Hi,
I would like to store the deposited/absorbed dose inside a detector. Until now, I’m only using the deposited energy ( G4double partEdep = aStep->GetTotalEnergyDeposit(); )
in principle the dose is simply D = dE/dM but how do I get the mass of the detector? Is it also just a simple calculation or is there already something built inside Geant4 for the dose?
In your code, you can use G4VPhysicalVolume::GetLogicalVolume()->GetMass(). Look at G4LogicalVolume.hh to see what the optional arguments to GetMass() are.
Note that you should sum up all of the Edeps in your volume to get a total DeltaE/M value.
thank you! I’m trying to use this but I don’t get it how to use it (in my code…).
I got this inside my detector.cc:
G4bool MySensitiveDetector::ProcessHits(G4Step *aStep, G4TouchableHistory *ROhist)
{
G4StepPoint *preStepPoint = aStep->GetPreStepPoint();
G4StepPoint *postStepPoint = aStep->GetPostStepPoint();
if(preStepPoint->GetStepStatus() == fGeomBoundary)
{
const G4VTouchable *touchable = aStep->GetPreStepPoint()->GetTouchable();
G4VPhysicalVolume *physVol = touchable->GetVolume();
G4double mass = physVol->GetMass();
}
}
but this results in
C:\geant4\sim\detector.cc(82,28): error C2039: 'GetMass': is not a member of 'G4VPhysicalVolume' [C:\geant4\build\toy_e
x.vcxproj]
Why is that?
intellisense suggests this:
touchable->GetVolume()->GetLogicalVolume()->GetMass()
(the physical properties are encapsulated in the logical volume, although the name suggests otherwise 
)
indeed, this is working… in a different world it’s probably making sense but however, I’m always struggling how to solve issues like this.
How exactly are you using intellisense that it provided the solution?
However, when I print mass I receive mass: 2.32505e+20 as value. Which unit is it, but anyway, it seems to be quite a lot?
edit: I saw About the molar mass and absorbed dose - #4 by mkelsey and used G4cout << "mass: " << mass/kg << " kg" << G4endl; which gives mass: 3.72514e-05 kg which equals to 37 µg. Tbh, I have to check. The value is not far off but could be a bit little nevertheless. But it could be a valid value, I will check…
but is this correct, what I am doing?
And when I wanna’ know the dose I won’t convert it into other units, right?
it does make sense when you think of the “physical representation” of the volume, so kind of the actual placement of it → hence also the term “touchable”.
to be honest it did not suggest the whole solution, just that “GetMass()” is available for the “GetLogicalVolume”. Using visual studio code, the auto-complete suggestions appear when I start typing the arrow ->
seemingly
yes. just don’t use any units until you store/display results, then you divide by the (combined) final unit that you prefer, e.g., (keV/kg) or CLHEP::joule/CLHEP::kilogram, or …
Alright, thank you!
I checked the value meanwhile and I found a huge discrepancy. My detector is defined as follows:
G4Material *LiF = nist->FindOrBuildMaterial("G4_LITHIUM_FLUORIDE");
G4Tubs *solidDetector = new G4Tubs("solidDetector", 0*mm, 6/2*mm, 0.5/2*mm, 0., 360.*deg);
logicDetector = new G4LogicalVolume(solidDetector, LiF, "logicDetector");
and when I print out the mass I receive:
G4cout << "mass: " << mass/kg << " kg" << G4endl;
mass: 3.72514e-05 kg
which is way too less?! When I calculate it manually I get:
density LiF: 2.64 g/cm³
volume dectector: Pi*(3mm)²*0.25mm = 7.069 mm³ = 0.07 cm³
m = rho * V = 0.18 g = 1.866e-4 kg
do I make a mistake or G4?
Hello,
I see two math mistakes:
volume dectector: Pi*(3mm)²*0.25mm = …
This should be
volume dectector: Pi*(3mm)²*0.5mm = …
since your G4Tubs is 5 mm long making your total volume 14.137mm³ = 0.014 cm³ (you missed one decimal place in your calculation: 7mm³ = 0.007 cm³
Then the mass becomes 0.037g, which is exactly what Geant is showing.
Regards
Max
Thank you very much! My mistake and so obvious… but glad to have that verified.
What would I do without you people
Thanks again!
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