Hesaplamalı Nükleer Fizik

# For a Geant4 application that uses G4ParticleGun.
# Example geometry assumption: a slab normal to z, downstream of z = -10 cm.
# Change source position to match your geometry.
/run/initialize
/gun/particle gamma
/gun/energy 661.7 keV
/gun/position 0 0 -10 cm
/gun/direction 0 0 1
/run/beamOn 100000

#include <cmath>
#include <iomanip>
#include <iostream>

int main() {
    double mu = 0.0;
    double thickness = 0.0;
    if (!(std::cin >> mu >> thickness) || !std::isfinite(mu) ||
        !std::isfinite(thickness) || mu < 0.0 || thickness < 0.0) {
        std::cerr << "Enter a nonnegative coefficient (cm^-1) and thickness (cm).\n";
        return 1;
    }

    std::cout << "thickness_cm,transmitted_fraction\n" << std::setprecision(8);
    for (int step = 0; step <= 20; ++step) {
        const double depth = thickness * (step / 20.0);
        std::cout << depth << ',' << std::exp(-mu * depth) << '\n';
    }
}

#include <TCanvas.h>
#include <TH1D.h>
#include <TRandom3.h>

// Run with: root -l gamma_spectrum.C
void gamma_spectrum() {
    constexpr double peakEnergyKeV = 661.7;
    constexpr double fwhmKeV = 40.0;
    TRandom3 random(42);
    auto* spectrum = new TH1D("synthetic_gamma", "Synthetic spectrum;Energy (keV);Counts / 10 keV", 80, 0, 800);

    for (int event = 0; event < 1800; ++event)
        spectrum->Fill(random.Gaus(peakEnergyKeV, fwhmKeV / 2.35482));

    // A uniform background makes the peak easier to study independently.
    for (int event = 0; event < 5000; ++event)
        spectrum->Fill(random.Uniform(0.0, 800.0));

    auto* canvas = new TCanvas("gamma_spectrum_canvas", "Gamma spectrum", 820, 460);
    spectrum->SetLineColor(kBlue + 2);
    spectrum->Draw("HIST");
    canvas->Update();
}