// calculate time from sample to detector
void ModeratorTzeroLinear::calculateTfLi(const SpectrumInfo &spectrumInfo,
size_t i, double &t_f, double &L_i) {
static const double convFact = 1.0e-6 * sqrt(2 * PhysicalConstants::meV /
PhysicalConstants::NeutronMass);
static const double TfError = -1.0; // signal error when calculating final
// time
if (!spectrumInfo.hasDetectors(i)) {
t_f = TfError;
return;
}
if (spectrumInfo.isMonitor(i)) {
L_i = spectrumInfo.sourcePosition().distance(spectrumInfo.position(i));
t_f = 0.0; // t_f=0.0 since there is no sample to detector path
} else {
L_i = spectrumInfo.l1();
// Get final energy E_f, final velocity v_f
auto wsProp = spectrumInfo.detector(i).getNumberParameter("Efixed");
if (!wsProp.empty()) {
double E_f = wsProp.at(0); //[E_f]=meV
double v_f = convFact * sqrt(E_f); //[v_f]=meter/microsec
t_f = spectrumInfo.l2(i) / v_f;
} else {
g_log.debug() << "Efixed not found for detector " << i << '\n';
t_f = TfError;
}
}
}
double RemoveLowResTOF::calcTofMin(const std::size_t workspaceIndex,
const SpectrumInfo &spectrumInfo) {
const double l1 = spectrumInfo.l1();
// Get a vector of detector IDs
std::vector<detid_t> detNumbers;
const auto &detSet = m_inputWS->getSpectrum(workspaceIndex).getDetectorIDs();
detNumbers.assign(detSet.begin(), detSet.end());
double tmin = 0.;
if (isEmpty(m_wavelengthMin)) {
std::map<detid_t, double> offsets; // just an empty offsets map
Geometry::Instrument_const_sptr instrument = m_inputWS->getInstrument();
double dspmap = Conversion::tofToDSpacingFactor(
l1, spectrumInfo.l2(workspaceIndex),
spectrumInfo.twoTheta(workspaceIndex), detNumbers, offsets);
// this is related to the reference tof
double sqrtdmin =
sqrt(m_Tmin / m_DIFCref) + m_K * log10(dspmap * m_DIFCref);
if (sqrtdmin <= 0.)
return 0.;
tmin = sqrtdmin * sqrtdmin / dspmap;
if (tmin != tmin) {
g_log.warning() << "tmin is nan because dspmap = " << dspmap << ".\n";
}
} else {
const double l2 = spectrumInfo.l2(workspaceIndex);
Kernel::Unit_sptr wavelength = UnitFactory::Instance().create("Wavelength");
// unfortunately there isn't a good way to convert a single value
std::vector<double> X(1), temp(1);
X[0] = m_wavelengthMin;
wavelength->toTOF(X, temp, l1, l2, 0., 0, 0., 0.);
tmin = X[0];
}
g_log.debug() << "tmin[" << workspaceIndex << "] " << tmin << "\n";
return tmin;
}