Benchmark problem calculation by MCNP-- limestone 20 PU 
1      1  -1.0   -2  1  -3                                    $source chamber
2      2  -3.67  -4  5  -6                                   $near NaI
3      1  -1.0   1   -7  4  -3                               $near collimator
4      2  -3.67  -8  9  -10                                 $far NaI
5      1  -1.0   1   -11 8  -3                              $far collimator
6      3  -19.3   14 -15  -3 #1 #2 #3 #4 #5     $tool
7      4  -1.0       3   -12   14  -15                      $borehole
8      5  -2.36    14  -15   12  -13                     $formation
9      0             -14:15:13                                 $outside world

1      px  0.0
2      gq  0.5 1.0 0.5 0.0 0.0 -1.0 0.0 0.0 0.0 -1.0 
3      cz   5.0
4      cz   1.0
5      pz   19
6      pz   21
7      c/x  0.0   20.0  1.0
8      cz   2.0
9      pz   38
10     pz   42
11     c/x  0.0   40.0  2.0
12     c/z  -5.0  0.0   10.0
13     c/z  -5.0  0.0   200.
14     pz     -100.
15     pz      200.

mode p      
imp:p  1 7r 0
sdef   erg=0.662 pos=0.0001 0  0  dir=d1 vec=0.707  0  0.707
sb1     -31  3          
idum    3   1  30 
                 -1  15  
                  1  30  
                  1     1
rdum           -31     60.1  
                 0.001     45.0  
                     -22     70.1  
                        0     1e20
wwg   11  1   0   0  0 40
wwge:p  0.134  0.268  0.402  0.536  0.670
m1     8000.01p   1.
m2     11000.01p  0.5      53000.01p  0.5 
m3     26000.01p  1. 
m4     1000.01p   0.66667  8000.01p   0.33333
m5     1000.01p   -0.01    6000.01p   -0.11 
          8000.01p   -0.514   20000.01p  -0.366   
f14:p  4  
f24:p  4
e24     25e-3    50e-3   75e-3  100e-3  125e-3  150e-3  
       175e-3   200e-3  225e-3  250e-3  275e-3  300e-3  325e-3 
       350e-3   375e-3  400e-3  425e-3  450e-3  475e-3  500e-3 
       525e-3   550e-3  575e-3  600e-3  625e-3  650e-3  675e-3 
f1:p  8
c1    0  1
f11:p 8
cut:p  j  0.010       
prdmp  -900         -4000  
nps    4000000