I have two questions about how the USRBIN card works when scoring energy deposition in FLUKA:
When I score energy deposition by region using USRBIN, is the output in GeV/cm³ per primary or just GeV per primary? I’ve read on the forum that it might be GeV per primary, but I couldn’t understand it in the FLUKA course material for my case. Until now, I’ve assumed it’s in GeV/cm³/primary, and I multiply it by the volume of each crystal (0.6 cm3) to get the total energy deposited.
[ sorted point 2] In my setup (please see the attached image), I built the stack by starting with a rectangular slab and using XYP planes to divide it into alternating regions of scintillator crystals and air gaps. Each crystal region is 0.2 cm thick, separated by 0.2 cm air gaps. I’ve defined 15 crystal regions (named sc1 to sc15) and 15 air regions (names sa1 to sa15) then I used USRBIN to score energy deposition in regions (R1from:sc1 to R1to:sc15). The results show energy deposition only in these 15 regions. Does this mean that the air gap regions (sa2 to sa14) are not included in the scoring? also, Is this the correct way to score the energy in all 15 crystals like R1from:sc1 to R1to:sc15 ? I am assigning void also as air.
I’m asking because we are comparing the energy deposition from FLUKA and Geant4, and they’re quite different. I’m wondering if I might be misunderstanding or doing something wrong in FLUKA.
I now understand point 2 from my previous question regarding region-wise energy deposition. The issue arose because I was including both void and blackbody regions, and I had assigned the void as air. As a result, energy deposited in the void was being added to the first crystal’s region, while the other crystals showed consistent values. When I isolate a single crystal, I can clearly see that the void’s energy deposition is also being included.
if I assign the void as vacuum instead of air, the energy deposited in that region becomes negligible or nearly zero, and hence does not significantly affect the result.
I also realize that region-wise energy deposition depends on the order in which regions are defined. So, point 2 is now clear to me.
However, I would still like to clarify point 1 in my case. I modeled a rectangular slab and divided it using planes. For the energy deposition in these regions, are the USRBIN results given in GeV/cm³ per primary or simply GeV per primary for my case?
USRBIN per region: FLUKA results are not normalised by volume.
USRBIN meshes: FLUKA results are normalised by volume.
This because FLUKA does not calculate regions volumes (which can be arbitrarily complex), while the volume computation of the available scoring meshes is trivial.
I am glad that your second inquiry is already solved. This forum post can also give you some hints about how to exploit the “Step1” field in your USRBIN cards with region type scoring.
Thank you for your response. I’m still a bit unclear on one specific point and would appreciate your clarification.
Let’s say I use USRBIN to score region-wise ENERGY in my region sc1, and I get a result of 2.3021E-05. I know that the actual volume of sc1 is 0.6 cm³, but FLUKA, as I understand, does not internally calculate volumes in the scoring of energy region wise. So it assumes the region volume to be 1 cm³ by default.
Given that, could you please confirm what the unit of the scored value actually is?
Is it 2.3021E-05 GeV/cm³/primary?
Or 2.3021E-05 GeV·cm³/primary?
Or simply 2.3021E-05 GeV/primary?
Also, to get the correct total energy deposited in my actual region, should I multiply this value by 0.6 cm³, divide by it, or just leave it as is?
I realize this may be a basic question, but I am a bit confused here, and I’d like to be precise with energy deposition in units. Ultimately, I want my energy deposition to be in the units of GeV/primary for sc1 region.
Dear @talktoshubhama,
In FLUKA if you score energy using USRBIN with regular spatial structure such as XYZ or RPhiZ, the unit is GeV/primary, not GeV/cm3/primary.
As for the example given by you, your value will be 2.3021E-05 GeV/primary.
Scenario changes when you score with region based volume (FLUKA itself cannot calculate the volume of that region). There you need divide by the volume of the region.
I found one statement from the Fluka manual "scoring by region the total energy density, if generalised particle ENERGY has been selected.
Results will be in GeV/cm3 per primary if volumes have been input, otherwise in GeV per region per primary. To obtain dose in Gy, multiply GeV/cm3 by 1.602176462E-7/
(
= density in g/cm3)."
The USRBIN energy deposition value for my crystal region (sc1) is shown as, for example, 2.3E-5.
My crystal volume is 0.6 cm³.
Since FLUKA does not internally normalize by actual volume and assumes 1 cm³ by default, I interpret this value as the total energy deposited in the entire region per primary particle, assuming a unit volume.
Therefore, if I want the energy density (GeV/cm³), I would divide this value by 0.6. Does this statement refers for the “Results will be in GeV/cm3 per primary if volumes have been input”
However, I want my values to be in GeV/primary for further analysis.
So, if FLUKA assumes 1 cm³ by default, does this mean that the value 2.3E-5 is already the correct total energy deposition (GeV/region/primary) or (GeV/primary) for my crystal volume of 0.6 cm³, without any volume adjustment?
Could you please confirm if this interpretation is correct? I want to be sure before using these values in my response matrix calculations.
In that case you get GeV per primary, i.e., the total energy deposited over the region volume.
If you divide by the latter, you will get the average energy density in GeV/cm3 per primary.
Thank you @ceruttif for correcting me. As most of the time we score dose, instead of energy, which we average over the entire region, so it stayed in my mind.
If we score dose instead of energy for region based scoring, then we divide it by region volume, right ?
Thank you once again.
With regards,
Sujoy
Good point.
In the first case (regular mesh), if you score DOSE instead of ENERGY, you get dose in GeV/g instead of energy density in GeV/cm3.
In the case of region scoring, with ENERGY - as mentioned above - you get the total energy in GeV (which is a different quantity than energy density), while with DOSE you get a meaningless quantity, which - as you say - must be divided by the region volume in order to get the average dose over the region in GeV/g.
[Every quantity should be intended per primary].
