How to get dE/dx value for different gas pressures?

Recently I was simulating the energy deposition in a gas detector, I used the new G4Material(name, z, a, density, state, temp, pressure) method to create a 48 atm xenon gas as the filling gas for the gas detector, and got the deposition energy through the GetTotalEnergyDeposit() method, I changed the above pressure from 48 to 1 and found that the value of the energy deposition got bigger by about 5%, I would like to know how the gas pressure affects the energy deposition process, and how should I see the value of dE/dx for different gas pressures in geant4?


Changing gas pressure will change in gas density and therefore more will be gas particles in the same volume.
more particles means more interaction chances.

G4Step is a base class and provide method GetTotalEnergyDeposit(), however, to have total energy loss you must integrate all steps of a track in gas medium at the end of event Action.

A keen beginner will look example B1 which covers all details you are looking for.


1 Like

Thank you drvijayraj. I’ve summed up all the energy deposited by the STEP into the RUN. I agree with you about the greater chance of reaction with a higher gas pressure, I have corrected the gas density using the van der Waals equation, and after I changed the pressure of the gas to a smaller one, the value of the energy deposition became larger instead, which is what I don’t understand.

Dear @Song_Yuanpeng

I too not understanding, however,
please check the materiel definition,
an e.g. is

 auto a = 131.29*g/mole;
 G4Element* Xe = new G4Element(name="Xe", symbol="Xe", z=54., a);
 auto density = 5.858*mg/cm3;  
 double pressure = X*bar;  // [X->Your choice]
 double temperature = 296.15*kelvin;  // [your choice]
 G4Material* matXe  = new G4Material("matXe", density, 1, kStateGas, temperature, pressure);
 matXe->AddElement(Xe, 1);  //--> Monoatomic nature

Maybe problem comes from the definition you using in your code while defining the material.
If you change pressure/temperature [without changing density] de/dx will change.


I repeated your exercise with example TestEm0, definition of Xenon in attachement.

As expected, dE/dx increases with pressure and density.
XenonGas.txt (758 Bytes)
song.mac.txt (314 Bytes)
song.out.txt (5.7 KB)

Thanks for your replies @drvijayraj @maire , I’ll take a closer look at it later if I have time.

This topic was automatically closed 7 days after the last reply. New replies are no longer allowed.