Helical data collection

The purpose of this macro is to collect data when moving a sample between two centred positions in the beam. It exists today as test version using line commands in spec(exp). It is not really "user friendly" and it is intended to be used by "experts" due to some limitations (see section caution below). Integration in mxCuBE will be done if this feature is giving good results, feedback is wellcome.

In spec(exp):

- helical_oscil_on  (to initialize the macro)
- helical_getpos 2 (after having centered the end position)
- helical_getpos 1 (after having centered the starting position)
- start the data collection  (in mxCuBE, as usual)
- helical_oscil_off  (when you have finish to use it).

 

Caution:
- test images to check the crystal centring can not be collected when the macro is in use, be sure you can center properly the crystal before using.
- centring positions stay in the system memory, even if a new crystal is loaded : MAKE SURE THAT THE MACRO IS DISABLED (helical_oscil_off) WHEN YOU HAVE FINISHED, a "reconfig" in spec(exp) should do it too.
- the macro gives best results when the crystal is homogeneous; parameters like mosaicity can vary along a crystal and it will affect the data quality.
- data processing is fine when using XDS. Using MOSFLM may lead to warning messages (like "crystal slippage") and refinement of the orientation matrix may be necessary.