Hi Fellows,
the idea for this work came from my initial excitement about the FEL, because a
coherent source of photons
would I principle allow a reflection-wise interference experiment. The reasons
Ed gave, make this kind
of experiment impractical. The key difference is, that the proposed experiment
is a single photon experiment,
and absent some of the instrumental challenges Gerd alluded to, the remaining
problem is the probe photon
interaction in the delayed-probe experiment (tactfully omitted in fig 1).
I am sure I will have an update in a year from now.
Cheers, BR
-----Original Message-----
From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> On Behalf Of Rosenbaum, Gerold
Sent: Wednesday, April 1, 2020 19:31
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] New phasing approach
The x-ray interferometer is not a joke. In about 1974, Gerd Materlik built one
for his thesis and inserted it in front of my beamline at the DESY synchrotron.
The beam splitters and "mirrors" were all carved out of a single block of
perfect single crystal silicon. He inserted a wedge of plastic in one arm
acting as a phase shifter and produced dark and white bands in a film. I was
really, really impressed.
As for the three-beam experiments by Edgar Weckert and K. Hümmer, carried on by
Bob Sweet, as impressive it is to get precise phase measurements for a
reflection, there is a practical downsided: the radiation dose for measuring
one reflection to a few % is as high as the dose for a whole data set from
which we conventionally extract the phases of all reflection though only at
about 30% but still good enough to solve the structure.
I have the inkling that Bernhard's phase retrieval would suffer the same death:
only the ultra-parallel fraction of the x-ray beam passes through the
interferometer cutting down tremendously the intensity of reflections from
macromolecular crystals which tend to be far from parallel.
Gerd
On 01.04.2020, 16:02, "CCP4 bulletin board on behalf of Tim Gruene"
<CCP4BB@JISCMAIL.AC.UK on behalf of tim.gru...@univie.ac.at> wrote:
Dear Bernhard,
your paper is actually not so much of a joke. Are you aware of K. Huemmer's
and E. Weckert's three-beam experiments? See e.g.
https://link.springer.com/chapter/10.1007/978-1-4615-5879-8_24
Best regards,
Tim
On Wednesday, April 1, 2020 4:00:19 AM CEST Bernhard Rupp wrote:
> Hi Fellows,
>
>
>
> just in time for a little reading during quarantine-induced boredom here
> preprint pages
>
> (embargoed until 04.01) from my recent Phys. Rev. paper with a different
> take on phasing
>
> https://tinyurl.com/Phys-Rev-2020
>
>
>
> Enjoy, BR
>
> ------------------------------------------------------
>
> Bernhard Rupp
>
> <http://www.hofkristallamt.org/> http://www.hofkristallamt.org/
>
> <mailto:b...@hofkristallamt.org> b...@hofkristallamt.org
>
> +1 925 209 7429
>
> ------------------------------------------------------
>
> Department of Genetic Epidemiology
>
> Medical University Innsbruck
>
> Schöpfstr. 41
>
> A 6020 Innsbruck
>
> <mailto:bernhard.r...@i-med.ac.at> bernhard.r...@i-med.ac.at
>
> +43 676 571 0536
>
> ------------------------------------------------------
>
> Many plausible ideas vanish
>
> at the presence of thought
>
> ------------------------------------------------------
>
>
>
>
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--
--
Tim Gruene
Head of the Centre for X-ray Structure Analysis
Faculty of Chemistry
University of Vienna
Phone: +43-1-4277-70202
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