diff --git a/tracy/tracy/src/nsls-ii_lib.cc b/tracy/tracy/src/nsls-ii_lib.cc
index 5a81b423b520ee7cc4311c751a5e21a1cda48d0e..04020b2398915957383df9b5bd0493311d5470d8 100644
--- a/tracy/tracy/src/nsls-ii_lib.cc
+++ b/tracy/tracy/src/nsls-ii_lib.cc
@@ -5,9 +5,9 @@
    T. Shaftan, I. Pinayev, Y. Luo, C. Montag, B. Nash
 
 */
-/* Current revision $Revision: 1.14 $
+/* Current revision $Revision: 1.15 $
  On branch $Name: not supported by cvs2svn $
- Latest change by $Author: nadolski $
+ Latest change by $Author: zhang $
 */
 
 // global params
@@ -478,7 +478,7 @@ void GetEmittance(const int Fnum, const bool prt)
   phi0 = fabs(asin(globval.U0/V_RF));
   globval.delta_RF =
     sqrt(-V_RF*cos(M_PI-phi0)*(2.0-(M_PI-2.0*(M_PI-phi0))
-    *tan(M_PI-phi0))/(globval.Alphac*M_PI*h_RF*1e9*globval.Energy));
+    *tan(M_PI-phi0))/(abs(globval.Alphac)*M_PI*h_RF*1e9*globval.Energy));
 
   // compute diffusion coeffs. for eigenvectors [sigma_xx, sigma_yy, sigma_zz]
   putlinmat(6, globval.Ascr, Ascr_map); Ascr_map += globval.CODvect;
@@ -5160,7 +5160,8 @@ void get_alphac2(void)
 
    Comments:
        change the initial coorinates from (0 0 0 0 delta 0) to 
-              (x_co,px_co,y_co,py_co,delta,0).	   
+              (x_co,px_co,y_co,py_co,delta,0).	i.e., track
+	      around the off-momentum close orbit but not zero orbit.      
 
 *******************************************************************/
 
@@ -5194,7 +5195,7 @@ void get_alphac2(void)
     
     cod = getcod(delta[n-1], lastpos);   
     x =  globval.CODvect;
-        
+      
    
       Cell_Pass(0, globval.Cell_nLoc, x, lastpos);
       alphac[n-1] = x[ct_]/Cell.S; // this is not mcf but DT/T