MCNPX Visual Editor Version X_24J 
c     Created on: Saturday, August 15, 2015 at 09:50                            
    1     0         -1  imp:n=1  
    2     0         -2 1  imp:n=1  
    3     0         2  imp:n=0  

    1       trc 0 0 -50 0 0 100 40 20 
    2        so 100 

mode  n
sdef rad=d1 ext=d2 axs= 0 0 1 pos= 0 0 -50   cel=1                              
si1  40                                                                         
si2  0 50 100                                                                   
sp2  0 1 1                                                                      
c sb2  0 1 5 $ Source biasing with cell rejection gives wrong answers             
nps  10000                                                                      
f1:n  2