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Diffraction is a process that occurs over dozens of unit cells. There must be long-range distortions to impact it.
James, thanks for the useful comments on radiation damage! Long range effects are sometimes seen as lattice parameter drifts. Ending up with a distribution of unit cell parameters in the crystal ought to smear out the high resolution peaks more than low resolution peaks. I would be interested to hear (simple) explanations as to why the unit cell generally expands with increasing dose, and if there is an equally simple reason why it sometimes starts off by contracting and then later expands as for "normal" samples... For this particularly sensitive sample it might be interesting to check how the cell parameters vary with time and check if that variation is very different from crystals which last longer in the beam.
As to reducing radiation damage, try to grow a bigger crystal. A 2X bigger crystal scatters 8X stronger and so should give 8X more data...
Jon
