Within the concept of the AbstractDiffractometer there are certain number of roles, which are fixed and define a corresponding motor or nstate actuator object.
This allows them to be used in a standard way by the MXCuBE application (web or Qt).
We also introduce a convention about the direction of the alignment and centring motors:
- z axis is in the direction of gravity. Positive direction is upwards.
- y axis is perpendicular to the z axis and to the nominal beam direction. Positive direction is so that x,y,z would form a right-handed coordinate system.
- x axis is orthogonal to the y and z axes (and approximately parallel to the beam). Positive direction is from the sample towards the detector.
Here follows the list of the fixed roles and the description of the corresponding objects, accessible via beamline.diffractometer hardware object.
1. Motor objects (roles) and their functionality:
- omega - the rotation axis, independent of the orientation (up, down or side). Positive direction is clockwise
- kappa - the rotation axis between the omega and kappa_phi axes. Positive direction is a right-handed rotation. Not present on all goniostats.
- kappa_phi - the rotation axis directly attached to the sample. Positive direction is a right-handed rotation. Not present on all goniostats.
- sampx - centring table x axis
- sampy - centring table y axis
- focus - alignment table x axis
- phiy - alignment table y axis
- phiz - alignment table z axis
- sample_horizontal - Pseudomotor approximately along the y axis. Generated by phiy or a combination of sampx, sampy depending on goniostat
- sample_vertical - Pseudomotor approximately along the z axis. Generated or phiz or a combination of sampx, sampy depending on goniostat
- backlight - adjust the intensity of the back light
- frontlight - adjust the intensity of the front light
2. Discrete (N) state equipment and its functionality:
- zoom - zoom levels
- fshutter - fast shutter - allow beam on the sample
- beamstop - put in front of a detector to avoid the direct beam.
- capillary - if present, a tube to reduce the scattering background.
- backlightswitch - move the backlight on the level of the onaxis viewer
- frontlightswitch - switch on/off the front light
- fluo_detector - if present, actuator to move a fluorescence detector close to the sample
Possibly there is equipment physically part of the diffractometer, but not accessed via beamline.diffractometer:
- aperture - Device to define the beam size - beamline.beam.aperture
- cryostream - beamline.cryo