Shutterless data collection


Shutterless data collection is achieved performing a continuous rotation around the Phi (or Omega) axis while the Pilatus 6M is acquiring with a predefined frame rate for a total number of frames.

The frame rate (also called exposure period) is given by the exposure time + readout time. The readout time is set to be of 3ms and is a hardware limit of the Pilatus 6M.

As in a classical data collection, users need to provide the following parameters:

Oscillation start, Oscillation range, Exposure time and Number of frames.

To have better data it is advisable to use "fine slicing" (or small oscillation range) and of course short exposure time for each frame.

At present the minimum exposure time achievable is 125ms (0.125 s, corresponding to the frame rate of 8Hz, or 8 images/s). Fine slicing is intended as oscillation range being half of mosaicity of the crystal.

For example if you want to collect 90 degrees from a crystal with mosaicity 0.4 an advisable diffraction plan as the following:

  • Oscillation start: as given by strategy
  • Oscillation range: 0.2 degree
  • Exposure time: 0.125 s
  • Number of frames: 450

In this way every frame will be collected every 0.128 s (0.125 s + 0.003 s) for a total of 450 frames. The diffractometer will take care of setting the right (constant) speed (in this case 0.2degree/0.128s). The data not acquired during the 3ms of readout time should be neglectable.

Please note the following:

  • Shutterless is the default mode to collect data (it can always be disabled in the collect pop-up window, see image below)
  • Shutterless is automatically disable if overlap is different from 0
  • Inverse beam works only in "classic" data collection (for the moment)
  • Same applies to Helical and Mesh Scan

pilatus_mxcube1.jpg (shutterless popup)