Polarization correction #122
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Can we use esspolarization to perform the correction?
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Right now we can't because of scipp/esspolarization#84
When that is fixed we should be able to use esspolarization to do the correction.
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The notebook might need some clean up - I'll take a look at that later today. |
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| if "Q" in ref.coords: | ||
| ref.coords.pop("Q") | ||
| if "theta" in ref.coords: | ||
| ref.coords.pop("theta") | ||
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Unclear why this was added or what it may break. Can you add a comment?
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It was added so that if the input already has a Q or theta coordinate those are still recomputed in the coordinate transformation further down in the function.
For Amor theta is typically a binnned coordinate, so it's not present in ReducedReference (because that is a histogram).
But I noticed that if theta is computed without gravity correction then it will not be a binned coordinate, and it might be preserved on ReducedReference and so it will not be replaced by the coordinate transformation below, and that leads to incorrect results.
Removing them here is just defensive - we always want them to be replaced.
Q is always a binned coordinate, so it should not be a coordinate on ReducedReference, unless explicitly added.
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I've changed it now to only remove Changed it back to remove both theta.Q and theta. Not removing Q would risk a silent bug if a Q coord is ever added to the input. Best to be safe.
src/ess/estia/calibration.py
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| spin anti-parallel to instrument polarization.''' | ||
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| @classmethod | ||
| def from_reference_measurements(cls, Io, Is): |
src/ess/estia/calibration.py
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| Rspp_plus_Rsaa = ( | ||
| 4 | ||
| * (rho * alp * Ipp + Iaa + rho * Ipa + alp * Iap) | ||
| / ((1 + rho) * (1 + alp) * I0) | ||
| ) | ||
| Pp = sc.sqrt( | ||
| (Ipp + Iaa - Ipa - Iap) | ||
| * (alp * (Ipp - Iap) - Iaa + Ipa) | ||
| / ( | ||
| (rho * alp * Ipp + Iaa + rho * Ipa + alp * Iap) | ||
| * (rho * (Ipp - Ipa) - Iaa + Iap) | ||
| ) | ||
| ) | ||
| Ap = sc.sqrt( | ||
| (Ipp + Iaa - Ipa - Iap) | ||
| * (rho * (Ipp - Ipa) - Iaa + Iap) | ||
| / ( | ||
| (rho * alp * Ipp + Iaa + rho * Ipa + alp * Iap) | ||
| * (alp * (Ipp - Iap) - Iaa + Ipa) | ||
| ) | ||
| ) | ||
| Rs = sc.sqrt( | ||
| (alp * (Ipp - Iap) - Iaa + Ipa) | ||
| * (rho * (Ipp - Ipa) - Iaa + Iap) | ||
| / ( | ||
| (rho * alp * Ipp + Iaa + rho * Ipa + alp * Iap) | ||
| * (Ipp + Iaa - Ipa - Iap) | ||
| ) |
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Write this in a less repetitive manner, this is hard to read/review
src/ess/estia/normalization.py
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| if "Q" in ref.coords: | ||
| ref.coords.pop("Q") |
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Same as above. For Estia there is no gravity correction, so theta is a coordinate on ReducedReference, but that coordinate should be replaced here.
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| def reduce_to_q(da, qbins): |
tests/estia/calibration_test.py
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| Io = intensity_from_parameters( | ||
| I0, Pp, Pa, Ap, Aa, sc.scalar(1), sc.scalar(0), sc.scalar(0), sc.scalar(1) | ||
| ) | ||
| Is = intensity_from_parameters( | ||
| I0, Pp, Pa, Ap, Aa, Rspp, sc.scalar(0), sc.scalar(0), Rsaa | ||
| ) |
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Unclear why passing the same values to both is a reasonable test. Same for passing zeros? Does this mean the test has gaps?
Also, keyword args and type hints would help.
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The test verifies that PolarizationCalibrationParameters.from_reference_measurements is the inverse of intensity_from_parameters.
It does that for 10 different seeds. It's a hypothesis test.
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Unclear why passing the same values to both is a reasonable test.
Maybe it's better if we talk in person since there seems to be some misunderstanding here.
tests/estia/calibration_test.py
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| def polarization_matrix_from_beamline_parameters(Pp, Pa, Ap, Aa): | ||
| return _polarization_matrix(Pp, Pa, Ap, Aa) |
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Why this wrapper, it seems _polarization_matrix is used only once and could be reused?
| supermirror_reflectivities = [ | ||
| sc.scalar(1), | ||
| sc.scalar(0), | ||
| sc.scalar(0), | ||
| sc.scalar(1), | ||
| ] | ||
| magnetic_supermirror_reflectivities = [Rspp, sc.scalar(0), sc.scalar(0), Rsaa] | ||
| Io = [I0 * v for v in _matvec(polmat, supermirror_reflectivities)] | ||
| Is = [I0 * v for v in _matvec(polmat, magnetic_supermirror_reflectivities)] |
Polarization correction for ESTIA
Only important differences from #108 are in
src/ess/estia/calibration.py: https://github.com/scipp/essreflectometry/pull/122/files#diff-df676f2a67f8251976ea2fcc161ea759d49deef6ef66c5adbf01d10665230077