Remove source position from monitor

src/ess/reduce/nexus/workflow.py

@@ -434,7 +434,6 @@ def get_calibrated_monitor(
     monitor: NeXusComponent[MonitorType, RunType],
     transform: NeXusTransformation[MonitorType, RunType],
     offset: MonitorPositionOffset[RunType, MonitorType],
-    source_position: Position[snx.NXsource, RunType],
 ) -> EmptyMonitor[RunType, MonitorType]:
     """
     Extract the data array corresponding to a monitor's signal field.
@@ -450,15 +449,12 @@ def get_calibrated_monitor(
         Transformation matrix for the monitor.
     offset:
         Offset to add to the monitor position.
-    source_position:
-        Position of the neutron source.
     """
     transform_unit = transform.value.unit
     return EmptyMonitor[RunType, MonitorType](
         nexus.extract_signal_data_array(monitor).assign_coords(
             position=transform.value * sc.vector([0, 0, 0], unit=transform_unit)
             + offset.to(unit=transform_unit),
-            source_position=source_position,
         )
     )
 

src/ess/reduce/time_of_flight/eto_to_tof.py

@@ -317,7 +317,19 @@ def _time_of_flight_data_events(
     parts = da.bins.constituents
     parts["data"] = tofs
     result = da.bins.assign_coords(tof=sc.bins(**parts, validate_indices=False))
-    return result.bins.drop_coords("event_time_offset")
+    out = result.bins.drop_coords("event_time_offset")
+
+    # The result may still have an 'event_time_zero' dimension (in the case of an
+    # event monitor where events were not grouped by pixel).
+    if "event_time_zero" in out.dims:
+        if ("event_time_zero" in out.coords) and (
+            "event_time_zero" not in out.bins.coords
+        ):
+            out.bins.coords["event_time_zero"] = sc.bins_like(
+                out, out.coords["event_time_zero"]
+            )
+        out = out.bins.concat("event_time_zero")
+    return out
 
 
 def detector_ltotal_from_straight_line_approximation(
@@ -357,6 +369,7 @@ def detector_ltotal_from_straight_line_approximation(
 
 def monitor_ltotal_from_straight_line_approximation(
     monitor_beamline: EmptyMonitor[RunType, MonitorType],
+    source_position: Position[snx.NXsource, RunType],
 ) -> MonitorLtotal[RunType, MonitorType]:
     """
     Compute Ltotal for the monitor.
@@ -369,7 +382,10 @@ def monitor_ltotal_from_straight_line_approximation(
         Beamline data for the monitor that contains the positions necessary to compute
         the straight-line approximation to Ltotal (source and monitor positions).
     """
-    graph = scn.conversion.graph.beamline.beamline(scatter=False)
+    graph = {
+        **scn.conversion.graph.beamline.beamline(scatter=False),
+        'source_position': lambda: source_position,
+    }
     return MonitorLtotal[RunType, MonitorType](
         monitor_beamline.transform_coords(
             "Ltotal", graph=graph, keep_intermediate=False

tests/nexus/workflow_test.py

@@ -502,13 +502,12 @@ def test_get_calibrated_monitor_extracts_data_field_from_nexus_monitor(
     monitor = workflow.get_calibrated_monitor(
         nexus_monitor,
         offset=workflow.no_offset,
-        source_position=sc.vector([0.0, 0.0, -10.0], unit='m'),
         transform=NeXusTransformation.from_chain(
             workflow.get_transformation_chain(nexus_monitor),
         ),
     )
     assert_identical(
-        monitor.drop_coords(('position', 'source_position')),
+        monitor.drop_coords('position'),
         compute_component_position(nexus_monitor)['data'],
     )
 
@@ -520,7 +519,6 @@ def test_get_calibrated_monitor_subtracts_offset_from_position(
     monitor = workflow.get_calibrated_monitor(
         nexus_monitor,
         offset=offset,
-        source_position=sc.vector([0.0, 0.0, -10.0], unit='m'),
         transform=NeXusTransformation.from_chain(
             workflow.get_transformation_chain(nexus_monitor),
         ),
@@ -551,17 +549,12 @@ def test_get_calibrated_monitor_with_time_dependent_transformation(
     )
 
     # Get the calibrated monitor
-    source_position = sc.vector([0.0, 0.0, -10.0], unit='m')
     monitor = workflow.get_calibrated_monitor(
-        nexus_monitor,
-        transform=transform,
-        offset=workflow.no_offset,
-        source_position=source_position,
+        nexus_monitor, transform=transform, offset=workflow.no_offset
     )
 
     # Verify the monitor has the correct structure
     assert 'position' in monitor.coords
-    assert 'source_position' in monitor.coords
 
     # Verify the position is correctly computed
     # The transformation: translate (1, 0, 0) then translate (0, 2, 0)
@@ -571,9 +564,6 @@ def test_get_calibrated_monitor_with_time_dependent_transformation(
         monitor.coords['position'], expected_position, rtol=sc.scalar(1e-10)
     )
 
-    # Verify source position is preserved
-    assert_identical(monitor.coords['source_position'], source_position)
-
 
 @pytest.fixture
 def calibrated_monitor() -> workflow.EmptyMonitor[SampleRun, FrameMonitor1]:
@@ -685,7 +675,6 @@ def test_load_event_monitor_workflow(loki_tutorial_sample_run_60250: Path) -> No
     wf[NeXusName[FrameMonitor1]] = 'monitor_1'
     da = wf.compute(RawMonitor[SampleRun, FrameMonitor1])
     assert 'position' in da.coords
-    assert 'source_position' in da.coords
     assert da.bins is not None
     assert da.dims == ('event_time_zero',)
     assert da.bins.constituents['data'].variances is not None
@@ -697,7 +686,6 @@ def test_load_histogram_monitor_workflow(dream_coda_test_file: Path) -> None:
     wf[NeXusName[FrameMonitor1]] = 'monitor_bunker'
     da = wf.compute(RawMonitor[SampleRun, FrameMonitor1])
     assert 'position' in da.coords
-    assert 'source_position' in da.coords
     assert da.bins is None
     assert set(da.dims) == {'time', 'frame_time'}
     assert 'time' in da.coords.keys()
@@ -755,7 +743,6 @@ def test_generic_nexus_workflow(
     assert da.dims == ('detector_number',)
     da = wf.compute(RawMonitor[SampleRun, FrameMonitor1])
     assert 'position' in da.coords
-    assert 'source_position' in da.coords
     assert da.bins is not None
     assert da.dims == ('event_time_zero',)