[Ifeffit] Brain teaser

[Kirill LOMACHENKO]

Hi Anatoly,

maybe the high voltage of the I0 chamber is off?

All the best,
Kirill


Dr. Kirill A. Lomachenko
Scientist at BM23/ID24 beamlines
European Synchrotron Radiation Facility
71 avenue des Martyrs
CS 40220
38043 Grenoble Cedex 9, France
Tel: +33 438 88 19 14
www.esrf.eu

On 15/06/2023 08:09, ifeffit-request at millenia.cars.aps.anl.gov wrote:
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>     1. Re: Brain teaser (Anatoly Frenkel)
>     2. Re: [Ext]  Brain teaser (Jeffrey Terry)
>     3. Re: [Ext] Brain teaser (matthew marcus)
>
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 15 Jun 2023 00:30:41 -0400
> From: Anatoly Frenkel <anatoly.frenkel at stonybrook.edu>
> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] Brain teaser
> Message-ID: <866EACCF-DAD2-4486-AAE0-AC3F6B28023E at stonybrook.edu>
> Content-Type: text/plain; charset=utf-8
>
> Amazing idea. I thunk you were the only one who succeeded to use third harmonic of Si for taking EXAFS at high atomic number elements. But that does not explain the peaks and dips.
>
> Anatoly
>
>> On Jun 15, 2023, at 12:22 AM, matthew marcus <mamarcus at lbl.gov> wrote:
>>
>> ?Suppose the mono is being used at the 333 reflection (for Si), intentionally working at the 3rd harmonic.  In that case, if the fundamental isn't filtered out, you could get just what we see, with the sample doing the filtering before the beam gets to the transmission chamber.
>>     mam
>>
>>> On 6/14/2023 9:16 PM, Anatoly Frenkel wrote:
>>> Thank you, Matthew and Robert, but I think the explanation is more simplle. The fact that there are peaks in I0 and dips in transmission is a clue that explains why transmission is almost linear while I0 curves up.
>>> Anatoly
>>>>> On Jun 14, 2023, at 11:34 PM, matthew marcus <mamarcus at lbl.gov> wrote:
>>>> ?One thing that's pretty odd is that the glitches are peaks in I0, and dips in It.  It would be much easier to explain if It was the one that increased steeply and I0 was more linear, but the presence of the edge in It shows that you didn't switch them.  Red = It.  What's that sudden drop at the end?
>>>>
>>>> Could it be that the I0 chamber is misaligned so that beam is scraping one of the plates?  That could cause all sorts of odd things to happen.
>>>>     mam
>>>>
>>>>> On 6/14/2023 5:27 PM, Anatoly Frenkel 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.png
>>>>> _______________________________________________
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> ------------------------------
>
> Message: 2
> Date: Thu, 15 Jun 2023 00:17:35 -0500
> From: Jeffrey Terry <terryj at iit.edu>
> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] [Ext]  Brain teaser
> Message-ID: <C024E52C-2EDF-49C0-9B5A-168A2B14F8D3 at iit.edu>
> Content-Type: text/plain; charset="utf-8"
>
> 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.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.png>
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit at millenia.cars.aps.anl.gov
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> Message: 3
> Date: Wed, 14 Jun 2023 23:09:45 -0700
> From: matthew marcus <mamarcus at lbl.gov>
> To: ifeffit at millenia.cars.aps.anl.gov
> Subject: Re: [Ifeffit] [Ext] Brain teaser
> Message-ID: <0df910ac-01ff-976d-dc34-19514d973574 at lbl.gov>
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> 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.frenkel at stonybrook.edu
>>> <mailto: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.png>
>>> _______________________________________________
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