General data collection strategy (very important on 23-2 and 29)

- Start with either a known sample (benchmark?) or a crystal that is less important. It will allow you to see how your sample behaves in the beam (radiation damage, etc...) and to learn how to use the beamline (exposure time, oscillation range, etc...). It is better to make mistakes with a bad crystal than with the only possible good crystal from your most important project...

- Crystal centering can be long and difficult with very small crystals. It is better to try to collect a test diffraction image when the loop is face on (input  the correct phi position at the start of the data collection) in order to assess the crystal quality. If it is worthwhile, you can then spend time rather than wasting time when centering a non diffracting crystal...

- Crystal centering is a critical issue with very small crystals. Start from low magnification and go to higher magnification with repetitive centering. The three click centering works well if you click always on the same point on the crystal: take care to click always along the same vertical line and be careful with the lens effect when the crystal is like a little fish in a large amount of cryoprotectant.

- Small crystal + small intense beam = RADIATION DAMAGE! Do not expect to collect 360 degrees from a single crystal section with 100 % beam transmission... Generally, you may have to collect several datasets from several parts of the same crystal or from several crystals. 100 s total exposure time with 100 % transmission seems to be a realistic limit.

The data collection software running on the MX Beamlines is called MXCuBE (MX Customised Beamline Environment).

Data Collection using MXCuBE

Data collection is controlled from the beamline control computers using the beamline control module (BCM) MxCuBE. To launch the GUI, click on the MxCuBE icon on the desktop. You also need to have the Experimental Spec session running (to start the Exp Spec session click on the Spec icon on the desktop). A snapshot of the GUI with main features is shown below.

Single Wavelength Experiment

For a single-wavelength experiment follow the steps below :

Login with your proposal name and password (e.g. mx123 and smmx123 where Smith is the name of the main proposer). Fill in the data collection parameters (such as exposure time/no. of frames/passes etc). Give directory and image pre-fix (the default directory path is suggested by MXCuBE and should be /data/idxxehx/external/mx123/). Start/stop the data collection with the start/stop button!

Multiple Wavelength Experiment (MAD)

In addition to the steps for single wavelength experiments, using the pull down sample exposure mode menu in the Collect tab of the MXCuBE GUI, select MAD mode. This will result in an "Edge Scan" button appearing next to the Energy tab. Clicking on this button will launch a MAD energy scan window (snapshot coming soon on this page). From here it is possible to select an absorption edge to scan. The GUI will automatically perform the edge scan for you and run Chooch to calculate the experimental anomalous scattering factors for your sample. All data are saved in a sub-directory specified in this window.