[Ifeffit] [Ext] Re: Brain teaser

[Carlo Segre]

I would have guessed that the increase in I0 is primarily due to Pt
fluorescence.  The yield does increase as the energy rises.

Carlo

On Thu, Jun 15, 2023 at 9:45 AM Matt Newville <newville at cars.uchicago.edu>
wrote:

> I'm not sure why the intensity would go up unless the ion chamber was
> poorly set up.   But, as others have pointed out, the mirror reflectivity
> for a Pt mirror should not change significantly over this energy range -
> the energy range is not that close to the Pt L3 or L2 edges.    Depending
> on where it was located, fluorescence from the Pt mirror might pollute the
> signal in the I0 ion chamber, but that would also likely be a fairly
> constant background.
>
> But, why would you fill the I0 ion chamber with Argon?  A 10-cm ion
> chamber filled with Ar would absorb about 50% of the beam at 12 keV.   Even
> at 24 keV, that would absorb 8% of the beam - not necessarily a problem but
> also probably generating at least a micro-Amp, so way more signal than you
> would need.
>
> For mirror reflectivity curves, allow me to humbly remind everyone of
>
> https://xraydb.xrayabsorption.org/reflectivity/Pt/21.45/2.5/10/s/1000/51000/50/platinum/linear
>
> which is both interactive and works with X-ray energies above 30 keV.
>
>
> On Wed, Jun 14, 2023 at 7:28 PM Anatoly Frenkel <
> anatoly.frenkel at 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
>>
>> [image: image.png]
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit at millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
>>
>
>
> --
> --Matt Newville <newville at cars.uchicago.edu> 630-327-7411
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
>


-- 
Carlo U. Segre (he/him) -- Duchossois Leadership Professor of Physics
Professor of Materials Science & Engineering
Director, Center for Synchrotron Radiation Research and Instrumentation
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://phys.iit.edu/~segre   segre at debian.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20230615/7dd78da3/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 37377 bytes
Desc: not available
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20230615/7dd78da3/attachment-0001.png>