The UB Matrix Widget

The figure below displays the UbMatrix widget.

Figure 8.16: The UB Matrix Widget

The explanation of the elements:

 Crystal

 Delete
Deletes the current crystal.

 New Creates a new crystal. The name is prompted.

 Misc

 Alignment
Starts the alignment widget.

 UB Matrix
It is read from the diffractometer server. The server calculates the UB matrix using the lattice parameters and two reflections (ComputeU) or using the lattice parameters and the U vector (UpdDiffSrv).

 Reflections
The reflections are used to find the orientation of the crystal (ComputeU, Affine). They are stored by th Alignment widget.

 U Vector
Describes the rotations about the various axes. The angles are specified in degree. The U vector is read/write. For the 'UpdDiffSrv' command it is an input and in case the 'ComputeU' command has been executed, it displays the result.

 Lattice
The entry widgets contain the lattice parameters. Depending on the way how the UB matrix is calculated these parameters are input or output.
ComputeU: The lattice parameters are supplied by the user. If the 'ComputeU' button is pressed the parameters are copied to the server and the UB matrix is calculated using the first two reflections.
Affine: The lattice parameters are copied from the server after the UB matrix is calculated from more than 2 reflections.

 Parameters:

 Mode
This menu button specifies the constraints.

 ASN
A point in momentum space corresponds to various sets of angles. ASN is an index that selects one of these sets. ASN = 0 points to the nearest angular combination.

 Xtal
Selects the current crystal (UB matrix).

 Wavelength
The current wavelength.

 Edit Reflections
Invokes a widget that allows you to change the parameters of the reflections and to change the order of the reflections. Note the 'ComputeU' looks at the first two reflection.

 UpdDiffSrv
Writes the lattice parameters and the U vector to the diffractometer server and reads the UB matrix.

 ComputeU
Executes the ComputeU command on the diffractometer server. The lattice parameters and the first two reflections are used to calculate the UB matrix and the U vector.

 Affine
Uses the simplex method to calculate the lattice parameters and the U matrix. Needs at least 3 reflections. The SOLEIL GUI can be used to select the parameters that are optimized. 'Affine' is not fully tested.