diff --git a/NPLib/Physics/NPBeam.cxx b/NPLib/Physics/NPBeam.cxx
index d9487db7aaf14d5c7e0b7b9dcd77498aecf55d93..e7644c7e4076621954b17203ce309dcb608e451a 100644
--- a/NPLib/Physics/NPBeam.cxx
+++ b/NPLib/Physics/NPBeam.cxx
@@ -50,6 +50,7 @@ using namespace NPL;
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... 
 Beam::Beam(){
+  fExcitationEnergy = 0; 
   fEnergy = 0;
   fSigmaEnergy = -1 ;
   fMeanX = 0 ;