On 10-10-15 10:37 AM, James Holton wrote:
...
In fact, anyone with a Pilatus detector (and a lot of extra beam
time) can verify the self-interference of photons in macromolecular
crystal diffraction. Since the source-to-detector distance of a
typical MX beamline is about 30 m, it takes 100 nanoseconds for a
"photon" generated in the storage ring to fly down the beam pipe, do
whatever it is going to do in the crystal, and then (perhaps)
increment a pixel on the detector. So, as long as you keep the time
between photons much greater than 100 nanoseconds you can be fairly
confident that there is never more than one photon anywhere in the
beamline at a given instant.
...
Does the length of the beamline really matter? As long as the photons
are spaced apart more than the coherence length (several 1000 A to
several 10um on a synchrotron beamline according to Bernard's post) they
should be considered independent events. So the photon rate can probably
be 5 to 6 orders of magnitude higher while still doing "single photon
diffraction" experiments.
Bart
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Bart Hazes (Associate Professor)
Dept. of Medical Microbiology& Immunology
University of Alberta
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phone: 1-780-492-0042
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