Question about alpha transport in EGSnrc

[ShahinGHD]

Hi everyone,
When we have alphas we expect that the range is short.
However, running a DPK simulation with alpha emitters of the Ac-225 chain in a 10x10x10 cm phantom showed me that I am losing a lot of energy going outside my small phantom. and the total energy deposited is not equal to the Q value of that nuclide. ( I am scoring alphas with alpha scoring = local)
however, choosing a 200x200x200 cm phantom, can accurately do the dpk simulation and the results are equal to the Q value.
please take a look at this image for details.
DPK CHART CALCULATED WITH different phantom size

My question is: Why I am losing SO MUCH energy going outside that phantom when my nuclide is just an alpha emitter (such as At-217 or Po-213)
The results of the big 200cm phantom and NO-transport simulations are correct.
it is very urgent so thank you for answering.

[ftessier]

EGSnrc currently does not handle the transport of $\large\alpha$ particles. If this question is about egs_mird, please address your issue there.

[rtownson]

I would guess this is just due to x-rays and internal transition gammas exiting the geometry. With alpha scoring = local all of the alpha particles will be absorbed in the creation region, but all other decay products are still created and transported.

[rtownson]

I'm using egs_app with egs_radionuclide_source

[ShahinGHD]

I will try to test the geometry with the egs_app, if it is working there then the problem is with the egs_mird

Thank you so much

[ShahinGHD]

I am using MoboXterm to execute my input file, are you using the windows version? what command should I type to run?

I usually type egs_mird -i myinput.egsinp

[rtownson]

egs_app -i myinput.egsinp

I am on linux but it makes no difference.

##############################################################################
### Run control
##############################################################################
:start run control:
    ncase = 2e5
:stop run control:


##############################################################################
### Geometry
##############################################################################
:start geometry definition:
    :start geometry:
        name     = my_spheres
        library  = egs_spheres
        midpoint = 0 0 0
        radii    = 1 2 3
        :start media input:
            media = water air water
            set medium = 1 1
            set medium = 2 2
        :stop media input:
    :stop geometry:

    simulation geometry = my_spheres

:stop geometry definition:

:start MC transport parameter:
Rayleigh Scattering = Off
Atomic relaxations = On
Global Ecut = 0.521
Global Pcut = 0.01

Set ECUT = 21
Set ECUT start region = 0
Set ECUT stop region = 1
:stop MC transport parameter:

##############################################################################
### Media
##############################################################################
#:start media definition:

    ### particle production thresholds
    ae = 0.521                                  # MeV
    ap = 0.010                                  # MeV
    ue = 50.511                                 # MeV
    up = 50                                     # MeV

    ### air
    :start air:
        density correction file = air_dry_nearsealevel
    :stop air:

    ### water
    :start water:
        density correction file = water_liquid
    :stop water:

    ### See $HEN_HOUSE/pegs4/density_corrections/ for more materials, or create
    ### you own: https://github.com/nrc-cnrc/EGSnrc/wiki/Generating-density-correction-files

:stop media definition:


##############################################################################
### Ausgab objects
##############################################################################
:start ausgab object definition:

    ### generate particle tracks
#     :start ausgab object:
        name    = tracks
        library = egs_track_scoring
    :stop ausgab object:

    ### report dose in all regions
    :start ausgab object:
        name    = dose
        library = egs_dose_scoring
    :stop ausgab object:


:stop ausgab object definition:


##############################################################################
### Viewer control
##############################################################################
:start view control:
    set color = air    0 200  50  50               # r g b alpha
    set color = water  0 220 255 200
:stop view control:



##############################################################################
### SOURCE
##############################################################################
:start source definition:



    :start source:
        name                = sph_source
        library             = egs_isotropic_source
        charge              = 0
        geometry            = my_spheres

        :start shape:
            type     = sphere
            radius   = 1
        :stop shape:
        :start spectrum:
            type = monoenergetic
            energy = 1
        :stop spectrum:
    :stop source:

    :start source:
        name                = my_mixture
        library             = egs_radionuclide_source
        activity            = 28e6 # total of mixture, assumed constant
                                   # the value of this doesn't affect output
                                   # just the emission times which are not used
        charge              = -1 0 1 2 # optional (if excluded use all)
                                       # an array of allowed charges (-1,0,1,2)
                                       # All disintegration types are still
                                       # sampled, but only the allow types
                                       # will be transported.
        base source = sph_source


        # The spectrum of the source
        # Replace the nuclide term with the radionuclide of interest, e.g. Co-60
        :start spectrum:
            type            = radionuclide
            nuclide         = Po-213
            atomic relaxations = eadl # [optional, default=eadl] eadl or ensdf
#                                  By default, 'eadl' relaxations use the EGSnrc
#                                  algorithm for emission correlated with
#                                  disintegration events. Alternatively, 'ensdf'
#                                  relaxations statistically sample fluorescent
#                                  photons and Auger emission using comments
#                                  in the ensdf file.
            output beta spectra = no # [optional, defaults=no] no or yes
#                                     Whether or not to output an energy spectrum
#                                     for every possible beta decay
#                                     The file is named {nuclide}_d_{energy}.spec
            extra transition approximation = On
            alpha scoring = local
        :stop spectrum:
    :stop source:


    simulation source = my_mixture

:stop source definition:

[ShahinGHD]

Thank you so much