22. Neutron Transport Calculations¶

RMC currently supports neutron-photon-electron coupled transport calculations

22.1. Neutron Transport Calculation Physics Switch¶

Physics
ParticleMode < particle type >
Neutron MinEnergy=<params>

where,

Physics is the keyword for calculating physical switches for neutron transport；
ParticleMode represents the particle type corresponding to the Particle Transport Calculation Physics Switch, where N represents neutrons, P represents photons, and E represents electrons;
Neutron is the keyword of the Neutron Physics Process Option.
MinEnergy refers to the minimum energy for neutron transport, where the units are in MeV, and the default value is 1.0E-20. If the neutron energy is found to be lower than MinEnergy during the neutron transport process, the neutron is killed.

22.2. Neutron Transport Calculation Physics Switch Input Example¶

If the neutron energy during transport is lower than 1E-11MeV, the neutron will be killed.

Physics
ParticleMode n
Neutron MinEnergy=1E-11

23. Photon Transport Calculations¶

RMC currently supports neutron-photon-electron coupled transport calculations

23.1. Photon Transport Calculation Physics Switch¶

Physics
ParticleMode < particle type >
Photon PPRODUCEE=<params> TTB=<params> ADTTB=<params> ANNIHILATION=<params> COHERENT=<params> PHOTONNUCLEUS=<params> DOPPLER=<params> UPERERG=<params> ERGCUTGMA=<params> ELECMULTITIMES=<params> DelayedPhotonScaling=<params> Newphoton=<params>

where,

Physics is the keyword for calculating physical switches for neutron-photon-electron coupled transport;
ParticleMode represents the particle type corresponding to the Particle Transport Calculation Physics Switch, where N represents neutrons, P represents photons, and E represents electrons;
Photon is the indicator of the Physics Switch for Photon Transport, which then corresponds to the Physics Switch for particle transport;
PPRODUCEE specifies whether electrons are generated during photon transport. A value of 1 means that electrons are generated, and 0 means that electrons are not generated. The default value is 0, that is, it is not turned on by default;
TTB specifies whether the simplified TTB model (which does not take into account the angular distribution of photons) is used to process electrons during photon transport. A value of 0 means that the simplified TTB model is not used, 1 means that the simplified TTB model is used, The default value is 0, that is, it is not turned on by default;
ADTTB specifies whether the ADTTB model (which takes into account the angular distribution of photons) is used to process electrons during photon transport. A value of 0 means that the ADTTB model is not used, 1 means that the ADTTB model is used, The default value is 0, that is, it is not turned on by default;(Note: The TTB and ADTTB options cannot be turned on at the same time)
ANNIHILATION is not in use at the moment. This option specifies whether the Annihilation Model is used to process electrons during photon transport. A value of 1 means that the Annihilation Model is used, while a value of 0 indicates that the model is not being used. The default value is 0, that is, it is not turned on by default;
COHERENT specifies whether Thompson scattering is processed during photon transport. A value of 1 means that Thompson scattering is processed, and a value of 0 means that Thompson scattering is not processed. The default value is 1, that is, it is turned on by default;
PHOTONNUCLEUS specifies whether the photon nuclear reaction is processed during photon transport. A value of 1 means that the photon nuclear reaction is processed, and 0 means that the photon nuclear reaction is not processed. The default value is 0, that is, it is not turned on by default;
DOPPLER specifies whether Doppler broadening is processed during photon transport. A value of 1 means that Doppler broadening is processed, and 0 means that Doppler broadening is not processed. The default value is 0, that is, it is not turned on by default;
UPERERG specifies the energy boundary value in the photon transport process. If the photon energy is greater than the energy boundary value, then the simple photon transport model is used instead. The unit for the energy boundary value is MeV, with the default value being 100MeV;
ERGCUTGMA specifies the lower energy limit during photon transport. The unit of the lower energy limit is MeV, and the default value is 1.0E-03 MeV;
ELECMULTITIMES specifies the multiplication factor of electrons generated during photon transport. The default value is 1.0.
delayedphotonscaling specifies the method for simulating delayed photons in the neutron photon production process by adjusting the weight of photons. A value of 1 indicates that it is enabled (default), while 0 indicates that it is not enabled.
newphoton Specifies the use of a new photon transport process that considers atomic relaxation processes. A value of 1 indicates that it is enabled, while 0 indicates that it is not enabled (default). When using this option, users must ensure that the photon_hdf5 photon and atomic relaxation HDF5 nuclear database is present in the RMC_DATA directory to ensure proper calculation by the RMC.

注解

The current version of RMC is compatible with the MCNP photon ACE nuclear database from mcplib04p. Additionally, RMC supports HDF5 format databases for photons that consider atomic relaxation processes. The former simulates vacancies produced during Compton scattering and photoelectric effects using a fluorescence approximation, which has certain limitations. The latter simulates atomic relaxation processes based on photoelectric subshell data from the database, providing higher accuracy. Users are recommended to use the latter option.

23.2. Photon Transport Calculation Physics Switch Input Example¶

The fixed source releases 10,000 source neutrons. The fixed source is a point source, located at the coordinates of the origin point, and the source neutron energy is 0.1 MeV. During pure photon transport calculation, the photon transport process does not produce electrons, and the simplified TTB model is not used to process electrons. Thompson scattering and photonuclear reactions are processed, and Doppler broadening operations are not performed. The upper energy limit is 100MeV, the lower energy limit is 1.0E-3, and the multiplication factor of electrons generated by photon transport is 1.0.

Physics
ParticleMode p
Photon  PPRODUCEE = 0  TTB = 0  ANNIHILATION = 0  COHERENT = 1 PHOTONNUCLEUS =1  DOPPLER = 0  UPERERG = 100 ERGCUTGMA = 1.0E-3  ELECMULTITIMES = 1.0

24. Electron Transport Calculations¶

24.1. Electron Transport Calculation Physics Switch¶

Physics
ParticleMode < particle type >
Electron MaxEnergy=<params> MinEnergy=<params> EPRODUCEP=<params>  ErgLossStraggle=<params> BREMS=<params> BREMSANGLE=<params>  BREMSEACHSUBTEP=<params> BREMSERGLOSSMETHOD=<params>  BREMSPHOTONMULTITIMES=<params> XRAYMULTITIMES=<params> KNOCKONMULTITIMES=<params>

where,

Physics is the keyword for calculating physical switches for neutron-photon-electron coupled transport;
ParticleMode represents the particle type corresponding to the Particle Transport Calculation Physics Switch, where N represents neutrons, P represents photons, and E represents electrons;
Electron is the keyword for Electron Physics Process Input Option;
EproducePis the option controls the generation of photons by electrons (default is true).
MaxEnergy represents the highest energy of an electron during electron transport, with the units in MeV. The default value is 100. At present, the RMC database requires that MaxEnergy cannot be greater than 100. If the electron energy is found to be greater than MaxEnergy during electron transport, an error will be reported;
MinEnergy represents the minimum energy for electron transport, with the units in MeV, and the default value as 1.0E-3. If the electron energy is lower than MinEnergy during electron transport, the electron is killed;
ErgLossStraggle indicates if the blocking ability undergoes fluctuation.The default value is 1, indicating fluctuation. If there is no fluctuation, the blocking ability of electrons in the determined material and energy is a fixed value;
BREMS specifies if electrons caused by Bremsstrahlung are considered in the calculations;
BREMSANGLE specifies if the direction of the secondary Bremsstrahlung photons are to be sampled in detail. The default is 1, indicating detailed sampling. If the value is set to 0, then simple sampling will be performed instead;
BREMSPHOTONMULTITIMES indicates the number of secondary Bremsstrahlung photons generated in a single bremsstrahlung process. It should be a real number greater than or equal to 0, with the default value being 1. The weightage of the secondary Bremsstrahlung photons is divided by the value of BREMSPHOTONMULTITIMES accordingly. When BREMSPHOTONMULTITIMES is greater than 1, the variance of the secondary Bremsstrahlung photons can be reduced, and when it is less than 1, the simulation time of the secondary Bremsstrahlung photons can be reduced.
BREMSEACHSUBTEP specifies if the generation of secondary Bremsstrahlung photons is to be forced at each range sub-step. The value of this can be set to either 0 or 1, with the default value being 0. If the value is set to 1, BREMSPHOTONMULTITIMES = 1 is required, and the weightages of secondary Bremsstrahlung photons are adjusted as desired.
BREMSERGLOSSMETHOD controls the calculation method of the energy loss of electrons due to Bremsstrahlung, which can be set to either 0 or 1, with the default value being 1. A value of 1 means that the energy of the first Bremsstrahlung photon is used to calculate the electron energy loss, and 0 means that the average energy of all Bremsstrahlung photons is used to calculate the electron energy loss.
XRAYMULTITIMES represents the number of secondary X-ray fluorescence or Auger electrons generated during one X-ray fluorescence or Auger electron generation process. It should be a real number greater than or equal to 0, with the default value being 1. The weightage of the secondary X-ray fluorescence or Auger electron will be divided by the value of XRAYMULTITIMES accordingly. When XRAYMULTITIMES is greater than 1, the variance of the secondary X-ray fluorescence or Auger electron can be reduced, and when it is less than 1, the simulation time of the secondary X-ray fluorescence or Auger electron can be reduced.
KNOCKONMULTITIMES represents the number of secondary electrons produced during a single electron collision. It should be a real number greater than or equal to 0, with the default value being 1. The weightage of the secondary collided electrons will be divided by the value of XRAYMULTITIMES accordingly. When the value of KNOCKONMULTITIMES is greater than 1, the variance of collided electrons can be reduced, and when the value is less than 1, the simulation time of collided electrons can be reduced. If the number of electrons collided is large, the simulation time required for transport increases by approximately two hours after the Switch is turned on.

24.2. Electron Transport Calculation Physics Switch Input Example¶

Photoelectronic coupling transport calculation, where the upper limit of electron energy is 100MeV, the lower limit is 0.001 MeV, the electron transport process produces photons, prevents energy fluctuations, and produces Bremsstrahlung electrons. The direction of the secondary Bremsstrahlung photons is sampled in detail, and the secondary Bremsstrahlung photons are not forced to be generated at each range sub-step. The energy of the first Bremsstrahlung photon is used to calculate the electron energy loss, and a secondary X-ray fluorescence or Auger electron is generated during the generation of an X-ray fluorescence or Auger electron, and no collided electrons are generated.

Physics
ParticleMode P E
Photon    PPRODUCEE=1  TTB=0  ANNIHILATION=0  COHERENT=1
          PHOTONNUCLEUS=0  DOPPLER=1  UPERERG=100  ERGCUTGMA=1.0E-3  ELECMULTITIMES=1.0
Electron  MaxEnergy=100  MinEnergy=1.0E-3  EPRODUCEP=1  ErgLossStraggle=1  BREMS=1
          BREMSANGLE=1  BREMSEACHSUBTEP=0  BREMSERGLOSSMETHOD=1  BREMSPHOTONMULTITIMES=1.0
          XRAYMULTITIMES=1.0  KNOCKONMULTITIMES=0.0