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////////////////////////////////////////////////////////////////////////////////
// //
// This file is part of NCrystal (see https://mctools.github.io/ncrystal/) //
// //
// Copyright 2015-2022 NCrystal developers //
// //
// Licensed under the Apache License, Version 2.0 (the "License"); //
// you may not use this file except in compliance with the License. //
// You may obtain a copy of the License at //
// //
// http://www.apache.org/licenses/LICENSE-2.0 //
// //
// Unless required by applicable law or agreed to in writing, software //
// distributed under the License is distributed on an "AS IS" BASIS, //
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. //
// See the License for the specific language governing permissions and //
// limitations under the License. //
// //
////////////////////////////////////////////////////////////////////////////////
//Include all NCrystal public headers:
#include "NCrystal/NCrystal.hh"
//Other includes (<random> is for the std::mt19937_64 example below):
#include <iostream>
#include <random>
namespace NC = NCrystal;
int main() {
///////////////////////////////////////////////////////
// Sanity check the NCrystal installation (optional) //
///////////////////////////////////////////////////////
//This checks that the included NCrystal headers and the linked NCrystal
//library are from the same release of NCrystal:
NC::libClashDetect();
///////////////////////////////////////
// Setup random generator (optional) //
///////////////////////////////////////
//NCrystal already ships with a high quality generator, so this is done here
//merely as an example for users who needs to use their own source of random
//numbers. The example wraps the C++11 mt19937_64 generator and only
//implements the actualGenerate function. Additional functions can be
//overridden to enable more advanced capabilities concerning multi-threading,
//RNG state manipulation, etc. See the NCRNG.hh file for details. Of course,
//if we had NOT registered a custom RNG source here, NCrystal would be using
//the built-in source, which IS multi-thread safe (due to usage of jump-ahead
//features).
class CustomRNG : public NC::RNGStream {
std::mt19937_64 m_gen;
protected:
double actualGenerate() override { return NC::randUInt64ToFP01(static_cast<uint64_t>(m_gen())); }
//For the sake of example, we wrongly claim that this generator is safe and
//sensible to use multithreaded (see NCRNG.hh for how to correctly deal with
//MT safety, RNG states, etc.):
bool useInAllThreads() const override { return true; }
};
//The NCrystal makeSO function is similar to std::make_shared
//and should be used instead of raw calls to new and delete:
auto rng = NC::makeSO<CustomRNG>();
//Register:
NC::setDefaultRNG(rng);
//////////////////////////////////////
// Create and use aluminium powder: //
//////////////////////////////////////
auto pc = NC::createScatter( "Al_sg225.ncmat;dcutoff=0.5;temp=25C" );
//Specify neutron energy state using either wavelength (angstrom) or energy
//(eV), and get the cross section (the material is isotropic so we don't need
//to specify a direction):
auto wl = NC::NeutronWavelength{1.8};//Or in eV as e.g. NC::NeutronEnergy{0.0253}
auto xsect = pc.crossSectionIsotropic( wl );
//The wl and xsect object are strongly typed, and will print out their values
//along with units (use wl.get() or xsect.get() to access raw doubles):
std::cout << "Powder Al x-sect at " << wl << " is " << xsect << std::endl;
//Carry out some scatterings (again, using the isotropic material interface,
//to get just mu=cos(theta_scat) instead of actual directions):
for (unsigned i=0;i<5;++i) {
auto outcome = pc.sampleScatterIsotropic( wl );
std::cout <<"Powder Al random angle/delta-e at "<<wl<<" Aa is mu="<<outcome.mu
<<" ("<<std::acos(outcome.mu.get())*NC::kToDeg<<" degrees) and new energy state is "
<< outcome.ekin << " ("<<outcome.ekin.wavelength()<<")" <<std::endl;
}
//It is cheap and easy to clone Scatter objects, which is usually done in
//order to ensure each thread of a multi-threaded programme will use the same
//physics model, but with its own independent RNG stream and other caches:
auto pc_clone = pc.clone();
(void)pc_clone;//avoid compiler warnings about unused variable
//////////////////////////////////////////////
// Create and use single crystal germanium: //
//////////////////////////////////////////////
//Create and use single crystal germanium. We orient it carefully to select a
//scattering on the hkl=511 plane with 1.540 aangstrom:
NC::MatCfg cfg("Ge_sg227.ncmat;dcutoff=0.5");
cfg.set_mos( NC::MosaicityFWHM{ 40.0*NC::kArcSec });
cfg.set_dir1( NC::HKLPoint{5,1,1}, NC::LabAxis{0,0,1} );
cfg.set_dir2( NC::HKLPoint{0,-1,1}, NC::LabAxis{0,1,0} );
auto sc = NC::createScatter( cfg );
wl = NC::NeutronWavelength{1.540};
xsect = sc.crossSection( wl, { 0.0, 1.0, 1.0 } );
std::cout << "single crystal Ge x-sect at "<<wl<<" Aa is "<<xsect<<" barn (orientation 1)"<<std::endl;
xsect = sc.crossSection( wl, { 1.0, 1.0, 0.0 } );
std::cout << "singlecrystal Ge x-sect at "<<wl<<" Aa is "<<xsect<<" barn (orientation 2)"<<std::endl;
auto outcome1 = sc.sampleScatter( wl, { 0.0, 1.0, 1.0 } );
std::cout << "A random scattering in orientation 1 gives: "
<< outcome1.ekin.wavelength()
<<" and direction "<<outcome1.direction<<std::endl;
return 0;
}
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