The mirror was set up for a run at the Pd K-edge, according to the
problem statement. Therefore, its nominal angle must be such as to put
the critical energy >25keV. An angle of 3mrad would do it. At that
angle, the reflectivity (assuming no roughness) goes up with energy in
the relevant range, but only by a few percent.
We're not told what the ratio of gains of the current amps is, or
whether the ion chambers have the same path length, so we can't tell
whether the signals are comparable, as shown on the graph, or orders of
magnitude different.
mam
On 6/14/2023 10:17 PM, Jeffrey Terry wrote:
Well, I’ll take a shot. Looks like the mirror angle is totally fubared,
you are getting Bragg peaks from the coating or substrate that are
giving you the peaks in Io. Since you have no idea what angle those are
going through Io, they are unlikely to make it into either the sample or
It. Since those photons are removed from the beam hitting the sample,
they would show up as intensity dips in It. I’d bet that most (all?) of
the reflected beam is not going into the sample. I’m kind of surprised
It signal is as clean as it is, but then I don’t know the gains on
either measurement amplifiers. I couldn’t find a flat mirror angle that
would cause the cutoff at 12870? eV but since it is a collimating mirror
who knows what range of angles were actually being hit.
Jeff Terry
Interim Chair, Department of Biology
Interim Chair, Department of Social Sciences
Professor of Physics
Professor of Mechanical, Materials, and Aerospace Engineering
Editor, Applied Surface Science
Illinois Institute of Technology
3101 S. Dearborn St.
Chicago IL 60616
630-252-9708
On Jun 14, 2023, at 7:27 PM, Anatoly Frenkel
<anatoly.fren...@stonybrook.edu
<mailto:anatoly.fren...@stonybrook.edu>> wrote:
Hello, all. It is a low- to medium- level brain teaser.
Pt-coated collimating mirror was in place for Pd K-edge measurement,
but Au L3-edge of Pd-Au alloy was measured (for testing purposes). I0
and It detectors were both Ar filled ionization chambers. Because of
the energy dependence of reflectivity of the Pt mirror, I0 intensity
was strongly nonlinear (blue curve). However, the transmission
intensity in the It detector was almost linear (red curve). Why?
Anatoly
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