/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/MagneticField/ParametrizedEngine/plugins/BFit.cc

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#include "BFit.h"
#include <cstring>

using namespace std;
using namespace magfieldparam;

//_______________________________________________________________________________


#ifdef BFit_PW
const double BFit::Z_nom[4] = { -2.37615687260664e-2,
                                -1.86400109250045e-2,
                                -1.80502358070104e-2,
                                -1.60470955291956e-2 };

const double BFit::B_nom[4] = {  2.02156567013928,  //Nominal foeld values
                                 3.51622117206486,
                                 3.81143026675623,
                                 4.01242188708911 };

const double BFit::C_nom[4][16] = {{  1.0,                  -3.61278802720839e-3,
                                      6.36561393690475e-6,   8.32541914664693e-5,
                                     -2.42108313492765e-6,  -1.87295909297299e-5,
                                      3.06832709074461e-7,   1.91827319271226e-6,
                                     -2.15392717311725e-8,  -1.25266203359502e-7,
                                      3.87507522135914e-10,  4.85518568040635e-9,
                                      4.42080729840719e-11, -8.83065447433858e-11,
                                     -2.41380148377896e-12,  0.0 },
                                   {  1.0,                  -5.04020236643808e-3,
                                      2.03224205921125e-6,   6.79444854179620e-5,
                                     -1.98082200052911e-6,  -1.93324798138490e-5,
                                      3.15120940544812e-7,   1.82623212354924e-6,
                                     -3.30483297560429e-8,  -1.13251951654739e-7,
                                      1.96974144659278e-9,   4.25153392971594e-9,
                                     -6.12986034064675e-11, -7.59031334826116e-11,
                                      6.40295019219590e-13,  0.0 },
                                   {  1.0,                  -5.23012318846739e-3,
                                      8.80302231241395e-7,   6.51341641212249e-5,
                                     -1.68564063895995e-6,  -1.93693613146655e-5,
                                      2.58178734098114e-7,   1.81311192824207e-6,
                                     -2.79301520182866e-8,  -1.11679980224632e-7,
                                      1.72615649164433e-9,   4.17328869038146e-9,
                                     -5.72514160410955e-11, -7.41998111228714e-11,
                                      7.30938527053447e-13,  0.0 },
                                   {  1.0,                  -5.34172971309074e-3,
                                      2.48943649506081e-7,   6.23054033447814e-5,
                                     -1.60390978074464e-6,  -1.92618217244767e-5,
                                      2.42461261622770e-7,   1.78772142159379e-6,
                                     -2.61432416866515e-8,  -1.09159464672341e-7,
                                      1.62705377496138e-9,   4.02967933726133e-9,
                                     -5.48168162195020e-11, -7.00249566028285e-11,
                                      8.22254619144001e-13,  0.0 }};
#else
const double BFit::dZ_0 = -2.62328760352034e-2;
const double BFit::dZ_2 =  5.94363870284212e-4;

const double BFit::C_0[16] = {  1.0,                  -2.52864632909442e-3, 
                                8.76365790071351e-6,   9.19077286315044e-5, 
                               -2.49284256023752e-6,  -1.80143891826520e-5, 
                                2.29295162454016e-7,   1.96139195659245e-6, 
                               -3.47342625923464e-9,  -1.32147627969588e-7, 
                               -1.50735830442900e-9,   5.17724172101696e-9, 
                                1.54539960459831e-10, -9.30914368388717e-11, 
                               -5.20466591966397e-12,  0.0 };

const double BFit::C_2[16] = {  0.0,                  -2.96314154618866e-4, 
                               -6.04246295125223e-7,  -2.22393436573694e-6, 
                                2.84133631738674e-9,  -2.07090716476209e-7, 
                                2.55850963123821e-8,  -1.06689136150163e-8, 
                               -5.48842256680751e-9,   1.78987539969165e-9, 
                                5.57809366992069e-10, -8.25055601520632e-11, 
                               -3.18509299957904e-11,  1.11714602344300e-12, 
                                7.90102331886296e-13,  0.0 };

const double BFit::C_4[16] = {  0.0,                   7.57194953855834e-6, 
                                4.48169046115052e-9,   2.49606093449927e-8, 
                                3.42264285146368e-9,   7.95338846845187e-9, 
                               -1.57711106312732e-9,   1.02715424120585e-11, 
                                2.57261485255293e-10, -2.41682937761163e-11, 
                               -2.27894837943020e-11,  7.98570801347331e-13, 
                                1.17889573705870e-12,  1.64571374852252e-14, 
                               -2.60212133934707e-14,  0.0 };
#endif
//_______________________________________________________________________________
BFit::BFit()
{
   dZ = 0.;
   memset(C, 0, 16*sizeof(double));
   rz_poly *P_base = new rz_poly(16); //Potential basis
   
   Bz_base = new rz_poly(P_base->Diff(1));  //Bz basis
   Bz_base->SetOFF(1);                      //Switch off linear term

   Br_base = new rz_poly(P_base->Diff(0));  //Br basis is shifted, so
   Br_base->SetOFF(0);                      //"0" term is ignored
   
   delete P_base;
}

//_______________________________________________________________________________
void BFit::SetField(double B)
{
//Set nominal field [Tesla]
//
   unsigned int jj;

#ifdef BFit_PW
   unsigned int kk = 1;
   double w_0, w_1;
   if (B <= B_nom[0]) {
      dZ = Z_nom[0];
      for (jj = 0; jj < 16; ++jj) {
         C[jj] = B*C_nom[0][jj];
      }
   } else if (B >= B_nom[3]) {
      dZ = Z_nom[3];
      for (jj = 0; jj < 16; ++jj) {
         C[jj] = B*C_nom[3][jj];
      }
   } else {
      while (B_nom[kk] < B) ++kk;
      w_1 = (B - B_nom[kk-1])/(B_nom[kk] - B_nom[kk-1]);
      w_0 = 1.0 - w_1;
      dZ = Z_nom[kk-1]*w_0 + Z_nom[kk]*w_1;
      for (jj = 0; jj < 16; ++jj) {
         C[jj] = B*(C_nom[kk-1][jj]*w_0 + C_nom[kk][jj]*w_1);
      }
   }
#else
   double B2 = B*B;
   dZ = dZ_0 + dZ_2*B2;
   for (jj = 0; jj < 16; ++jj) {
      C[jj] = B*((C_4[jj]*B2 + C_2[jj])*B2 + C_0[jj]);
   }
#endif
}

//_______________________________________________________________________________
void BFit::GetField(double r,   double z,   double phi,
                    double &Br, double &Bz, double &Bphi)
{
//Get field components in the point (r,z,phi). Always return Bphi=0. 
//Parameters phi and Bphi introduced in order to keep interface
//compatible with future trully 3D version
//
   double zc = z + dZ;

   Bz   = Bz_base->GetSVal(r, zc, C);
   Br   = Br_base->GetSVal(r, zc, C+1);
   Bphi = 0.;
}