Sample Centering

The goniostat at BM16 is a single HUBER rotation axis which can be controlled using the SampleVideo application running on xPicasso (the computer in the experimental hutch) or via MxCube running on bm16mach in the control hutch. The GUI is very intuitive but is still in beta testing mode so please report any bugs or problems to your LC!

SampleVideo

The SampleVideo GUI provides an interface to assist in sample manipulation, visualization and centering, and enables the user to align the crystal semi-automatically using the 3-click method. The GUI also provides an accurate scale (in green at the bottom of the screen) for accessing the size of your crystals and has a snapshot option for taking high resolution images of your sample before or after a data collection.

3-Click Centring using the SampleVideo application

The blue box represents the beam profile at maximum zoom the red cross represents the rotation axis.

1. click on the arrow next to the Zoom button and select Zoom 0
2. if you still cannot see your sample or loop when the camera is at minimum zoom (Zoom 0) the sample is off the edge of the screen and should be translated horizontally to bring it into the cameras field of view. To do this input a new value into the box marked gonioz and press return or use the arrows next to the gonioz box to translate the sample horizontally in small steps until it is roughly centered on the small red cross.

   Note: you can change the speed of each of the gonio motors by clicking on the box next to the motor and selecting a different step-size or by typing a new value in the step size box and pressing return (fastest speed 0.5 mm/step)

3. once the sample is aligned horizontally you can rotate it by clicking on the Phi buttons in the bottom left section of the GUI which allow you to make absolute movements to 0, 90, 180 or 270 degrees phi or relative movements of +/- 90 or +/-1 degrees phi. The current position of the phi is displayed at all times in the Phi box.

   Tip: you can also rotate the phi motor freely rotated to any value you input into this box.

4. to be begin centering your sample select the 3-Click button at the top left of the screen
5. a line will appear at the top of the screen asking you to click on the center of your crystal. When you have done this a small green cross will appear at the point you click and the crystal will be rotated by 90 degrees.
6. when the crystal stops moving click on the center of the crystal again and it will be rotated by another 90 degrees

   Note: if your crystal doesnt move read the message on the screen to see if your last click has been accepted.

7. when the crystal stops moving make the final click on the center of the crystal and your sample will be aligned horizontally and vertically
8. after this rough alignment at minimum zoom select Zoom 8 from the Zoom box and redo the 3 click alignment at the highest magnification
9. at maximum zoom the beam profile is given by the blue box on the screen and the rotation axis is marked by a red cross. Both these parameters will be set by your LC at the beginning of your beamtime.

If the SampleVideo application crashes or hangs - just click on the X in the top right hand corner of the window to close the application then restart the application by clicking on the SampleVideo icon  on the desktop of xpicasso.