/**
* Return the reference 2theta angle and the corresponding horizon angle.
*
* @param spectrumInfo [in] :: a spectrum info of the input workspace.
* @return :: the reference angle struct
*/
ReflectometrySumInQ::Angles
ReflectometrySumInQ::referenceAngles(const API::SpectrumInfo &spectrumInfo) {
Angles a;
const double beamCentre = getProperty(Prop::BEAM_CENTRE);
const bool isFlat = getProperty(Prop::IS_FLAT_SAMPLE);
if (isFlat) {
a.horizon = centreTwoTheta(beamCentre, spectrumInfo) / 2.;
} else {
a.horizon = 0.;
}
a.referenceWSIndex = static_cast<size_t>(beamCentre);
a.twoTheta = spectrumInfo.twoTheta(a.referenceWSIndex);
a.delta = a.twoTheta - a.horizon;
return a;
}
void ConvertToDiffractionMDWorkspace::convertEventList(
int workspaceIndex, const API::SpectrumInfo &specInfo, EventList &el) {
size_t numEvents = el.getNumberEvents();
DataObjects::MDBoxBase<DataObjects::MDLeanEvent<3>, 3> *box = ws->getBox();
// Get the position of the detector there.
const auto &detectors = el.getDetectorIDs();
if (!detectors.empty()) {
// Check if a detector is located at this workspace index, returns
// immediately if one is not found.
if (!specInfo.hasDetectors(workspaceIndex)) {
this->failedDetectorLookupCount++;
return;
}
// Neutron's total travelled distance
double distance = l1 + specInfo.l2(workspaceIndex);
// Vector between the sample and the detector
const V3D detPos = specInfo.position(workspaceIndex);
// Detector direction normalized to 1
const V3D detDir = detPos / detPos.norm();
// The direction of momentum transfer in the inelastic convention ki-kf
// = input beam direction (normalized to 1) - output beam direction
// (normalized to 1)
V3D Q_dir_lab_frame = beamDir - detDir;
double qSign = -1.0;
std::string convention =
ConfigService::Instance().getString("Q.convention");
if (convention == "Crystallography")
qSign = 1.0;
Q_dir_lab_frame *= qSign;
// Multiply by the rotation matrix to convert to Q in the sample frame (take
// out goniometer rotation)
// (or to HKL, if that's what the matrix is)
const V3D Q_dir = mat * Q_dir_lab_frame;
// For speed we extract the components.
coord_t Q_dir_x = coord_t(Q_dir.X());
coord_t Q_dir_y = coord_t(Q_dir.Y());
coord_t Q_dir_z = coord_t(Q_dir.Z());
// For lorentz correction, calculate sin(theta))^2
double sin_theta_squared = 0;
if (LorentzCorrection) {
// Scattering angle = 2 theta = angle between neutron beam direction and
// the detector (scattering) direction
// The formula for Lorentz Correction is sin(theta), i.e. sin(half the
// scattering angle)
double theta = specInfo.twoTheta(workspaceIndex) / 2.0;
sin_theta_squared = sin(theta);
sin_theta_squared = sin_theta_squared * sin_theta_squared; // square it
}
/** Constant that you divide by tof (in usec) to get wavenumber in ang^-1 :
* Wavenumber (in ang^-1) = (PhysicalConstants::NeutronMass * distance) /
* ((tof (in usec) * 1e-6) * PhysicalConstants::h_bar) * 1e-10; */
const double wavenumber_in_angstrom_times_tof_in_microsec =
(PhysicalConstants::NeutronMass * distance * 1e-10) /
(1e-6 * PhysicalConstants::h_bar);
// This little dance makes the getting vector of events more general (since
// you can't overload by return type).
typename std::vector<T> *events_ptr;
getEventsFrom(el, events_ptr);
typename std::vector<T> &events = *events_ptr;
// Iterators to start/end
auto it = events.begin();
auto it_end = events.end();
for (; it != it_end; it++) {
// Get the wavenumber in ang^-1 using the previously calculated constant.
coord_t wavenumber =
coord_t(wavenumber_in_angstrom_times_tof_in_microsec / it->tof());
// Q vector = K_final - K_initial = wavenumber * (output_direction -
// input_direction)
coord_t center[3] = {Q_dir_x * wavenumber, Q_dir_y * wavenumber,
Q_dir_z * wavenumber};
// Check that the event is within bounds
if (center[0] < m_extentsMin[0] || center[0] >= m_extentsMax[0])
continue;
if (center[1] < m_extentsMin[1] || center[1] >= m_extentsMax[1])
continue;
if (center[2] < m_extentsMin[2] || center[2] >= m_extentsMax[2])
continue;
if (LorentzCorrection) {
// double lambda = 1.0/wavenumber;
// (sin(theta))^2 / wavelength^4
float correct = float(sin_theta_squared * wavenumber * wavenumber *
wavenumber * wavenumber);
// Push the MDLeanEvent but correct the weight.
box->addEvent(MDE(float(it->weight() * correct),
float(it->errorSquared() * correct * correct),
center));
} else {
// Push the MDLeanEvent with the same weight
box->addEvent(
MDE(float(it->weight()), float(it->errorSquared()), center));
}
}
// Clear out the EventList to save memory
if (ClearInputWorkspace)
el.clear();
}
prog->reportIncrement(numEvents, "Adding Events");
}