Gain of a plane parallel geometry

Hi experts,

I’m curently simulating a plane parrallel ionization chamber geometry filled with air in order to get the gain of the IC. I’m at low field (5000 V/cm) so no multiplication. The gain should then be the total number of electrons created. I shoot protons with E_{kinetic} = 230 MeV across 0.1 cm gap.

Using TrachHeed and taking the mean on 1000 tracks I get 10.4.

Multiplying the mean energy loss on those 1000 tracks by the mean energy of pair W track.GetW() I get 12.89.

And using the stoping power S track.GetStoppingPower() and calculating this way Gain = \frac{S~d}{W} I get 12.26

Shouldn’t those 3 ways give the same result ? Which one is the more realistic ?

Thank you in advance for your help

Kind regards


Hi Pierre,
the observable ionisation in a thin-gap chamber is typically less than what you would get by dividing the stopping power by W, since part of the energy loss “escapes” in the form of high-energy delta electrons or fluorescence photons.

I guess you calculated the mean energy loss by summing up the “cluster energies”? This number should indeed converge to the stopping power if you run more tracks.

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Hi @hschindl and thank you for your answer. Effectively I use the cluster energy (since I’m based on the edep.C exemple file. And yes, with more events the convergence is clear !

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