anchor.diff:         if(xi < frac_check) then
             if(.not.in_correct_cell(p)) then
                call warn("grid_escape_tau","not in correct cell - killing")
  +             killed_photons_geo = killed_photons_geo + 1
                killed = .true.
                return
             end if
  
positive.code:        if(xi < frac_check) then
            if(.not.in_correct_cell(p)) then
               call warn("grid_escape_column_density","not in correct cell - killing")
               killed = .true.
               return
            end if
  
negative.code: 
         if(id_min == no_wall) then
            call warn("grid_escape_column_density","cannot find next wall - killing")
            killed_photons_geo = killed_photons_geo + 1
            killed = .true.
            return
         end if
  