Merge pull request #170 from scipp/provider-for-qbins

Provider for qbins

Author: jokasimr

docs/user-guide/amor/amor-reduction.ipynb

@@ -24,6 +24,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "%matplotlib widget\n",
     "import warnings\n",
     "import scipp as sc\n",
     "from ess import amor\n",
@@ -60,7 +61,6 @@
     "workflow[ChopperPhase[ReferenceRun]] = sc.scalar(-7.5, unit='deg')\n",
     "workflow[ChopperPhase[SampleRun]] = sc.scalar(-7.5, unit='deg')\n",
     "\n",
-    "workflow[QBins] = sc.geomspace(dim='Q', start=0.005, stop=0.3, num=391, unit='1/angstrom')\n",
     "workflow[WavelengthBins] = sc.geomspace('wavelength', 2.8, 12.5, 2001, unit='angstrom')\n",
     "\n",
     "# The YIndexLimits and ZIndexLimits define ranges on the detector where\n",
@@ -235,7 +235,7 @@
    "outputs": [],
    "source": [
     "from ess.reflectometry.tools import combine_curves\n",
-    "combined = combine_curves(scaled_reflectivity_curves, workflow.compute(QBins))\n",
+    "combined = combine_curves(scaled_reflectivity_curves, sc.geomspace('Q', 0.005, 0.4, 499, unit='1/angstrom'))\n",
     "combined.plot(norm='log')"
    ]
   },
@@ -336,7 +336,7 @@
     "q_theta_figure(\n",
     "    [res[ReflectivityOverZW] for res in diagnostics.values()],\n",
     "    theta_bins=[res[ThetaBins[SampleRun]] for res in diagnostics.values()],\n",
-    "    q_bins=workflow.compute(QBins)\n",
+    "    q_bins=sc.geomspace('Q', 0.005, 0.4, 499, unit='1/angstrom')\n",
     ")"
    ]
   },
@@ -527,7 +527,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.14"
+   "version": "3.10.18"
   }
  },
  "nbformat": 4,

src/ess/amor/utils.py

@@ -1,7 +1,17 @@
 # Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
 import scipp as sc
 
-from ..reflectometry.types import DetectorRotation, RunType, SampleRotation, ThetaBins
+from ..reflectometry.conversions import reflectometry_q
+from ..reflectometry.types import (
+    BeamDivergenceLimits,
+    DetectorRotation,
+    QBins,
+    RunType,
+    SampleRotation,
+    SampleRun,
+    ThetaBins,
+    WavelengthBins,
+)
 from .geometry import Detector
 
 
@@ -55,4 +65,33 @@ def theta_grid(
     return grid
 
 
-providers = (theta_grid,)
+def qgrid(
+    detector_rotation: DetectorRotation[SampleRun],
+    sample_rotation: SampleRotation[SampleRun],
+    wbins: WavelengthBins,
+    bdlims: BeamDivergenceLimits,
+) -> QBins:
+    '''Generates a suitable Q-binnning from
+    the limits on wavelength and divergence angle.
+
+    The binning is a geometric grid starting from
+    the minimum achievable Q value or ``1e-3 A``, whichever is larger.
+    '''
+    theta_min = (
+        bdlims[0].to(unit='rad', copy=False)
+        + detector_rotation.to(unit='rad', dtype='float64')
+        - sample_rotation.to(unit='rad', dtype='float64')
+    )
+    theta_max = (
+        bdlims[-1].to(unit='rad', copy=False)
+        + detector_rotation.to(unit='rad', dtype='float64')
+        - sample_rotation.to(unit='rad', dtype='float64')
+    )
+    wmin, wmax = wbins[0], wbins[-1]
+    qmin = reflectometry_q(wavelength=wmax, theta=theta_min)
+    qmax = reflectometry_q(wavelength=wmin, theta=theta_max)
+    qmin = max(qmin, sc.scalar(1e-3, unit='1/angstrom'))
+    return QBins(sc.geomspace('Q', qmin, qmax, 501))
+
+
+providers = (theta_grid, qgrid)

tests/amor/utils_test.py

@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright (c) 2024 Scipp contributors (https://github.com/scipp)
+# flake8: noqa: F403, F405
+
+import scipp as sc
+import scipp.constants
+import scipp.testing
+
+from ess.amor.utils import qgrid
+
+
+def test_qgrid_provider():
+    grid = qgrid(
+        detector_rotation=sc.scalar(2, unit='deg'),
+        sample_rotation=sc.scalar(0.9, unit='deg'),
+        wbins=sc.linspace('wavelength', 3, 12, 10, unit='angstrom'),
+        bdlims=(sc.scalar(-0.75, unit='deg'), sc.scalar(0.75, unit='deg')),
+    )
+    sc.testing.assert_allclose(
+        grid[0],
+        4
+        * sc.constants.pi
+        * sc.sin(
+            sc.scalar(-0.75, unit='deg').to(unit='rad')
+            + sc.scalar(1.1, unit='deg').to(unit='rad')
+        )
+        / sc.scalar(12, unit='angstrom'),
+    )
+    sc.testing.assert_allclose(
+        grid[-1],
+        4
+        * sc.constants.pi
+        * sc.sin(
+            sc.scalar(0.75, unit='deg').to(unit='rad')
+            + sc.scalar(1.1, unit='deg').to(unit='rad')
+        )
+        / sc.scalar(3, unit='angstrom'),
+    )
+
+
+def test_qgrid_provider_minimum_q():
+    grid = qgrid(
+        detector_rotation=sc.scalar(1.2, unit='deg'),
+        sample_rotation=sc.scalar(0.7, unit='deg'),
+        wbins=sc.linspace('wavelength', 3, 12, 10, unit='angstrom'),
+        bdlims=(sc.scalar(-0.75, unit='deg'), sc.scalar(0.75, unit='deg')),
+    )
+    sc.testing.assert_allclose(grid[0], sc.scalar(0.001, unit='1/angstrom'))