anchor.diff:      y_flk  = zero
       xp_flk = zero
       yp_flk = zero
  +
  +! Log input energy + nucleons as per the FLUKA coupling
  +    nnuc0   = nnuc0 + naa(j)
  +    ien0    = ien0 + rcp(j) * c1e3
  +
   
       ! Transform particle coordinates to get into collimator coordinate  system
       ! First do rotation into collimator frame
  
positive.code:   real(kind=fPrec) xIn,xpIn,yIn,ypIn,xOut,xpOut,yOut,ypOut,sImp,sOut
    real(kind=fPrec) x_in0,xp_in0
  
    ! Initilaisation
    mat    = cdb_cMaterialID(icoll)
    length = c_length
  
negative.code:   sRot   = sin_mb(c_rotation)
    cRRot  = cos_mb(-c_rotation)
    sRRot  = sin_mb(-c_rotation)
  
    !Set energy and nucleon change variables as with the coupling
    nnuc0 = 0
    ien0  = zero
    nnuc1 = 0
    ien1  = zero
  
    do j=1,napx
  
  