anchor.diff:    epsilon=c1m15
     gteps=one+epsilon
     lteps=one-epsilon
  +  r1lteps=cheby_r1(icheby(ix))*lteps
  +  r2gteps=cheby_r2(icheby(ix))*gteps
     
     XCLO=cheby_offset_x(icheby(ix))
     YCLO=cheby_offset_y(icheby(ix))
  
positive.code: subroutine cheby_potentialMap(iLens,ix)
  
    ! A. Mereghetti (CERN, BE-ABP-HSS)
    ! last modified: 01-03-2019
    ! dump map of potential
  
    use mod_common, only : bez
  
negative.code:   ax=abs(XA) ;
    ay=abs(YA) ;
    ! (x,y)<r1 or ( (xx>r2) || (yy>r2) ): no kick from lens
    if (.not. ( (ax.lt.r1lteps.and.ay.lt.r1lteps) .or. (ax.gt.r2gteps.or.ay.gt.r2gteps) ) ) then
       
      if (st_debug) then
        write(lout,'(2(a,1pe22.15))')'CHEBY> CHEBY_KICK_FOX computing at XA=',XA,' - YA=',YA
  