Analysis¶
Five different types of analysis are possible in MULASSIS:
Fluence versus energy spectra;
Non-ionising energy loss (NIEL) - more strictly, the (total) non-ionising dose or displacement damage dose;
Energy deposition/Total ionising dose;
ICRP-60 Dose Equivalent;
Pulse-height energy deposition spectra (PHS);
Solar Cell Radiation Environment Analysis Model (SCREAM).
Fluence, NIEL and SCREAM analyses are applied to surface of a layer or boundary between two layers. Dose, Dose Equivalent, and PHS analysis can be applied to any layer. All analysis results are normalised to the particle current density (see Normalisation Factor).
Note
In the following analysis commands, if the layer index identified in the
/analysis/<analysis_mode>/addor/analysis/<analysis_mode>/deletecommands is 0 (zero), then all geometry layers will be added for analysis or deleted respectively.
Fluence analysis¶
The fluence analysis allows the user to measurement of particle fluence spectra at the boundaries between the different layers, e.g.
Idle> /analysis/fluence/add 2selects the boundary between the first and second layers for fluence analysis. There are three special cases:
Selecting layer one performs the fluence analysis at the incident surface.
For planar/slab geometry user can specify fluence analysis for last layer +1, which measures the particles which penetrated the whole geometry.
To select all layers, use the command:
Idle> /analysis/fluence/add 0The user can select whether the fluence for protons, neutrons, electrons, gamma rays, charged-pions and muons are to be logged and histogrammed, e.g.
Idle> /analysis/fluence/particle/add neutron Idle> /analysis/fluence/particle/add pionThese configure MULASSIS to perform a fluence analysis for neutron and pion particles. The histogram binning scheme can be defined by the user in energy and angle. The default binning scheme for energy is logarithmic from 1keV to 1 GeV comprising 60 bins, and the default binning scheme for angles is linear from 0 deg to 180 deg comprising two bins, i.e., to separately monitor forward propagation and backward propagation at the boundary. The user may define their own energy and angle binning schemes by entering the edges of each of the bins, e.g.
Idle> /analysis/fluence/angle/mode arb Idle> /analysis/fluence/angle/min 0 deg Idle> /analysis/fluence/angle/max 180 deg Idle> /analysis/fluence/angle/clear Idle> /analysis/fluence/angle/add 90 deg Idle> /analysis/fluence/angle/list The angle binning scheme is arbitrary between 0 deg to 180 deg with bin edges at: 90 degThe units of fluence used in the MULASSIS output may be selected as particles/cm2 per bin or particles/m2 per bin according the input of the
/analysis/fluence/unitcommand, e.g.Idle> /analysis/fluence/unit cm2The type of fluence measurement can be selected as omni or planar with the
/analysis/fluence/typecommand. The difference between these two is:
planar: the fluence is based purely on the number of boundary crossing events (i.e., the particle current) and is applicable to count rates in planar detectors or charge deposition, for example.
omni: The omnidirectional fluence includes a modification to the weight of the boundary-crossing particle according to the cosine of the angle of incidence, and is applicable to determination of dose using stopping powers and NIEL coefficients.
Non ionising energy loss (NIEL)¶
The user can request a NIEL analysis to be carried out at the boundaries between the layers, in a manner similar to that for fluence analysis, e.g.
PreInit> /analysis/niel/add 4 PreInit> /analysis/niel/function cern PreInit> /analysis/niel/unit MeV/gIn this example we selected the boundary between layers 3 and 4 for the NIEL analysis, using the “cern” NIEL coefficients. The NIEL is reported in units of “MeV/g”.
The NIEL can be reported in units of “rad”, or “Gy”, or “MeV/g”, based on the fluence results and NIEL coefficients from CERN [R4] [R5] [R6] [R7] [R8], JPL [R9], INFN/SR-NIEL [R14] or the NRL/SAVANT[R9]_ [R10] [R11] [R12] [R13] data.
Note
Note that, currently NIEL is only calculated for silicon for the CERN and JPL curves - the JPL coefficients are only applicable to incident protons, whereas neutron, electron and pion NIEL is included using the CERN/ROSE data. The NRL/SAVANT data includes data for GaAs and InP for protons, electrons and neutrons. It is anticipated that this will be expanded in the future for other materials.
Energy deposition/total ionising dose (TID)¶
Total energy deposition or total ionising dose in any layer can be requested. These quantities can be calculated in all Geant4 energy or dose units, e.g. MeV, keV, rad etc.
PreInit> /analysis/dose/delete 0 PreInit> /analysis/dose/add 4 PreInit> /analysis/dose/unit rad PreInit> /analysis/dose/list ------------------------------------------------------------- Dose analysis will be carried out for the following layers: Layer No. 4 Aluminium: 100 um ------------------------------------------------------------- PreInit>The above example first deleted all previous total dose analysis requests before selecting layer 4; the total dose is to be calculated in unit of rad(Al); and finally it lists which layers have been included for total dose analysis.
ICRP-60 Dose Equivalent¶
The ICRP-60 Dose Equivalent deposition in any layer can be requested. Dose-Equivalent can be calculated in units of sievert and rem.
PreInit> /analysis/doseEq/delete 0 PreInit> /analysis/doseEq/add 4 PreInit> /analysis/doseEq/unit Sv PreInit> /analysis/doseEq/list ------------------------------------------------------------- Dose analysis will be carried out for the following layers: Layer No. 4 Aluminium: 100 um -------------------------------------------------------------The above example first deleted all previous dose equivalent analysis requests before selecting layer 4; the dose equivalent is to be calculated in units of sieverts; and finally it lists which layers have been included for the dose equivalent analysis.
Pulse-height spectrum (PHS)¶
In addition to TID analysis, the user can select any layer for pulse-height energy deposition spectrum analysis. Such data may be used, for example, to predict the spectra in planar silicon detectors. Like the fluence spectra, the user can control the binning scheme of the spectrum. The PHS is in units of events/bin/cm2, e.g.
PreInit> /analysis/phs/add 4 PreInit> /analysis/phs/energy/mode log PreInit> /analysis/phs/energy/min 1 MeV PreInit> /analysis/phs/energy/max 100 MeV PreInit> /analysis/phs/energy/nbin 20The above example defines a PHS analysis to be performed for layer 4, using a logarithmic energy binning scheme of 20 bins from 1 to 100 MeV.
Solar Cell Radiation Environment Analysis Model (SCREAM)¶
This analysis module implements the NIEL based degradation model developed by S. Messenger at NRL [R13][R15]. The user can request a SCREAM analysis to be carried out at the boundaries between the layers, in the same way as for the NIEL and fluence analysis, e.g.
PreInit> /analysis/solarCell/add 2 PreInit> /analysis/solarCell/function JPL_NRL_NASA_2003_GaAs PreInit> /analysis/solarCell/delParameter default PreInit> /analysis/solarCell/setParameters Pmax 1.70 0.322 0.322 1.86E+09 4.70E+09 PreInit> /analysis/solarCell/setParameters Voc 1.70 0.099 0.099 9.00E+08 2.80E+09In this example we selected the boundary between layers 1 and 2 for a SCREAM analysis, using the JPL_NRL_NASA_2003_GaAs NIEL coefficients. The parameters used with the
setParametersmacro are determined experimentally.Setting the layer number to 0 when using the
/analysis/solarCell/addcommand will result in the solar cell analysis being performed for all boundaries between layers in the geometry as well as external surfaces.
Mulassis/ml-v02-00/r342
