SolenoidBField.hpp

Go to the documentation of this file. Or view the newest version in sPHENIX GitHub for file SolenoidBField.hpp

// This file is part of the Acts project.
//
// Copyright (C) 2017-2018 CERN for the benefit of the Acts project
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#pragma once

#include "Acts/Definitions/Algebra.hpp"
#include "Acts/MagneticField/MagneticFieldContext.hpp"
#include "Acts/MagneticField/MagneticFieldProvider.hpp"
#include "Acts/Utilities/Result.hpp"

#include <cstddef>
#include <functional>

namespace Acts {

//
class SolenoidBField final : public MagneticFieldProvider {
 public:
  struct Cache {
    Cache(const MagneticFieldContext& mctx) { (void)mctx; }
  };

  struct Config {
    double radius;
    double length;
    size_t nCoils;
    double bMagCenter;
  };

  SolenoidBField(Config config);

  Vector2 getField(const Vector2& position) const;

  MagneticFieldProvider::Cache makeCache(
      const MagneticFieldContext& mctx) const override;

  Vector3 getField(const Vector3& position) const;

  Result<Vector3> getField(const Vector3& position,
                           MagneticFieldProvider::Cache& cache) const override;

  Result<Vector3> getFieldGradient(
      const Vector3& position, ActsMatrix<3, 3>& derivative,
      MagneticFieldProvider::Cache& cache) const override;

 private:
  Config m_cfg;
  double m_scale;
  double m_dz;
  double m_R2;

  Vector2 multiCoilField(const Vector2& pos, double scale) const;

  Vector2 singleCoilField(const Vector2& pos, double scale) const;

  double B_r(const Vector2& pos, double scale) const;

  double B_z(const Vector2& pos, double scale) const;

  double k2(double r, double z) const;
};

}  // namespace Acts