Merge branch 'master' into 87-issues-when-running-on-a-machine-with-c…

…uda-gpus

CHANGELOG.md

@@ -16,6 +16,7 @@ None
 - Fix the transfer maps in `Drift` and `Dipole`; Add R56 in horizontal and vertical correctors modelling (see #90) (@cr-xu)
 - Fix fringe_field_exit of `Dipole` is overwritten by `fringe_field` bug (see #99) (@cr-xu)
 - Fix error caused by mismatched devices on machines with CUDA GPUs (see #97) (@jank324)
+- Fix error raised when tracking a `ParameterBeam` through an active `BPM` (see #101) (@jank324)
 
 ### 🐆 Other
 

cheetah/accelerator.py

@@ -1186,7 +1186,7 @@ def track(self, incoming: Beam) -> Beam:
         if incoming is Beam.empty:
             self.reading = None
         elif isinstance(incoming, ParameterBeam):
-            self.reading = torch.stack([incoming._mu_x, incoming._mu_y])
+            self.reading = torch.stack([incoming.mu_x, incoming.mu_y])
         elif isinstance(incoming, ParticleBeam):
             self.reading = torch.stack([incoming.mu_x, incoming.mu_y])
         else:

tests/test_bpm.py

@@ -0,0 +1,22 @@
+import pytest
+import torch
+
+import cheetah
+
+
+@pytest.mark.parametrize("is_bpm_active", [True, False])
+@pytest.mark.parametrize("beam_class", [cheetah.ParticleBeam, cheetah.ParameterBeam])
+def test_no_tracking_error(is_bpm_active, beam_class):
+    """Test that tracking a beam through an inactive BPM does not raise an error."""
+    segment = cheetah.Segment(
+        elements=[
+            cheetah.Drift(length=torch.tensor(1.0)),
+            cheetah.BPM(name="my_bpm"),
+            cheetah.Drift(length=torch.tensor(1.0)),
+        ],
+    )
+    beam = beam_class.from_astra("benchmark/cheetah/ACHIP_EA1_2021.1351.001")
+
+    segment.my_bpm.is_active = is_bpm_active
+
+    _ = segment.track(beam)