From 86e337c17cbac59edef693efc839d52d29fd01d5 Mon Sep 17 00:00:00 2001
From: Jan-Lukas Wynen <jan-lukas.wynen@ess.eu>
Date: Tue, 3 Mar 2026 16:22:18 +0100
Subject: [PATCH 1/2] Add measurement metadata to CIF

---
 src/ess/dream/io/cif.py | 7 +++++++
 src/ess/powder/types.py | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/src/ess/dream/io/cif.py b/src/ess/dream/io/cif.py
index 050735a6..2bc4ebd0 100644
--- a/src/ess/dream/io/cif.py
+++ b/src/ess/dream/io/cif.py
@@ -12,6 +12,7 @@
     CIFAuthors,
     EmptyCanSubtractedIntensityTof,
     IntensityTof,
+    Measurement,
     ReducedEmptyCanSubtractedTofCIF,
     ReducedTofCIF,
     ReducerSoftware,
@@ -26,6 +27,7 @@ def prepare_reduced_tof_cif(
     authors: CIFAuthors,
     beamline: Beamline[SampleRun],
     source: Source[SampleRun],
+    measurement: Measurement[SampleRun],
     reducers: ReducerSoftware,
     calibration: OutputCalibrationData,
 ) -> ReducedTofCIF:
@@ -61,6 +63,7 @@ def prepare_reduced_tof_cif(
         authors=authors,
         beamline=beamline,
         source=source,
+        measurement=measurement,
         reducers=reducers,
         calibration=calibration,
     )
@@ -72,6 +75,7 @@ def prepare_reduced_empty_can_subtracted_tof_cif(
     authors: CIFAuthors,
     beamline: Beamline[SampleRun],
     source: Source[SampleRun],
+    measurement: Measurement[SampleRun],
     reducers: ReducerSoftware,
     calibration: OutputCalibrationData,
 ) -> ReducedEmptyCanSubtractedTofCIF:
@@ -107,6 +111,7 @@ def prepare_reduced_empty_can_subtracted_tof_cif(
         authors=authors,
         beamline=beamline,
         source=source,
+        measurement=measurement,
         reducers=reducers,
         calibration=calibration,
     )
@@ -118,12 +123,14 @@ def _prepare_reduced_tof_cif_impl(
     authors: CIFAuthors,
     beamline: Beamline[SampleRun],
     source: Source[SampleRun],
+    measurement: Measurement[SampleRun],
     reducers: ReducerSoftware,
     calibration: OutputCalibrationData,
 ) -> ReducedTofCIF:
     to_save = _prepare_data(da)
     return ReducedTofCIF(
         cif.CIF('reduced_tof')
+        .with_measurement(measurement)
         .with_reducers(*(reducer.compact_repr for reducer in reducers))
         .with_authors(*authors)
         .with_beamline(beamline, source)
diff --git a/src/ess/powder/types.py b/src/ess/powder/types.py
index 5d34ffdd..aeace7df 100644
--- a/src/ess/powder/types.py
+++ b/src/ess/powder/types.py
@@ -215,6 +215,9 @@ class RawDataAndMetadata(sciline.Scope[RunType, sc.DataGroup], sc.DataGroup):
 Beamline = reduce_t.Beamline
 """Beamline metadata."""
 
+Measurement = reduce_t.Measurement
+"""Measurement metadata."""
+
 ReducerSoftware = NewType('ReducerSoftware', list[Software])
 """Pieces of software used to reduce the data."""
 

From db53d6b26dde57e03dbf26f370f02e4b7f5c60af Mon Sep 17 00:00:00 2001
From: Jan-Lukas Wynen <jan-lukas.wynen@ess.eu>
Date: Wed, 4 Mar 2026 10:06:36 +0100
Subject: [PATCH 2/2] Set Measurement metadata in geant4 pipeline

---
 src/ess/dream/workflows.py | 5 +++++
 tests/dream/io/cif_test.py | 9 ++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/ess/dream/workflows.py b/src/ess/dream/workflows.py
index b8742f05..b7a984fe 100644
--- a/src/ess/dream/workflows.py
+++ b/src/ess/dream/workflows.py
@@ -19,6 +19,7 @@
     EmptyCanRun,
     KeepEvents,
     LookupTableRelativeErrorThreshold,
+    Measurement,
     PixelMaskFilename,
     Position,
     ReducerSoftware,
@@ -211,6 +212,10 @@ def DreamGeant4Workflow(*, run_norm: RunNormalization, **kwargs) -> sciline.Pipe
         AccumulatedProtonCharge[EmptyCanRun]: charge,
         CaveMonitorPosition: sc.vector([0.0, 0.0, -4220.0], unit='mm'),
         LookupTableRelativeErrorThreshold: 0.02,
+        # The GEANT4 files do not encode measurement information
+        Measurement[SampleRun]: Measurement[SampleRun](title=None),
+        Measurement[VanadiumRun]: Measurement[VanadiumRun](title=None),
+        Measurement[EmptyCanRun]: Measurement[EmptyCanRun](title=None),
     }
     for key, value in additional_parameters.items():
         wf[key] = value
diff --git a/tests/dream/io/cif_test.py b/tests/dream/io/cif_test.py
index 2a58b923..69420668 100644
--- a/tests/dream/io/cif_test.py
+++ b/tests/dream/io/cif_test.py
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
-
+import datetime
 import io
 
 import pytest
@@ -14,6 +14,7 @@
     Beamline,
     CIFAuthors,
     IntensityTof,
+    Measurement,
     ReducerSoftware,
     Software,
 )
@@ -60,6 +61,10 @@ def test_save_reduced_tof(ioftof: IntensityTof, cal: OutputCalibrationData) -> N
             site="ESS",
         ),
         source=ESS_SOURCE,
+        measurement=Measurement(
+            title="Test measurement",
+            start_time=datetime.datetime(2026, 1, 2, 14, 58, 2, tzinfo=datetime.UTC),
+        ),
         reducers=ReducerSoftware(
             [
                 Software.from_package_metadata('ess.diffraction'),
@@ -78,6 +83,8 @@ def test_save_reduced_tof(ioftof: IntensityTof, cal: OutputCalibrationData) -> N
     assert f"ess.dream {__version__}" in result
     assert f"ess.powder {__version__}" in result
     assert '_diffrn_source.beamline DREAM' in result
+    assert "_sc_meas.title 'Test measurement'" in result
+    assert "_pd_meas.datetime_initiated 2026-01-02T14:58:02" in result
     assert 'ZERO 0 0.2' in result
     assert 'DIFC 1 1.2' in result
     assert 'DIFA 2 -1.4' in result