Add event time offset to component reading

src/tof/chopper.py

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
+from __future__ import annotations
 
-from dataclasses import dataclass
+from dataclasses import dataclass, replace
 from enum import Enum
 
 import scipp as sc
@@ -215,3 +216,8 @@ def __repr__(self) -> str:
 
     def __str__(self) -> str:
         return self.__repr__()
+
+    def __getitem__(self, val: int | slice | tuple[str, int | slice]) -> ChopperReading:
+        if isinstance(val, int):
+            val = ('pulse', val)
+        return replace(self, data=self.data[val])

src/tof/detector.py

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
+from __future__ import annotations
 
-from dataclasses import dataclass
+from dataclasses import dataclass, replace
 
 import scipp as sc
 
@@ -53,3 +54,10 @@ def __repr__(self) -> str:
 
     def __str__(self) -> str:
         return self.__repr__()
+
+    def __getitem__(
+        self, val: int | slice | tuple[str, int | slice]
+    ) -> DetectorReading:
+        if isinstance(val, int):
+            val = ('pulse', val)
+        return replace(self, data=self.data[val])

src/tof/model.py

@@ -139,6 +139,9 @@ def run(self):
             container[c.name]['data'] = self.source.data.copy(deep=False)
             t = birth_time + (c.distance / speed).to(unit=birth_time.unit, copy=False)
             container[c.name]['data'].coords['toa'] = t
+            container[c.name]['data'].coords['eto'] = t % (
+                1 / self.source.frequency
+            ).to(unit=t.unit, copy=False)
             container[c.name]['data'].coords['distance'] = c.distance
             # TODO: remove 'tof' coordinate once deprecation period is over
             container[c.name]['data'].coords['tof'] = t

src/tof/reading.py

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2025 Scipp contributors (https://github.com/scipp)
 
+from __future__ import annotations
+
 from dataclasses import dataclass
 
 import plopp as pp
@@ -57,7 +59,9 @@ def __repr__(self) -> str:
     def __str__(self) -> str:
         return self.__repr__()
 
-    def __getitem__(self, val):
+    def __getitem__(self, val: int | slice | tuple[str, int | slice]) -> ReadingField:
+        if isinstance(val, int):
+            val = ('pulse', val)
         return self.__class__(data=self.data[val], dim=self.dim)
 
 
@@ -80,18 +84,37 @@ class ComponentReading:
 
     @property
     def toa(self) -> ReadingField:
+        """
+        Time of arrival of the neutrons at the component.
+        """
         return _make_reading_field(self.data, dim="toa")
 
+    @property
+    def eto(self) -> ReadingField:
+        """
+        Event time offset of the neutrons at the component (= toa modulo pulse period).
+        """
+        return _make_reading_field(self.data, dim="eto")
+
     @property
     def wavelength(self) -> ReadingField:
+        """
+        Wavelength of the neutrons at the component.
+        """
         return _make_reading_field(self.data, dim="wavelength")
 
     @property
     def birth_time(self) -> ReadingField:
+        """
+        Birth time of the neutrons at the source.
+        """
         return _make_reading_field(self.data, dim="birth_time")
 
     @property
     def speed(self) -> ReadingField:
+        """
+        Speed of the neutrons at the component.
+        """
         return _make_reading_field(self.data, dim="speed")
 
     def plot(self, bins: int = 300) -> Plot:

tests/result_test.py

@@ -216,6 +216,51 @@ def test_component_results_data_slice_step(chopper, detector, multi_pulse_source
     assert 'event' in toas.dims
 
 
+def test_component_results_slice_all_results(chopper, detector, multi_pulse_source):
+    model = tof.Model(
+        source=multi_pulse_source, choppers=[chopper], detectors=[detector]
+    )
+    res = model.run()
+    ch = res.choppers['chopper']
+
+    reading = ch['pulse', 0]
+    toas = reading.toa.data
+    assert 'pulse' not in toas.dims
+    assert 'event' in toas.dims
+    wavelengths = reading.wavelength.data
+    assert 'pulse' not in wavelengths.dims
+    assert 'event' in wavelengths.dims
+
+
+def test_component_results_slice_no_pulse_dim(chopper, detector, multi_pulse_source):
+    model = tof.Model(
+        source=multi_pulse_source, choppers=[chopper], detectors=[detector]
+    )
+    res = model.run()
+    ch = res.choppers['chopper']
+
+    reading = ch[0]  # No pulse dim
+    data = reading.data
+    assert 'pulse' not in data.dims
+    assert 'event' in data.dims
+
+    toas = ch.toa[1].data
+    assert 'pulse' not in toas.dims
+    assert 'event' in toas.dims
+
+
+def test_component_results_eto(chopper, detector, multi_pulse_source):
+    model = tof.Model(
+        source=multi_pulse_source, choppers=[chopper], detectors=[detector]
+    )
+    res = model.run()
+    data = res['detector'].data
+    assert 'eto' in data.coords
+    assert data.coords['eto'].max() < (1 / model.source.frequency).to(
+        unit=data.coords['eto'].unit
+    )
+
+
 def test_result_plot_does_not_raise():
     model = make_ess_model()
     res = model.run()