I wondered how the temperature of a beryllium filter might affect the
distribution of an approximately monochromatic neutron beam. Longer
wavelengths are more strongly absorbed, so the distribution should shift
to shorter wavelengths as the beam goes through materials. Filter area
increases as temperature increases, which drops the cross-section
accordingly, so a higher temperature should shift the peak to a shorter
wavelength. Less dense material means the higher-order harmonics aren't
filtered quite as thoroughly, too.
But what about Doppler shifting? There's no resonances to broaden at the
wavelengths beryllium would be a filter material for (I'm using five
Angstrom). It seems like something Doppler-related should happen, like
increasing the effective speed of a typical neutron. But I don't know how
to estimate that effect.
Know of any good reading material?
--
"Things should be made as simple as possible -- but no simpler."
-- Albert Einstein
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