
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this mode, only the sample two theta and energy motors will be driven, sample
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rotation and tilt cradles will be left at their respective positions. This is
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commonly used to analyze the energy transfer of powder samples. </para>
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<para> There are other important command: <variablelist>
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<varlistentry>
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<term><command>tasub update </command></term>
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<listitem>
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<para>This command will force a recalculation of the current Q-E
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position for the virtual motors from angles. Normally tasub will
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take care of this. However, if any of the angle motors are moved
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directly or manually, this command might be required. The SICS dr
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wrapper command, however, even takes care of this. </para>
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</listitem>
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</varlistentry>
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</variablelist><variablelist>
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<varlistentry>
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<term><command>tasub updatetargets</command>
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</term>
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<listitem>
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<para>This command makes the QE targets match the current position. This
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is useful after initialization in the instrument.tcl file.</para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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</sect2>
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<sect2>
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<title>Internal Commands</title>
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<para>The tasub module supports some more commands which are used by SICS in order to
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restore the tasub configuration between instantiations of SICS. These commands are
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documented here for the sake of completeness: <variablelist>
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<varlistentry>
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<term><command>tasub setub </command><replaceable>ub11 ub12 ub13 ub21 ub22
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ub23 ub31 ub32 ub33 </replaceable></term>
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<listitem>
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<para>Sets the UB matrix. Nine values are required. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub setnormal </command><replaceable>n1 n2 n3
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</replaceable></term>
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<listitem>
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<para>This command sets the plane normal which is required in
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calculations. Normally this plane normal is automatically generated
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during the calculation of the UB matrix. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub settarget </command><replaceable> qh qk ql qm ki kf
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</replaceable></term>
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<listitem>
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<para>Sets the Q-E target. </para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub</command>
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<replaceable> r1 qh qk ql a3 a4 sgu sgl ki kf </replaceable></term>
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<listitem>
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<para/>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>tasub </command><replaceable>r2 qh qk ql a3 a4 sgu sgl ki kf
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</replaceable></term>
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<listitem>
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<para>These commands set the values for the two reflections used for
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generating the UB matrix. </para>
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</listitem>
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</varlistentry>
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</variablelist></para>
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</sect2>
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</sect1>
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</chapter>
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