BFit3D.cc

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#include <cmath>
#ifndef M_PI
#define M_PI 3.1415926535897932385
#endif
 
#include "BFit3D_data.h"
 
using namespace magfieldparam;
 
//_______________________________________________________________________________
void BFit3D::SetCoeff_Linear(const double B) {
  unsigned jj, kk = 1;
  double w_0, w_1, B_mod = fabs(B);
  if (B_mod <= B_nom[0]) {
    w_0 = B / B_nom[0];
    for (jj = 0; jj < 360; ++jj) {
      C[jj] = w_0 * C0[jj][0];
    }
  } else if (B_mod >= B_nom[3]) {
    w_0 = B / B_nom[3];
    for (jj = 0; jj < 360; ++jj) {
      C[jj] = w_0 * C0[jj][3];
    }
  } else {
    while (B_nom[kk] < B_mod)
      ++kk;  //Simple linear search
    w_1 = (B_mod - B_nom[kk - 1]) / (B_nom[kk] - B_nom[kk - 1]);
    w_0 = 1.0 - w_1;
    if (B < 0.) {
      w_0 = -w_0;
      w_1 = -w_1;
    }
    for (jj = 0; jj < 360; ++jj) {
      C[jj] = w_0 * C0[jj][kk - 1] + w_1 * C0[jj][kk];
    }
  }
}
 
//_______________________________________________________________________________
void BFit3D::SetCoeff_Spline(const double B) {
  int jc, k0 = 0, k1 = 1;
  double dB2, dB = fabs(B);
  if (dB >= B_nom[3]) {  //Linear extrapolation for a large field
    dB -= B_nom[3];
    for (jc = 0; jc < 360; ++jc)
      C[jc] = C0[jc][3] + C1[jc][4] * dB;
  } else {
    if (dB < B_nom[0]) {
      dB2 = dB * dB / (3. * B_nom[0]);
      for (jc = 0; jc < 360; ++jc)
        C[jc] = (C2[jc][0] * dB2 + C1[jc][0]) * dB;
    } else {
      while (B_nom[k1] < dB)
        ++k1;  //Simple linear search
      k0 = k1 - 1;
      dB2 = (dB -= B_nom[k0]) / (3. * (B_nom[k1] - B_nom[k0]));
      if (k1 < 3) {  //"Regular" interval
        for (jc = 0; jc < 360; ++jc)
          C[jc] = (((C2[jc][k1] - C2[jc][k0]) * dB2 + C2[jc][k0]) * dB + C1[jc][k1]) * dB + C0[jc][k0];
      } else {  //The last interval
        dB2 = (1. - dB2) * dB;
        for (jc = 0; jc < 360; ++jc)
          C[jc] = (C2[jc][k0] * dB2 + C1[jc][k1]) * dB + C0[jc][k0];
      }
    }
  }
  if (B < 0)
    for (jc = 0; jc < 360; ++jc)
      C[jc] = -C[jc];
}
 
//_______________________________________________________________________________
void BFit3D::GetField(const double r, const double z, const double phi, double &Br, double &Bz, double &Bphi) {
  //Return field components in Br, Bz, Bphi. SetField must be called before use.
  //
  if (signed_rad || (r >= 0.))
    HB->SetPoint(r, z, phi);
  else
    HB->SetPoint(-r, z, phi + M_PI);
  HB->EvalBr();
  HB->EvalBz();
  HB->EvalBphi();
  Br = HB->GetBr(C);
  Bz = HB->GetBz(C);
  Bphi = HB->GetBphi(C);
}
 
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