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Material.cpp
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1 // This file is part of the Acts project.
2 //
3 // Copyright (C) 2019-2020 CERN for the benefit of the Acts project
4 //
5 // This Source Code Form is subject to the terms of the Mozilla Public
6 // License, v. 2.0. If a copy of the MPL was not distributed with this
7 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 
10 
12 
13 #include <cmath>
14 #include <ostream>
15 
16 namespace {
18  eRadiationLength = 0,
19  eInteractionLength = 1,
20  eRelativeAtomicMass = 2,
21  eNuclearCharge = 3,
22  eMolarDensity = 4,
23 };
24 
25 // Avogadro constant
26 constexpr double kAvogadro = 6.02214076e23 / Acts::UnitConstants::mol;
27 } // namespace
28 
30  float z, float massRho) {
31  using namespace Acts::UnitLiterals;
32 
33  Material mat;
34  mat.m_x0 = x0;
35  mat.m_l0 = l0;
36  mat.m_ar = ar;
37  mat.m_z = z;
38  // mass density is defined as
39  //
40  // mass-density = atomic-mass * number-of-atoms / volume
41  // = atomic-mass * molar-density * avogadro-constant
42  // -> molar-density = mass-density / (atomic-mass * avogadro-constant)
43  //
44  // with the atomic mass given by
45  //
46  // atomic-mass = relative-atomic-mass * atomic-mass-unit
47  //
48  // perform computations in double precision to avoid loss of precision
49  const double atomicMass = static_cast<double>(ar) * 1_u;
50  mat.m_molarRho = static_cast<double>(massRho) / (atomicMass * kAvogadro);
51  return mat;
52 }
53 
55  float z, float molarRho) {
56  Material mat;
57  mat.m_x0 = x0;
58  mat.m_l0 = l0;
59  mat.m_ar = ar;
60  mat.m_z = z;
61  mat.m_molarRho = molarRho;
62  return mat;
63 }
64 
66  : m_x0(parameters[eRadiationLength]),
67  m_l0(parameters[eInteractionLength]),
68  m_ar(parameters[eRelativeAtomicMass]),
69  m_z(parameters[eNuclearCharge]),
70  m_molarRho(parameters[eMolarDensity]) {}
71 
73  using namespace Acts::UnitLiterals;
74 
75  // perform computations in double precision to avoid loss of precision
76  const double atomicMass = static_cast<double>(m_ar) * 1_u;
77  const double numberDensity = static_cast<double>(m_molarRho) * kAvogadro;
78  return atomicMass * numberDensity;
79 }
80 
82  using namespace Acts::UnitLiterals;
83 
84  // use approximative computation as defined in ATL-SOFT-PUB-2008-003
85  return 16_eV * std::pow(m_z, 0.9f);
86 }
87 
90  parameters[eRadiationLength] = m_x0;
91  parameters[eInteractionLength] = m_l0;
92  parameters[eRelativeAtomicMass] = m_ar;
93  parameters[eNuclearCharge] = m_z;
94  parameters[eMolarDensity] = m_molarRho;
95  return parameters;
96 }
97 
98 std::ostream& Acts::operator<<(std::ostream& os, const Material& material) {
99  if (!material) {
100  os << "vacuum";
101  } else {
102  os << "x0=" << material.X0();
103  os << "|l0=" << material.L0();
104  os << "|ar=" << material.Ar();
105  os << "|z=" << material.Z();
106  os << "|molar_rho=" << material.molarDensity();
107  }
108  return os;
109 }