Using egs++ cavity to score dose or SPR without known cavity volume or cavity mass for each individual region

[karenrex1023]

Hello,
I am trying to score dose to a region of air in a spherical ionization geometry that I have made in egs cavity. Based on how I created the geometry, the air includes several regions in egs_view. Although I have the mass for the overall, cumulative air region, I don't know the volumes or masses for the individual/specific regions of air as specified by egs_view. Is there a way I can combine all the individual regions into an overall air region in egs++ or that I can score dose to the air region without knowing the individual region masses? Below is the code I have so far:
:start scoring options:

calculation type = dose

:start calculation geometry:
    geometry name = chamber_in_air #spherical ion chamber
    cavity regions = 662 617 619 621 623 625 661 #regions of air within the chamber
    cavity mass = 0.00426329  #air density*volume for overall inner chamber air volume
:stop calculation geometry:

:stop scoring options:

In addition, the documentation mentioned cavity could be used to get the stopping power ratio (SPR) as well as dose. I was wondering how the code above would change if I was trying to calculate the SPR?

[rtownson]

cavity doesn't calculate SPR, but I can see that it's easy to misread the sentence Features available in CAVRZnrc but *not* provided by cavity are:.

I suggest setting cavity mass = 1. Then the "dose" reported will actually just be the sum of the energies deposited (almost, it's actually normalized by a constant factor for unit conversion). Then you can divide by the total mass manually to get the actual dose per fluence.

[karenrex1023]

Thank you for the suggestion!!! What is the numerical value normalization factor? I imagine if I am trying to get the actual energy deposited, I would need to divide the value given in the output file for the "dose" by the normalization factor?

[rtownson]

It's a constant, so if you want the dose deposited you can leave it since only the mass is varying between regions. If you actually want the energy deposited per fluence, just divide by 1.602e-10.