[Fix] ExponentialDamper

mbtrack2/tracking/feedback.py

@@ -30,15 +30,12 @@ class ExponentialDamper(Element):
         self.plane = plane
         if self.plane == "x":
             self.action = "xp"
-            self.damp_idx = 0
             self.mean_idx = 1
         elif self.plane == "y":
             self.action = "yp"
-            self.damp_idx = 1
             self.mean_idx = 3
         elif self.plane == "s":
             self.action = "delta"
-            self.damp_idx = 2
             self.mean_idx = 5
         else:
             raise ValueError(f"plane should be x, y or s, not {self.plane}")
@@ -55,7 +52,7 @@ class ExponentialDamper(Element):
         bunch : Bunch or Beam object
         """
         bunch[self.action] -= (2*self.ring.T0/
-                               self.damping_time[self.damp_idx]*
+                               self.damping_time*
                                np.sin(self.phase_diff)*
                                bunch.mean[self.mean_idx])