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Fix PolarizerEfficiency Equation #37966

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Merged
merged 2 commits into from
Sep 13, 2024
Merged

Fix PolarizerEfficiency Equation #37966

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4d3ccac
Fix calculation of efficiency and error
cailafinn Sep 11, 2024
61c7cff
Update equations in documentation
cailafinn Sep 11, 2024
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8 changes: 4 additions & 4 deletions Framework/Algorithms/src/PolarizationCorrections/PolarizerEfficiency.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,7 @@ void PolarizerEfficiency::calculatePolarizerEfficiency() {

const MatrixWorkspace_sptr effCell = getProperty(PropertyNames::ANALYSER_EFFICIENCY);

auto &&effPolarizer = (t00Ws - t01Ws) / (4 * (2 * effCell - 1) * (t00Ws + t01Ws)) + 0.5;
auto &&effPolarizer = (t00Ws - t01Ws) / (2 * (2 * effCell - 1) * (t00Ws + t01Ws)) + 0.5;

calculateErrors(t00Ws, t01Ws, effCell, effPolarizer);

Expand Down Expand Up @@ -199,9 +199,9 @@ void PolarizerEfficiency::calculateErrors(const MatrixWorkspace_sptr &t00Ws, con
const auto &twoCellEffMinusOne = 2 * effCellY[i] - 1;
const auto &t00PlusT01 = t00Y[i] + t01Y[i];

const auto &delta00 = (t01Y[i]) / (2 * (twoCellEffMinusOne)*pow(t00PlusT01, 2));
const auto &delta01 = (-1 * t00Y[i]) / (2 * (twoCellEffMinusOne)*pow(t00PlusT01, 2));
const auto &deltaEffCell = (t01Y[i] - t00Y[i]) / (2 * pow(twoCellEffMinusOne, 2) * (t00PlusT01));
const auto &delta00 = (t01Y[i]) / ((twoCellEffMinusOne)*pow(t00PlusT01, 2));
const auto &delta01 = (-1 * t00Y[i]) / ((twoCellEffMinusOne)*pow(t00PlusT01, 2));
const auto &deltaEffCell = (t01Y[i] - t00Y[i]) / (pow(twoCellEffMinusOne, 2) * (t00PlusT01));
effPolarizerE[i] = sqrt(pow(delta00 * t00E[i], 2) + pow(delta01 * t01E[i], 2) + pow(deltaEffCell * effCellE[i], 2));
}
}
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11 changes: 5 additions & 6 deletions Framework/Algorithms/test/PolarizationCorrections/PolarizerEfficiencyTest.h
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Expand Up @@ -132,9 +132,9 @@ class PolarizerEfficiencyTest : public CxxTest::TestSuite {
polariserEfficiency->getProperty("OutputWorkspace"));

// The T_para and T_anti curves are 4 and 2 (constant wrt wavelength) respectively, and the analyser
// efficiency is 1 for all wavelengths, which should give us a polarizer efficiency of 7/12
// efficiency is 1 for all wavelengths, which should give us a polarizer efficiency of 2/3
for (const double &y : calculatedPolariserEfficiency->dataY(0)) {
TS_ASSERT_DELTA(7.0 / 12.0, y, 1e-8);
TS_ASSERT_DELTA(2.0 / 3.0, y, 1e-8);
}
}

Expand All @@ -151,9 +151,9 @@ class PolarizerEfficiencyTest : public CxxTest::TestSuite {
polariserEfficiency->getProperty("OutputWorkspace"));

// The T_para and T_anti curves are 4 and 2 (constant wrt wavelength) respectively, and the analyser
// efficiency is 1 for all wavelengths, which should give us a polarizer efficiency of 7/12
// efficiency is 1 for all wavelengths, which should give us a polarizer efficiency of 2/3
for (const double &y : calculatedPolariserEfficiency->dataY(0)) {
TS_ASSERT_DELTA(7.0 / 12.0, y, 1e-8);
TS_ASSERT_DELTA(2.0 / 3.0, y, 1e-8);
}
}

Expand All @@ -164,8 +164,7 @@ class PolarizerEfficiencyTest : public CxxTest::TestSuite {
polarizerEfficiency->getProperty("OutputWorkspace"));
const auto &errors = eff->dataE(0);
// Skip the first error because with this toy data it'll be NaN
const std::vector<double> expectedErrors{44.194173824159222, 19.641855032959654, 11.048543456039805,
7.0710678118654755};
const std::vector<double> expectedErrors{88.3883476283, 39.2837100613, 22.0970869124, 14.1421356255};
for (size_t i = 0; i < expectedErrors.size(); ++i) {
TS_ASSERT_DELTA(expectedErrors[i], errors[i + 1], 1e-7);
}
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8 changes: 4 additions & 4 deletions docs/source/algorithms/PolarizerEfficiency-v1.rst
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Expand Up @@ -22,7 +22,7 @@ The polarization of the polarizer, :math:`P_{SM}`, is given by [#KRYCKA]_
Since the efficiency, :math:`\epsilon_{SM}`, is given by :math:`\frac{1 + P_{SM}}{2}`, we have that

.. math::
\epsilon_{SM} = \frac{1}{2} + \frac{T_{00} - T_{01}}{4(2\epsilon_{cell} - 1)(T_{00} + T_{01})}
\epsilon_{SM} = \frac{1}{2} + \frac{T_{00} - T_{01}}{2(2\epsilon_{cell} - 1)(T_{00} + T_{01})}

The error in the calculation can then be determined thus:

Expand All @@ -34,13 +34,13 @@ The error in the calculation can then be determined thus:
where:

.. math::
\frac{\delta \epsilon_{SM}}{\delta T_{00}} = \frac{T_{01}}{2(2\epsilon_{cell} - 1)(T_{00} + T_{01})^2}
\frac{\delta \epsilon_{SM}}{\delta T_{00}} = \frac{T_{01}}{(2\epsilon_{cell} - 1)(T_{00} + T_{01})^2}

.. math::
\frac{\delta \epsilon_{SM}}{\delta T_{01}} = \frac{-T_{00}}{2(2\epsilon_{cell} - 1)(T_{00} + T_{01})^2}
\frac{\delta \epsilon_{SM}}{\delta T_{01}} = \frac{-T_{00}}{(2\epsilon_{cell} - 1)(T_{00} + T_{01})^2}

.. math::
\frac{\delta \epsilon_{SM}}{\delta \epsilon_{cell}} = \frac{T_{01} - T_{00}}{2(2\epsilon_{cell} - 1)^2(T_{00} + T_{01})}
\frac{\delta \epsilon_{SM}}{\delta \epsilon_{cell}} = \frac{T_{01} - T_{00}}{(2\epsilon_{cell} - 1)^2(T_{00} + T_{01})}

Usage
-----
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