BFieldComponent3d Class Reference

The BFieldComponent3d class. More...

#include <BFieldComponent3d.h>

Inheritance diagram for BFieldComponent3d:

Public Member Functions
	BFieldComponent3d ()=default
	The BFieldComponent3d constructor.
virtual	~BFieldComponent3d ()=default
	The BFieldComponent3d destructor.
virtual void	initialize () override
	Initializes the magnetic field component.
virtual ROOT::Math::XYZVector	calculate (const ROOT::Math::XYZVector &point) const override
	Calculates the magnetic field vector at the specified space point.
virtual void	terminate () override
	Terminates the magnetic field component.
void	setMapFilename (const std::string &filename)
	Sets the filename of the magnetic field map.
void	setMapSize (int sizeR, int sizePhi, int sizeZ)
	Sets the size of the magnetic field map.
void	setMapRegionZ (double minZ, double maxZ, double offset)
	Sets the size of the magnetic field map.
void	setMapRegionR (double minR, double maxR)
	Sets the size of the magnetic field map.
void	setGridPitch (double pitchR, double pitchPhi, double pitchZ)
	Sets the grid pitch of the magnetic field map.
void	setExcludeRegionZ (double minZ, double maxZ)
	Sets the size of the magnetic field map to exclude.
void	setExcludeRegionR (double minR, double maxR)
	Sets the size of the magnetic field map to exclude.
void	setErrorRegionR (double minR=-1., double maxR=-1., double errBr=0.0, double errBphi=0.0, double errBz=0.0)
	Sets the size of the magnetic field map to apply error on B.
void	mirrorPhi (bool mirrorPhi=0.)
void	doInterpolation (bool interpolate=true)
void	enableCoordinate (const std::string &mapEnable="rphiz")
	Option to reduce 3D to 2D map (in coordinates, NOT Br, Bphi, Bz components)

Private Member Functions
ROOT::Math::XYZVector	interpolate (unsigned int ir, unsigned int iphi, unsigned int iz, double wr, double wphi, double wz) const
	Interpolate the value of B-field between (ir, iphi, iz) and (ir+1, iphi+1, iz+1) using weights (wr, wphi, wz)

Private Attributes
std::string	m_mapFilename {""}
	The filename of the magnetic field map.
std::vector< ROOT::Math::XYZVector >	m_bmap
	The memory buffer for the magnetic field map.
std::string	m_mapEnable {"rphiz"}
	Enable different dimension, "rphiz", "rphi", "phiz" or "rz" >
bool	m_interpolate {true}
	Flag to switch on/off interpolation >
int	m_mapSize [3]
	The size of the map in r, phi and z.
double	m_mapRegionZ [2] {0}
	The min and max boundaries of the map region in z.
double	m_mapOffset {0}
	Offset required because the accelerator group defines the Belle center as zero.
double	m_mapRegionR [2] {0}
	The min and max boundaries of the map region in r.
double	m_gridPitch [3] {0}
	The grid pitch in r,phi,z.
double	m_igridPitch [3] {0}
	The inverted grid pitch in r,phi,z.
double	m_exRegionZ [2] {0}
	The min and max boundaries of the excluded region in z.
double	m_exRegionR [2] {0}
	The min and max boundaries of the excluded region in r.
bool	m_exRegion {true}
	Flag to indicate whether there is a region to exclude.
bool	m_mirrorPhi {true}
	Flag to indicate whether there is a region to exclude.
double	m_errRegionR [2] {0}
	The min and max boundaries of the region in r to apply error.
double	m_errB [3] {0}
	The error Br, Bphi, Bz as a scale factor (B_new = m_errB * B_old).

Detailed Description

The BFieldComponent3d class.

This class represents a 3d magnetic field map. The magnetic field map is stored as a grid in cylindrical coordinates. It is defined by a minimum radius and a maximum radius, a minimum z and a maximum z value (phi is assumed to be in 360 degrees range, option to mirror about the x-y plane exist), a pitch size in both, r, z and phi and the number of grid points. The ZOffset is used to account for the fact that the acceleration group defines 0 to be in the center of the detector, while the detector group defines the IP to be the center. The filename points to the zip file containing the magnetic field map.

Definition at line 36 of file BFieldComponent3d.h.

Member Function Documentation

calculate()

ROOT::Math::XYZVector calculate ( const ROOT::Math::XYZVector &  point ) const

overridevirtual

Calculates the magnetic field vector at the specified space point.

Parameters

point

The space point in [cm] at which the magnetic field vector should be calculated.

Returns

The magnetic field vector at the given space point in [T]. Returns a zero vector XYZVector(0,0,0) if the space point lies outside the region described by the component.

Implements BFieldComponentAbs.

Definition at line 187 of file BFieldComponent3d.cc.

{
  auto getPhiIndexWeight = [this](double y, double x, double & wphi) -> unsigned int {
    double phi = fast_atan2_minimax<4>(y, x);
    wphi = phi * m_igridPitch[1];
    auto iphi = static_cast<unsigned int>(wphi);
    iphi = min(iphi, static_cast<unsigned int>(m_mapSize[1] - 2));
    wphi -= iphi;
    return iphi;
  };
 
  ROOT::Math::XYZVector B(0, 0, 0);
 
  // If both '3d' and 'Beamline' components are defined in xml file,
  // '3d' component returns zero field where 'Beamline' component is defined.
  // If no 'Beamline' component is defined in xml file, the following function will never be called.
  if (BFieldComponentBeamline::Instance().isInRange(point)) {
    return B;
  }
 
  double z = point.Z();
  // Check if the point lies inside the magnetic field boundaries
  if (z < m_mapRegionZ[0] || z > m_mapRegionZ[1]) return B;
 
  double r2 = point.Perp2();
  // Check if the point lies inside the magnetic field boundaries
  if (r2 < m_mapRegionR[0]*m_mapRegionR[0] || r2 >= m_mapRegionR[1]*m_mapRegionR[1]) return B;
  // Check if the point lies in the exclude region
  if (m_exRegion && (z >= m_exRegionZ[0]) && (z < m_exRegionZ[1]) &&
      (r2 >= m_exRegionR[0]*m_exRegionR[0]) && (r2 < m_exRegionR[1]*m_exRegionR[1])) return B;
 
  // Calculate the lower index of the point in the Z grid
  // Note that z coordinate is inverted to match ANSYS frame
  double wz = (m_mapRegionZ[1] - z) * m_igridPitch[2];
  unsigned int iz = static_cast<int>(wz);
  iz = min(iz, static_cast<unsigned int>(m_mapSize[2] - 2));
  wz -= iz;
 
  if (r2 > 0) {
    double r = sqrt(r2);
 
    // Calculate the lower index of the point in the R grid
    double wr = (r - m_mapRegionR[0]) * m_igridPitch[0];
    auto ir = static_cast<unsigned int>(wr);
    ir = min(ir, static_cast<unsigned int>(m_mapSize[0] - 2));
    wr -= ir;
 
    // Calculate the lower index of the point in the Phi grid
    double ay = std::abs(point.Y());
    double wphi;
    unsigned int iphi = getPhiIndexWeight(ay, point.X(), wphi);
 
    // Get B-field values from map
    ROOT::Math::XYZVector b = interpolate(ir, iphi, iz, wr, wphi, wz); // in cylindrical system
    double norm = 1 / r;
    double s = ay * norm, c = point.X() * norm;
    // Flip sign of By if y<0
    const double sgny = (point.Y() >= 0) - (point.Y() < 0);
    // in cartesian system
    B.SetXYZ(-(b.X() * c - b.Y() * s), -sgny * (b.X() * s + b.Y() * c), b.Z());
  } else {
    // Get B-field values from map in cartesian system assuming phi=0, so Bx = Br and By = Bphi
    B = interpolate(0, 0, iz, 0, 0, wz);
  }
 
  return B;
}

doInterpolation()

void doInterpolation ( bool  interpolate = true )

inline

Parameters

interpolate

Flag to switch on/off interpolation

Definition at line 137 of file BFieldComponent3d.h.

{ m_interpolate = interpolate; }

enableCoordinate()

void enableCoordinate ( const std::string &  mapEnable = "rphiz" )

inline

Option to reduce 3D to 2D map (in coordinates, NOT Br, Bphi, Bz components)

Parameters

mapEnable

List of dimensions to enable: "rphiz", "rphi", "phiz" or "rz"

Definition at line 143 of file BFieldComponent3d.h.

{ m_mapEnable = mapEnable; }

initialize()

void initialize ( )

overridevirtual

Initializes the magnetic field component.

This method opens the magnetic field map file.

Reimplemented from BFieldComponentAbs.

Definition at line 27 of file BFieldComponent3d.cc.

{
 
  // Input field map
  if (m_mapFilename.empty()) {
    B2ERROR("The filename for the 3d magnetic field component is empty !");
    return;
  }
  string fullPath = FileSystem::findFile("/data/" + m_mapFilename);
  if (!FileSystem::fileExists(fullPath)) {
    B2ERROR("The 3d magnetic field map file '" << m_mapFilename << "' could not be found !");
    return;
  }
 
  // Options to reduce 3D to 2D
  if (m_mapEnable != "rphiz" && m_mapEnable != "rphi" && m_mapEnable != "phiz" && m_mapEnable != "rz") {
    B2ERROR("BField3d:: enabled coordinates must be \"rphiz\", \"rphi\", \"phiz\" or \"rz\"");
    return;
  }
 
  // Excluded region
  m_exRegion = true;
  if ((m_exRegionR[0] == m_exRegionR[1]) || (m_exRegionZ[0] == m_exRegionZ[1])) m_exRegion = false;
 
  // Print initial input parameters
  B2DEBUG(100, "BField3d:: initial input parameters");
  B2DEBUG(100, Form("   map filename:          %s",                   m_mapFilename.c_str()));
  B2DEBUG(100, Form("   map dimension:         %s",                   m_mapEnable.c_str()));
  if (m_interpolate) { B2DEBUG(100, Form("   map interpolation:     on")); }
  else               { B2DEBUG(100, Form("   map interpolation:     off")); }
  B2DEBUG(100, Form("   map r pitch & range:   %.2e [%.2e, %.2e] cm", m_gridPitch[0], m_mapRegionR[0], m_mapRegionR[1]));
  B2DEBUG(100, Form("   map phi pitch:         %.2e deg",             m_gridPitch[1] * 180 / M_PI));
  B2DEBUG(100, Form("   map z pitch & range:   %.2e [%.2e, %.2e] cm", m_gridPitch[2], m_mapRegionZ[0], m_mapRegionZ[1]));
  if (m_exRegion) {
    B2DEBUG(100, Form("   map r excluded region: [%.2e, %.2e] cm",    m_exRegionR[0], m_exRegionR[1]));
    B2DEBUG(100, Form("   map z excluded region: [%.2e, %.2e] cm",    m_exRegionZ[0], m_exRegionZ[1]));
  }
 
  m_bmap.reserve(m_mapSize[0]*m_mapSize[1]*m_mapSize[2]);
  // Load B-field map file
  io::filtering_istream fieldMapFile;
  fieldMapFile.push(io::gzip_decompressor());
  fieldMapFile.push(io::file_source(fullPath));
 
  char tmp[256];
  for (int k = 0; k < m_mapSize[2]; k++) { // z
    for (int i = 0; i < m_mapSize[0]; i++) { // r
      for (int j = 0;  j < m_mapSize[1]; j++) { // phi
        double Br, Bz, Bphi;
        //r[m]  phi[deg]  z[m]  Br[T]  Bphi[T]  Bz[T]
        fieldMapFile.getline(tmp, 256);
        // sscanf(tmp+33,"%lf %lf %lf",&Br,&Bphi,&Bz);
        char* next;
        Br   = strtod(tmp + 33, &next);
        Bphi = strtod(next, &next);
        Bz   = strtod(next, nullptr);
        m_bmap.emplace_back(-Br, -Bphi, -Bz);
      }
    }
  }
 
  // Introduce error on B field
  if (m_errRegionR[0] != m_errRegionR[1]) {
    auto it = m_bmap.begin();
    for (int k = 0; k < m_mapSize[2]; k++) { // z
      double r = m_mapRegionR[0];
      for (int i = 0; i < m_mapSize[0]; i++, r += m_gridPitch[0]) { // r
        if (!(r >= m_errRegionR[0] && r < m_errRegionR[1])) { it += m_mapSize[1];  continue;}
        for (int j = 0;  j < m_mapSize[1]; j++) { // phi
          ROOT::Math::XYZVector& B = *it;
          B.SetX(B.X() * m_errB[0]);
          B.SetY(B.Y() * m_errB[1]);
          B.SetZ(B.Z() * m_errB[2]);
        }
      }
    }
  }
 
  m_igridPitch[0] = 1 / m_gridPitch[0];
  m_igridPitch[1] = 1 / m_gridPitch[1];
  m_igridPitch[2] = 1 / m_gridPitch[2];
 
  B2DEBUG(100, Form("BField3d:: final map region & pitch: r [%.2e,%.2e] %.2e, phi %.2e, z [%.2e,%.2e] %.2e",
                    m_mapRegionR[0], m_mapRegionR[1], m_gridPitch[0], m_gridPitch[1],
                    m_mapRegionZ[0], m_mapRegionZ[1], m_gridPitch[2]));
  B2DEBUG(100, "Memory consumption: " << m_bmap.size()*sizeof(ROOT::Math::XYZVector) / (1024 * 1024.) << " Mb");
}

interpolate()

ROOT::Math::XYZVector interpolate ( unsigned int  ir, unsigned int  iphi, unsigned int  iz, double  wr, double  wphi, double  wz  ) const

private

Interpolate the value of B-field between (ir, iphi, iz) and (ir+1, iphi+1, iz+1) using weights (wr, wphi, wz)

Definition at line 259 of file BFieldComponent3d.cc.

{
  const unsigned int strideZ = m_mapSize[0] * m_mapSize[1];
  const unsigned int strideR = m_mapSize[1];
 
  const double wz0 = 1 - wz1, wr0 = 1 - wr1, wphi0 = 1 - wphi1;
  const unsigned int j000 = iz * strideZ + ir * strideR + iphi;
  const unsigned int j001 = j000 + 1;
  const unsigned int j010 = j000 + strideR;
  const unsigned int j011 = j001 + strideR;
  const unsigned int j100 = j000 + strideZ;
  const unsigned int j101 = j001 + strideZ;
  const unsigned int j110 = j010 + strideZ;
  const unsigned int j111 = j011 + strideZ;
  const double w00 = wphi0 * wr0;
  const double w10 = wphi0 * wr1;
  const double w01 = wphi1 * wr0;
  const double w11 = wphi1 * wr1;
  const vector<ROOT::Math::XYZVector>& B = m_bmap;
  return
    (B[j000] * w00 + B[j001] * w01 + B[j010] * w10 + B[j011] * w11) * wz0 +
    (B[j100] * w00 + B[j101] * w01 + B[j110] * w10 + B[j111] * w11) * wz1;
}

mirrorPhi()

void mirrorPhi ( bool  mirrorPhi = 0. )

inline

Parameters

mirrorPhi

Flag to enable mirroring in phi about x-z plane

Definition at line 132 of file BFieldComponent3d.h.

{ m_mirrorPhi = mirrorPhi; }

setErrorRegionR()

void setErrorRegionR ( double  minR = -1., double  maxR = -1., double  errBr = 0.0, double  errBphi = 0.0, double  errBz = 0.0  )

inline

Sets the size of the magnetic field map to apply error on B.

Parameters

minR	The left (min) border of the magnetic field map region in r [m] -> [cm].
maxR	The right (max) border of the magnetic field map region in r [m] -> [cm].
errBr	The size of the error on Br, Br_new = errBr*Br [fraction].
errBphi	The size of the error on Bphi, Bphi_new = errBphi*Bphi [fraction].
errBz	The size of the error on Bz, Bz_new = errBz*Bz [fraction].

Definition at line 126 of file BFieldComponent3d.h.

    { m_errRegionR[0] = minR; m_errRegionR[1] = maxR; m_errB[0] = errBr; m_errB[1] = errBphi; m_errB[2] = errBz; }

setExcludeRegionR()

void setExcludeRegionR ( double  minR, double  maxR  )

inline

Sets the size of the magnetic field map to exclude.

Parameters

minR	The left (min) border of the magnetic field map region in r [m] -> [cm].
maxR	The right (max) border of the magnetic field map region in r [m] -> [cm].

Definition at line 116 of file BFieldComponent3d.h.

{ m_exRegionR[0] = minR; m_exRegionR[1] = maxR; }

setExcludeRegionZ()

void setExcludeRegionZ ( double  minZ, double  maxZ  )

inline

Sets the size of the magnetic field map to exclude.

Parameters

minZ	The left (min) border of the magnetic field map region in z [m] -> [cm].
maxZ	The right (max) border of the magnetic field map region in z [m] -> [cm].

Definition at line 109 of file BFieldComponent3d.h.

{ m_exRegionZ[0] = minZ + m_mapOffset; m_exRegionZ[1] = maxZ + m_mapOffset; }

setGridPitch()

void setGridPitch ( double  pitchR, double  pitchPhi, double  pitchZ  )

inline

Sets the grid pitch of the magnetic field map.

Parameters

pitchR	The pitch of the grid in r [m] -> [cm].
pitchPhi	The pitch of the grid in phi [degrees] -> [rad] converted back to degrees in the code.
pitchZ	The pitch of the grid in z [m] -> [cm].

Definition at line 102 of file BFieldComponent3d.h.

{ m_gridPitch[0] = pitchR; m_gridPitch[1] = pitchPhi; m_gridPitch[2] = pitchZ; }

setMapFilename()

void setMapFilename ( const std::string &  filename )

inline

Sets the filename of the magnetic field map.

Parameters

filename

The filename of the magnetic field map.

Definition at line 71 of file BFieldComponent3d.h.

{ m_mapFilename = filename; };

setMapRegionR()

void setMapRegionR ( double  minR, double  maxR  )

inline

Sets the size of the magnetic field map.

Parameters

minR	The left (min) border of the magnetic field map region in r [m] -> [cm].
maxR	The right (max) border of the magnetic field map region in r [m] -> [cm].

Definition at line 94 of file BFieldComponent3d.h.

{ m_mapRegionR[0] = minR; m_mapRegionR[1] = maxR; }

setMapRegionZ()

void setMapRegionZ ( double  minZ, double  maxZ, double  offset  )

inline

Sets the size of the magnetic field map.

Parameters

minZ	The left (min) border of the magnetic field map region in z [m] -> [cm].
maxZ	The right (max) border of the magnetic field map region in z [m] -> [cm].
offset	The offset in z [m] -> [cm] which is required because the accelerator group defines the Belle center as zero.

Definition at line 87 of file BFieldComponent3d.h.

{ m_mapRegionZ[0] = minZ; m_mapRegionZ[1] = maxZ; m_mapOffset = offset; }

setMapSize()

void setMapSize ( int  sizeR, int  sizePhi, int  sizeZ  )

inline

Sets the size of the magnetic field map.

Parameters

sizeR	The number of points in the r direction.
sizePhi	The number of points in the phi direction.
sizeZ	The number of points in the z direction.

Definition at line 79 of file BFieldComponent3d.h.

{ m_mapSize[0] = sizeR; m_mapSize[1] = sizePhi; m_mapSize[2] = sizeZ; }

terminate()

void terminate ( )

overridevirtual

Terminates the magnetic field component.

This method closes the magnetic field map file.

Reimplemented from BFieldComponentAbs.

Definition at line 255 of file BFieldComponent3d.cc.

{
}

Member Data Documentation

m_bmap

std::vector<ROOT::Math::XYZVector> m_bmap

private

The memory buffer for the magnetic field map.

Definition at line 156 of file BFieldComponent3d.h.

m_errB

double m_errB[3] {0}

private

The error Br, Bphi, Bz as a scale factor (B_new = m_errB * B_old).

Definition at line 184 of file BFieldComponent3d.h.

m_errRegionR

double m_errRegionR[2] {0}

private

The min and max boundaries of the region in r to apply error.

Definition at line 182 of file BFieldComponent3d.h.

m_exRegion

bool m_exRegion {true}

private

Flag to indicate whether there is a region to exclude.

>

Definition at line 178 of file BFieldComponent3d.h.

m_exRegionR

double m_exRegionR[2] {0}

private

The min and max boundaries of the excluded region in r.

Definition at line 176 of file BFieldComponent3d.h.

m_exRegionZ

double m_exRegionZ[2] {0}

private

The min and max boundaries of the excluded region in z.

Definition at line 174 of file BFieldComponent3d.h.

m_gridPitch

double m_gridPitch[3] {0}

private

The grid pitch in r,phi,z.

Definition at line 170 of file BFieldComponent3d.h.

m_igridPitch

double m_igridPitch[3] {0}

private

The inverted grid pitch in r,phi,z.

Definition at line 172 of file BFieldComponent3d.h.

m_interpolate

bool m_interpolate {true}

private

Flag to switch on/off interpolation >

Definition at line 160 of file BFieldComponent3d.h.

m_mapEnable

std::string m_mapEnable {"rphiz"}

private

Enable different dimension, "rphiz", "rphi", "phiz" or "rz" >

Definition at line 158 of file BFieldComponent3d.h.

m_mapFilename

std::string m_mapFilename {""}

private

The filename of the magnetic field map.

Definition at line 154 of file BFieldComponent3d.h.

m_mapOffset

double m_mapOffset {0}

private

Offset required because the accelerator group defines the Belle center as zero.

Definition at line 166 of file BFieldComponent3d.h.

m_mapRegionR

double m_mapRegionR[2] {0}

private

The min and max boundaries of the map region in r.

Definition at line 168 of file BFieldComponent3d.h.

m_mapRegionZ

double m_mapRegionZ[2] {0}

private

The min and max boundaries of the map region in z.

Definition at line 164 of file BFieldComponent3d.h.

m_mapSize

int m_mapSize[3]

private

The size of the map in r, phi and z.

Definition at line 162 of file BFieldComponent3d.h.

m_mirrorPhi

bool m_mirrorPhi {true}

private

Flag to indicate whether there is a region to exclude.

>

Definition at line 180 of file BFieldComponent3d.h.

---

The documentation for this class was generated from the following files:

• geometry/bfieldmap/include/BFieldComponent3d.h
• geometry/bfieldmap/src/BFieldComponent3d.cc