G4SPSEneDistribution.cc

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//
// MODULE:        G4SPSEneDistribution.cc
//
// Version:      1.0
// Date:         5/02/04
// Author:       Fan Lei 
// Organisation: QinetiQ ltd.
// Customer:     ESA/ESTEC
//
//
// CHANGE HISTORY
// --------------
//
//
// Version 1.0, 05/02/2004, Fan Lei, Created.
//    Based on the G4GeneralParticleSource class in Geant4 v6.0
//
//

#include "G4SPSEneDistribution.hh"

#include "G4SystemOfUnits.hh"
#include "Randomize.hh"

G4SPSEneDistribution::G4SPSEneDistribution()
  : particle_definition(0), eneRndm(0), Splinetemp(0)
{
    //
    // Initialise all variables
    particle_energy = 1.0 * MeV;

    EnergyDisType = "Mono";
    weight = 1.;
    MonoEnergy = 1 * MeV;
    Emin = 0.;
    Emax = 1.e30;
    alpha = 0.;
    biasalpha = 0.;
        prob_norm = 1.0;
    Ezero = 0.;
    SE = 0.;
    Temp = 0.;
    grad = 0.;
    cept = 0.;
    Biased = false; // not biased
    EnergySpec = true; // true - energy spectra, false - momentum spectra
    DiffSpec = true; // true - differential spec, false integral spec
    IntType = "NULL"; // Interpolation type
    IPDFEnergyExist = false;
    IPDFArbExist = false;

    ArbEmin = 0.;
    ArbEmax = 1.e30;

    verbosityLevel = 0;

}

G4SPSEneDistribution::~G4SPSEneDistribution() {
}

void G4SPSEneDistribution::SetEnergyDisType(G4String DisType) {
    EnergyDisType = DisType;
    if (EnergyDisType == "User") {
        UDefEnergyH = IPDFEnergyH = ZeroPhysVector;
        IPDFEnergyExist = false;
    } else if (EnergyDisType == "Arb") {
        ArbEnergyH = IPDFArbEnergyH = ZeroPhysVector;
        IPDFArbExist = false;
    } else if (EnergyDisType == "Epn") {
        UDefEnergyH = IPDFEnergyH = ZeroPhysVector;
        IPDFEnergyExist = false;
        EpnEnergyH = ZeroPhysVector;
    }
}

void G4SPSEneDistribution::SetEmin(G4double emi) {
    Emin = emi;
}

void G4SPSEneDistribution::SetEmax(G4double ema) {
    Emax = ema;
}

void G4SPSEneDistribution::SetMonoEnergy(G4double menergy) {
    MonoEnergy = menergy;
}

void G4SPSEneDistribution::SetBeamSigmaInE(G4double e) {
    SE = e;
}
void G4SPSEneDistribution::SetAlpha(G4double alp) {
    alpha = alp;
}

void G4SPSEneDistribution::SetBiasAlpha(G4double alp) {
    biasalpha = alp;
    Biased = true;
}

void G4SPSEneDistribution::SetTemp(G4double tem) {
    Temp = tem;
}

void G4SPSEneDistribution::SetEzero(G4double eze) {
    Ezero = eze;
}

void G4SPSEneDistribution::SetGradient(G4double gr) {
    grad = gr;
}

void G4SPSEneDistribution::SetInterCept(G4double c) {
    cept = c;
}

void G4SPSEneDistribution::UserEnergyHisto(G4ThreeVector input) {
    G4double ehi, val;
    ehi = input.x();
    val = input.y();
    if (verbosityLevel > 1) {
        G4cout << "In UserEnergyHisto" << G4endl;
        G4cout << " " << ehi << " " << val << G4endl;
    }
    UDefEnergyH.InsertValues(ehi, val);
    Emax = ehi;
}

void G4SPSEneDistribution::ArbEnergyHisto(G4ThreeVector input) {
    G4double ehi, val;
    ehi = input.x();
    val = input.y();
    if (verbosityLevel > 1) {
        G4cout << "In ArbEnergyHisto" << G4endl;
        G4cout << " " << ehi << " " << val << G4endl;
    }
    ArbEnergyH.InsertValues(ehi, val);
}

void G4SPSEneDistribution::ArbEnergyHistoFile(G4String filename) {
    std::ifstream infile(filename, std::ios::in);
    if (!infile)
        G4Exception("G4SPSEneDistribution::ArbEnergyHistoFile",
                "Event0301",FatalException,
                "Unable to open the histo ASCII file");
    G4double ehi, val;
    while (infile >> ehi >> val) {
        ArbEnergyH.InsertValues(ehi, val);
    }
}

void G4SPSEneDistribution::EpnEnergyHisto(G4ThreeVector input) {
    G4double ehi, val;
    ehi = input.x();
    val = input.y();
    if (verbosityLevel > 1) {
        G4cout << "In EpnEnergyHisto" << G4endl;
        G4cout << " " << ehi << " " << val << G4endl;
    }
    EpnEnergyH.InsertValues(ehi, val);
    Emax = ehi;
    Epnflag = true;
}

void G4SPSEneDistribution::Calculate() {
    if (EnergyDisType == "Cdg")
        CalculateCdgSpectrum();
    else if (EnergyDisType == "Bbody")
        CalculateBbodySpectrum();
}

void G4SPSEneDistribution::CalculateCdgSpectrum() {
    // This uses the spectrum from The INTEGRAL Mass Model (TIMM)
    // to generate a Cosmic Diffuse X/gamma ray spectrum.
    G4double pfact[2] = { 8.5, 112 };
    G4double spind[2] = { 1.4, 2.3 };
    G4double ene_line[3] = { 1. * keV, 18. * keV, 1E6 * keV };
    G4int n_par;

    ene_line[0] = Emin;
    if (Emin < 18 * keV) {
        n_par = 2;
        ene_line[2] = Emax;
        if (Emax < 18 * keV) {
            n_par = 1;
            ene_line[1] = Emax;
        }
    } else {
        n_par = 1;
        pfact[0] = 112.;
        spind[0] = 2.3;
        ene_line[1] = Emax;
    }

    // Create a cumulative histogram.
    CDGhist[0] = 0.;
    G4double omalpha;
    G4int i = 0;

    while (i < n_par) {
        omalpha = 1. - spind[i];
        CDGhist[i + 1] = CDGhist[i] + (pfact[i] / omalpha) * (std::pow(
                ene_line[i + 1] / keV, omalpha) - std::pow(ene_line[i] / keV,
                omalpha));
        i++;
    }

    // Normalise histo and divide by 1000 to make MeV.
    i = 0;
    while (i < n_par) {
        CDGhist[i + 1] = CDGhist[i + 1] / CDGhist[n_par];
        //      G4cout << CDGhist[i] << CDGhist[n_par] << G4endl;
        i++;
    }
}

void G4SPSEneDistribution::CalculateBbodySpectrum() {
    // create bbody spectrum
    // Proved very hard to integrate indefinitely, so different
    // method. User inputs emin, emax and T. These are used to
    // create a 10,000 bin histogram.
    // Use photon density spectrum = 2 nu**2/c**2 * (std::exp(h nu/kT)-1)
    // = 2 E**2/h**2c**2 times the exponential
    G4double erange = Emax - Emin;
    G4double steps = erange / 10000.;
    G4double Bbody_y[10000];
    G4double k = 8.6181e-11; //Boltzmann const in MeV/K
    G4double h = 4.1362e-21; // Plancks const in MeV s
    G4double c = 3e8; // Speed of light
    G4double h2 = h * h;
    G4double c2 = c * c;
    G4int count = 0;
    G4double sum = 0.;
    BBHist[0] = 0.;
    while (count < 10000) {
        Bbody_x[count] = Emin + G4double(count * steps);
        Bbody_y[count] = (2. * std::pow(Bbody_x[count], 2.)) / (h2 * c2
                * (std::exp(Bbody_x[count] / (k * Temp)) - 1.));
        sum = sum + Bbody_y[count];
        BBHist[count + 1] = BBHist[count] + Bbody_y[count];
        count++;
    }

    Bbody_x[10000] = Emax;
    // Normalise cumulative histo.
    count = 0;
    while (count < 10001) {
        BBHist[count] = BBHist[count] / sum;
        count++;
    }
}

void G4SPSEneDistribution::InputEnergySpectra(G4bool value) {
    // Allows user to specifiy spectrum is momentum
    EnergySpec = value; // false if momentum
    if (verbosityLevel > 1)
        G4cout << "EnergySpec has value " << EnergySpec << G4endl;
}

void G4SPSEneDistribution::InputDifferentialSpectra(G4bool value) {
    // Allows user to specify integral or differential spectra
    DiffSpec = value; // true = differential, false = integral
    if (verbosityLevel > 1)
        G4cout << "Diffspec has value " << DiffSpec << G4endl;
}

void G4SPSEneDistribution::ArbInterpolate(G4String IType) {
    if (EnergyDisType != "Arb")
        G4cout << "Error: this is for arbitrary distributions" << G4endl;
    IntType = IType;
    ArbEmax = ArbEnergyH.GetMaxLowEdgeEnergy();
    ArbEmin = ArbEnergyH.GetMinLowEdgeEnergy();

    // Now interpolate points
    if (IntType == "Lin")
        LinearInterpolation();
    if (IntType == "Log")
        LogInterpolation();
    if (IntType == "Exp")
        ExpInterpolation();
    if (IntType == "Spline")
        SplineInterpolation();
}

void G4SPSEneDistribution::LinearInterpolation() {
    // Method to do linear interpolation on the Arb points
    // Calculate equation of each line segment, max 1024.
    // Calculate Area under each segment
    // Create a cumulative array which is then normalised Arb_Cum_Area

    G4double Area_seg[1024]; // Stores area under each segment
    G4double sum = 0., Arb_x[1024], Arb_y[1024], Arb_Cum_Area[1024];
    G4int i, count;
    G4int maxi = ArbEnergyH.GetVectorLength();
    for (i = 0; i < maxi; i++) {
        Arb_x[i] = ArbEnergyH.GetLowEdgeEnergy(size_t(i));
        Arb_y[i] = ArbEnergyH(size_t(i));
    }
    // Points are now in x,y arrays. If the spectrum is integral it has to be
    // made differential and if momentum it has to be made energy.
    if (DiffSpec == false) {
        // Converts integral point-wise spectra to Differential
        for (count = 0; count < maxi - 1; count++) {
            Arb_y[count] = (Arb_y[count] - Arb_y[count + 1])
                    / (Arb_x[count + 1] - Arb_x[count]);
        }
        maxi--;
    }
    //
    if (EnergySpec == false) {
        // change currently stored values (emin etc) which are actually momenta
        // to energies.
        if (particle_definition == NULL)
            G4cout << "Error: particle not defined" << G4endl;
        else {
            // Apply Energy**2 = p**2c**2 + m0**2c**4
            // p should be entered as E/c i.e. without the division by c
            // being done - energy equivalent.
            G4double mass = particle_definition->GetPDGMass();
            // convert point to energy unit and its value to per energy unit
            G4double total_energy;
            for (count = 0; count < maxi; count++) {
                total_energy = std::sqrt((Arb_x[count] * Arb_x[count]) + (mass
                        * mass)); // total energy

                Arb_y[count] = Arb_y[count] * Arb_x[count] / total_energy;
                Arb_x[count] = total_energy - mass; // kinetic energy
            }
        }
    }
    //
    i = 1;
    Arb_grad[0] = 0.;
    Arb_cept[0] = 0.;
    Area_seg[0] = 0.;
    Arb_Cum_Area[0] = 0.;
    while (i < maxi) {
        // calc gradient and intercept for each segment
        Arb_grad[i] = (Arb_y[i] - Arb_y[i - 1]) / (Arb_x[i] - Arb_x[i - 1]);
        if (verbosityLevel == 2)
            G4cout << Arb_grad[i] << G4endl;
        if (Arb_grad[i] > 0.) {
            if (verbosityLevel == 2)
                G4cout << "Arb_grad is positive" << G4endl;
            Arb_cept[i] = Arb_y[i] - (Arb_grad[i] * Arb_x[i]);
        } else if (Arb_grad[i] < 0.) {
            if (verbosityLevel == 2)
                G4cout << "Arb_grad is negative" << G4endl;
            Arb_cept[i] = Arb_y[i] + (-Arb_grad[i] * Arb_x[i]);
        } else {
            if (verbosityLevel == 2)
                G4cout << "Arb_grad is 0." << G4endl;
            Arb_cept[i] = Arb_y[i];
        }

        Area_seg[i] = ((Arb_grad[i] / 2) * (Arb_x[i] * Arb_x[i] - Arb_x[i - 1]
                * Arb_x[i - 1]) + Arb_cept[i] * (Arb_x[i] - Arb_x[i - 1]));
        Arb_Cum_Area[i] = Arb_Cum_Area[i - 1] + Area_seg[i];
        sum = sum + Area_seg[i];
        if (verbosityLevel == 2)
            G4cout << Arb_x[i] << Arb_y[i] << Area_seg[i] << sum << Arb_grad[i]
                    << G4endl;
        i++;
    }

    i = 0;
    while (i < maxi) {
        Arb_Cum_Area[i] = Arb_Cum_Area[i] / sum; // normalisation
        IPDFArbEnergyH.InsertValues(Arb_x[i], Arb_Cum_Area[i]);
        i++;
    }

    // now scale the ArbEnergyH, needed by Probability()
    ArbEnergyH.ScaleVector(1., 1./sum);

    if (verbosityLevel >= 1) {
        G4cout << "Leaving LinearInterpolation" << G4endl;
        ArbEnergyH.DumpValues();
        IPDFArbEnergyH.DumpValues();
    }
}

void G4SPSEneDistribution::LogInterpolation() {
    // Interpolation based on Logarithmic equations
    // Generate equations of line segments
    // y = Ax**alpha => log y = alpha*logx + logA
    // Find area under line segments
    // create normalised, cumulative array Arb_Cum_Area
    G4double Area_seg[1024]; // Stores area under each segment
    G4double sum = 0., Arb_x[1024], Arb_y[1024], Arb_Cum_Area[1024];
    G4int i, count;
    G4int maxi = ArbEnergyH.GetVectorLength();
    for (i = 0; i < maxi; i++) {
        Arb_x[i] = ArbEnergyH.GetLowEdgeEnergy(size_t(i));
        Arb_y[i] = ArbEnergyH(size_t(i));
    }
    // Points are now in x,y arrays. If the spectrum is integral it has to be
    // made differential and if momentum it has to be made energy.
    if (DiffSpec == false) {
        // Converts integral point-wise spectra to Differential
        for (count = 0; count < maxi - 1; count++) {
            Arb_y[count] = (Arb_y[count] - Arb_y[count + 1])
                    / (Arb_x[count + 1] - Arb_x[count]);
        }
        maxi--;
    }
    //
    if (EnergySpec == false) {
        // change currently stored values (emin etc) which are actually momenta
        // to energies.
        if (particle_definition == NULL)
            G4cout << "Error: particle not defined" << G4endl;
        else {
            // Apply Energy**2 = p**2c**2 + m0**2c**4
            // p should be entered as E/c i.e. without the division by c
            // being done - energy equivalent.
            G4double mass = particle_definition->GetPDGMass();
            // convert point to energy unit and its value to per energy unit
            G4double total_energy;
            for (count = 0; count < maxi; count++) {
                total_energy = std::sqrt((Arb_x[count] * Arb_x[count]) + (mass
                        * mass)); // total energy

                Arb_y[count] = Arb_y[count] * Arb_x[count] / total_energy;
                Arb_x[count] = total_energy - mass; // kinetic energy
            }
        }
    }
    //
    i = 1;
    Arb_alpha[0] = 0.;
    Arb_Const[0] = 0.;
    Area_seg[0] = 0.;
    Arb_Cum_Area[0] = 0.;
    if (Arb_x[0] <= 0. || Arb_y[0] <= 0.) {
        G4cout << "You should not use log interpolation with points <= 0."
                << G4endl;
        G4cout << "These will be changed to 1e-20, which may cause problems"
                << G4endl;
        if (Arb_x[0] <= 0.)
            Arb_x[0] = 1e-20;
        if (Arb_y[0] <= 0.)
            Arb_y[0] = 1e-20;
    }

    G4double alp;
    while (i < maxi) {
        // Incase points are negative or zero
        if (Arb_x[i] <= 0. || Arb_y[i] <= 0.) {
            G4cout << "You should not use log interpolation with points <= 0."
                    << G4endl;
            G4cout
                    << "These will be changed to 1e-20, which may cause problems"
                    << G4endl;
            if (Arb_x[i] <= 0.)
                Arb_x[i] = 1e-20;
            if (Arb_y[i] <= 0.)
                Arb_y[i] = 1e-20;
        }

        Arb_alpha[i] = (std::log10(Arb_y[i]) - std::log10(Arb_y[i - 1]))
                / (std::log10(Arb_x[i]) - std::log10(Arb_x[i - 1]));
        Arb_Const[i] = Arb_y[i] / (std::pow(Arb_x[i], Arb_alpha[i]));
        alp = Arb_alpha[i] + 1;
        if (alp == 0.) {
          Area_seg[i] = Arb_Const[i] * (std::log(Arb_x[i]) - std::log(Arb_x[i - 1])); 
        } else {
          Area_seg[i] = (Arb_Const[i] / alp) * (std::pow(Arb_x[i], alp)
                - std::pow(Arb_x[i - 1], alp));
        }
        sum = sum + Area_seg[i];
        Arb_Cum_Area[i] = Arb_Cum_Area[i - 1] + Area_seg[i];
        if (verbosityLevel == 2)
            G4cout << Arb_alpha[i] << Arb_Const[i] << Area_seg[i] << G4endl;
        i++;
    }

    i = 0;
    while (i < maxi) {
        Arb_Cum_Area[i] = Arb_Cum_Area[i] / sum;
        IPDFArbEnergyH.InsertValues(Arb_x[i], Arb_Cum_Area[i]);
        i++;
    }

    // now scale the ArbEnergyH, needed by Probability()
    ArbEnergyH.ScaleVector(1., 1./sum);

    if (verbosityLevel >= 1)
        G4cout << "Leaving LogInterpolation " << G4endl;
}

void G4SPSEneDistribution::ExpInterpolation() {
    // Interpolation based on Exponential equations
    // Generate equations of line segments
    // y = Ae**-(x/e0) => ln y = -x/e0 + lnA
    // Find area under line segments
    // create normalised, cumulative array Arb_Cum_Area
    G4double Area_seg[1024]; // Stores area under each segment
    G4double sum = 0., Arb_x[1024], Arb_y[1024], Arb_Cum_Area[1024];
    G4int i, count;
    G4int maxi = ArbEnergyH.GetVectorLength();
    for (i = 0; i < maxi; i++) {
        Arb_x[i] = ArbEnergyH.GetLowEdgeEnergy(size_t(i));
        Arb_y[i] = ArbEnergyH(size_t(i));
    }
    // Points are now in x,y arrays. If the spectrum is integral it has to be
    // made differential and if momentum it has to be made energy.
    if (DiffSpec == false) {
        // Converts integral point-wise spectra to Differential
        for (count = 0; count < maxi - 1; count++) {
            Arb_y[count] = (Arb_y[count] - Arb_y[count + 1])
                    / (Arb_x[count + 1] - Arb_x[count]);
        }
        maxi--;
    }
    //
    if (EnergySpec == false) {
        // change currently stored values (emin etc) which are actually momenta
        // to energies.
        if (particle_definition == NULL)
            G4cout << "Error: particle not defined" << G4endl;
        else {
            // Apply Energy**2 = p**2c**2 + m0**2c**4
            // p should be entered as E/c i.e. without the division by c
            // being done - energy equivalent.
            G4double mass = particle_definition->GetPDGMass();
            // convert point to energy unit and its value to per energy unit
            G4double total_energy;
            for (count = 0; count < maxi; count++) {
                total_energy = std::sqrt((Arb_x[count] * Arb_x[count]) + (mass
                        * mass)); // total energy

                Arb_y[count] = Arb_y[count] * Arb_x[count] / total_energy;
                Arb_x[count] = total_energy - mass; // kinetic energy
            }
        }
    }
    //
    i = 1;
    Arb_ezero[0] = 0.;
    Arb_Const[0] = 0.;
    Area_seg[0] = 0.;
    Arb_Cum_Area[0] = 0.;
    while (i < maxi) {
        G4double test = std::log(Arb_y[i]) - std::log(Arb_y[i - 1]);
        if (test > 0. || test < 0.) {
            Arb_ezero[i] = -(Arb_x[i] - Arb_x[i - 1]) / (std::log(Arb_y[i])
                    - std::log(Arb_y[i - 1]));
            Arb_Const[i] = Arb_y[i] / (std::exp(-Arb_x[i] / Arb_ezero[i]));
            Area_seg[i] = -(Arb_Const[i] * Arb_ezero[i]) * (std::exp(-Arb_x[i]
                    / Arb_ezero[i]) - std::exp(-Arb_x[i - 1] / Arb_ezero[i]));
        } else {
            G4cout << "Flat line segment: problem" << G4endl;
            Arb_ezero[i] = 0.;
            Arb_Const[i] = 0.;
            Area_seg[i] = 0.;
        }
        sum = sum + Area_seg[i];
        Arb_Cum_Area[i] = Arb_Cum_Area[i - 1] + Area_seg[i];
        if (verbosityLevel == 2)
            G4cout << Arb_ezero[i] << Arb_Const[i] << Area_seg[i] << G4endl;
        i++;
    }

    i = 0;
    while (i < maxi) {
        Arb_Cum_Area[i] = Arb_Cum_Area[i] / sum;
        IPDFArbEnergyH.InsertValues(Arb_x[i], Arb_Cum_Area[i]);
        i++;
    }

    // now scale the ArbEnergyH, needed by Probability()
    ArbEnergyH.ScaleVector(1., 1./sum);

    if (verbosityLevel >= 1)
        G4cout << "Leaving ExpInterpolation " << G4endl;
}

void G4SPSEneDistribution::SplineInterpolation() {
    // Interpolation using Splines.
    // Create Normalised arrays, make x 0->1 and y hold
    // the function (Energy)
        // 
        // Current method based on the above will not work in all cases. 
        // new method is implemented below.
  
    G4double sum, Arb_x[1024], Arb_y[1024], Arb_Cum_Area[1024];
    G4int i, count;

    G4int maxi = ArbEnergyH.GetVectorLength();
    for (i = 0; i < maxi; i++) {
        Arb_x[i] = ArbEnergyH.GetLowEdgeEnergy(size_t(i));
        Arb_y[i] = ArbEnergyH(size_t(i));
    }
    // Points are now in x,y arrays. If the spectrum is integral it has to be
    // made differential and if momentum it has to be made energy.
    if (DiffSpec == false) {
        // Converts integral point-wise spectra to Differential
        for (count = 0; count < maxi - 1; count++) {
            Arb_y[count] = (Arb_y[count] - Arb_y[count + 1])
                    / (Arb_x[count + 1] - Arb_x[count]);
        }
        maxi--;
    }
    //
    if (EnergySpec == false) {
        // change currently stored values (emin etc) which are actually momenta
        // to energies.
        if (particle_definition == NULL)
                    G4Exception("G4SPSEneDistribution::SplineInterpolation",
                                "Event0302",FatalException,
                    "Error: particle not defined");
        else {
            // Apply Energy**2 = p**2c**2 + m0**2c**4
            // p should be entered as E/c i.e. without the division by c
            // being done - energy equivalent.
            G4double mass = particle_definition->GetPDGMass();
            // convert point to energy unit and its value to per energy unit
            G4double total_energy;
            for (count = 0; count < maxi; count++) {
                total_energy = std::sqrt((Arb_x[count] * Arb_x[count]) + (mass
                        * mass)); // total energy

                Arb_y[count] = Arb_y[count] * Arb_x[count] / total_energy;
                Arb_x[count] = total_energy - mass; // kinetic energy
            }
        }
    }

    //
    i = 1;
    Arb_Cum_Area[0] = 0.;
    sum = 0.;
    Splinetemp = new G4DataInterpolation(Arb_x, Arb_y, maxi, 0., 0.);
    G4double ei[101],prob[101];
    while (i < maxi) {
      // 100 step per segment for the integration of area
      G4double de = (Arb_x[i] - Arb_x[i - 1])/100.;
      G4double area = 0.;

      for (count = 0; count < 101; count++) {
        ei[count] = Arb_x[i - 1] + de*count ;
        prob[count] =  Splinetemp->CubicSplineInterpolation(ei[count]);
        if (prob[count] < 0.) { 
              G4ExceptionDescription ED;
          ED << "Warning: G4DataInterpolation returns value < 0  " << prob[count] <<" "<<ei[count]<< G4endl;
              G4Exception("G4SPSEneDistribution::SplineInterpolation","Event0303",
              FatalException,ED);
        }
        area += prob[count]*de;
      }
      Arb_Cum_Area[i] = Arb_Cum_Area[i - 1] + area;
      sum += area; 

      prob[0] = prob[0]/(area/de);
      for (count = 1; count < 100; count++)
        prob[count] = prob[count-1] + prob[count]/(area/de);

      SplineInt[i] = new G4DataInterpolation(prob, ei, 101, 0., 0.);
      // note i start from 1!
      i++;
    }
    i = 0;
    while (i < maxi) {
        Arb_Cum_Area[i] = Arb_Cum_Area[i] / sum; // normalisation
        IPDFArbEnergyH.InsertValues(Arb_x[i], Arb_Cum_Area[i]);
        i++;
    }
    // now scale the ArbEnergyH, needed by Probability()
    ArbEnergyH.ScaleVector(1., 1./sum);

    if (verbosityLevel > 0)
      G4cout << "Leaving SplineInterpolation " << G4endl;
}

void G4SPSEneDistribution::GenerateMonoEnergetic() {
    // Method to generate MonoEnergetic particles.
    particle_energy = MonoEnergy;
}

void G4SPSEneDistribution::GenerateGaussEnergies() {
    // Method to generate Gaussian particles.
    particle_energy = G4RandGauss::shoot(MonoEnergy,SE);
    if (particle_energy < 0) particle_energy = 0.;
}

void G4SPSEneDistribution::GenerateLinearEnergies(G4bool bArb = false) {
    G4double rndm;
    G4double emaxsq = std::pow(Emax, 2.); //Emax squared
    G4double eminsq = std::pow(Emin, 2.); //Emin squared
    G4double intersq = std::pow(cept, 2.); //cept squared

    if (bArb)
        rndm = G4UniformRand();
    else
        rndm = eneRndm->GenRandEnergy();

    G4double bracket = ((grad / 2.) * (emaxsq - eminsq) + cept * (Emax - Emin));
    bracket = bracket * rndm;
    bracket = bracket + (grad / 2.) * eminsq + cept * Emin;
    // Now have a quad of form m/2 E**2 + cE - bracket = 0
    bracket = -bracket;
    //  G4cout << "BRACKET" << bracket << G4endl;
    if (grad != 0.) {
        G4double sqbrack = (intersq - 4 * (grad / 2.) * (bracket));
        //      G4cout << "SQBRACK" << sqbrack << G4endl;
        sqbrack = std::sqrt(sqbrack);
        G4double root1 = -cept + sqbrack;
        root1 = root1 / (2. * (grad / 2.));

        G4double root2 = -cept - sqbrack;
        root2 = root2 / (2. * (grad / 2.));

        //      G4cout << root1 << " roots " << root2 << G4endl;

        if (root1 > Emin && root1 < Emax)
            particle_energy = root1;
        if (root2 > Emin && root2 < Emax)
            particle_energy = root2;
    } else if (grad == 0.)
        // have equation of form cE - bracket =0
        particle_energy = bracket / cept;

    if (particle_energy < 0.)
        particle_energy = -particle_energy;

    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GeneratePowEnergies(G4bool bArb = false) {
    // Method to generate particle energies distributed as
    // a power-law

    G4double rndm;
    G4double emina, emaxa;

    emina = std::pow(Emin, alpha + 1);
    emaxa = std::pow(Emax, alpha + 1);

    if (bArb)
        rndm = G4UniformRand();
    else
        rndm = eneRndm->GenRandEnergy();

    if (alpha != -1.) {
        particle_energy = ((rndm * (emaxa - emina)) + emina);
        particle_energy = std::pow(particle_energy, (1. / (alpha + 1.)));
    } else {
        particle_energy = (std::log(Emin) + rndm * (std::log(Emax) - std::log(
                Emin)));
        particle_energy = std::exp(particle_energy);
    }
    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GenerateBiasPowEnergies() {
    // Method to generate particle energies distributed as
    // in biased power-law and calculate its weight

        G4double rndm;
    G4double emina, emaxa, emin, emax;

    G4double normal = 1. ;

    emin = Emin;
    emax = Emax;
    //  if (EnergyDisType == "Arb") { 
    //  emin = ArbEmin;
    //  emax = ArbEmax;
    //}

    rndm = eneRndm->GenRandEnergy();

    if (biasalpha != -1.) {
            emina = std::pow(emin, biasalpha + 1);
            emaxa = std::pow(emax, biasalpha + 1);
        particle_energy = ((rndm * (emaxa - emina)) + emina);
        particle_energy = std::pow(particle_energy, (1. / (biasalpha + 1.)));
        normal = 1./(1+biasalpha) * (emaxa - emina);
    } else {
        particle_energy = (std::log(emin) + rndm * (std::log(emax) - std::log(
                emin)));
        particle_energy = std::exp(particle_energy);
        normal = std::log(emax) - std::log(emin) ;
    }
    weight = GetProbability(particle_energy) / (std::pow(particle_energy,biasalpha)/normal);

    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GenerateExpEnergies(G4bool bArb = false) {
    // Method to generate particle energies distributed according
    // to an exponential curve.
    G4double rndm;

    if (bArb)
        rndm = G4UniformRand();
    else
        rndm = eneRndm->GenRandEnergy();

    particle_energy = -Ezero * (std::log(rndm * (std::exp(-Emax / Ezero)
            - std::exp(-Emin / Ezero)) + std::exp(-Emin / Ezero)));
    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GenerateBremEnergies() {
    // Method to generate particle energies distributed according
    // to a Bremstrahlung equation of
    // form I = const*((kT)**1/2)*E*(e**(-E/kT))

    G4double rndm;
    rndm = eneRndm->GenRandEnergy();
    G4double expmax, expmin, k;

    k = 8.6181e-11; // Boltzmann's const in MeV/K
    G4double ksq = std::pow(k, 2.); // k squared
    G4double Tsq = std::pow(Temp, 2.); // Temp squared

    expmax = std::exp(-Emax / (k * Temp));
    expmin = std::exp(-Emin / (k * Temp));

    // If either expmax or expmin are zero then this will cause problems
    // Most probably this will be because T is too low or E is too high

    if (expmax == 0.)
        G4cout << "*****EXPMAX=0. Choose different E's or Temp" << G4endl;
    if (expmin == 0.)
        G4cout << "*****EXPMIN=0. Choose different E's or Temp" << G4endl;

    G4double tempvar = rndm * ((-k) * Temp * (Emax * expmax - Emin * expmin)
            - (ksq * Tsq * (expmax - expmin)));

    G4double bigc = (tempvar - k * Temp * Emin * expmin - ksq * Tsq * expmin)
            / (-k * Temp);

    // This gives an equation of form: Ee(-E/kT) + kTe(-E/kT) - C =0
    // Solve this iteratively, step from Emin to Emax in 1000 steps
    // and take the best solution.

    G4double erange = Emax - Emin;
    G4double steps = erange / 1000.;
    G4int i;
    G4double etest, diff, err;

    err = 100000.;

    for (i = 1; i < 1000; i++) {
        etest = Emin + (i - 1) * steps;

        diff = etest * (std::exp(-etest / (k * Temp))) + k * Temp * (std::exp(
                -etest / (k * Temp))) - bigc;

        if (diff < 0.)
            diff = -diff;

        if (diff < err) {
            err = diff;
            particle_energy = etest;
        }
    }
    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GenerateBbodyEnergies() {
    // BBody_x holds Energies, and BBHist holds the cumulative histo.
    // binary search to find correct bin then lin interpolation.
    // Use the earlier defined histogram + RandGeneral method to generate
    // random numbers following the histos distribution.
    G4double rndm;
    G4int nabove, nbelow = 0, middle;
    nabove = 10001;
    rndm = eneRndm->GenRandEnergy();

    // Binary search to find bin that rndm is in
    while (nabove - nbelow > 1) {
        middle = (nabove + nbelow) / 2;
        if (rndm == BBHist[middle])
            break;
        if (rndm < BBHist[middle])
            nabove = middle;
        else
            nbelow = middle;
    }

    // Now interpolate in that bin to find the correct output value.
    G4double x1, x2, y1, y2, t, q;
    x1 = Bbody_x[nbelow];
    x2 = Bbody_x[nbelow + 1];
    y1 = BBHist[nbelow];
    y2 = BBHist[nbelow + 1];
    t = (y2 - y1) / (x2 - x1);
    q = y1 - t * x1;

    particle_energy = (rndm - q) / t;

    if (verbosityLevel >= 1) {
        G4cout << "Energy is " << particle_energy << G4endl;
    }
}

void G4SPSEneDistribution::GenerateCdgEnergies() {
    // Gen random numbers, compare with values in cumhist
    // to find appropriate part of spectrum and then
    // generate energy in the usual inversion way.
    //  G4double pfact[2] = {8.5, 112};
    // G4double spind[2] = {1.4, 2.3};
    // G4double ene_line[3] = {1., 18., 1E6};
    G4double rndm, rndm2;
    G4double ene_line[3];
    G4double omalpha[2];
    if (Emin < 18 * keV && Emax < 18 * keV) {
        omalpha[0] = 1. - 1.4;
        ene_line[0] = Emin;
        ene_line[1] = Emax;
    }
    if (Emin < 18 * keV && Emax > 18 * keV) {
        omalpha[0] = 1. - 1.4;
        omalpha[1] = 1. - 2.3;
        ene_line[0] = Emin;
        ene_line[1] = 18. * keV;
        ene_line[2] = Emax;
    }
    if (Emin > 18 * keV) {
        omalpha[0] = 1. - 2.3;
        ene_line[0] = Emin;
        ene_line[1] = Emax;
    }
    rndm = eneRndm->GenRandEnergy();
    rndm2 = eneRndm->GenRandEnergy();

    G4int i = 0;
    while (rndm >= CDGhist[i]) {
        i++;
    }
    // Generate final energy.
    particle_energy = (std::pow(ene_line[i - 1], omalpha[i - 1]) + (std::pow(
            ene_line[i], omalpha[i - 1]) - std::pow(ene_line[i - 1], omalpha[i
            - 1])) * rndm2);
    particle_energy = std::pow(particle_energy, (1. / omalpha[i - 1]));

    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GenUserHistEnergies() {
    // Histograms are DIFFERENTIAL.
    //  G4cout << "In GenUserHistEnergies " << G4endl;
    if (IPDFEnergyExist == false) {
        G4int ii;
        G4int maxbin = G4int(UDefEnergyH.GetVectorLength());
        G4double bins[1024], vals[1024], sum;
        sum = 0.;

        if ((EnergySpec == false) && (particle_definition == NULL))
            G4cout << "Error: particle definition is NULL" << G4endl;

        if (maxbin > 1024) {
            G4cout << "Maxbin > 1024" << G4endl;
            G4cout << "Setting maxbin to 1024, other bins are lost" << G4endl;
        }

        if (DiffSpec == false)
            G4cout << "Histograms are Differential!!! " << G4endl;
        else {
            bins[0] = UDefEnergyH.GetLowEdgeEnergy(size_t(0));
            vals[0] = UDefEnergyH(size_t(0));
            sum = vals[0];
            for (ii = 1; ii < maxbin; ii++) {
                bins[ii] = UDefEnergyH.GetLowEdgeEnergy(size_t(ii));
                vals[ii] = UDefEnergyH(size_t(ii)) + vals[ii - 1];
                sum = sum + UDefEnergyH(size_t(ii));
            }
        }

        if (EnergySpec == false) {
            G4double mass = particle_definition->GetPDGMass();
            // multiply the function (vals) up by the bin width
            // to make the function counts/s (i.e. get rid of momentum
            // dependence).
            for (ii = 1; ii < maxbin; ii++) {
                vals[ii] = vals[ii] * (bins[ii] - bins[ii - 1]);
            }
            // Put energy bins into new histo, plus divide by energy bin width
            // to make evals counts/s/energy
            for (ii = 0; ii < maxbin; ii++) {
                bins[ii] = std::sqrt((bins[ii] * bins[ii]) + (mass * mass))
                        - mass; //kinetic energy
            }
            for (ii = 1; ii < maxbin; ii++) {
                vals[ii] = vals[ii] / (bins[ii] - bins[ii - 1]);
            }
            sum = vals[maxbin - 1];
            vals[0] = 0.;
        }
        for (ii = 0; ii < maxbin; ii++) {
            vals[ii] = vals[ii] / sum;
            IPDFEnergyH.InsertValues(bins[ii], vals[ii]);
        }

        // Make IPDFEnergyExist = true
        IPDFEnergyExist = true;
        if (verbosityLevel > 1)
            IPDFEnergyH.DumpValues();
    }

    // IPDF has been create so carry on
    G4double rndm = eneRndm->GenRandEnergy();
    particle_energy = IPDFEnergyH.GetEnergy(rndm);

    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::GenArbPointEnergies() {
    if (verbosityLevel > 0)
        G4cout << "In GenArbPointEnergies" << G4endl;
    G4double rndm;
    rndm = eneRndm->GenRandEnergy();
    //      IPDFArbEnergyH.DumpValues();
    // Find the Bin
    // have x, y, no of points, and cumulative area distribution
    G4int nabove, nbelow = 0, middle;
    nabove = IPDFArbEnergyH.GetVectorLength();
    //      G4cout << nabove << G4endl;
    // Binary search to find bin that rndm is in
    while (nabove - nbelow > 1) {
      middle = (nabove + nbelow) / 2;
      if (rndm == IPDFArbEnergyH(size_t(middle)))
        break;
      if (rndm < IPDFArbEnergyH(size_t(middle)))
        nabove = middle;
      else
        nbelow = middle;
    }
    if (IntType == "Lin") {
      Emax = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow + 1));
      Emin = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow));
      grad = Arb_grad[nbelow + 1];
      cept = Arb_cept[nbelow + 1];
      //      G4cout << rndm << " " << Emax << " " << Emin << " " << grad << " " << cept << G4endl;
      GenerateLinearEnergies(true);
    } else if (IntType == "Log") {
      Emax = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow + 1));
      Emin = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow));
      alpha = Arb_alpha[nbelow + 1];
      //      G4cout << rndm << " " << Emax << " " << Emin << " " << alpha << G4endl;
      GeneratePowEnergies(true);
    } else if (IntType == "Exp") {
      Emax = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow + 1));
      Emin = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow));
      Ezero = Arb_ezero[nbelow + 1];
      //      G4cout << rndm << " " << Emax << " " << Emin << " " << Ezero << G4endl;
      GenerateExpEnergies(true);
    } else if (IntType == "Spline") {
      Emax = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow + 1));
      Emin = IPDFArbEnergyH.GetLowEdgeEnergy(size_t(nbelow));
      particle_energy = -1e100;
      rndm = eneRndm->GenRandEnergy();
      while (particle_energy < Emin || particle_energy > Emax) {
        particle_energy = SplineInt[nbelow+1]->CubicSplineInterpolation(rndm);
        rndm = eneRndm->GenRandEnergy();
      }
      if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
    } else
        G4cout << "Error: IntType unknown type" << G4endl;
}

void G4SPSEneDistribution::GenEpnHistEnergies() {
    //  G4cout << "In GenEpnHistEnergies " << Epnflag << G4endl;

    // Firstly convert to energy if not already done.
    if (Epnflag == true)
    // epnflag = true means spectrum is epn, false means e.
    {
        // convert to energy by multiplying by A number
        ConvertEPNToEnergy();
        // EpnEnergyH will be replace by UDefEnergyH.
        //      UDefEnergyH.DumpValues();
    }

    //  G4cout << "Creating IPDFEnergy if not already done so" << G4endl;
    if (IPDFEnergyExist == false) {
        // IPDF has not been created, so create it
        G4double bins[1024], vals[1024], sum;
        G4int ii;
        G4int maxbin = G4int(UDefEnergyH.GetVectorLength());
        bins[0] = UDefEnergyH.GetLowEdgeEnergy(size_t(0));
        vals[0] = UDefEnergyH(size_t(0));
        sum = vals[0];
        for (ii = 1; ii < maxbin; ii++) {
            bins[ii] = UDefEnergyH.GetLowEdgeEnergy(size_t(ii));
            vals[ii] = UDefEnergyH(size_t(ii)) + vals[ii - 1];
            sum = sum + UDefEnergyH(size_t(ii));
        }

        for (ii = 0; ii < maxbin; ii++) {
            vals[ii] = vals[ii] / sum;
            IPDFEnergyH.InsertValues(bins[ii], vals[ii]);
        }
        // Make IPDFEpnExist = true
        IPDFEnergyExist = true;
    }
    //  IPDFEnergyH.DumpValues();
    // IPDF has been create so carry on
    G4double rndm = eneRndm->GenRandEnergy();
    particle_energy = IPDFEnergyH.GetEnergy(rndm);

    if (verbosityLevel >= 1)
        G4cout << "Energy is " << particle_energy << G4endl;
}

void G4SPSEneDistribution::ConvertEPNToEnergy() {
    // Use this before particle generation to convert  the
    // currently stored histogram from energy/nucleon
    // to energy.
    //  G4cout << "In ConvertEpntoEnergy " << G4endl;
    if (particle_definition == NULL)
        G4cout << "Error: particle not defined" << G4endl;
    else {
        // Need to multiply histogram by the number of nucleons.
        // Baryon Number looks to hold the no. of nucleons.
        G4int Bary = particle_definition->GetBaryonNumber();
        //      G4cout << "Baryon No. " << Bary << G4endl;
        // Change values in histogram, Read it out, delete it, re-create it
        G4int count, maxcount;
        maxcount = G4int(EpnEnergyH.GetVectorLength());
        //      G4cout << maxcount << G4endl;
        G4double ebins[1024], evals[1024];
        if (maxcount > 1024) {
            G4cout << "Histogram contains more than 1024 bins!" << G4endl;
            G4cout << "Those above 1024 will be ignored" << G4endl;
            maxcount = 1024;
        }
        if (maxcount < 1) {
            G4cout << "Histogram contains less than 1 bin!" << G4endl;
            G4cout << "Redefine the histogram" << G4endl;
            return;
        }
        for (count = 0; count < maxcount; count++) {
            // Read out
            ebins[count] = EpnEnergyH.GetLowEdgeEnergy(size_t(count));
            evals[count] = EpnEnergyH(size_t(count));
        }

        // Multiply the channels by the nucleon number to give energies
        for (count = 0; count < maxcount; count++) {
            ebins[count] = ebins[count] * Bary;
        }

        // Set Emin and Emax
        Emin = ebins[0];
        if (maxcount > 1)
            Emax = ebins[maxcount - 1];
        else
            Emax = ebins[0];
        // Put energy bins into new histogram - UDefEnergyH.
        for (count = 0; count < maxcount; count++) {
            UDefEnergyH.InsertValues(ebins[count], evals[count]);
        }
        Epnflag = false; //so that you dont repeat this method.
    }
}

//
void G4SPSEneDistribution::ReSetHist(G4String atype) {
    if (atype == "energy") {
        UDefEnergyH = IPDFEnergyH = ZeroPhysVector;
        IPDFEnergyExist = false;
        Emin = 0.;
        Emax = 1e30;
    } else if (atype == "arb") {
        ArbEnergyH = IPDFArbEnergyH = ZeroPhysVector;
        IPDFArbExist = false;
    } else if (atype == "epn") {
        UDefEnergyH = IPDFEnergyH = ZeroPhysVector;
        IPDFEnergyExist = false;
        EpnEnergyH = ZeroPhysVector;
    } else {
        G4cout << "Error, histtype not accepted " << G4endl;
    }
}

G4double G4SPSEneDistribution::GenerateOne(G4ParticleDefinition* a) {
    particle_definition = a;
    particle_energy = -1.;

    while ((EnergyDisType == "Arb") ? (particle_energy < ArbEmin
            || particle_energy > ArbEmax) : (particle_energy < Emin
            || particle_energy > Emax)) {
        if (Biased) {
            GenerateBiasPowEnergies();
        } else {
            if (EnergyDisType == "Mono")
                GenerateMonoEnergetic();
            else if (EnergyDisType == "Lin")
                GenerateLinearEnergies();
            else if (EnergyDisType == "Pow")
                GeneratePowEnergies();
            else if (EnergyDisType == "Exp")
                GenerateExpEnergies();
            else if (EnergyDisType == "Gauss")
                GenerateGaussEnergies();
            else if (EnergyDisType == "Brem")
                GenerateBremEnergies();
            else if (EnergyDisType == "Bbody")
                GenerateBbodyEnergies();
            else if (EnergyDisType == "Cdg")
                GenerateCdgEnergies();
            else if (EnergyDisType == "User")
                GenUserHistEnergies();
            else if (EnergyDisType == "Arb")
                GenArbPointEnergies();
            else if (EnergyDisType == "Epn")
                GenEpnHistEnergies();
            else
                G4cout << "Error: EnergyDisType has unusual value" << G4endl;
        }
    }
    return particle_energy;
}

G4double G4SPSEneDistribution::GetProbability(G4double ene) {
    G4double prob = 1.;

    if (EnergyDisType == "Lin") {
      if (prob_norm == 1.) {
        prob_norm = 0.5*grad*Emax*Emax + cept*Emax - 0.5*grad*Emin*Emin - cept*Emin;
      }
      prob = cept + grad * ene;
      prob /= prob_norm;
    }
    else if (EnergyDisType == "Pow") {
      if (prob_norm == 1.) {
        if (alpha != -1.) {
          G4double emina = std::pow(Emin, alpha + 1);
          G4double emaxa = std::pow(Emax, alpha + 1);
          prob_norm = 1./(1.+alpha) * (emaxa - emina);
        } else {
          prob_norm = std::log(Emax) - std::log(Emin) ;
        }
      }
      prob = std::pow(ene, alpha)/prob_norm;
    }
    else if (EnergyDisType == "Exp"){
      if (prob_norm == 1.) {
        prob_norm = -Ezero*(std::exp(-Emax/Ezero) - std::exp(Emin/Ezero));
      }  
      prob = std::exp(-ene / Ezero);
      prob /= prob_norm;
    }
    else if (EnergyDisType == "Arb") {
      prob = ArbEnergyH.Value(ene);
      //  prob = ArbEInt->CubicSplineInterpolation(ene);
      //G4double deltaY;
      //prob = ArbEInt->PolynomInterpolation(ene, deltaY);
      if (prob <= 0.) {
        //G4cout << " Warning:G4SPSEneDistribution::GetProbability: prob<= 0. "<<prob <<" "<<ene << " " <<deltaY<< G4endl;
        G4cout << " Warning:G4SPSEneDistribution::GetProbability: prob<= 0. "<<prob <<" "<<ene << G4endl;
        prob = 1e-30;
      }
      // already normalised
    }
    else
        G4cout << "Error: EnergyDisType not supported" << G4endl;
       
    return prob;
}