src/aare/daq/devices.py

@@ -27,6 +27,8 @@ from aare.devices.tell_client import make_tell_client
 
 logger = setup_logger("aareDAQ")
 
+CHI_ZERO_TOLERANCE_DEG = 1e-3
+
 
 class BeamlineDevices:
     def __init__(self, beamline: MXBeamline, dispatch: BeamlineDispatch):
@@ -346,6 +348,10 @@ class BeamlineDevices:
         return self._smargon.readback
 
     def set_smargon_pos(self, pos: SmargonCoordinate, /, wait: bool = True):
+        # TELL air blower must be off before chi leaves zero
+        if pos.chi_deg is not None and abs(pos.chi_deg) > CHI_ZERO_TOLERANCE_DEG:
+            logger.info(f"Switching TELL blower off before moving chi to {pos.chi_deg:.3f} deg")
+            self.tell.blower_off()
         self._smargon.target = pos
 
     @smargon_pos.setter