fix(eiger): Eiger should take initial energy from ccm

csaxs_bec/devices/jungfraujoch/eiger.py

@@ -36,6 +36,7 @@ import os
 import time
 from typing import TYPE_CHECKING, Literal
 
+import numpy as np
 import yaml
 from bec_lib.file_utils import get_full_path
 from bec_lib.logger import bec_logger
@@ -117,6 +118,8 @@ class Eiger(PSIDeviceBase):
         self._full_path = ""
         self._num_triggers = 0
         self._wait_for_on_complete = 20  # seconds
+        # Initial incident energy in keV, if restarted None
+        self._incident_energy: float | None = None
         if self.device_manager is not None:
             self.device_manager: DeviceManagerDS
         self.scan_parameters: ScanServerScanInfo | None = None
@@ -272,7 +275,25 @@ class Eiger(PSIDeviceBase):
 
         # TODO: Check mono energy from device in BEC
         # Setting incident energy in keV
-        incident_energy = 12.0
+
+        try:
+            incident_energy = self._get_beam_energy(self.device_manager)
+            if self._incident_energy is None:
+                self._incident_energy = incident_energy
+            elif not np.isclose(
+                self._incident_energy, incident_energy, atol=0.01
+            ):  # 10 keV tolerance
+                logger.warning(
+                    f"Incident energy changed from {self._incident_energy} keV to {incident_energy} keV for device {self.name}. "
+                )
+                self._incident_energy = incident_energy
+        except Exception as e:
+            logger.warning(f"Failed to set up beam energy for {self.name}: {e}")
+            incident_energy = 12.0  #    default to 12 keV if error occurs
+            self._incident_energy = incident_energy
+
+        logger.info(f"Device {self.name} uses incident energy of {incident_energy} keV.")
+
         # Setting up exp_time and num_triggers acquisition parameter
         exp_time = self.scan_parameters.exp_time
         if exp_time <= self._readout_time:  # Exp_time must be at least the readout time
@@ -417,3 +438,18 @@ class Eiger(PSIDeviceBase):
         self.jfj_preview_client.stop()
         self.on_stop()
         return super().on_destroy()
+
+    def _get_beam_energy(self, device_manager: DeviceManagerDS) -> float:
+        """
+        Fetch the beam energy from the device manager.
+
+        Args:
+            device_manager (DeviceManagerDS): The device manager to fetch the beam energy from.
+
+        Returns:
+            float: The beam energy in keV.
+        """
+        if hasattr(device_manager, "devices") and hasattr(device_manager.devices, "ccm_energy"):
+            energy = device_manager.devices.ccm_energy.get()
+
+        return energy