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Detailed specifications for SANS options at DREAM #36

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Different workflows for different insruments / specifications will have to be created following the current sans-polarization-analysis-methodology. There will be workflows according to DREAM-SANS, SKADI-SANS, and DREAM-Diffraction - all having slightly different polarizers/analyzers & monitors, and hence slightly different time-dependencies etc.

Here I add the detailed specifications for SANS options at DREAM.

…ve to be created following the current sans-polarization-analysis-methodology. Here I add the detailed specifications for SANS options at DREAM
"source": [
"# DREAM-SANS methodology\n",
"\n",
"The general data reduction scheme presented in \"SANS Polarization Analysis Methodology\" will be adapted for the SANS option at the DREAM instrument at the ESS. Following considerations have to be changed with respect to the general methodology:\n",
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As a general comment, it is much easier for reviewing and later editing if you have one sentence per line.
See for example this note in our guidelines.

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Thanks for the info! I am just changing it

"source": [
"# DREAM-SANS methodology\n",
"\n",
"The general data reduction scheme presented in \"SANS Polarization Analysis Methodology\" will be adapted for the SANS option at the DREAM instrument at the ESS. Following considerations have to be changed with respect to the general methodology:\n",
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Following considerations have to be changed with respect to the general methodology:

I'm not sure I understand what this means.
I understood it as "some things in the SANS workflow we currently have will have to be changed so we can accommodate the DREAM instrument. And we are giving the list of those things below."
Is that correct?

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Yes, exactly

"The general data reduction scheme presented in \"SANS Polarization Analysis Methodology\" will be adapted for the SANS option at the DREAM instrument at the ESS. Following considerations have to be changed with respect to the general methodology:\n",
"\n",
"### Polarizer:<br>\n",
"The DREAM-polarizer is a movable in-situ SEOP <sup>3</sup>He-cell of which the neutron polarization $P^{^3\\textup{He, p}}$ has to be pre-characterized in commissioning measurements and inserted into this workflow. Its wavelength-independent opacity $O^{\\textup{0, p}}$, empty-glass transmission $T^{\\textup{g, p}}$, pre-factor of nuclear polarization $C^{\\textup{p}}$, and its time-decay constant $T^{\\textup{1, p}}$ can be measured once in every commissioning time via Workflow 2 of \"SANS Polarization Analysis Methodology\". The resulting $P^{^3\\textup{He, p}}$ can be inserted into the workflow as constant parameter. To account for sudden fluctuations of $P^{^3\\textup{He, p}}$, which can occur due to changes in pressure or the like, the beam intensity after the polarizer has to be continuously recorded as function of time. Sudden fluctuations in intensity above a pre-defined difference in time must pop out an error message \"Critical intensity fluctuations detected in polarizer-monitor. Re-measure $P^{^3\\textup{He, p}}$!\".<br>\n",
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Can you explain what SEOP stands for?

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$P^{^3\\textup{He, p}}$

I am not sure what the p superscript stands for? I'm not sure I've seen it before.

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Sudden fluctuations in intensity above a pre-defined difference in time must pop out an error message

Is it the frequency of fluctuations that is important, or is it the amplitude of them, or both?
Also, "pop out" -> "raise".

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Can you explain what SEOP stands for?

  • I am adding explanations for SEOP and MEOP cells

I am not sure what the p superscript stands for? I'm not sure I've seen it before.

  • It stands for polarizer ("p") and analyzer ("a"). It was defined in sans-polarization-analysis-methodology.ipynb for the transmissions of the polarizer and analyzer (Tp, and Ta, respectively), but yes I will define them here again!

Is it the frequency of fluctuations that is important, or is it the amplitude of them, or both? Also, "pop out" -> "raise".

  • the amplitude

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Can you explain what SEOP stands for?

I will add a footnote for SEOP and MEOP

"\n",
"### Polarizer:<br>\n",
"The DREAM-polarizer is a movable in-situ SEOP <sup>3</sup>He-cell of which the neutron polarization $P^{^3\\textup{He, p}}$ has to be pre-characterized in commissioning measurements and inserted into this workflow. Its wavelength-independent opacity $O^{\\textup{0, p}}$, empty-glass transmission $T^{\\textup{g, p}}$, pre-factor of nuclear polarization $C^{\\textup{p}}$, and its time-decay constant $T^{\\textup{1, p}}$ can be measured once in every commissioning time via Workflow 2 of \"SANS Polarization Analysis Methodology\". The resulting $P^{^3\\textup{He, p}}$ can be inserted into the workflow as constant parameter. To account for sudden fluctuations of $P^{^3\\textup{He, p}}$, which can occur due to changes in pressure or the like, the beam intensity after the polarizer has to be continuously recorded as function of time. Sudden fluctuations in intensity above a pre-defined difference in time must pop out an error message \"Critical intensity fluctuations detected in polarizer-monitor. Re-measure $P^{^3\\textup{He, p}}$!\".<br>\n",
"Note: Workflow 1 of \"SANS Polarization Analysis Methodology\" cannot be used for this polarizer. \n",
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cannot be used for this polarizer

Can you give a brief reason?

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@astellhorn astellhorn May 3, 2024

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Well, actually it can be adapted to be used here. I will change this in the text. We should sit together and speak about it directly to define where we have to make new workflows or where we can use the existing one but with different options for different instruments and use-cases. Maybe one could add different "workflows" for different instruments, similar to the workflows 1 and 2 for the different kinds of He cells. I initially thought that this could get very messy in the end, as it will be adaptations for each instrument, and then I thought better a new workflow per instrument?

"Note: Workflow 1 of \"SANS Polarization Analysis Methodology\" cannot be used for this polarizer. \n",
"\n",
"### Analyzer:<br>\n",
"In the current scope, DREAM will be equipped with 3 different SANS analyzers: (i) an ex-situ SEOP <sup>3</sup>He-cell, (ii) an in-situ SEOP <sup>3</sup>He-cell, and (iii) a SANS-window being part of a wide angle MEOP based <sup>3</sup>He-cell.\n",
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Explain MEOP?

"(iii) The ex-situ MEOP wide angle <sup>3</sup>He-cell with a small SANS window is a rotatable, time-dependent cell and has to be treated as the analyzer described in \"DREAM-diffraction methodology\".\n",
"\n",
"### Monitors:<br>\n",
"For an optimal SANS data-reduction, three monitors would be ideal: (i) an incident beam monitor $M_{\\textup{in}}$ before the polarizer, (ii) a monitor after the polarizer $M_{\\textup{p}}$, and (iii) a monitor after the analyzer $M_{\\textup{a}}$ (alternatively on the main detector if the direct beam can be recorded). At DREAM, only two monitors will be inserted: $M_{\\textup{p}}$ and $M_{\\textup{a}}$. In general, the total beam intensity is corrected by $M_{\\textup{in}}$. Due to the time-independence of $P^{^3\\textup{He, p}}$, the beam intensity of $M_{\\textup{p}}$ can be used instead.\n",
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At DREAM, only two monitors will be inserted: $M_{\textup{p}}$ and $M_{\textup{a}}$.

Are there plans to maybe use one of the mobile monitors that is able to be shared between instruments for $M_{\rm{in}}$?

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For M_in we would need continuous monitoring, so shared equipment will not work. It should be checked in between by just moving the polarizer in and out, but cannot be measured together with having the polarizer in (at least not within the beamtime).

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@astellhorn Have you had a chance to look at Neil's comments?

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OOH! Thanks for reminding me! I will answer as soon as possible ! (need to prepare something for this friday urgently)

@SimonHeybrock SimonHeybrock requested a review from nvaytet May 7, 2024 05:47
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