TimeAtSampleStrategyDirect.cpp

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#include "MantidAPI/TimeAtSampleStrategyDirect.h"
#include "MantidAPI/MatrixWorkspace.h"
#include "MantidGeometry/IComponent.h"
#include "MantidGeometry/IDetector.h"
#include "MantidGeometry/Instrument.h"
#include "MantidGeometry/Instrument/ReferenceFrame.h"
#include "MantidKernel/Logger.h"
#include "MantidKernel/PhysicalConstants.h"
#include "MantidKernel/Property.h"
#include "MantidKernel/V3D.h"
#include <cmath>
 
using namespace Mantid::Kernel;
using namespace Mantid::Geometry;
 
namespace Mantid::API {
 
namespace {
// A constant among all spectra
constexpr double TWO_MEV_OVER_MASS = 2. * PhysicalConstants::meV / PhysicalConstants::NeutronMass;
} // namespace
 
//----------------------------------------------------------------------------------------------
TimeAtSampleStrategyDirect::TimeAtSampleStrategyDirect(const MatrixWorkspace_const_sptr &ws, double ei) {
  // Get L1
  const auto &samplepos = ws->getInstrument()->getSample()->getPos();
  const auto &sourcepos = ws->getInstrument()->getSource()->getPos();
  const double l1 = samplepos.distance(sourcepos);
 
  // Calculate constant (to all spectra) shift
  m_constShift = l1 / std::sqrt(ei * TWO_MEV_OVER_MASS);
}
 
Correction Mantid::API::TimeAtSampleStrategyDirect::calculate(const size_t & /*workspace_index*/) const {
  constexpr double SET_TOF_TO_ZERO{0.};
  // Correction is L1 and Ei dependent only. Detector positions are not required.
  return Correction(SET_TOF_TO_ZERO, m_constShift);
}
} // namespace Mantid::API