diff --git a/eos/file_reader.py b/eos/file_reader.py
index 3f64e81..3bc1806 100644
--- a/eos/file_reader.py
+++ b/eos/file_reader.py
@@ -575,13 +575,12 @@ class AmorEventData(AmorHeader):
         plse = np.array([0, 5, 6, 11])
         base = np.array([2, 3, 8, 9])
         _time = self._beam_monitor.time
-        _signal = self._beam_monitor.signal[(self.eventStartTime<=_time)&
-                                            (_time<=packets.time[-1])]
-        _time = _time[(self.eventStartTime<=_time)&
-                      (_time<=packets.time[-1])]
-        beam_monitor = np.recarray(shape=np.shape(_time)[0], dtype=BM_TYPE)
+        fltr = (self.eventStartTime<=_time)&(_time<=packets.time[-1])
+        _time = _time[fltr]
+        _signal = self._beam_monitor.signal[fltr]
+        beam_monitor = np.recarray(shape=_time.shape[0], dtype=BM_TYPE)
         beam_monitor.time = _time
-        beam_monitor.value[:] =  np.sum(_signal[:, plse], axis=1) - np.sum(_signal[:, base], axis=1)
+        beam_monitor.value = _signal[:, plse].sum(axis=1) - _signal[:, base].sum(axis=1)
         return beam_monitor
 
     def info(self):