jl-wynen · Nov 13, 2026
diff --git a/packages/essdiffraction/docs/user-guide/dream/dream-make-wavelength-lookup-table.ipynb b/packages/essdiffraction/docs/user-guide/dream/dream-make-wavelength-lookup-table.ipynb
@@ -20,7 +20,7 @@
     "import scipp as sc\n",
     "import scippnexus as snx\n",
     "from ess.reduce import unwrap\n",
-    "from ess.reduce.nexus.types import AnyRun, Position\n",
+    "from ess.reduce.nexus.types import AnyRun, NeutronSourcePosition\n",
     "from ess.dream.beamline import InstrumentConfiguration, choppers"
    ]
   },
@@ -65,7 +65,7 @@
     "\n",
     "wf[unwrap.LtotalRange[AnyRun, snx.NXdetector]] = sc.scalar(5.0, unit=\"m\"), sc.scalar(80.0, unit=\"m\")\n",
     "wf[unwrap.NumberOfSimulatedNeutrons] = 200_000  # Increase this number for more reliable results\n",
-    "wf[Position[snx.NXsource, AnyRun]] = sc.vector([0, 0, 0], unit='m')\n",
+    "wf[NeutronSourcePosition[AnyRun]] = sc.vector([0, 0, 0], unit='m')\n",
     "wf[unwrap.DiskChoppers[AnyRun]] = disk_choppers\n",
     "wf[unwrap.DistanceResolution] = sc.scalar(0.1, unit=\"m\")\n",
     "wf[unwrap.TimeResolution] = sc.scalar(250.0, unit='us')\n",

diff --git a/packages/essdiffraction/src/ess/beer/conversions.py b/packages/essdiffraction/src/ess/beer/conversions.py
@@ -8,7 +8,7 @@
 from scippneutron.chopper import DiskChopper
 from scippneutron.conversion.tof import wavelength_from_tof
 
-from ess.reduce.nexus.types import DiskChoppers, Position
+from ess.reduce.nexus.types import DiskChoppers, NeutronSourcePosition, Position
 from ess.reduce.unwrap.lut import ActiveDiskChoppers, chopper_distance_along_beam
 from ess.reduce.unwrap.types import DetectorLtotal
 
@@ -97,7 +97,7 @@ def _modulation_period(choppers: DiskChoppers[RunType]) -> sc.Variable:
 
 
 def powder_beamline_geometry_graph(
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
 ) -> BeamlineGeometryGraph[RunType]:
@@ -113,7 +113,7 @@ def powder_beamline_geometry_graph(
 
 
 def modulation_beamline_geometry_graph(
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
     choppers: ActiveDiskChoppers[RunType],

diff --git a/packages/essdiffraction/src/ess/beer/mcstas/load.py b/packages/essdiffraction/src/ess/beer/mcstas/load.py
@@ -7,7 +7,13 @@
 import mcstastox
 import scipp as sc
 import scippnexus as snx
-from ess.powder.types import CaveMonitor, EmptyDetector, RunType, WavelengthMonitor
+from ess.powder.types import (
+    CaveMonitor,
+    EmptyDetector,
+    NeutronSourcePosition,
+    RunType,
+    WavelengthMonitor,
+)
 
 from ess.reduce.nexus.types import DiskChoppers, Position
 from ess.reduce.unwrap.types import DetectorLtotal
@@ -273,7 +279,7 @@ def chopper_mode_from_mcstas_mode(mode: str) -> PulseShapingMode | ModulationMod
 
 def mcstas_source_position(
     fname: Filename[RunType], sample_position: Position[snx.NXsample, RunType]
-) -> Position[snx.NXsource, RunType]:
+) -> NeutronSourcePosition[RunType]:
     """Return the effective source position for the McStas geometry.
 
     ``sourceMantid`` is close to the choppers and its direction towards the sample
@@ -314,7 +320,7 @@ def mcstas_sample_position(
 
 def mcstas_choppers(
     da: RawDetector[RunType],
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
 ) -> DiskChoppers[RunType]:
     """Return BEER choppers for the McStas mode in the data."""
     mode = chopper_mode_from_mcstas_mode(da.coords['mode'].value)
@@ -323,7 +329,7 @@ def mcstas_choppers(
 
 def _mcstas_choppers_from_file(
     fname: Filename[RunType],
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
 ) -> DiskChoppers[RunType]:
     """Return BEER choppers without loading detector events."""
     fname = Path(fname)
@@ -334,7 +340,7 @@ def _mcstas_choppers_from_file(
 
 def mcstas_detector_ltotal(
     detector: EmptyDetector[RunType],
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
 ) -> DetectorLtotal[RunType]:
     """Return moderator-to-detector flight path lengths for BEER McStas data."""

diff --git a/packages/essdiffraction/src/ess/dream/io/geant4.py b/packages/essdiffraction/src/ess/dream/io/geant4.py
@@ -16,6 +16,7 @@
     Filename,
     MonitorFilename,
     MonitorType,
+    NeutronSourcePosition,
     NeXusComponent,
     NeXusDetectorName,
     Position,
@@ -319,8 +320,8 @@ def assemble_monitor_data(
     return RawMonitor[RunType, MonitorType](monitor)
 
 
-def dummy_source_position() -> Position[snx.NXsource, RunType]:
-    return Position[snx.NXsource, RunType](
+def dummy_source_position() -> NeutronSourcePosition[RunType]:
+    return NeutronSourcePosition[RunType](
         sc.vector([np.nan, np.nan, np.nan], unit="mm")
     )
 

diff --git a/packages/essdiffraction/src/ess/dream/workflows.py b/packages/essdiffraction/src/ess/dream/workflows.py
@@ -18,6 +18,7 @@
     LookupTableFilename,
     LookupTableRelativeErrorThreshold,
     Measurement,
+    NeutronSourcePosition,
     Position,
     ReducerSoftware,
     SampleRun,
@@ -219,9 +220,9 @@ def DreamGeant4Workflow(*, run_norm: RunNormalization, **kwargs) -> sciline.Pipe
         Position[snx.NXsample, SampleRun]: sample_position,
         Position[snx.NXsample, VanadiumRun]: sample_position,
         Position[snx.NXsample, EmptyCanRun]: sample_position,
-        Position[snx.NXsource, SampleRun]: source_position,
-        Position[snx.NXsource, VanadiumRun]: source_position,
-        Position[snx.NXsource, EmptyCanRun]: source_position,
+        NeutronSourcePosition[SampleRun]: source_position,
+        NeutronSourcePosition[VanadiumRun]: source_position,
+        NeutronSourcePosition[EmptyCanRun]: source_position,
         AccumulatedProtonCharge[SampleRun]: charge,
         AccumulatedProtonCharge[VanadiumRun]: charge,
         AccumulatedProtonCharge[EmptyCanRun]: charge,

diff --git a/packages/essdiffraction/src/ess/powder/calibration.py b/packages/essdiffraction/src/ess/powder/calibration.py
@@ -16,6 +16,7 @@
     DetectorTwoTheta,
     EmptyDetector,
     GravityVector,
+    NeutronSourcePosition,
     Position,
     RunType,
     SampleRun,
@@ -105,7 +106,7 @@ def to_cif_format(self) -> sc.DataArray:
 
 def detector_two_theta(
     detector: EmptyDetector[RunType],
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
 ) -> DetectorTwoTheta[RunType]:

diff --git a/packages/essdiffraction/src/ess/powder/conversion.py b/packages/essdiffraction/src/ess/powder/conversion.py
@@ -21,6 +21,7 @@
     IntensityDspacing,
     IntensityTof,
     MonitorCoordTransformGraph,
+    NeutronSourcePosition,
     Position,
     QDetector,
     RunType,
@@ -145,7 +146,7 @@ def to_dspacing_with_calibration(
 
 
 def powder_coordinate_transformation_graph(
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
 ) -> ElasticCoordTransformGraph[RunType]:
@@ -256,7 +257,7 @@ def convert_reduced_to_empty_can_subtracted_tof(
 
 
 def powder_monitor_coordinate_transformation_graph(
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
 ) -> MonitorCoordTransformGraph[RunType]:

diff --git a/packages/essdiffraction/src/ess/powder/types.py b/packages/essdiffraction/src/ess/powder/types.py
@@ -30,6 +30,7 @@
 GravityVector = reduce_t.GravityVector
 RawMonitor = reduce_t.RawMonitor
 MonitorPositionOffset = reduce_t.MonitorPositionOffset
+NeutronSourcePosition = reduce_t.NeutronSourcePosition
 NeXusDetectorName = reduce_t.NeXusDetectorName
 NeXusMonitorName = reduce_t.NeXusName
 NeXusComponent = reduce_t.NeXusComponent

diff --git a/packages/essdiffraction/src/ess/snspowder/powgen/data.py b/packages/essdiffraction/src/ess/snspowder/powgen/data.py
@@ -19,6 +19,7 @@
     GravityVector,
     MonitorCoordTransformGraph,
     MonitorType,
+    NeutronSourcePosition,
     Position,
     ProtonCharge,
     RawDataAndMetadata,
@@ -242,9 +243,9 @@ def extract_accumulated_proton_charge(
     return AccumulatedProtonCharge[RunType](data.coords["gd_prtn_chrg"])
 
 
-def source_position(dg: RawDataAndMetadata[RunType]) -> Position[snx.NXsource, RunType]:
+def source_position(dg: RawDataAndMetadata[RunType]) -> NeutronSourcePosition[RunType]:
     """Return the source position from a loaded data group."""
-    return Position[snx.NXsource, RunType](dg["data"].coords["source_position"])
+    return NeutronSourcePosition[RunType](dg["data"].coords["source_position"])
 
 
 def sample_position(dg: RawDataAndMetadata[RunType]) -> Position[snx.NXsample, RunType]:
@@ -268,7 +269,7 @@ def _coordinate_transformation_graph(
 
 
 def detector_coordinate_transformation_graph(
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
 ) -> ElasticCoordTransformGraph[RunType]:
@@ -296,7 +297,7 @@ def detector_coordinate_transformation_graph(
 
 
 def monitor_coordinate_transformation_graph(
-    source_position: Position[snx.NXsource, RunType],
+    source_position: NeutronSourcePosition[RunType],
     sample_position: Position[snx.NXsample, RunType],
     gravity: GravityVector,
 ) -> MonitorCoordTransformGraph[RunType]:

diff --git a/packages/essdiffraction/tests/beer/mcstas_beamline_test.py b/packages/essdiffraction/tests/beer/mcstas_beamline_test.py
@@ -12,7 +12,7 @@
 from ess.beer.types import SampleRun
 
 from ess.reduce import unwrap
-from ess.reduce.nexus.types import Position
+from ess.reduce.nexus.types import NeutronSourcePosition
 from ess.reduce.unwrap import lut
 
 
@@ -24,7 +24,7 @@ def test_can_make_analytical_lookup_table_from_beer_choppers(
         run_types=[SampleRun], monitor_types=[], wavelength_from="analytical"
     )
     source_position = sc.vector([0.0, 0.0, 0.0], unit="m")
-    wf[Position[snx.NXsource, SampleRun]] = source_position
+    wf[NeutronSourcePosition[SampleRun]] = source_position
     wf[unwrap.DiskChoppers[SampleRun]] = simulation_choppers(mode, source_position)
     wf[lut.LtotalRange[SampleRun, snx.NXdetector]] = (
         sc.scalar(150.0, unit="m"),

diff --git a/packages/essdiffraction/tests/beer/mcstas_reduction_test.py b/packages/essdiffraction/tests/beer/mcstas_reduction_test.py
@@ -49,6 +49,7 @@
     ElasticCoordTransformGraph,
     EmptyDetector,
     KeepEvents,
+    NeutronSourcePosition,
     NormalizedDspacing,
     PixelMasks,
     QDetector,
@@ -229,7 +230,7 @@ def test_beer_workflows_compute_dspacing_bins(make_workflow, mode, pulse_skippin
 
     if pulse_skipping:
         # Use pulse-skipping choppers with the existing detector geometry.
-        source_position = wf.compute(Position[snx.NXsource, SampleRun])
+        source_position = wf.compute(NeutronSourcePosition[SampleRun])
         chopper_mode = ModulationMode.ds0 if mode == 7 else PulseShapingMode.ds1
         wf[DiskChoppers[SampleRun]] = simulation_choppers(chopper_mode, source_position)
 

diff --git a/packages/essdiffraction/tests/dream/geant4_reduction_test.py b/packages/essdiffraction/tests/dream/geant4_reduction_test.py
@@ -31,6 +31,7 @@
     KeepEvents,
     LookupTableFilename,
     MonitorFilename,
+    NeutronSourcePosition,
     NeXusDetectorName,
     OutFilename,
     PixelMaskFilenames,
@@ -44,11 +45,10 @@
     WavelengthMask,
 )
 from scippneutron import metadata
-from scippnexus import NXsource
 
 from ess.reduce import unwrap
 from ess.reduce import workflow as reduce_workflow
-from ess.reduce.nexus.types import AnyRun, Position
+from ess.reduce.nexus.types import AnyRun
 
 PARAMETRIZATION = ("detector_name", ["mantle", "endcap_backward", "endcap_forward"])
 
@@ -62,7 +62,7 @@
     MonitorFilename[VanadiumRun]: dream.data.simulated_monitor_vanadium_sample(),
     MonitorFilename[EmptyCanRun]: dream.data.simulated_monitor_empty_can(),
     dream.InstrumentConfiguration: dream.beamline.InstrumentConfiguration.high_flux_BC215,  # noqa: E501
-    Position[NXsource, AnyRun]: sc.vector(value=[0, 0, -76.55], unit="m"),
+    NeutronSourcePosition[AnyRun]: sc.vector(value=[0, 0, -76.55], unit="m"),
     CalibrationFilename: None,
     UncertaintyBroadcastMode: UncertaintyBroadcastMode.drop,
     DspacingBins: sc.linspace('dspacing', 0.0, 2.3434, 201, unit='angstrom'),

diff --git a/packages/essimaging/docs/odin/odin-data-reduction.ipynb b/packages/essimaging/docs/odin/odin-data-reduction.ipynb
@@ -66,7 +66,7 @@
    "source": [
     "from ess.odin.beamline import choppers\n",
     "\n",
-    "disk_choppers = choppers(source_position=wf.compute(Position[snx.NXsource, SampleRun]))\n",
+    "disk_choppers = choppers(source_position=wf.compute(NeutronSourcePosition[SampleRun]))\n",
     "wf[unwrap.DiskChoppers[SampleRun]] = disk_choppers"
    ]
   },

diff --git a/packages/essimaging/docs/odin/odin-make-wavelength-lookup-table.ipynb b/packages/essimaging/docs/odin/odin-make-wavelength-lookup-table.ipynb
@@ -18,7 +18,7 @@
     "import scipp as sc\n",
     "import scippnexus as snx\n",
     "from ess.reduce import unwrap\n",
-    "from ess.reduce.nexus.types import AnyRun, Position\n",
+    "from ess.reduce.nexus.types import AnyRun, NeutronSourcePosition\n",
     "from ess.odin.beamline import choppers"
    ]
   },
@@ -42,7 +42,7 @@
     "\n",
     "wf = unwrap.LookupTableWorkflow()\n",
     "wf[unwrap.DiskChoppers[AnyRun]] = disk_choppers\n",
-    "wf[Position[snx.NXsource, AnyRun]] = source_position\n",
+    "wf[NeutronSourcePosition[AnyRun]] = source_position\n",
     "wf[unwrap.NumberOfSimulatedNeutrons] = 200_000  # Increase this number for more reliable results\n",
     "wf[unwrap.SimulationSeed] = 1234\n",
     "wf[unwrap.LtotalRange[AnyRun, snx.NXdetector]] = sc.scalar(5.0, unit=\"m\"), sc.scalar(65.0, unit=\"m\")\n",

diff --git a/packages/essimaging/docs/tbl/tbl-make-wavelength-lookup-table.ipynb b/packages/essimaging/docs/tbl/tbl-make-wavelength-lookup-table.ipynb
@@ -18,7 +18,7 @@
     "import scipp as sc\n",
     "import scippnexus as snx\n",
     "from ess.reduce import unwrap\n",
-    "from ess.reduce.nexus.types import AnyRun, Position"
+    "from ess.reduce.nexus.types import AnyRun, NeutronSourcePosition"
    ]
   },
   {
@@ -40,7 +40,7 @@
     "\n",
     "wf = unwrap.LookupTableWorkflow()\n",
     "wf[unwrap.DiskChoppers[AnyRun]] = {}\n",
-    "wf[Position[snx.NXsource, AnyRun]] = source_position\n",
+    "wf[NeutronSourcePosition[AnyRun]] = source_position\n",
     "wf[unwrap.NumberOfSimulatedNeutrons] = 200_000  # Increase this number for more reliable results\n",
     "wf[unwrap.SimulationSeed] = 1234\n",
     "wf[unwrap.LtotalRange[AnyRun, snx.NXdetector]] = sc.scalar(5.0, unit=\"m\"), sc.scalar(35.0, unit=\"m\")\n",

diff --git a/packages/essimaging/tests/odin/data_reduction_test.py b/packages/essimaging/tests/odin/data_reduction_test.py
@@ -15,10 +15,9 @@
     Filename,
     LookupTableFilename,
     MaskingRules,
+    NeutronSourcePosition,
     NeXusDetectorName,
-    NXsource,
     OpenBeamRun,
-    Position,
     RawDetector,
     SampleRun,
     TofDetector,
@@ -40,7 +39,7 @@ def _make_workflow(wavelength_from: unwrap.WavelengthLutMode) -> sl.Pipeline:
         wf[LookupTableFilename] = odin.data.odin_wavelength_lookup_table()
     else:
         disk_choppers = odin_choppers(
-            source_position=wf.compute(Position[NXsource, SampleRun])
+            source_position=wf.compute(NeutronSourcePosition[SampleRun])
         )
         # Shortcut to set DiskChoppers for both [SampleRun, NXdetector] and
         # [OpenBeamRun, NXdetector] at once

diff --git a/packages/essnmx/src/ess/nmx/types.py b/packages/essnmx/src/ess/nmx/types.py
@@ -15,6 +15,7 @@
 
 RunType = nexus_types.RunType
 SampleRun = nexus_types.SampleRun
+NeutronSourcePosition = nexus_types.NeutronSourcePosition
 TofDetector = unwrap_types.TofDetector
 
 

diff --git a/packages/essnmx/src/ess/nmx/workflows.py b/packages/essnmx/src/ess/nmx/workflows.py
@@ -10,6 +10,7 @@
 from ess.reduce.nexus.types import (
     EmptyDetector,
     Filename,
+    NeutronSourcePosition,
     NeXusComponent,
     NeXusTransformation,
     Position,
@@ -86,7 +87,7 @@ def assemble_sample_metadata(
 
 
 def assemble_source_metadata(
-    source_position: Position[snx.NXsource, SampleRun],
+    source_position: NeutronSourcePosition[SampleRun],
 ) -> NMXSourceMetadata:
     """Assemble source metadata for NMX reduction workflow."""
     return NMXSourceMetadata(position=source_position)
@@ -150,7 +151,7 @@ def assemble_detector_metadata(
     detector_component: NeXusComponent[snx.NXdetector, SampleRun],
     transformation: NeXusTransformation[snx.NXdetector, SampleRun],
     sample_position: Position[snx.NXsample, SampleRun],
-    source_position: Position[snx.NXsource, SampleRun],
+    source_position: NeutronSourcePosition[SampleRun],
     empty_detector: EmptyDetector[SampleRun],
 ) -> NMXDetectorMetadata:
     """Assemble detector metadata for NMX reduction workflow."""