Re: Meanwhile, back in the lab...

In article <d6i7e3$h7v$1@xxxxxxxxxxxxxxxxxxxxxxxx>, glhansen@xxxxxxxxxxxxxxxxxxxxx (Gregory L. Hansen) writes:
>In article <1116467397.252775.237190@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
>Sbharris[atsign]ix.netcom.com <sbharris@xxxxxxxxxxxxx> wrote:
>>Greg, was my last question to you too difficult to answer off hand?
>>
>>The question I have is this: what happens when you run "few mev"
>>protons or neutrons through single crystals of (say) graphite at small
>>angles in comparison to the plane defined by the sheets of C atoms.
>>With the beam passing orthogonally (the 001 direction) through the
>>common plane defined by the stacked sheets, you'd get one attenuation
>>coeefficient. And presumably at right angles to that, so the particles
>>were passing straight down the "alleys" between the sheets (the 112
>>direction) you'd get another coefficient. In both cases these would
>>related to the average density of the crystal in the direction of
>>interest. But now, what happens when you tilt the thing just a little
>>in either direction from 112??? Do the particles now go off greatly to
>>one side or the other? And is the effective shielding coefficient per
>>mass a LOT greater in the direction where the particles DON'T go, than
>>you could get with other materials?
>>
>
>
>Sorry, I didn't see it before. I search for "hansen", so that's a sure
>way to catch my attention. Otherwise, whether I read a message or not is
>more or less by chance.
>
>But the angle of incidence still equals the angle of reflection, and that
>angle is relative to a scattering plane. The Bragg peaks in an ideal
>crystal are delta functions, any real crystal has peaks of a certain
>width, the Darwin width(?), that depends on its size and quality.

Oh, no. The Darwin width of a perfect crystal with unlimited size is
still finite. Imperfections, absorption and other issues may broaden
it further but even an ideal crystal doesn't give a delta function.

Mati Meron | "When you argue with a fool,
meron@xxxxxxxxxxxxxxxxx | chances are he is doing just the same"
.