Acts::Material Class Reference

Material description for interactions with matter. More...

#include <Acts/Material/Material.hpp>

Public Types
using	ParametersVector = Eigen::Matrix<float, 5, 1>
	Opaque parameters vector for serialization.

Public Member Functions
	Material (const ParametersVector &parameters)
	Construct from an encoded parameters vector.
constexpr float	Ar () const
	Return the relative atomic mass.
bool	isVacuum () const
	Check if the material is vacuum.
constexpr float	L0 () const
	Return the nuclear interaction length.
float	massDensity () const
	Return the mass density.
constexpr float	meanExcitationEnergy () const
	Return the mean electron excitation energy.
constexpr float	molarDensity () const
	Return the molar density.
constexpr float	molarElectronDensity () const
	Return the molar electron density.
ParametersVector	parameters () const
	Encode the properties into an opaque parameters vector.
constexpr float	X0 () const
	Return the radiation length.
constexpr float	Z () const
	Return the nuclear charge number.

Static Public Member Functions
static Material	fromMassDensity (float x0, float l0, float ar, float z, float massRho)
	Construct from material parameters using the mass density.
static Material	fromMolarDensity (float x0, float l0, float ar, float z, float molarRho)
	Construct from material parameters using the molar density.
static Material	fromMolarDensity (float x0, float l0, float ar, float z, float molarRho, float molarElectronRho, std::optional< float > meanExcitationEnergy)
	Construct from material parameters using the molar density.
static constexpr Material	Vacuum ()
	Create a vacuum material.

Detailed Description

Material description for interactions with matter.

The following parameters are used to specify the material and its interactions with traversing particles:

• radiation length X0 (native length units)
• nuclear interaction length L0 (native length units)
• relative atomic mass Ar (unitless number)
• nuclear charge number Z (elementary charge e)
• molar density (native amount-of-substance unit / (native length unit)³)

The parameters can be effective or average parameters e.g. when a mixture of materials is described.

Note

Always use the opaque parameters vector to serialize/deserialize the material information. Since the internal storage might be different from the external accessors, this ensures that always the numerically optimal parameters are stored. Use the ParametersVector type and do not assume any particular size since we might consider to store more parameters in the future.

Constructor & Destructor Documentation

Material()

Acts::Material::Material ( const ParametersVector & parameters )

explicit

Construct from an encoded parameters vector.

Parameters

parameters

Encoded material parameters

Member Function Documentation

Ar()

float Acts::Material::Ar ( ) const

constexpr

Return the relative atomic mass.

Returns

Relative atomic mass

fromMassDensity()

Material Acts::Material::fromMassDensity ( float x0, float l0, float ar, float z, float massRho )

static

Construct from material parameters using the mass density.

Parameters

x0	is the radiation length
l0	is the nuclear interaction length
ar	is the relative atomic mass
z	is the nuclear charge number
massRho	is the mass density

Returns

Material instance constructed from the given parameters

Warning

Due to the choice of native mass units, using the mass density can lead to numerical problems. Typical mass densities lead to computations with values differing by 20+ orders of magnitude.

fromMolarDensity() [1/2]

Material Acts::Material::fromMolarDensity ( float x0, float l0, float ar, float z, float molarRho )

static

Construct from material parameters using the molar density.

Parameters

x0	is the radiation length
l0	is the nuclear interaction length
ar	is the relative atomic mass
z	is the nuclear charge number
molarRho	is the molar density

Returns

Material instance constructed from the given parameters

fromMolarDensity() [2/2]

Material Acts::Material::fromMolarDensity ( float x0, float l0, float ar, float z, float molarRho, float molarElectronRho, std::optional< float > meanExcitationEnergy )

static

Construct from material parameters using the molar density.

Parameters

x0	is the radiation length
l0	is the nuclear interaction length
ar	is the relative atomic mass
z	is the nuclear charge number
molarRho	is the molar density
molarElectronRho	is the molar electron density
meanExcitationEnergy	is the mean electron excitation energy. If not provided it will be approximated.

Returns

Material instance constructed from the given parameters

isVacuum()

bool Acts::Material::isVacuum

(

)

const

Check if the material is vacuum.

Returns

True if the material is vacuum

L0()

float Acts::Material::L0 ( ) const

constexpr

Return the nuclear interaction length.

Infinity in case of vacuum.

Returns

Nuclear interaction length

massDensity()

float Acts::Material::massDensity

(

)

const

Return the mass density.

Returns

Mass density

meanExcitationEnergy()

float Acts::Material::meanExcitationEnergy ( ) const

constexpr

Return the mean electron excitation energy.

Returns

Mean electron excitation energy

molarDensity()

float Acts::Material::molarDensity ( ) const

constexpr

Return the molar density.

Returns

Molar density

molarElectronDensity()

float Acts::Material::molarElectronDensity ( ) const

constexpr

Return the molar electron density.

Returns

Molar electron density

parameters()

ParametersVector Acts::Material::parameters

(

)

const

Encode the properties into an opaque parameters vector.

Returns

Encoded parameters vector

Vacuum()

constexpr Material Acts::Material::Vacuum ( )

staticconstexpr

Create a vacuum material.

Returns

Vacuum material

X0()

float Acts::Material::X0 ( ) const

constexpr

Return the radiation length.

Infinity in case of vacuum.

Returns

Radiation length

Z()

float Acts::Material::Z ( ) const

constexpr

Return the nuclear charge number.

Returns

Nuclear charge number